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266 Cards in this Set
- Front
- Back
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cell division
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new cells arise from through the division of preexisting cells
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2 types of cell division
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mitosis and meiosis
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gametes
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sperm or egg cell produced by meiosis in animals
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somatic cells
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body cells formed by mitosis in animals
cells other than sperm and egg |
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cytokinesis
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division of the cytoplasm into two daughter cells
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mitosis and meiosis are responsible for which fundamental attribute of life?
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reproduction
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what is the purpose of mitosis and cytokinesis
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growth, wound repair, reproduction
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asexual reproduction
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produces offspring that are genetically identical to the parent
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chromosome
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single DNA double helix that is wrapped around proteins in a highly organized manner
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chromatid
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one of the to identical strands composing a replicated chromosome that is connected at the centromere to the other strand
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centromere
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specialized region of the chromosome where the two sister chromatids are joined
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sister chromatid
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chromatids from the same chromosome that are connected to the centromere
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4 phases of the cell cycle
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M phase, G1 phase, S phase, G2 phase
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synthesis phase (S phase)
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part of interphase where replication of the DNA is separated from the chromosome copies
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cell cycle
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ordered sequence of events where eukaryotic cells replicate its chromosomes, creates 2 daughter cells, and undergoes division of the cytoplasm
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G2 phase
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gap between S phase and M phase
the cell prepares to divide by checking for errors in DNA replication, and multiplying important organelles like mitochondria. |
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G1 phase
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gap that occurs after M phase but before S phase
the time cell grows in size and carries out normal functions |
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phases of interphase in the cell cycle
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G1, S, G2
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why are the gap phases necessary?
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provide the time for parent cells to grow large enough and synthesize enough organelles that its daughter cells will be normal in size and function
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mitosis
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division of replicated chromosomes and the formation of two daughter nuclei with identical chromosomes and genes
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histones
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positively charged protein associated with DNA in the chromatin of eukaryotic cells
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chromatin
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mainly histones that compose eukaryotic chromosomes
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structure of chromatin
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can be relaxed like in interphase or highly compact
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5 stages of mitosis
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prophase, prometaphase, metaphase, anaphase, telophase
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prophase
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chromosomes condense and sister chromatids become visible. Centrosomes divide and migrate to opposite poles of the cells, forming a spindle of microtubules.
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spindle apparatus
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structure that pulls the chromosomes to the poles of the cell during mitosis and push the poles of the cell away from eacother
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2 types of spindle apparatus
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polar microtubules and kinetochore microtubules
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polar microtubules
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extend from each spindle and overlap one another in the middle of the cell
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kinetochore microtubules
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attach to the chromosome
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centrosome
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contains 2 centrioles and serves as the microtubule organizing center for the spindle apparatus
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centriole
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one of two small cylinderical structures found within the centrosome
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prometaphase
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nuclear envelope disappears, spindle fibers from opposite poles attach to kinetochores of sister chromatids
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kinetochore
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attaches the kinetochore microtubule and each chromatid
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metaphase
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Chromosomes align at the center of the cell, sister chromatids attach to spindle fibers.
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metaphase plate
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imaginary plate that the chromosomes line up along during metaphase
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anaphase
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Spindle fibers shrink pulling sister chromatids of each chromosome apart from each other, towards opposite poles.
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telophase
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new nuclear envelopes form at opposite ends of the cell. Chromosomes stretch again to threadlike form.
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what follows mitosis?
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cytokinesis
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cell plate
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double layer of new plasma membrane that appears in the middle of a dividing cell which ultimately divides the cytoplasm into 2 cells
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cleavage furrow
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pinching in of the plasma membrane that occurs as cytokinesis begins
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fertilzation
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the process of uniting sperm and egg
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meiosis
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This happens only during the production of gametes. The purpose of meiosis is to divide the hereditary material in the nucleus by half, and to produce unique gametes
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sex chromosome
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the x chromosome that carries genes involved in determining the sex of an individual
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autosomes
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any chromosome that is not a sex chromosome
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what chromosomes do females possess?
