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BIOA01 > chapter 12 > Flashcards

chapter 12 Flashcards

1
Q

What is replication?

A

Cells can make exact copies of their DNA

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2
Q

what’s the name given to errors that are caused during replication?

A

mutations

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3
Q

How does replication happen? Explain

A
  • two strands of parental DNA separate
  • each serves as the template for
    synthesis of a daughter strand
  • Replication occurs from 5’ to 3’
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4
Q

What are the different hypothetical models
for replication

A

semiconservative

conservative

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5
Q

what’s a semiconservative mode of replication?

A

New DNA duplex consists of one old
strand (parental) and one new strand
(daughter)

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6
Q

what’s a conservative mode of replication?

A

New DNA complex consists of two newly
synthesized daughter strands leaving the
parental duplex intact

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7
Q

who discovered that DNA replication is
semiconservative?

A

Matthew Meselson & Franklin Stahl

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8
Q

How did they discover the semi-conservative model of replication?

A

Nonradioactive “heavy” nitrogen isotope (15N) to tag
parental DNA strands

DNA molecules with different densities were separated
by a special type of centrifugation

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9
Q

what’s the Meselson & Stahl
Experiment

A
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10
Q

How are proteins involved in replication?

A
  • DNA polymerase - main molecule synthesizing DNA strands
  • Helicase - responsible for unwinding DNA
    *
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11
Q

The function of sliding DNA clamp

A

•Protein that encircles DNA and attaches to the rear of DNA polymerase (relative to
forward movement)
•Tethers DNA polymerase to the template strand and increases the rate of DNA
synthesis

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12
Q

DNA polymerase structure

A

thumb structure

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13
Q

where does replication starts?

A

origin of replication (ori)

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14
Q

function of topisomerase

A

prevents twisting as DNA unwinds

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15
Q

function of single stranded binding proteins SSBs

A

coat and stabilize single stranded DNA, preventing two strands from re-forming double stranded DNA

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16
Q

what’s okazaki fragments?

A

DNA polymerase copies the other strand in short lengths

synthesis of lagging strand occurs in small discontinous stretches

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17
Q

what is discontinuous replication?

A

The synthesis of a new strand of a replicating DNA molecule as a series of short fragments that are subsequently joined together.

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18
Q

what’s leading strand ?

A
  • In DNA replication, the new DNA strand synthesized in the direction of DNA unwinding
  • Synthesized on the leading strand template
  • One primer is required
    •Replication continues to the end.
    •The strand is replaced by DNA when the last fragment
    catches up to it.
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19
Q

what’s lagging strand?

A

•New DNA strand synthesized discontinuously, in the direction opposite DNA
unwinding
•Synthesized on the lagging strand template

  • Multiple RNA primers are required.
  • The final primer is added 100 nucleotides from the 3’ end of
    the template leaving the new daughter strand shortened by
    about 100 nucleotides.
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20
Q

DNA polymerase ass nucleotides only to an existing strand

T/F

A

T

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21
Q

How does a new strand beings and what enzyme is used?

A
  • new strand begins with a short chain of RNA primer synthesized by enzyme primase
  • Primase leaves the template, and DNA polymerase takes over, extending the RNA
    primer with DNA nucleotides as it synthesizes the new DNA chain
  • RNA primers are replaced with DNA later in replication
22
Q

How does DNA plymerase correct its own errors?

A
  • proofreading, detects the mispairing of improper hydrogen bonds
  • when the error is detected DNA polymerase activates cleavage function removes and replace
23
Q

what is origin of replication?

A
  • each point where DNA replication is initiated
  • The opening of the double helix at each
    origin of replication forms a replication
    bubble with a replication fork on each side.
24
Q

large linear chromosomes have one origin of replication

T/F

A

F many origins of replication

25
Q

examples of circular DNA

A

mitochondria, chloroplasts

26
Q

how do circular DNA replicate?

A
  • there is a single origin of replication
  • Replication proceeds in both directions
    until the replication forks meet and fuse
    on the opposite side, completing one
    round of replication.
27
Q

what is telomere?

A

End of a eukaryotic chromosome is capped by a repeating sequence called the telomere

28
Q

How many telomeres do humans have?

