Chapter 11 - DNA replication Flashcards

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1
Q

what macromolecule did scientists in the early 1900s believe to carry genetic material

A

proteins because they had the most diversity (20 amino acids vs 4 nucleotides)

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2
Q

Four criteria necessary for genetic material

A
  1. information
  2. replication
  3. transmission
  4. variation
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3
Q

Describe Griffith’s experiment

A
  • Rough and heat-killed smooth is non-toxic
  • Smooth S. pneumoniae toxic because of its capsule
  • Rough with heat-killed smooth is toxic
    Conclusion: the genetic material had been transferred from the heat-killed S-type to the R-type
  • gave R the capsule-secreting trait that was passed on to their offspring
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4
Q

Avery, MacLeod, and McCarty

A
  • used DNase, DNase, and proteases
  • only DNase resulted in to transformation
  • concluded that DNA is the genetic material
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5
Q

genome

A

complete complement of genetic material in an organism

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6
Q

How are the two strands of DNA aligned?

A

antiparallel in a double helix

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7
Q

three components of DNA

A
  1. phosphate group
  2. pentose sugar
    - deoxyribose
  3. nitrogenous base (a,g,c,t)
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8
Q

three components of RNA

A
  1. phosphate group
  2. pentose sugar
    - ribose
    - OH at 2’
  3. nitrogenous base (a,g,c,u)
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9
Q

numbering of nucleotides

A
  • sugar carbons numbered 1’-5’
  • base attached to 1’
  • phosphate attached to 5’
  • exposed 3’ of one sugar attaches
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10
Q

backbone of DNA

A
  • made of phosphates and sugars
  • phosphodiester bonds
  • written: 5’-TACG-3’
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11
Q

how was the structure of DNA solved

A
  • Watson and Crick proposed the structure of the double helix using the ball and stick model
  • Relied on Rosalin Franklin’s X-ray diffraction findings suggesting a double helix with
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12
Q

Erwin Chargoff

A
  • analyzed base composition of DNA
  • found that the amount of adenine was always the same as thyme and cytosine the same as gaunine
  • supports idea of a uniform diameter
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13
Q

features of DNA structure

A
  • right-handed double helix
  • antiparallel, complementary strands
  • sugar-phosphate backbone
  • base pairing on the inside via H-bonding
  • consistent distance of about 2nm
  • one helical turn is about 10 nucleotides
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14
Q

major vs minor grooves

A
  • major grooves are larger and allow proteins to bind to help with gene expression
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15
Q

semiconservative model

A
  • DNA replication produces DNA molecules with 1 parent and 1 daughter strand
  • discovered by Meselson and Stahl using isotopes
  • not conservative or dispersive
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16
Q

Meselson and Stahl

A
  • used isotopes of nitrogen to discover the semiconservative model
17
Q

Origin of replication

A
  • sequence that signals the opening of the replication fork
  • allows the beginning of DNA replication
  • bacteria have one
  • eukaryotes have multiple
18
Q

DNA helicase

A

binds to DNA and travels 5’ to 3’ to separate the strands

19
Q

topoisomerase

A
  • removes knots caused by the helicase
20
Q

single strand binding proteins

A

hold parent strands open to be replicated

21
Q

DNA polymerase 3

A
  • covalently links nucleotides
  • requires primer because it needs something to build off of
  • builds 5’ to 3’
  • reads 3’ to 5’
22
Q

deoxynucleoside triphosphate (DNTP)

A
  • free nucleotides with three phosphate groups
  • two terminal phosphates are broken off for energy in to bind nucleotides together in DNA synthesis
23
Q

how does primer work?

A
  • primate adds and RNA primer must so polymerase can add nucleotides
  • DNA polymerase 1 removes the primer after replication and makes it DNA (for okazakis - can’t do this for leading)
24
Q

Leading vs. lagging strand

A

Leading:
- synthesized 5’-3’ as one long molecule
Lagging:
- synthesized 5’-3’ as Okazaki fragments
- fragments covalently bonded by ligase
both have RNA primer that is later replaced by DNA

25
Q

3 mechanisms for DNA replication accuracy

A
  1. H-bonding between A and T and between G and C is more stable than mismatched combinations
  2. DNA polymerase is unlikely to form bonds if the pairs are mismatched
  3. DNA polymerase can proofread to removed mismatched pairs
    • other DNA repair enzymes also exist
26
Q

DNA polymerases

A
  • there are many different types of DNA polymerases that perform different functions
  • bacteria and human cells have different types of polymerases with different specialized functions
27
Q

telomeres

A
  • series of nonsensical nucleotide sequences at the 3’ end of chromosomes
  • cannot be replicated because there is nowhere for upstream primer to be made
  • also called the 3’ overhang
  • makes sure that all important DNA can be replicated
  • progressively shorten
28
Q

how does telomerase work

A
  • makes telomeres
  • attaches many copies of DNA repeat sequence to the ends of chromosomes
29
Q

what is a chromosome

A
  • discrete unit of genetic material
  • composed of chromatin
  • about 1 meter in length
30
Q

three levels of DNA compaction

A
  1. DNA wrapping
  2. 30 nanometer fiber
  3. formation of loop domains
31
Q

DNA wrapping

A
  • DNA wraps around proteins called histones to form a nucleosome
  • shortens DNA 7x
32
Q

30nm fibers

A
  • asymmetric, 3D zig zag of nucleosomes
  • shortens length another 7x
33
Q

radial loop domains

A
  • interactions between 30nm fibers and nuclear matrix
  • each chromosome located in discrete territory
34
Q

Chromosomes during cell division

A
  • chromosomes compact more during cell division
  • Euchromatin - not as compact
  • heterochromatin - more compact
35
Q

how can the charge of histone affect the compactness of chromatin

A
  • DNA is negatively charged
  • Positive histones favor compactness/heterochromatin
  • negative histones will favor euchromatin