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BIOL-L 112 Exam 3 > Molecular Basis of Inheritance > Flashcards

Molecular Basis of Inheritance Flashcards

1
Q

What technique was used to study molecular structure?

A

X-Ray Crystalography

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2
Q

Franklin’s X-Ray Crystallographic images of DNA enabled Watson to deduce that DNA was

A

helical

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3
Q

X-Ray images also enabled Watson to deduce the

A

width of the helix and the spacing of the nitrogenous bases

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4
Q

Pattern in the photo suggested that the DNA molecule was made up of _____ , forming a ______

A

Two Strands

Double Helix

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5
Q

Watson and Crick built models of a double helix to conform to the _____ and _____ of DNA

A

X-Rays

Chemistry

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6
Q

Franklin had concluded that there were two outer ______, with the Nitrogenous ______

A

Sugar-Phosphate backbones

Nitrogenous bases paired in the molecule’s interior

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7
Q

Watson built a model in which the backbones were ____

A

antiparallel (their subunits run in opposite directions)

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8
Q

Pairing a ___ with a ____ resulted in a uniform width consistent with the X-Ray Data

A

Purine

Pyrimidine

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9
Q

Purine + Purine =

A

Too wide

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10
Q

Pyrimidine + Pyrimidine =

A

Too Narrow

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11
Q

DNA Base Parings

A

Adenine - Thymine

Guanine - Cytosine

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12
Q

Watson - Crick Model explains

A

Chargaff’s Rules

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13
Q

Chargaffs Rules

A

In any organism, the amount of A=T will be equal to the amount of G=C

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14
Q

Since the two strands of DNA are complementary, ____

A

each strand acts as a template for building a new strand in replication

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15
Q

In DNA replication, the parent molecule unwinds, and two new daughter strands are built based on ____

A

base-pairing rules

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16
Q

Semiconservative Model

A

Predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or “conserved” from the parent molecular) and one newly made strand

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17
Q

Conservative Model

A

Two parent strands rejoin

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18
Q

Dispersive Model

A

Each strand is a mix of old and new

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19
Q

Replication begins at particular sites called _____

A

Origins of Replication

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20
Q

What happens at the origin of Replication?

A

Two DNA strands are separated, opening up a replication “bubble”

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21
Q

A eukaryotic chromosome may have _____ origins of replications

A

hundreds or even thousands

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22
Q

Replication proceeds in ____ , until the entire molecule is copied

A

both directions from each origin

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23
Q

At the end of each replication bubble is a ____

A

replication fork, a Y-shaped region where new DNA strands are elongating

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24
Q

____ are enzymes that untwist the double helix at the replication forks

A

Helicases

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25
Q

_____ bind to and stabilize single-stranded DNA

A

Single-strand binding proteins

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26
Q

______ corrects “overwinding” ahead of replication forks by braking, swiveling, and rejoining DNA strands

A

Topoisomerase

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27
Q

DNA polymerases cannot initiate synthesis of a polynucleotide; they can only ____

A

add nucleotides to an existing 3’ end

28
Q

The initial nucleotide strand is a short ____

A

RNA primer

29
Q

what does Primase do?

A

Can start a RNA chain from scratch and adds RNA nucleotides one at a time using the parental DNA as a template

30
Q

The primer is _______ and the _ end serves as te starting point for the new DNA strand

A

short (5-10 nucleotides long)

3’

31
Q

What do DNA Polymerase do?

A

Catalyze the elongation of new DNA at replication fork

32
Q

Most DNa polymerases require a ____ and a ____

A

Primer

DNA Template Strand

33
Q

The rate of elongation is what in bacteria and humans?

A

500 nucleotides per second in bacteria and 50 per second in human cells

34
Q

A ____ structure of a double helix affects replication

A

Anti parallel

35
Q

DNa polymerases add nucleotides only to the ____ of a growing strand

A

Free 3’ End

36
Q

New DNA strand can elongate only in the ____ direction

A

5’ to 3’

37
Q

Along one template strand of DNA, the DNA polymerase synthesizes a ____

A

leading strand continuously, moving toward the replication fork

38
Q

To elongate the other new strand, called the ____, DNA polymerase must work in the direction ___ from the replication fork

A

Lagging Strand

away

39
Q

Lagging strand is synthesized as a series of segments called ____ , which are joied together by _____

A

Okazaki Fragments

DNA ligase

40
Q

Okazaki Fragmet size in Eukaryotes and Prokaryotes

A

100-200 n in Eukaryotes and 1000-2000 in prokaryotes

41
Q

Helicase Function

A

Unwinds parental double helix at replication forks

42
Q

Single-Strand Binding Protein

A

Binds to and stabilizes single-stranded DNA until it is used as a template

43
Q

Topoisomerase

A

Relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands

44
Q

Primase

A

Synthesizes an RNA primer at 5’ end of leading strand, and at 5’ end of each Okazaki fragment of lagging strand

45
Q

DNA Poll III

A

Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand

46
Q

DNA Pol I

A

Removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides

47
Q

DNA Ligase

A

Joins Okazaki fragments of lagging strand; On leading strand, joins 3’ end of DNA that replaces primer to rest of leading strand DNA

48
Q

DNA Polymerases job is to

A

proofread newly made DNA, replacing any incorrect nucleotide

49
Q

In mismatch repair of DNA, repair enzymes

A

correct errors in base pairing

50
Q

DNA ca be damged by

A

exposure to harmful chemical or physical agents such as cigarette smoke and X-Rays; it can also undergo spontaneous changes

51
Q

In Nucleotide excision repair, a nuclease _____

A

cuts out and replaces damaged stretches of DNA

52
Q

Can sequence changes become permanent?

A

Yes, and they can be passed on to the next genertion

53
Q

Mutations due to sequence changes are the source of ____ upon which natural selection operates

A

Genetic Variation

54
Q

The unusual replication machinery provides no way to complete the ___ , so repeated rounds of replication produce __ DNA molecules

A

5’ Ends

Shorter

55
Q

Telomeres are located where?

A

At the ends of eukaryotic chromosomes

56
Q

What do Telomeres do?

A

They are like a protective cap, to ensure all genetic information is passed from one generation to next after replication. Prevents damage to end and joining with adjacent chromosomes

57
Q

How many times does TTAGGG repeat in Vertebrates?

A

2500 Times

58
Q

Average cell divides ____ , losing ____ of telomere with each division.

A

50-70 times

25-200 bp

59
Q

Aging driven by

A

Telomere shorterning

60
Q

What happens when the telomere is too short?

A

Chromosome reaches “critial length” and can no loger replicate and cell dies (apoptosis)

61
Q

Tekinerase

A

RNP - Reverse TRabscriptase, carries its own RNA

62
Q

Telomerase; what is the strand name that is carried in Vertebrates?

A

CCCAAUCCC

63
Q

Telomerase; Adds telomere repeat _ to 3” end of chromosomes

A

TTAGGG

64
Q

Why is telomerase activated?

A

To treat aging and age related diseases

65
Q

Using Telomerase _____ to treat cancer

A

Inhibition

Cancer cells cause then to be 10-20 more active. Shorting protect cells from cancerous growth by limiting number of cell divisions

66
Q

What would happen if chromosomes of germ cells became shorter in every cell cycle?

A

Essential genes would eventually be missing from the gametes they produce

67
Q

What does the enzyme telomerase do?

A

Catalyzes the lengthening of telomeres in germ cells?

BIOL-L 112 Exam 3 (4 decks)

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