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Biology 1A03 > Chapter 14: DNA and the Gene > Flashcards

Chapter 14: DNA and the Gene Flashcards

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1
Q

What did Alfred Hershey and Martha Chase study?

A

how T2 virus infects E.coli and whether genes were made of protein or DNA…whether viral genes consisted of DNA or protein

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2
Q

Viral genes consist of:

A

DNA

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3
Q

Viral coats consist of:

A

protein

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4
Q

Phosphorus is found in:

A

DNA, but not protein

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5
Q

Sulfur is found in:

A

protein, but not phosphorus

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6
Q

What were the results from the Hershey-Chase experiment? (need more info)

A
  • all radioactive proteins were in the viral capsid

- all radioactive DNA was found inside the host cells

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7
Q

Who discovered that DNA was the hereditary material?

A

Alfred Hershey and Martha Chase

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8
Q

What experiment proved that DNA contained all the info for life?

A

the Hershey-Chase experiment

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9
Q

State why protein is not considered hereditary material.

A

ASK

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10
Q

Who were famous for their discovery for how DNA is synthesized?

A

Mathew Meselson and Franklin Stahl

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11
Q

What were the 3 potential mechanisms proposed by biologists for DNA synthesis?

A

1) Semi-conservative
2) Conservative
3) Dispersive

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12
Q

Semi-conservative

A

if parental strands of DNA are separated, each could be used as a template for the synthesis of new strands

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13
Q

Conservative

A

if bases turned outwards, complementary strands can serve as template for synthesis of an entirely new double at once

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14
Q

Dispersive

A

if parent helix was cut before being unwound, copied and put back together, then the old and new segments would alternate

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15
Q

The Meselson-Stahl experiment:

A

studied how E.coli DNA replicates

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16
Q

Berfore the Meselson-Stahl exp., what did they know?

A
  • bacteria is small and grows quickly

- the population doubles ~every 20-30 minutes

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17
Q

Step 1 of M-S experiment

A

bacteria was grown in Nitrogen 15 isotope only

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18
Q

G (not)

A

parental generation

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19
Q

G1

A

new daughter strand

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20
Q

G2

A

new second gen. daughter strand

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21
Q

Step 2 of M-S experiment

A

grew remainder of bacteria in Nitrogen 14 only and extracted the DNA after cells divide

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22
Q

Step 3 of M-S experiment

A

let remainder of bacterial culture grow and isolate the DNA (still in N14)

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23
Q

Who discovered the mechanisms of DNA replication/synthesis?

A

Meselson and Stahl

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24
Q

State why DNA replication is not dispersive or conservative.

A
  • If conservative, would result in 2 distinct DNA bands, a high and low density one
  • if dispersion, who result in one single band of intermediate density
  • however, found that there were 2 bands, but they were high and intermediate density (semiconservative)
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25
Q

What molecules are responsible for copying DNA (synthesis)?

A

1) DNA polymerase

2) dNTP

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26
Q

What do DNA polymerases do?

A

they polymerize deoxyribonucleotides to DNA

27
Q

the 3 types of DNA polymerases in bacteria are:

A

DNA polmerase I and III (replication) and DNA polymerase II (DNA repair)

28
Q

What are dNTP’s?

A

deoxyribonucleoside triphosphates (the N stands for any of the bases A,T,G,C)

29
Q

In what direction is DNA replicated?

A

in a 5’ to 3’ direction

30
Q

Origin of replication

A

the replication bubble formed at a specific sequence of bases
-produces a prepriming complex, making single stranded DNA available for replication

31
Q

How many origins of replication do bacteria have?

A

only one

32
Q

How many origins of replication can eukaryotes have?

A

multiple

33
Q

replication fork

A

a Y-shaped region where the parent DNA double helix is split into 2 single strands which are then copied

34
Q

What does helicase do?

A

breaks hydrogen bonds between the base pairs to open the double helix
MAIN: opening the double helix

35
Q

Function of single stranded binding proteins

A

to stabilize the single stranded DNA to prevent recoiling

MAIN: opening double helix

36
Q

Function of topoisomerase

A

to break and rejoins DNA double helix to RELIEVE tension caused b opening helix

37
Q

Function of primase

A

to catalyze the synthesis of RNA primer on leading and lagging strands

38
Q

Function of DNA polymerase III

A

to extend the leading strand and Okazaki fragment on lagging strand (replication)

39
Q

Function of sliding clamp

A

to hold DNA polmerase III in place during replication

40
Q

Function of DNA polymerase I

A

to remove RNA primer and replace with DNA

41
Q

DNA ligase

A

joins the Okazaki fragments into a continuous strand

42
Q

How are leading stranding synthesized?

A

continuously

43
Q

How are lagging strands synthesized?

A

in Okazaki fragments…discontinuously

44
Q

If DNA ligase were defective, what would the replicating DNA look like?

A

the lagging strand would remain in fragments

45
Q

What is the purpose of the RNA primer?

A

to provide a free 3’ hydroxyl group, so that an incoming dNTP can form a phosphodiester bond to

46
Q

replisome

A

…

47
Q

The region (cap) at the ends of linear chromosomes are called?

A

telomeres

48
Q

What results in the formation of an unreplicated end in dsDNA?

A

from that fact that there is not enough room for an RNA primer once the end of DNA strand is reached, therefore leaving behind an unreplicated region

49
Q

What happens to this unreplicated region on the lagging strand?

A

gets degraded, resulting in the shortening of chromosome

50
Q

Do telomeres contain genes that can be coded?

A

No.

51
Q

What is the base sequence of telomeres?

A

contains a unique DNA sequence that is REPEATED thousands of times

52
Q

The telomeres of humans contain the base sequence:

A

TTAGGG

53
Q

What is telomerase?

A

an enzyme that replicates telomeres by catalyzing DNA from RNA, using the RNA as a template to lengthen chromosomal ends

54
Q

Why do bacteria and archaea have this unreplicated region?

A

they have a single, CIRCULAR chromosome

55
Q

How can the ends of chromosomes be prevented from getting shorter?

A

with telomerase (add DNA onto the ends)

56
Q

In humans, where is telomerase mostly found?

A

in cells of reproductive organs, specifically cells that undergo meiosis to produce gametes (ie. ovaries, testes)

57
Q

Where is telomerase not commonly found?

A

somatic cells

58
Q

Genes that contain errors are:

A

defective

59
Q

How can the enzymes involved in DNA replication be as precise as they are?

A
  • DNA polymerase III is highly selective in matching complimentary pairs correctly (1 base in 100 000)
  • DNA pol. III can also proofread (can catch mismatch pairs and correct them)–exonuclease activity (1 base in 10 million)
  • mistakes after synthesis are removed and replaced with repair enzymes (1 base in a billion)
60
Q

How does UV light damage DNA?

A

causes covalent bonds to form between adjacent pyrimidine bases, therefore resulting in a deformed secondary DNA structure (kink)

61
Q

Exonuclease

A

enzyme that removes dNTP’s from end of DNA strands

62
Q

How does the kink of the deformed structure affect the DNA?

A
  • stalls the movement of the replication fork

- cell may die if not repaired

63
Q

How is damage DNA caused by radiation repaired?

A

Nucleotide excision repair (NER)

Biology 1A03 (4 decks)

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