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101 Cards in this Set

  • Front
  • Back
Nucleic Acids
macromolecules which dictate the amino acid sequence of proteins, which in turn control basic life processes
-Store genetic information in the form of a code
-oassed on from parent to offspring
Structure of nucleic acid
-Long chain of nucleotides
-A nucleotide has threeo parts: A suger, a phosphate group, and a nitrogen base
-If the sugar is ribose the nucleic acid is RNA if the sugar is deoxyribose the nucleic acid is DNA
-four different nitrogen bases occur: adenine, cytocine, guanine, and thymine
the double-helix nature of DNA
-hydrogen bonds hold DNA together
-bonding occurs only between adenine and thymine, and guanine and cytosine
-DNA is compoased ot 2 complementary strands of nucleic acids
-hydrogen bonds between complementary bases cause the twisting of the 2 chains
-the result is a spiral, or double-helix
DIfference between RNA and DNA
-thymine is not present, but a similar compound called uracil is instead
-occurs as a single strand, not a double helix
-may contain bending, folding, and hydrogen bonding within a strand
basic information on dna
controls protein synthesis, thereby controlling all cell structure and function
-DNA dictates protein function by directiong the primary structure of every protein in an organism
-DNA usually works through RNA, which directly carries out protein synthesis
Basic information on RNA
-recall that ribosomes are the site of protein synthesis in cells; ribosomes are made of 2 subunits of RNA
-messenger RNA is the specific type of RNA involved in the synthesis of amino acids
-mRNA is liek a photocopy of DNA which can travel throughout the cell
]-copying of DNA into mRNA must be exact or the wrong proteins will be synthesized
-the process utilized are transcription (making RNA) and translation (making proteins)
The genetic code
-althought strands of DNA may be very long, the essentially consist of only 4 different sununits
-A, C, G, T occur in various combinations of tiplets
-a tripled is what actually codes for amino acids
-they are triplets which code for the starting and stopping of protein synthesis, rahter than for the addition of a specific amino acid
RNA polymerase
enzymes that bond polymers of RNA
Three types of RNA
Messender RNA
Transfer RNA
ribosomal RNA
directs the formation ofthe amino acid sequence
binds to the amino acids and carries them to their places in polypeptide chains
forms ribosomes, the site of protein syntehesis
RNA synthesis
-only one strand of DNA (coding strand) is copied into RNA
-during transcription the RNA produced is complementary to the strand of DNA which creates it
-Uracil is substituted for thymine in the copying process
Three steps of translation/transcription
1. Initiation
2. Elongation
3. Termination
Stage one of transcription
-an enzyme called RNA polymerase is needed to get things started
-the enzyme binds to the promoter region of the DNA
-the promoter region is right in fromt of the section of DNA to be copied
Step 2 of transcription
-the enzyme leaves the romoter region of the DNA and moves along the sequence to be copied
-as teh enzyme reads the DNA, a complementary strand of DNA is synthesized
-the RNA strand is elongated as teh enzyme moves down the DNA sequence
Step 3 of transciption
-when the enzyme reaches the terminator region transcription stops
-this is the region right after teh sequence is being copied
-the newly synthesized RNA, called the primary RNA transcript, is released with the enzyme from the DNA
-transcription is complete, and processiong will begin
-a different type of RNA polymerase is used for eacy type of RNA in eukaryotes, but the process is the same
Steps of RNA processing
RNA molecules undergo extensice processiong prior to exiting the nucleus
-processing includes adding, modyfying, and deleting segments from the promary RNA ranscript

First a cap (guanine "mg")and tail (adenine "poly-a") are addded to the RNA to protect it from sunstances that may destroy t in the cyocol
-second, splicing occurs so that only the functional pairs of RNA enter the cytoplasm
-this completes the processing of mNA, which will enter the cytoplasm and begin working
noncoding regions of the DNA; these are removed from te RNA
functional units of DNA; these are linked directly together through splicing
Formation of tRNA
-the primary tRNA transcript spliced, modifyed, and folded into a clover shape
-amino acids atack to one end, while the opposite end contains the anticodon
-the anticodon is a triplet which complements teh codon on mRNA
-on a ribosome base pairing occurs between the codon of mRNA and he anticodon of tRNA so that correct correspondence occurs
formation of rRNA
-the primary rRna transcript is spliced and modified to form the subunits of ribosomes
-these are released through the nuclear envelops into the cytoplasm
-after further modification 2 subunits combinme to form a ribosome
-ribosomes recognize mRNA and tRNA and allow protein synthesis to occur
Where are all 3 types of RNA made?
nucleus (move to chloroplast
When aare proteins synthesized?