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xx
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what chromosomes do males posses?
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xy
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homologs
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chromosomes that are similar in size, shape, and gene content
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gene
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section of DNA that influences some hereditary trait in an individual
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allele
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particular version of a gene
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homologous chromosomes carry the same genes but may contain different ________
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alleles
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karyotype
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the number and type of chromosomes present
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diploid
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organisms that have 2 versions of each type of chromosome
have 2 alleles of each gene |
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haploid
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organisms that contain just one of each type of chromosome
dont contain homologous chromosomes |
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haploid number
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number of distinct types of chromosomes in a given cell
represented by the letter n |
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how is the number of complete chromosome sets indicated?
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a number is placed before n
humans are 2n |
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ploidy
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number of complete chromosome sets present
haploid = 1 diploid = 2 |
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polyploid
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species that have three or more of each type of chromosome in each cell
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tetrad
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homologous replicated chromosomes that are joined together
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non-sister chromatids
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chromatids belonging to homologous chromosomes
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how many cell divisions does meiosis consist of?
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2
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2 divisions of meiosis
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meiosis 1 and meiosis 2
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why is meiosis known as reduction division
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the outcome of meiosis is a reduction in chromosome number
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gametogenesis
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4 haploid daughter cells go to form egg cells and sperm cells
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when 2 gametes fuse during fertilization...
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a full compliment of chromosomes is restored
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zygote
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diploid cell that results from fertilization
1 haploid chromosome set from mother + 1 haploid chromosome set from father |
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when does meiosis begin
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after chromosomes have been replicated during S phase
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phases of meiosis 1
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prophase 1, metaphase 1, anaphase 1, telophase 1
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synapsis
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physical pairing of 2 homologous chromosomes during prophase 1 of meiosis
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chiasma
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x shaped structure formed during meiosis by crossing over between non sister chromatids
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crossing over
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exchange of segments of non-sister chromatids between a pair of homologous chromosomes that occurs during meiosis 1
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prophase 1
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Homologous chromosomes come together (synapsis), and exchange parts from each other’s sister chromatids (crossing over), which forms chiasma. Spindle fibers from opposite poles of the cell attach to each homolog
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metaphase 1
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pairs of homologous chromosomes move to the metaphase plate and line up
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anaphase 1
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homologs separate and begin moving to opposite sides of the cell
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telophase 1
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homologs finish moving to opposite sides of the cell, nuclear envelope may reappear in some species
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results of meiosis 2
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4 haploid cells, each with one chromosome of each type
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purpose of meiosis 2
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separate sister chromatids that are still attached
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prophase 2
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spindle apparatus forms
if a nuclear envelope formed at the end of meiosis, it breaks apart |
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metaphase 2
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replicated chromosomes consisting of 2 sister chromatids are lined up at the metaphase plate
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anaphase 2
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sister chromatids separate and are pulled to opposite sides of the cell due to shrinking of spindle fibers
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telophase 2
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a nuclear envelope forms around each haploid set of chromosomes
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differences between mitosis and meiosis
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homologous chromosomes pair early in meiosis but do not pair during mitosis
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synaptonemal complex
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network of proteins that holds non sister chromatids together during synapsis in meiosis 1
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asexual reproduction
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producing offspring that does not involve the fusion of gametes
offspring are clones of parent |
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sexual reproduction
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production of offspring through the fusion of gametes
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each cell in your body contains how many chromosomes total?
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46
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DNA polymerase
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any enzyme that catalyzes synthesis of DNA
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which direction does DNA synthesis proceed and why?
