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117 Cards in this Set
- Front
- Back
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Somatic Cells
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Grow, replace dead and worn out cells, and repair tissues.
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Germ Cells
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Cells that form gametes and undergo meiosis.
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What do the terms somatic and germ cells refer to?
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Mitosis and cytoplasmic division are the processes by which the body cells or somatic cells grow, replace dead and worn out cells, and repair tissues.
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What type of organisms are reproduced asexually by mitosis?
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Protistans, fungi, plants, and some animals reproduce asexually by mitotic cell division.
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What is prokaryotic fission?
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Bacterial mode of reproduction. Involves DNA replication, accumulation of new membrane (and usually wall material) at or near the cell midsection, then cytoplasmic division. Prokaryotic cells, the archaebacteria and eubacteria, reproduce by prokaryotic fission.
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How are clones produced?
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Through asexual reproduction
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Asexual Reproduction
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Any reproductive mode by which offspring arise from and inherit genes from just one parent.
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What are the products of mitosis and meiosis?
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Put DNA into daughter cells, somatic cells, and germ cells.
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What do the terms haploid and diploid refer to?
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Meiosis begins with diploid (2n=46) germ cells and produces haploid gametes (n=23). In 2n cells, there are two chromosomes of each type, called homologous chromosomes. Homologs chromosomes line up (even unequally matched sex chromosomes) during meiosis.
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Haploid
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Each gamete produced by meiosis has one of each pair of homologous chromosomes.
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Diploid
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Presence of two of each type of chromosome (i.e., pairs of homologs) in a cell nucleus at interphase.
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What type of proteins are associated with DNA?
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Histones and nucleosomes
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Histones
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Spools that wrap pieces of DNA twice around them, forming a nucleosome.
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Nucleosome
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A small stretch of eukaryotic DNA wound around histone proteins.
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What is a replicated chromosome and it’s duplicate called (while they are attached to each other during mitosis)?
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Sister chromatids
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Sister Chromatids
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Two identical DNA molecules (and associated proteins) attached at the centromere until they are separated from each other at mitosis or meiosis
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What occurs during mitosis?
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A diploid parent cell produces two daughter cells with 46 chromosomes. Each daughter cell must have two of each type of chromosome.
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What are the four stages of mitosis?
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Prophase, metaphase, anaphase, and telophase.
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Bipolar Mitotic spindle
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A structure made of microtubules that grows or shrinks as tubulin subunits are added or lost from their ends.
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Centrosome
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The site where microtubules originate.
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Dyneins and Kinesins
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Motor proteins
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Prophase
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Mitosis begins, the duplicated sister chromatids (threads) condense into chromosomes. Microtubules become assembled and they move the two centrioles to opposite poles of the cell. The centrioles are embedded in the centrosome. The nuclear envelope begins to break up.
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Metaphase
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In the middle of the cell. The chromosomes attach to the microtubules. The microtubules push-pull the chromosomes until they are aligned midway between the poles of the cell-using motor proteins. All duplicated chromosomes are pulled to a spindle pole.
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Anaphase
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The attachments between the sister chromatids are broken and the separate chromosomes are pulled to a spindle pole.
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Telophase
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Once the chromosomes arrive at their spindle pole, Telophase begins. The chromosomes return to threadlike form. Old nuclear envelope vesicles form new nuclear envelopes around the chromatin. Pulled until the cell splits into daughter cells, beginning interphase.
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Do all cells undergo mitosis?
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Yes
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What is cytokinesis?
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Cytoplasmic division
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What structures move chromosomes during mitosis?
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Microtubules
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Microtubules
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Cytoskeletal elements consist of tubulin subunits. Contributes to cell shape, growth, and motion
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When does DNA replication occur in the cell cycle?
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DNA replication is the process where a DNA molecule is duplicated before a cell divides during mitosis and cytokinesis.
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What are Alleles?