tRNA charging
-protein ynthesis is refered to as translation because the codon (triplet) sequence of mRNA is ranslated into the amino acid sequenc e of the protein
-tRNA must move appropriate amino acids from teh cytosol to the ribosomes
-Each rRNA molecule binds to a specific amino acid and movies i into place on the ribosome as needed
The 3 step binding process is called tRNA charging:
1. an enzyme binds to an amino acid and a molecule
2. of ATP, which loses 2 phosphate groups before binding to the amino acid
3. the tRNA displaces the ATP and is bound to the amino acid
Protein synthesis
-ribosomes contain 2 binding sites
-the "Psite" holds the tRNA holding thr growing polypeptiede chain
-the "a site" holds the tRNA beinging the next amino acid to beadded to the chain
-the ribosome moves down the mRNA strand one codon at a time
-initiation, elongation, and termination are involved just as in transcription
Initiation of translation
The cap of the mRNA threads the mRNA through the ribosome and the start codon (always AUG) signals the beginning of the sequence of codons
Elongation of translation
The codon of mRNA and the anticodon of the tRNA pair up, and an enzyme catalyzes the peptide binding of the newly arriving amin acid to the growing chain
Termination of translation
Elongation continues until a stop codon is read (Uaa, UAG, or UA) the completed polypeptide chain is released
Translation errors
erors can occur in the copying process, but most are caught and corrected
-the most commen error is shifting of the reading frame by one or 2 nucleotide, which alters the entire codon sequence
Transport and modification of proteins
-membrance and organelle proteins are generally synthesized by ribosomes on RER, which can then send the product to the Golgo Apparatus for packaging and shippin to the appropriate location
-the first few amino acids provide a signal sequence which provides directions for transport of the new protein
Are codons on mRNA or tRNA?
Are anticodons on mRNA or tRNA?
where are teh a and p site located?
ribosomes (hold mRNA in place)
each amino acid can have more than 1 codon
What links an amino acid to a chain?
What are the base pairs
Adenine and thymine (uracil)
Guanine and Cytosine
synthesis phase
-complex chains of events similar to transcription
-enzymatically controlled by DNA polymerase
1. unwinding
2. break hydroen bonds
3. add nucleotides
Resulting helices
-contain one original strand and one copy
-identical to eachother
-complete set of chromosomes
Replication forks
-replication does not go from end to end
-occurs simultaneously on many segments
-each such segment is a replication fork
correctiong replication errors
-a typical animal call has 3 billion nucleotide pairs, or 6 billion nucleotide
-abou 1/1000 nucleotides contain an arror immediately after replication
-self-correction occurs so that the final DNA conrains an error in only 1/billion nucleotides (high accurate)
-system of enzynmes acs to detect errors, remove faulty segment, and synthesize replacements
Whats the prime of a phosphate end of RNA
5 prime (5')
Whats the prime of the sugar end of RNA
3 prime (3')
how many nucleotides equal 1 amino acid?
Nondividing stages (G1, S, G2)
Grwoth or gap1 phase
-Cell growth jsut after it has been formed
-highly metobolically active
-cell grows upt o double in size
-Enzyme and organelle numbes double
-Duration depends on cell type
-Non-dividing cells remain in G1 forever; this is referred to as G0
S phase
-DNA replication
-takes roughly 3-6 hours
G2 phase
Growth 2 phase
-follows DNA replication
-preparation for mitosis
-rapid growth and synthesis of necessary structures
-takes roughly 2-5 hours
Steps of mitosis

Early Prophase
-centriole pairs move toward opposite poles
-doble chromosomes visible as long threads
-fibers extend outward from cenrioles and form star shaped structures called asters
Middle Prophse
-spindle fibers form and extend between poles
-sister chromatids are connected at the centromere
Late prophase
-doble chromosomes begin moving toward equator
-nuclear membrane and nucleolus disappear
-centromeres are lined up at the equator (middle of the cell)
-centromeres divide and the 2 chromotids seperate into du[licate chromosomes
Early Anaphase
duplicate chromosomes begin to move apart
Late anaphase
duplicate chromosomes move to opposite poles
-spindles and asters disappear
-nuclear membrane forms around daughter nuclei
-new nucleoli appear and furrow forms
The division of the cytoplasm which often begins during late anaphase and finishes during telophase. The word literally means cell movement. This is the movement of the 2 halves of the cell into 2 distinct cells
Difference between animal an dplant cytokinesis
-Only animal cells contain centrioles and asters
-Plant cells form a rigid cell plate (made of cellulose-->an extension of the cell wall) between the 2 daughter cells prior to pulling apart
-Animal cell cytokinesis generally occurs earlier in the process than plant cell cytokinesis
Timing of the cell cycle
-time span varies among organisms and tissues
-interphase is generally long compared to mitosis
-average humal cell culture: 1hr mitosis/cytokinesis --> 16-20 hr interphase
-some cells divide ver rapidly
-some cells never divide once formed
-uncontrollable cell division is aclled cancer
What initiates cell division?