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always proceeds in the 5'-->3' direction because DNA polymerase can only add to the 3' end of the growing DNA chain
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dNTPs
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monomer that can polymerize to form DNA
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structure of dNTP
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consists of deoxyribose, a base (A, T, G, C), and three phosphate groups
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when does a bubble form in a chromosome
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when DNA is actively being synthesized
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origin of replication
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the site on a chromosome at which DNA replication begins
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DNA replication is considered a _______ process
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semi-conservative
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replication bubble
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regions where bubbles appear on the double helix
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DNA synthesis is bidirectional because
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it occurs in both directions at the same time
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replication fork
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y shaped region where the parent-DNA double helix is split into two single strands which are then copied
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helicase
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enzyme that moves along the opening unzipping the double helix and expanding the replication bubble in both directions
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single-strand DNA-binding proteins (SSBPs)
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bind to the open region of the helix to keep the strands from joining again
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topoisomerase
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enzyme that cuts DNA, allows it to unwind, and rejoins it ahead of the advancing replication fork
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primer
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single stranded RNA molecule that base pairs with the 5' end of a DNA template strand and is elongated by DNA polymerase during DNA replication
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why does DNA polymerase require a primer?
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it provides a free 3' hydroxyl group that can combine with an incoming dNTP to form a phosphodiester bond
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primase
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enzyme that synthesizes a short stretch of RNA to use as a primer during DNA replication
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RNA polymerase
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one of a class of enzymes that catalyze synthesis of RNA from ribonucleotides using a DNA template
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leading strand
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strand of DNA that is synthesized in the direction of helix opening
synthesized continuously |
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lagging strand
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DNA strand that is synthesized in the opposite direction of the replication fork
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when does synthesis of the lagging strand start?
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when primase synthesizes a short stretch of RNA that acts as a primer
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okazaki fragments
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make up the lagging strand in synthesized DNA
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DNA ligase
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enzyme that catalyzes the formation of a phosphodiester bond between the adjacent okazaki fragments
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replisome
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multimolecular machine that copies DNA
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proteins required in opening the helix
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helicase, SSBP, topoisomerase
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proteins required in leading strand sythensis
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primase, DNA polymerase III, sliding clamp
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sliding clamp
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holds DNA polymerase in place during strand extension
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proteins required in lagging strand synthesis
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primase, DNA polymerase III, sliding clamp, DNA polymerase I, DNA ligase
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DNA polymerase III
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extends the leading strand or okazaki fragment
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DNA polymerase I
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removes the RNA primer and replaces it with DNA
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telomere
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region at the end of a linear chromosome that consist of short stretches of base that are repeated over and over
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problems that arise during replication of telomeres
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DNA unwinding completed, leading strand completed, lagging strand completed, lagging strand too short
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telomerase
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catalyzes the synthesis of DNA from an RNA
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somatic cells
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not involved in gamete formation
normally lack temomerase |
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why do chromosomes shorten during replication
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because the end of the lagging strand lacks a primer and cannot be synthesized
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telomeres shorten in most cells except
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gamete forming cells due to telomerase enzyme
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how can DNA polymerase III proofread
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if the wrong base is added during DNA synthesis it removes the mismatched base and then proceeds
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mismatch repair
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when mismatched bases are corrected after DNA synthesis is complete
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thymine dimer
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creates kinks in the secondary structure or DNA
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nucleotide excision repair
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enzyme complex checks DNA for damages constantly, if there is a damage it cuts off that area and makes a new strand to fill the gap, then DNA ligase joins the new DNA to the old DNA
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mRNA
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carry info from DNA to the site of protein synthesis
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central dogma
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summarizes the flow of info in cells
DNA codes for RNA which codes for proteins |
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transcription
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process of copying hereditary info in DNA to RNA
happens in the nucleus |
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translation
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converting in in the mRNA to proteins
happens in the ribosomes |
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genotype
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determined by the sequence of bases in its DNA
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phenotype
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product of the proteins it produces
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exceptions to central dogma
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some types of RNA arent translated to proteins, copying of DNA from mRNA
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reverse transciptase
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info flows from RNA to DNA
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genetic code
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rules that specify the relationship between a sequence of nucleotides in DNA or RNA and the sequence of amino acids in the protein
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triplet code
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3 base code provides enough messages to code all 20 amino acids
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codon
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the group of 3 bases that specifies a particular amino acid
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how many codons specify the 20 amino acids?