A

In humans, the telomere consists of the
sequence 5’-TTAGGG-3’ repeated
approximately 1500-3000 times.

29
Q

how many base pairs are lost by chromosomes after replication?

A

50–200 base pairs

30
Q

when does the cell die?

A

after 20-30 divisions

31
Q

what is telomerase?

A

enzyme that adds nucleotides to telomeres, especially in cancer cells.

32
Q

what is PCR?

A

Polymerase chain reaction - Cyclical process that makes
millions of copies of a section
of DNA

33
Q

what are the steps of PCR

A

Each cycle of amplification includes three steps

  1. Denaturation
  2. Annealing
  3. Extension
34
Q

what contains in the PCR mix?

A

Genomic DNA (contains target)
Primer A
Primer B
Buffer
dATP
dGTP
dCTP
dTTP
DNA polymerase

35
Q

Define denaturation in PCR

A

A solution containing double-stranded DNA (the template duplex) is heated to separate the DNA into two individual strands.

36
Q

Define annealing in PCR

A

When the solution is cooled, the two primers anneal to their complementary sequence on the strands of the template duplex.

37
Q

Define extension in PCR

A

DNA polymerase synthesizes new DNA strands (complementary to
the template duplex strands) by extending primers in a 5’ to 3’ direction.

38
Q

At what temperature is DNA polymerase optimal?

A

37 C

39
Q

whose DNA polymerase does not denature at high temperature?

A 
Thermus aquaticus (bacterium) – lives in hot springs at 
extremely hot temperatures
40
Q

what is PCR used for?

A
  • Author Ricki Lewis (Human Genetics), lists some very interesting applications:
  • A preserved quagga (a relative of the zebra) and a marsupial wolf, both extinct.
  • Poached moose meat in hamburger.
  • The brain of a 7,000-year-old human mummy.
  • The digestive tracts of carnivores, to reveal food web interactions.
  • Roadkill and carcasses washed ashore, to identify locally threatened species.
  • Products illegally made from endangered species.
  • Genetically modified bacteria released in field tests, to follow their dispersion.
  • One cell of an 8-celled human embryo to detect a disease-causing mutation.
  • Remains in Jesse James’s grave, to make a positive identification.
  • The intestines of genital crab lice on a rape victim, which matched the DNA of the suspect.
  • Fur from Snowball, a cat that linked a murder suspect to a crime.
41
Q

what is gel electrophoresis ?

A

In electrophoresis, DNA molecules separate by size. Larger molecules move more slowly because they take longer to work their
way through the pores in the gel.

42
Q

In addition to amplifying DNA, it can be useful to “cut” DNA at specific sites.

T/F

A

T

43
Q

what ahppens when you cut pieces of DNA?

A

allows pieces from the same or different organisms to be brought together in recombinant DNA technology.

44
Q

where are restriction enzymes sourced from?

A

bacteria

45
Q

what is restriction enzyme ?

A

A restriction enzyme is a protein isolated from bacteria that cleaves DNA sequences at sequence-specific sites, producing DNA fragments with a known sequence at each end

46
Q

what is southern blot?

A

a procedure for identifying specific sequences of DNA, in which fragments separated on a gel are transferred directly to a second medium on which detection by hybridization may be carried out.

47
Q

what goes in the sequencing PCR mix?

A

Genomic DNA (contains
target)
Primer A
Primer B
Buffer
dATP
dGTP
dCTP
dTTP
DNA polymerase
ddATP*
ddGTP*
ddCTP*
ddTTP*

48
Q

what is dna sequencing ?

A

DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA.

49
Q

what is recombinant DNA

A
  • Recombines DNA from two or more sources
    into a single molecule
  • The donor fragment may be a protein coding
    gene, a regulatory part of a gene, or any
    DNA segment of interest.
  • Vector carries the donor fragment (often a
    bacterial plasmid.
50
Q

what is transformation of DNA ?

A
  • The recombinant DNA is introduced into a bacterial cell by means of transformation, in which bacteria are chemically induced into a state in which they take up DNA from outside the cell.
  • As the bacterial cell replicates and divides, it also replicates the recombinant DNA.
51
Q

what is DNA editing

A

DNA is inserted, deleted, modified or replaced in the genome of a living organism.

BIOA01 (8 decks)

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