-increase in cell size
-cells needed for growth and repair
-regular part of life cycle
-feedback loops in body signal
What are the chromosomes like in mitosis
Double standed durin prophase and metaphase
-single stranded during anaphase and telophase
Types of reproduction
Asexual and sexual
Asexual reproduction
-involves only one parent
-no special reproductive cells involved
-offspring genetically identical to parent
Sexual reproduction
-usually involves two parents
-involves special reproductive cells
-some variety in ofspring
Asexual reproduction and cell division
-Changes in the nucleus
>DNa in the form of chromatin uncoils from arounf proteins called histones
>chromatin shortens and thickens to take the form of chromosomes
-Processes USed
>Mitosis: nucleus divides in half
>Cytokinesis: cytoplasm divides in half
Number of chromosomes per cell
Haploid= single set
Diploid-doublt set
-homlogous pairs
-similar in structure and function
-Reproductive cells
-Sperm and Egg
-Haploids which come together to form a diploid zygote at fertilization
-special tyle of cell division
-produces haploid cells in diploid organisms
2 different ways of cell division
Pinching in the celter (animals
Building a cell wall (plants)
what is dupluicated in the G0 phase?
How many chromosomes are in 1 full set? (1n)
Sexual Reproduction
-2 different parent cells come together to produce genetically different offspring
-Enormous genetic diversity due to vast possible combinations
-The parent cells involved are specialied sex cells called gametes, which are formed by the reduction division called meiosis
-There is usually a male gamete and a female gamete
-When gametes fuse together fertilization occurs and a zygote forms
-The zygots is the original cell of a new organism
What is reduced in Meiosis?
Somatic Cells and Gametes
Somatic cells
-Body cells other than those specialized for reproduction
-have 46 chromosomes
-occur in 23 homologous pairs
-diploid (2n)
-specialized reproduction cells
-have 23 chromosomes
-no pairs
-haploid (1n)
Replication division (stages of meiosis)
-cells divide twice but replicate only once
-begins with one 2n cell and end with 4 1n cells
-replication is prior to the first meiotic division
-the second meiotic division is similar to mitosis
Advantages of Sexual reproduction
Variation (biggest advantage)
-does not ocur in asexual reproduction
-allows members of a species to adapt fo various environments
-members without traits necesary for survival will die out and the "betteR" genes will be passed on
-helps to ensure species survival
(variation of sexual reproduction)
-common in protists
-beidge of cytoplasm forms between two cells different mating types
-transfer of nuclear material takes place
-permits recombination of hereditary material, thus new variations of organisms
-increases chance of species survival
-sexes are not seperate --> one member has both sets of organs
-Rather than self-fertilization, partners exchange sperm then fertilize own eggs
-transfer of nuclear material takes place
-permits recombination of hereditary material, thus new variations of organisms
-increases chance of species survival
Reproductive systems in animals
-specialized sex organs where gametes develop
-the ovaries are the female gonads
>produce female gametes
>egg cells or ova
-the testes are he male gonads
>produces male gamets
>sperm cells
Difference between mitosis and meiosis
Chromosomes form tetrads during metaphase I of meiosis
-end of meiosis there are daughter chromatids (23 and 23)
-end of mitosis has single stranded chromosomes
Size of male cells
Equal sized cells
Size of female cells
Cells are not equal, there is one largetr cell
When does crossing over occur?
Meiosis I
What divides in mitosis and cytokinesis?
Mitosis-the nucleus divides

Cytokinesis- the cytoplasm divides
Prophase I
-each chromosomes has replicated, producing 2 chromatids
-pairs of chromatids line up as homologous pairs anre become fastenec at their centromeres
-Each group of 4 chromotids is a Tetrad
-strands of a tetrad may twist and exchange material; this is called crossing-over
-nuclear membrane disappears and spindle fibers form
Metaphase I
-centromeres of tetrads line up at the equator
-tetrads are fastened to spindle microtubules at centromeres
Anaphase I
Homologous chromosomes of each tetrad seperate and move toward opposite ends of the cell in a process called disjunction
-chromosomes are each pole are 1n but double stranded
Telophase I
-cytoplasm divides leaving 2 daughter cells
-daughter cells are 1n, having half the number of chromosomes as the parents
-daughter cell chromosomes are in the double-stranded replication form
Prophase II
-Daugher cells form spindles
-double-stranded chromosomes move towards middle of spindle
Metaphase II
-Centromeres fasten to spindle microtubules
-centromeres line up at equator
Anaphase I
Homologous chromosomes of each tetrad seperate and move toward opposite ends of the cell in a process called disjunction
-chromosomes are each pole are 1n but double stranded
Anaphase II
-centromeres divide and chromatids seperate
-singe-stranded chromosomes are produced
-chromosomes move towards opposite ends of spindle
Telophase I
-cytoplasm divides leaving 2 daughter cells
-daughter cells are 1n, having half the number of chromosomes as the parents
-daughter cell chromosomes are in the double-stranded replication form
Prophase II
-Daugher cells form spindles
-double-stranded chromosomes move towards middle of spindle
Metaphase II
-Centromeres fasten to spindle microtubules
-centromeres line up at equator
Anaphase II
-centromeres divide and chromatids seperate
-singe-stranded chromosomes are produced
-chromosomes move towards opposite ends of spindle
Telophase II
-daughter cells divide resulting in a 4-1n cells
-Chromosomes return to interphase state
-nuclear membrane reforms