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116 Cards in this Set
- Front
- Back
- 3rd side (hint)
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When did Watson and Crick propose double helix model for DNA? |
1953 ROSALIND FRANKLIN |
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What took place in Griffith’s experiment in 1928? |
Involves two strains of bacteria (pathogenic/harmless) Transformation: change due to the introduction of foreign DNA |
Ppl still thought protein was genetic material - a lot of heterogeneity and specificity of function. |
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What was involved in Hershey and Chase’s experiment? |
Studied viruses that infect bacteria known as bacteriophage |
A virus is DNA enclosed by a protective coat, often simply protein |
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In Hershey and Chase’s experiment, what did it show? |
DNA is the genetic material of a phage They concluded that the injected DNA of the phage provides the genetic info |
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What is a polymer of a nucleotide? |
DNA |
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What does DNA consist of? |
Nitrogenous base Sugar Phosphate group |
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What did Erwin Chargaff report in 1950? |
DNA composition varies from one species to the next |
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What are the two findings known as Chargaff’s Rules? |
- The base composition of DNA varies between species - IN any species the number of A and T bases is equal and the number of G and C bases are equal |
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Who used X-ray crystallography to study molecular structure? |
Rosalind Franklin and Maurice Wilkins |
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What did Watson use x-ray images to deduce? |
Helical structure Width of the helix Spacing of the nitrogenous bases |
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What did the pattern suggest? |
DNA molecule was made up of two strands, forming a double helix (Purine + Pyrimidine) |
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What did Franklin conclude about the structure of DNA? |
There were two outer sugar-phosphate backbones, with the nitrogenous ASR’s paired in the molecule’s interior |
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What did Watson’s model look like? |
Backbones were antiparallel |
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What are the purine pairs and what are the pyrimidine pairs? |
Purines are A or G Pyrimidines are C or T |
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The amount of A=T The amount of C=G |
!! |
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Is the double helix left handed or right handed? |
Right handed helix |
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Antiparallel (blank) (blank) backbone |
Sugar phosphate |
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What did Watson and crick determine about replication based on structure o the helix |
Specific base pairing suggested a possible copying mechanism |
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What does each strand act as? |
A template for a new strand in replication |
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What happens to the strands in DNA replication? |
The parent molecule unwinds, and two new daughter strands are built based on base pairing rules |
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What is Watson and Crick’s semiconservative model of replication? |
When a double helix replicated, each daughter molecule will have one old strand conserved the parent molecule and one newly made strand |
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What is Watson and Crick’s semiconservative model of replication? |
When a double helix replicated, each daughter molecule will have one old strand conserved the parent molecule and one newly made strand |
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What is the conservative model? |
The two parent strands rejoin |
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What is Watson and Crick’s semiconservative model of replication? |
When a double helix replicated, each daughter molecule will have one old strand conserved the parent molecule and one newly made strand |
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What is the conservative model? |
The two parent strands rejoin |
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What is the dispersive model? |
Each strand is a mix of old and new |
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Who’s experiments supported the semiconservative model? |
Mathew meselson and Franklin Stahl |
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Where does replication begin? |
Ori (origins of replication) Where the two DNA strands are separated opening up a replication (bubble) |
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How many oris do eukaryotic organisms have? |
Hundreds or thousands |
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Which direction does replication proceed? |
Both directions from each origin until the entire molecule is copied |
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What is the replication fork? |
It’s at the end of each replication bubble. Y shaped region where new DNA strands are elongating Paired one on either side of replication bubble |
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What is helicase? |
Enzyme that untwist the double helix at the replication forks |
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What are single-strand binding proteins ? |
Bind to and stabilize single-stranded DNA |
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What are single-strand binding proteins ? |
Bind to and stabilize single-stranded DNA |
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What is topoisomerase? |
Relieves the strain of twisting of the ovule helix by breaking, swivelling, and rejoining DNA strands |
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What is DNA polymerase and what does it do? |
Enzyme that catalyze synthesis of new DNA at replication fork Requires a primer so they can add nucleotides and a DNA template strand |
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What is the initial nucleotide strand? |
A short rna primer |
