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52 Cards in this Set

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In what fashion are the strands of DNA bonded?
H-bonded, Antiparallel--5' end of one chain w/ 3' end of other chain
What common protein structure depends on antiparallel H-bonding?
B-pleated sheet
How many bonds are GC/AT pairs are held together by?
GC 3 H-bonds
AT 2 H-bonds
What is hybridization?
Hybridization (aka annealing) is the binding of two complementary strands of DNA into a double-stranded structure
What is denaturation?
aka melting, the separation of DNA strands
If attached methyl groups to all the acidic phosphate oxygens along the length of DNA double helix, would the chain have higher/lower than normal Temp to denature DNA?
Higher than normal Temp because the lack of electrostatic repulsion b/t methyl ester backbones (that is present w/electrically repelling phosphate groups)
What sort of bonds stabilize the double helix?
hydrophobic interactions
When a purine is bound to a pyrimidine, what happens to the polar nature of the individual bases? Does this result in hydro-philic or -phobic interactions between the bases?
Polar nature disappears because charge dipoles are occupied in H-bonds, causing hydroPHOBIC interactions between the bases
The DNA helix pattern completes a full turn in how many angstroms?
1 complete turn every 34 angstroms (every 10 base pairs)
The bases of a DNA molecule are # angstroms apart from one another?
3.4 angstroms
What is the width of the DNA helix?
20 angstroms wide
1 Angstrom= ___ m
10^ -10
# Chromosomes in prokaryotes/eukaryotes?
Eukaryotes/humans: 46 chromosomes
Prokaryotes: 1 circular chromosome
Size comparison of bacterial/human genome
human genome: 10^ 9 bps
bacterial genome: 10^ 6 bps
What does DNA gyrase do?
It uses ATP to twist the circular chromosome in prokaryotes, so as to make it more compact--breaks the DNA and twists the 2 sides of circle around each other
-creates more twists in an already twisted DNA=super coils
For denser packaging of DNA, eukaryotes use...
histones (globular proteins) around which DNA is wrapped
-nucleosomes= bead-like groups of 8 histones around which DNA is wrapped
The area between nucleosomes is called...
linker DNA
What is fully packed DNA called? When does this condense into a chromosome?
chromatin,
Based on the chemical composition of the DNA, should histones be basic or acidic?
basic, b/c must be attracted to acidic exterior of DNA double helix
What is the flow equation for the structure of DNA in the nucleus?
DEOXYRIBOSE--> add base-->NUCLEOSIDE--> add 3 phosphates-->NUCLEOTIDE-->polymerize (add nucleosides together) with loss of 2 phosphates--> OLIGONUCLEOTIDE-->continues polymerization--> polynucleotide-->two complete chains H-bond in antiparallel orientation--> ds DNA CHAIN--> coiling occurs --> ds HELIX --> wrap around histones --> NUCLEOSOMES--> complete packaging --> CHROMATIN
# of "Letters" in DNA/ proteins?
4 letters in DNA, 20 letters in proteins
What did Oswald Avery discover?
Avery showed that DNA was the active agent in bacterial transformation, i.e., pure DNA from one type of E. Coli bacteria could transform E. Coli of another type--causing it to acquire the genetic nature of first type
Hershey and Chase
proved that DNA was the active chemical in the infection of E. Coli bacteria by bacteriophage T2
Process of protein synthesis from DNA
1) info contained in DNA is copied into a messenger
2) mRNA travels to cytoplasm where it encounters ribosome & other components of protein synthesis
3) ribosome synthesizes polypeptides according to DNA's original orders
What is a codon?
A codon is a 3 letter word, which encodes for a particular amino acid--4letters of DNS^3 (# letters in codon) = 64 possible codons, which specify the 20 aa's (more than one codon for many of the aa's)
How many codons specify amino acids?
61 codons specify amino acids; 3 codons are stop codons
What are stop codons?
aka nonsense codons, don't code for any amino acid
Wobble hypothesis
Switching the 3rd nucleotide in the majority of codons will have NO EFFECT
Why is the genetic code said to be degenerate?
Because it has SYNONYMS (two or more codons coding for the same amino acid)
What is intercalating?
When compounds that look like purines and pyrimidines (with large flat aromatic ring structures) cause mutations by inserting themselves between base pairs
3 Kinds of Mutations
1) Point mutations
2) Insertion mutations
3) Deletion mutations
What is a point mutation? What are their 2 classifications?
Single base pair substitutions.
1) TRANSITIONS- substitution of a pyrimidine for another pyrimidine or substitution of a purine for another purine)
2) TRANSVERSIONS: substitution of a purine for a pyrimidine or vice versa)
Point mutations that cause one amino acid to replace another amino acid?
missense mutations
Point mutations that cause a stop codon to replace a regular codon?
nonsense mutations
A missense mutation that causes little change in structure and function of the gene product is called...
a conservative mutation
3 Kinds of Mutations
1) Point mutations
2) Insertion mutations
3) Deletion mutations
What is a point mutation? What are their 2 classifications?
Single base pair substitutions.
1) TRANSITIONS- substitution of a pyrimidine for another pyrimidine or substitution of a purine for another purine)
2) TRANSVERSIONS: substitution of a purine for a pyrimidine or vice versa)
Point mutations that cause one amino acid to replace another amino acid?
missense mutations
Point mutations that cause a stop codon to replace a regular codon?
nonsense mutations
A missense mutation that causes little change in structure and function of the gene product is called...
a conservative mutation
Point mutations in genes that do not encode protein or alterations in the 3rd nucleotide of some codons=
silent mutations
Insertion and deletion cause:
A shift in the reading frame
Frameshift mutations
due to insertion or deletion, causes the whole piece of DNA to be read differently
-NOT caused by inserting or deleting a whole or multiple codons
Is DNA replication semiconservative, conservative, or dispersive? Who tested this?
Messelson and Stahl studied DNA replication to determine which it was.
ANSWER: Semiconservative
Not conservative: ds-DNA remains as is while the entirely new ds genome created
Not dispersive: both copies of genomes=composed of scattered pieces of new/old DNA
What is the function of DNA polymerase?
-catalyzes the elongation of the daughter strand using the parental template
-checks each new nucleotide to make sure it forms a correct base-pair before it is incorporated in the growing polymer
Polymerization occurs in which direction? What acts as the Nu- to displace pyrophosphate?
5' TO 3' !!!
The 3' hydroxyl group acts as the Nu-
What are two things that DNA Polymerase requires?
-a template
-a primer
The template is read...
3' to 5' because must end up antiparallel, and replicated strand is being constructed 5' to 3'
What is the primer and what is its purpose?
Primer- a small chain of RNA produced by RNA polymerase (primase)
-Purpose: begins DNA replication by creating a small RNA primer that DNA polymerase can elongate by adding deoxyribonuceotides to the existing ribonucleotide primer
Which enzyme unwinds the double helix and separates the DNA strands? Where does it begin?
Helicase. It begins @ Origin of Replication
What do topoisomerases do? How do the single-strand binding proteins help?
Topoisomerases cut one or both of the strands and unwrap the helix, releasing the excess tension created by helicase
-ss binding proteins help keep the strands separated
What are replication forks?
Areas where the parental double helix continues to unwind