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61
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can more than one codon specify the same amino acid?
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yes
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start codon
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AUG
signals protein synthesis should begin at that point |
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stop codon
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UAA, UAG, UGA
signals the protein is complete and the translation process ends |
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properties of genetic code
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redundant, unambiguous, nearly universal, conservative
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how many combinations of bases are there?
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64
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mutation
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permanent change in an organisms DNA
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2 types of mutations
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point mutation, chromosome level mutation
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point mutation
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change in a single base pair in a DNA molecule
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4 types of point mutation
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silent mutation, replacement mutation, nonsense mutation, frameshift mutation
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replacement mutation
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change in nucleotide that changes amino acid specified by codon
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consequences of replacement mutation
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change in primary structure can be beneficial, neutral, or deleterious
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silent mutation
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change in nucleotide that does not change amino acid specified by codon
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consequences of silent mutation
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change in genotype but no change in phenotype
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nonsense mutation
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change in nucleotide that results in early stop codon
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consequences of nonsense mutation
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premature termination, usually deleterious
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frameshift mutation
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addition or deletion of a nucleotide
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consequences of frameshift mutation
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reading frame is shifted, usually deleterious
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3 categories of mutation
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beneficial, neutral, deleterious
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aneuploidy
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addition or deletion of a chromosome
down syndrome |
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4 types of chromosome mutation
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aneuploidy, polyploidy, inversions and translocation
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inversion
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cause chunks of chromosomes to break and rejoin in the inverted orientation
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translocation
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cause chunks of chromosomes to break and join anther chromosome
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polyploidy
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having more than 2 homologs for all the chromosomes
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karyotype
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complete set of chromosomes in a cell
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template strand
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strand of DNA that is transcribed by RNA polymerase to create RNA
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non-template/coding strand
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its sequence matches the sequence of the RNA that is transcribed form the template strands and codes for a polypeptide
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3 parts of a gene
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promoter, transcribed region, terminator
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RNA polymerase I
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genes that code for most of the large RNA molecules found in ribosomes
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RNA polymerase II
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protein coding genes
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RNA polymerase III
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genes that code for tRNA for one of the small rRNAs found in ribosomes and for noncoding RNA
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sigma
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detachable protein subunit that must bind to the polymerase before transcription can begin
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holoenzyme
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multipart enzyme consisting of a core enzyme along with other required sites
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core enzyme
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enzyme responsible for catalysis in a multi part holoenzyme
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promoter
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section of DNA where transcription begins
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2 regions in the promoter that are important in prokaryotes
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-10 region, -35 region
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downstream
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DNA that is located in the direction RNA polymerase moves during transcription
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upstream
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DNA located in the opposite direction that RNA polymerase moves during transcription
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TATA box
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short DNA sequence in many eukaryotic promoters about 30 base pairs upstream from the transcription start site
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when does transcription begin in bacteria
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when sigma binds to the -10 and -35 boxes
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basal transcription factors
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initiate eukaryotic transcription by binding to the appropriate promoter region in DNA
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elongation phase
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process of RNA lengthens during transcription
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termination phase
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when transcription ends when RNA polymerase reaches a transcription termination signal
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RNA hairpin
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causes the RNA strand to separate form the RNA polymerase, terminating transcription
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primary transcript
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in eukaryotes, a newly transcribed mRNA molecule that hasn't been processed
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exons
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regions of eukaryotic genes that are part of the final mRNA
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introns
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sections of genes that are not represented in the final mRNA product
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splicing