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What is the rna primer synthesized by? |
Primase! |
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How does primase start an rna chain? |
Adds rna nucleotides one at a time Uses parental DNA as a template |
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What is the size of the primer?and what is it’s purpose? |
Short (5-10 nucleotides) and the 3’ end of primer serves as the starting point for the new DNA strand |
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What is a dNTP? |
Nucleosidetriphosphate Each nucleotide that is added to a growing DNA strand |
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What does dNTP do? |
Supplies adenine to DNA and is similar to the atp of energy metabolism |
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How does each monomer join the DNA strand? |
Dehydration reaction Two phosphate groups are lost as a molecule of pyrophosphate |
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DNA polymerase add what to where? |
Add nucleotides only to the free 3’ end of a growing strand |
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DNA polymerase add what to where? |
Add nucleotides only to the free 3’ end of a growing strand |
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Which direction can a new DNA strand elongate? |
Only in the 5’ - 3’ direction |
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When the replication bubble promotes replication in 2 directions, but nucleotides are only added in one direction, what happens? |
Leading and lagging strand synthesis |
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What does DNA polymerase do to the leading strand? |
The DNA polymerase synthesizes a leading strand continuously, moving towards the replication fork |
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What does leading strand synthesis require? (6 things) |
Rna primer, primase, DNA pol 3, template DNA, helicase, ssBPs |
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How does lagging strand synthesis work? |
DNA polymerase works in the direction away from the replication fork |
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What are Okazaki fragments? |
The lagging strand is synthesized as a series of segments. Joined together by DNA ligase |
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What are Okazaki fragments? |
The lagging strand is synthesized as a series of segments. Joined together by DNA ligase |
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What does DNA ligase do? |
Joins okazaki fragments |
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What is the function of helicase? |
Unwinds parental double helix at replication forks |
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What is the function of helicase? |
Unwinds parental double helix at replication forks |
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What is the purpose of single strand binding proteins |
Binds to and stabilizes single stranded DNA until it is used as a template |
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What is the function of helicase? |
Unwinds parental double helix at replication forks |
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What is the purpose of single strand binding proteins |
Binds to and stabilizes single stranded DNA until it is used as a template |
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What is the purpose of primase? |
Synthesized an rna primer at 5 end of the leading strand and at 5 end of each Okazaki fragment of lagging strand |
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What is the function of helicase? |
Unwinds parental double helix at replication forks |
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What is the purpose of single strand binding proteins |
Binds to and stabilizes single stranded DNA until it is used as a template |
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What is the purpose of primase? |
Synthesized an rna primer at 5 end of the leading strand and at 5 end of each Okazaki fragment of lagging strand |
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What is the purpose of DNA pol III? |
Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an rna primer or a pre existing DNA strand |
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What is the function of helicase? |
Unwinds parental double helix at replication forks |
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What is the purpose of single strand binding proteins |
Binds to and stabilizes single stranded DNA until it is used as a template |
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What is the purpose of primase? |
Synthesized an rna primer at 5 end of the leading strand and at 5 end of each Okazaki fragment of lagging strand |
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What is the purpose of DNA pol III? |
Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an rna primer or a pre existing DNA strand |
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What is the purpose of DNA Pol I? |
Removes rna nucleotides of primer from 5 end and replaces them with DNA nucleotides added to 3 end of adjacent fragment |
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What is the purpose of DNA ligase? |
Joins Okazaki fragments of lagging strand; on leading strand, joins 3’ end of DNA that replaces primer to rest of leading strand DNA |
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What do DNA polymerases do to new DNA? |
They proofread newly made DNA, replacing any incorrect nucleotides. |
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What do DNA polymerases do to new DNA? |
They proofread newly made DNA, replacing any incorrect nucleotides. |
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How can DNA be damaged? |
Exposure to harmful chemical or physical agents such as cigarette smoke, x-rays, or UV rays Spontaneous changes |
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What do DNA polymerases do to new DNA? |
They proofread newly made DNA, replacing any incorrect nucleotides. |
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How can DNA be damaged? |
Exposure to harmful chemical or physical agents such as cigarette smoke, x-rays, or UV rays Spontaneous changes |
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What is a mismatched repair? |