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One of two or more molecular forms of a gene that arise by mutation and specify slightly different versions of the same trait.
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What are Homologues?
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Two chromosomes of each type, 2n.
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How do mutations arise?
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Mutations are small-scale changes in the nucleotide sequence of genes in the DNA molecule. There may be some leeway here since more than one codon may specify the same amino acid. More often, however, gene mutations give rise to proteins with altered or lost function.
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When does crossing—over of chromosomes occur?
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Meiosis
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Meiosis produces:
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Gametes (germ) cells
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Mitosis produces:
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Somatic cells
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When does random alignment of chromosomes occur in meiosis?
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During metaphase I
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What are haploid resting cells of plants called?
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Haploid gamete-producing bodies
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What are the products of meiosis in males?
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Spermatogenesis
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What are the products of meiosis in females?
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Oogenesis
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Why did Mendel use the garden pea?
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This plant can fertilize itself
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Homozygous Dominant
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Individual has a par of dominant alleles (AA) for the trait being studied.
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Homozygous Recessive
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Individual has a pair of recessive alleles (aa).
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Heterozygous
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Individual has a pair of nonidentical alleles (Aa).
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What happened to the recessive allele in the F1 generation of Mendel’s experiments?
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White disappeared in the first generation offspring and showed up in the second generation.
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Why did Mendel use dihybrid crosses?
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To test dominant traits.
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Dihybrid Cross
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Crossing two traits
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What is pleiotropy?
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The expression of alleles at one location can have effects on two or more traits.
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Two examples of pleiotropy
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1. Sickle Cell Anemia 2. Marfan Syndrome: lanky skeleton, leaky heart valves and weakened blood vessels, deformed air sacs in lungs, pain, and lens displacement in the eyes.
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What does color variance in Siamese cats demonstrate?
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Fur on the extremities of Siamese cats will be darker because the enzyme for melanin production will operate at cooler temperatures but is sensitive to heat on the rest of the body.
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Why does continuous variation of traits in individuals occur?
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Interactions with other genes and environmental influences. Most traits are not qualitative but show continuous variation and are transmitted by quantitative inheritance.
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What is a testcross?
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Experimental cross to determine whether an individual of unknown genotype that shows dominance for a trait is either homozygous dominant or heterozygous.
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Genotype
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The sum of genes.
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Phenotype
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How the gene is expressed (what you observe).
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Sex Chromosomes
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Human X and Y chromosomes.
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Autosomes
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All other chromosomes that aren’t X or Y.
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Karyotypes
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A preparation of metaphase chromosomes based on their defining features. They are treated with colchicines to stop the cells at metaphase, stained, put on a slide, photographed, and arranged with their homologous partner.
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What is incomplete dominance?
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A dominant allele cannot completely mask the expression of another. Red and white snapdragons make pink snapdragons.
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Gene Linkage
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Genes on the same chromosome are physically linked together. They farther apart they are, the more likely they are to undergo crossing over.
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Crossing Over
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Homologous chromosomes exchange corresponding segments.
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Punnett Square
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A simple diagram that predicts the probable outcomes of a genetic cross.
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What happens if the SRY region is missing from the Y chromosome?
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Female organs (ovaries) form.
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SRY
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The master gene for male sex determination.
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Where does a daughter expressing an X-linked trait get the gene for the trait?
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Her father
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What are some autosomal dominant disorders?
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Huntington disorder, Achondroplasia
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Huntington Disorder
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Progressive involuntary movements and deterioration of the nervous system.
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Achondroplasia
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Effects about 1 in 10,000 people, leads to still birth, midgets.
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What are some X-linked recessive disorders?
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Color blindness, Hemophilia A
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Hemophilia A
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Blood clotting, Queen Victoria and 10 of 69 descendants had it.
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Deletion
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The loss of some segment of a chromosome. Most deletions are lethal or cause serious disorders in mammals.