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process by which introns are removed from primary RNA transcripts and the remaining exons are connected together
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snRNA
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specialized RNA that catalyzes splicing
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snRNP
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function in splicing as components of spliceosomes
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spliceosome
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large complex assembly of snRNPs that catalyzes removal of introns form primary RNA transcripts
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5' cap
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protects the 5' end from damages and directs ribosomes toward the 5' end
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poly(A) tail
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added to the 3' end of mRNA, protects from damage
longer the tail, the longer the lifespan of the mRNA in the cytoplasm |
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RNA processing
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term for any of the modifications, such as splicing, needed to convert a primary transcript into a mature RNA
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____ is the site of protein synthesis in the cell
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ribosomes
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transcription and translation are connected in _____ but separate in ______
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bacteria, eukaryotes
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what has to be present for translation to occur
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ribosomes, mRNA, amino acids, ATP, GTP
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aminoacyl tRNA synthetases
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catalyze the addition of amino acids to tRNA
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aminoacyl tRNA
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combination of a tRNA molecule covalently linked to an amino acid
act as interpreters in the translation process |
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tRNA
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transfers amino acids form the RNA to the growing end of a new polypeptide in translation
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anticodon
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set of 3 ribonucleotides that forms base pairs with the mRNA codon
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structure of tRNA
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shaped like an upside-down L that vary at the anticodon and attached amino acids
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how many tRNA are there
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40
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wobble hypothesis
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nonstandard base pairing is acceptable in the 3rd position for tRNA
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2 major substructures of ribosomes
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large subunits, small subunits
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small subunit
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holds the mRNA in place during translation
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large subunit
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where peptide-bond formation takes place
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3 sites of tRNA binding
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A-site, P-site, E-site
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A-site
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holds an aminoacyl tRNA and carries an amino acid
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P-site
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holds the growing polypeptide chain
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E-site
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holds a tRNA that will leave the ribosome
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1st step in protein synthesis in the ribsome
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aminoacyl tRNA diffuses into the A site, the anticodon binds to a codon in mRNA
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2nd step in protein synthesis in the ribosome
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peptide bond forms between amino acid in the A site and the growing polypeptide in the P site
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3rd step in protein synthesis in the ribosome
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the ribosome moves ahead and all 3 tRNAs move one position down in the line
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protein synthesis starts at the ____ end of a polypeptide and proceeds to the ____ end
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amino, carboxyl
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3 phases of protein synthesis
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initiation, elongation, termination
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ribosome binding site
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in a bacterial mRNA molecule the sequence just upstream of the start codon to which a ribosome binds to initiate translation
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initiation factors
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class of proteins that assist ribosomes in binding to a mRNA molecule to being translation
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translation initiation
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mRNA binds to a small ribosomal subunit, the initiator aminoacyl tRNA bearing f-met binds to the start codon, the large ribosomal subunit binds
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protein synthesis is catalyze by _____
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RNA
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translocation
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process by which a ribosome moves down a mRNA molecule during translation
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elongation factor
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move the mRNA so that it ratchets through the ribosome in the 5' --> 3' direction
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steps of elongation
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arrival of aminoacyl tRNA, peptide bond formation, translocation
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release factor
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protein that can trigger termination of translation when a ribosome reaches a stop codon
fills the A site |
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steps of terminating translation
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release factor binds to stop codon, polypeptide is released, ribosome subunits seperate
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post-translational modification
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series of steps that occur after termination to make the protein fully functional
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molecular chaperones
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proteins that speed up protein folding
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gene expression
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activating a gene to achieve the final purpose of that gene
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protein --> activated protein
the arrow represents |
post-translational modifications like folding, adding carb or lipid groups, phosphorylation
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transcriptional control
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cell would avoid making the mRNA for a particular
enzyme saves the most energy |
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post-translational control
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regulation of gene expression by modifications of proteins after translation
rapid response |
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inducer
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substrate in a reaction that stimulates the expression of a specific gene