Repair enzymes correct errors in base pairing |
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What do DNA polymerases do to new DNA? |
They proofread newly made DNA, replacing any incorrect nucleotides. |
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How can DNA be damaged? |
Exposure to harmful chemical or physical agents such as cigarette smoke, x-rays, or UV rays Spontaneous changes |
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What is a mismatched repair? |
Repair enzymes correct errors in base pairing |
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What happens in nucleotide excision repair? |
A nuclease cuts out and replaces damaged stretches of DNA |
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What do DNA polymerases do to new DNA? |
They proofread newly made DNA, replacing any incorrect nucleotides. |
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How can DNA be damaged? |
Exposure to harmful chemical or physical agents such as cigarette smoke, x-rays, or UV rays Spontaneous changes |
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What is a mismatched repair? |
Repair enzymes correct errors in base pairing |
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What happens in nucleotide excision repair? |
A nuclease cuts out and replaces damaged stretches of DNA |
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What are mutations? |
The source of the genetic variation upon which natural selection operates Ultimately responsible for the appearance of new species |
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What do DNA polymerases do to new DNA? |
They proofread newly made DNA, replacing any incorrect nucleotides. |
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How can DNA be damaged? |
Exposure to harmful chemical or physical agents such as cigarette smoke, x-rays, or UV rays Spontaneous changes |
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What is a mismatched repair? |
Repair enzymes correct errors in base pairing |
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What happens in nucleotide excision repair? |
A nuclease cuts out and replaces damaged stretches of DNA |
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What are mutations? |
The source of the genetic variation upon which natural selection operates Ultimately responsible for the appearance of new species |
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What do the limitations of DNA polymerase cause? |
Problems for the linear DNA of eukaryotic chromosomes Not a problem for prokaryotes |
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What are telomeres? |
Eukaryotic chromosomal DNA molecules have special nucleotide sequences at their ends |
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What DONT telomeres do? |
They don’t prevent the shortening of DNA molecules |
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What DONT telomeres do? |
They don’t prevent the shortening of DNA molecules |
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What do telomeres do? |
Postpone the erosion of genes near the ends of DNA molecules. Repeats o sequences at times of chromosomes Similar to aglets |
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What DONT telomeres do? |
They don’t prevent the shortening of DNA molecules |
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What do telomeres do? |
Postpone the erosion of genes near the ends of DNA molecules. Repeats o sequences at times of chromosomes Similar to aglets |
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What is the shortening of telomeres linked to? |
Aging |
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What DONT telomeres do? |
They don’t prevent the shortening of DNA molecules |
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What do telomeres do? |
Postpone the erosion of genes near the ends of DNA molecules. Repeats o sequences at times of chromosomes Similar to aglets |
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What is the shortening of telomeres linked to? |
Aging |
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What happens if every chromosome of germ cells became shorter in every cell cycle? |
Essential genes would eventually be missing from the gametes they produce |
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What is telomerase? |
An enzyme that catalyzes the lengthening of telomeres in germ cells |
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What does the shortening of telomeres do? |
It might protect cells from cancerous growth by limiting the number of cell divisions |
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What is chromatin? |
DNA is combined with proteins in a complex known as chromatin |
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What is chromatin? |
DNA is combined with proteins in a complex known as chromatin |
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What do histones do? |
Help with first level of DNA packing Histone tails involved in gene expression regulation |
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What is chromatin? |
DNA is combined with proteins in a complex known as chromatin |
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What do histones do? |
Help with first level of DNA packing Histone tails involved in gene expression regulation |
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What are nucleosomes? |
DNA wrapped around histones Beads on a string 10 nm fiber |
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Where are chromosomes in interphase? |
Occupy specific restricted regions in the nucleus |
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Are homologous chromosomes next to each other? |
Nope |
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Are homologous chromosomes next to each other? |
Nope |
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What is euchromatin? |
Loosely packed chromatin More accessible for gene expression |
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Are homologous chromosomes next to each other? |
Nope |
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What is euchromatin? |
Loosely packed chromatin More accessible for gene expression |
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What is heterochromatin? |
Highly condensed chromatin Less accessible for gene expression |
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