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Inversion
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A linear stretch of DNA within a chromosome becomes oriented in the reverse direction, with no molecular loss.
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Translocation
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A broken part of a chromosome becomes attached to a nonhomologous chromosome-most translocations are reciprocal (both chromosomes exchange broken parts).
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Duplication
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Gene sequences are repeated several to many hundreds or thousands of times.
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Aneuploidy/Aneuploids
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Individuals usually have one extra or one less chromosome. Causes reproductive failure.
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What is the most likely cause of aneuploidy?
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Occasionally, abnormal events occur before or during cell division, and gametes and new individuals end up with the wrong chromosome number.
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Example of Aneuploidy
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Down Syndrome
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What is Turner Syndrome?
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Inheriting one X-chromosome and no corresponding X or Y chromosome (1 in 2,500-10,000 newborn girls). 98% of XO zygotes abort in early pregnancy. Survivors are well proportioned to about 4tf 8in, infertile, no functional ovaries.
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How can one chromosome be distinguished from another?
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From where they are linked together.
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What is DNA Polymerase?
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Enzymes called DNA polymerases attach short stretches of free nucleotides to the unwound portions. The free nucleotides and abundant in the cell. The phosphate groups on the free nucleotides drives the strand assembly process.
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What makes up a DNA nucleotide?
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5-carbon sugar (deoxyribose), a phosphate group, four bases (adenine, guanine, cytosine, and thymine).
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What was the experiment that Hershey and Chase did?
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In one experiment, bacterial cells were injected with DNA from a virus particle with 35S. 35S remained in the virus and was not injected with the DNA. The other experiment, bacterial cells were injected with DNA from a virus particle with 32P. The 32P was injected with the DNA.
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DNA Replication
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Process by which a cell duplicates its DNA molecule before dividing.
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Transcription
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First stage of protein synthesis, in which a strand of RNA is assembled on a DNA template (gene). Occurs when Enzymes add nucleotides to a growing RNA strand one at a time in the 5’→3’ direction.
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Translation
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Second stage of protein synthesis. Information encoded in an mRNA transcript guides the synthesis of a new polypeptide chain from amino acids
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Initiation
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An initiator tRNA and an mRNA are loaded into a ribosome. Initiator tRNA binds with small ribosomal subunit. The START codon for the transcript, AUG, matches up with that tRNA’s anticodons-at the same time, the AUG binds with small subunit. A large ribosomal subunit binds with the small subunit.
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Elongation
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A polypeptide chain is assembled as the mRNA passes between the two ribosomal subunits. Part of the rRNA molecule at the center of the large ribosomal subunit functions as an enzyme-catalyzes the joining of individual amino acids. Peptide bonds form between the amino acids.
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Termination
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A STOP codon in the mRNA move into the platform. Proteins known as release factors bind to the ribosome
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Promoter
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A base sequence in RNA that signals the start of a gene.
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Semiconservative Replication
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Because the parent DNA strand is conserved during the replication process, half of every double-stranded DNA molecule is “old” and half is “new.”
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What are differences between DNA and RNA?
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Only a selected stretch of one DNA strand is used as the template. Enzyme RNA polymerase catalyzes nucleotide additions to a growing RNA strand. At the end of transcription, there is a single, free strand of RNA nucleotides, not a double helix.
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Where does RNA formation occur?
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RNA forms in the nucleus.
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Where does protein formation occur?
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Proteins form in ribosomes.
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What are finishing touches applied to mRNA transcript?
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A new mRNA transcript is unfinished in eukaryotic cells. This “pre-mRNA” must be modified before its protein-building instructions can be put to use. Enzymes attach a modified “cap” to the 5’ end. Enzymes attach a tail of about 100-300 adenine nucleotides- poly-A tail. Becomes wound up with proteins. The cap helps bind the mRNA to the ribosome
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Introns
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Base sequences that must be removed before translation. Introns stay in the nucleus. Introns could be evolutionary junk, the leftovers of past mutations that led nowhere. Some introns are sites where instructions for building one type of protein can be snipped apart and spliced together in various ways. Alternative splicing allows different cells in the body to make different versions of a pre-mRNA transcript.