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2 ways transcription can be regulated
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negative control, positive control
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negative control
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regulatory protein binds to DNA and shuts down transcription
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positive control
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regulatory protein binds to DNA and triggers transcription
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repressor
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any regulatory protein the inhibits transcription
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operon
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set of coordinately regulated bacterial genes that are transcribed together into one mRNA
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operator
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binding site for the repressor protein
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allosteric regulation
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regulation that causes the protein to change shape
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catabolite repression
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positive transcriptional control in which the end product of a catabolic pathway inhibits further transcription of the gene encoding an enzyme early in the pathway
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CAP
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protein that can bind to the cap binding site and faciliate binding of RNA polymerase and stimulating gene expression
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CAP binding sight
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DNA sequence upstream of certain prokaryotic operons to which catabolite activator proteins can bind, increasing gene transcription
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cAMP
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molecule derived from ATP that is widely used by cells in signal transduction and transcriptional control
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adenylyl cyclase
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enzyme that can catalyze the formation of cAMP from ATP
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differential gene expression
|
responsible for creating different cell types, arranging them into tissues, and coordinating their activity to form the multicelluar organism
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6 levels of gene expression in eukaryotes
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chromatin remodeling, transcription level, mRNA processing level, mRNA stability level, translation level, post-translational modification level
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chromtin remodeling
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process by which the DNA in chromatin is unwound form its associated proteins to allow transcription or replication
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mRNA processing
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changes the primary RNA transcript undergoes in the nucleus to become a mature mRNA molecule
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histones
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positively charged protein associated with DNA in the chromatin of eukatyotic cells
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nucleosomes
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repeating, beadlike unit of eukaryotic chromatin consisting of about 200 nucleotides of DNA wrapped twice around 8 histone proteins
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acetylation
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addition of an acetyl group to a molecule
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methylation
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the addition of a methyl group to a molecule
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histone acetyl transferases (HATs)
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in eukaryotes, one of a class of enzymes that loosen chromatin structure by adding acetyl groups to histone proteins
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histone deacetylase (HDAC)
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in eukaryotes, one of a class of enzymes that recondense chromatin by removing an acetyl group from histone proteins
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histone code
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hypothesis that specific combinations of chemical modifications of histone proteins contain info that influences gene ecpression
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epigenetic inheritance
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pattern of inheritance involving differences in phenotype that are not due to changes in the nucleotide sequences of genes
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TATA box
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short DNA sequence in many eukaryotic promoters about 30 base pairs upstream from the transcription start site
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TATA binding protein (TBP)
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a protein that binds to the TATA box in eukaryotic promoters and is a component of the basal transcription complex
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regulatory sequences
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any segment of DNA that is involved in controlling transpiration of a specific gene by binding certain proteins
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promoter-proximal elements
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in eukaryotes, regulatory sequences in DNA that are close to a promoter and that can bind regulatory transcription factors
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enahncer
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regulatory sequence in eukaryotic DNA that may be located far from the gene it controls or within introns of the gene
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silencer
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regulatory sequence in eukartyotic DNA to which repressor proteins can bind, inhibiting transcription of certain genes
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regulatory transcription factors
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proteins that bind to enhancers, silencers, or promoter-proximal elements
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basal transcription factors
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interact with the promoter and are not restricted to particular cell types
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mediator complex
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regulatory proteins that form a physical link between regulatory transpiration factors that are bound to DNA and the basal transcription complex
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basal transcription complex
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multi protein complex that assembles near the promoter of eukaryotic genes and initiates transcription
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spliceosome
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in eukaryotes, complex assembly of snRNPs that catalyzes removal of introns from primary RNA transcripts
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alternative splicing
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in eukaryotes, the splicing of primary RNA transcripts from a single gene in different ways to produce different mature mRNAs ans thus different polypeptides
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RNA interference
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degradation of an mRNA molecule or inhibition of its translation following its binding by a short RNA whose sequence is complementary to a portion of the mRNA
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microRNA
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single stranded RNA associated with proteins in an RNA induced silencing complex
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proteasome
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multi-molecular machine that destroys proteins that have been bound to ubiquitin
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