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Exons
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The base sequences that are translated. Exported from the nucleus.
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Codons
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Base triplets. Ribosomes read nucleotide bases three at a time, as triplets.
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Genetic Code
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The basis of protein synthesis in all organisms.
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Base-Pair Substitution
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Occurs when one amino acid replaces another during protein synthesis.
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Sickle-Cell Anemia
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Due to a base-pair substitution-valine was substituted into the beta chains of hemoglobin instead of glutamate.
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What purpose does tRNA serve?
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Transfer RNA delivers amino acids one by one to a ribosome in the order specified by mRNA.
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Where are the anticodons located?
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In the cytoplasm. A nucleotide that can base-pair with a codon.
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What are the three steps to protein synthesis?
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Activate, inhibit, and stabilize enzymes.
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What are cancers?
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Abnormally growing and dividing cells of a malignant neoplasm.
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Where must a mutation occur in order for it to enter the evolutionary process?
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In the DNA molecule
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What type of proteins control gene expressions?
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Homeotic genes code for regulatory proteins that include a “homeodomain,” a sequence of about 60 amino acids. The sequence binds to control elements in promoters and enhancers. More than 100 homeotic genes have identified in divers eukaryotes. Many of the genes are interchangeable among species as evolutionarily distant as yeasts and humans.
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What happens when the lactose concentration is high?
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When lactose concentration is high, some will bind with the repressor which alters its shape so that it can’t bind with the operator. The RNS polymerase can then bind to the promoter and transcription of the three genes on the DNA strand occurs.
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What sugar do cells prefer to use as an energy source?
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Glucose
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Where would you find a Barr Body?
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The condensed chromosome appears a dense spot in an interphase nucleus.
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What percentage of a cell’s genes are being used at nay one time?
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5%-10%
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Differentiation of Cells
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All cells of your body started out with the same genes (the cells arose by mitosis from the same fertilized egg)-they transcribe may of the same genes. Nearly all of your body cells became specialized in composition, structure, and function. This is cell differentiation that occurs during development. Different lineages of cells use different genes to perform their specific functions.
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Mosaic effect
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Each female mammal bears patches of tissue where genes of the maternal X chromosome are being expressed-and patches where genes of the parental X chromosome are being expressed. She is a “mosaic” for the X chromosomes. If the alleles on the two homologous chromosomes were not identical, the tissues may have different features from one patch to another. Mary Lyon was the discoverer of this mosaic disuse effect of random X chromosome inactivation.
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Anhidrotic Ectodermal Dysplasia
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A condition where the skin is a mosaic of tissues with and without sweat glands. Where sweat glands are missing, the mutant allele is on the active X chromosome
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Gene Locus
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A gene’s chromosomal location.
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What is E. Coli?
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Escherichia coli is an enteric bacterium (gut dweller-intestines) in all mammals-survives on glucose, lactose, and other digested nutrients. When milk is ingested, the E. coli in your large intestine quickly transcribe three genes for the enzymes that are necessary for sugar digesting reactions, starting with lactose.
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What does ABO blood typing system demonstrate? How is blood type determined?
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Blood type is determined by markers produced by three genes-a multiple allele system. Ia and IB are each dominant to I, but are codominant to each other. Some people can have AB blood. ii is O blood type.
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What were the results of Mendel’s crosses?
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The F1 plants showed both of the dominant alleles. The F2 plants showed 9/16 tall and purple, 1/16 were dwarf and white, 3/16 were short and purple, and 3/16 were tall and white.
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Pedigree Chart
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A chart of the genetic connections among individuals. Square (male), circle (female), offspring are read left to right, shaded (trait studied), diamond (sex not specified)
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