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Biology 151 > Unit 3 Lecture 4 10/24/22 > Flashcards

Unit 3 Lecture 4 10/24/22 Flashcards

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1
Q

In 1953, James Watson and Francis Crick introduced an elegant double-helical model for the structure of __________, or __________

A

deoxyribonucleic acid or DNA

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2
Q

__________information is encoded in DNA and reproduced in all cells of the body (DNA replication)

A

heredity

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3
Q

The two components of chromosomes—__________ and __________—became candidates for the genetic material

A

1.DNA
2.Protein

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4
Q

Viruses that infect bacteria are called __________

A

bacteriophages

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5
Q

Griffith worked with two strains of a bacterium, one __________ and one __________

A

1.pathogenic
2.harmless

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6
Q

He called this phenomenon __________, now defined as a change in genotype and phenotype due to assimilation of foreign DNA

A

transformation

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7
Q

Later work by Oswald Avery and others identified the transforming substance as __________

A

DNA

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8
Q

Many biologists remained skeptical, mainly because little was known about DNA and they thought __________were better candidates for the genetic material

A

Proteins

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9
Q

To determine this, they designed an experiment showing that only the __________of the T2 phage, and not the __________, enters an E. coli cell during infection

A

1.DNA
2.protein

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10
Q

It was known that DNA is a polymer of __________, each consisting of a nitrogenous base, a sugar, and a phosphate group

A

Nucleotides

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11
Q

Two findings became known as __________

A

Chargaff’s rules

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12
Q

The base composition of DNA ____________________

A

varies between species

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13
Q

In any species the number of __________bases is equal, and the number of __________bases is equal

A

A and T
G and C

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14
Q

The basis for these rules was not understood until the discovery of the __________

A

double helix

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15
Q

Maurice Wilkins and Rosalind Franklin were using a technique called ____________________to study molecular structure

A

X-ray Crystallography

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16
Q

The pattern in the photo suggested that the DNA molecule was made up of two strands, forming a __________

A

double helix

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17
Q

Franklin had concluded that there were two outer __________________________, with the ____________________ paired in the molecule’s interior

A

1.sugar-phosphate backbones
2.nitrogenous bases

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18
Q

Watson built a model in which the backbones were __________ (their subunits run in opposite directions)

A

antiparallel

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19
Q

Instead, pairing a __________with a __________ resulted in a uniform width consistent with the X-ray data

A

1.purine
2.pyrimidine

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20
Q

They determined that __________paired only with __________, and __________ paired only with __________

A

1&2.adenine with thymine
3&4.guanine with cytosine

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21
Q

The __________ explains __________: in any organism the amount __________, and the amount of __________

A

Watson-Crick model
Chargaff’s rules
A=T
G=C

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22
Q

The relationship between structure and function is manifest in the __________

A

Double helix

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23
Q

Watson and Crick noted that the specific base pairing suggested a possible __________for genetic material

A

Copying mechanism

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24
Q

Watson and Crick’s __________of replication predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or “conserved” from the parent molecule) and one newly made strand

A

Semiconservative model

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25
Q

Competing models were the __________ (the two parent strands rejoin) and the __________ (each strand is a mix of old and new)

A

conservative model
dispersive model

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26
Q

Experiments by Matthew Meselson and Franklin Stahl supported the __________

A

Semiconservative model

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27
Q

Replication begins at particular sites called ____________________, where the two DNA strands are separated, opening a ____________________

A

origins of replication
replication bubble

28
Q

At each end of a bubble is a ____________________, a Y-shaped region where the parental strands of DNA are being unwound

A

replication fork

29
Q

__________are enzymes that untwist the double helix at the replication forks

A

Helicases

30
Q

____________________bind to and stabilize single-stranded DNA

A

single-strand binding proteins

31
Q

__________ relieves the strain caused by tight twisting ahead of the replication fork by breaking, swiveling, and rejoining DNA strands

A

Topoisomerase

32
Q

__________replication bubbles form and eventually fuse, speeding up the copying of DNA

A

Multiple

33
Q

__________cannot initiate synthesis of a polynucleotide; they can only add nucleotides to an already existing chain base-paired with the template

A

DNA polymerases

34
Q

The initial nucleotide strand is a short __________

A

RNA primer

35
Q

The enzyme __________starts an RNA chain from a single RNA nucleotide and adds RNA nucleotides one at a time using the parental DNA as a template

A

Primase

36
Q

Enzymes called __________catalyze the elongation of new DNA at a replication fork

A

DNA polmerases

37
Q

The rate of elongation is about __________ per second in bacteria and __________in human cells

A

500 nucleotides
50 per second

38
Q

__________is used to make DNA and is similar to the ATP of energy metabolism

A

dATP

39
Q

The difference is in the sugars: dATP has __________, while ATP has __________

A

Deoxyribose
Ribose

40
Q

As each monomer nucleotide joins the DNA strand, it loses two phosphate groups as a molecule of __________

A

Pyrophosphate

41
Q

The __________structure of the double helix affects replication

A

antiparallel

42
Q

Along one template strand of DNA, the __________synthesizes a __________continuously, moving toward the replication fork

A

DNA polymerase
Leading strand

43
Q

To elongate the other new strand, called the __________, DNA polymerase must work in the direction __________from the replication fork

A

lagging strand
away

44
Q

The lagging strand is synthesized as a series of segments called __________

A

Okazaki fragments

45
Q

After formation of Okazaki fragments, __________ removes the __________and replaces the nucleotides with DNA

A

DNA polymerase 1
RNA primer

46
Q

The remaining gaps are joined together by DNA __________

A

ligase

47
Q

__________proofread newly made DNA, replacing any incorrect nucleotides

A

DNA polymerases

48
Q

In nucleotide__________, a __________cuts out and replaces damaged stretches of DNA

A

excision repair
nuclease

49
Q

Error rate after proofreading repair is low but __________zero

A

not

50
Q

These changes __________are the source of the genetic variation upon which __________operates

A

mutations
natural selection

51
Q

Limitations of DNA polymerase create problems for the __________of eukaryotic chromosomes

A

linear DNA

52
Q

Eukaryotic chromosomal DNA molecules have special nucleotide sequences at their ends called __________

A

telomeres

53
Q

__________ do not prevent the shortening of DNA molecules, but they do postpone it

A

Telomeres

54
Q

It has been proposed that the shortening of telomeres is connected to __________

A

aging

55
Q

An enzyme called __________ catalyzes the lengthening of telomeres in germ cells Telomerase is not active in most human somatic cells

A

telomerase

56
Q

The bacterial chromosome is a double-stranded, __________ DNA molecule associated with a __________ amount of protein

A

circular
small

57
Q

Eukaryotic chromosomes have __________ DNA molecules associated with a __________ amount of protein

A

linear
large

58
Q

In a bacterium, the DNA is “supercoiled” and found in a region of the cell called the __________

A

nucleoid

59
Q

__________, a complex of DNA and protein, is found in the nucleus of eukaryotic cells

A

Chromatin

60
Q

__________ fit into the nucleus through an elaborate, multilevel system of packing

A

Chromosomes

61
Q

__________ undergoes striking changes in the degree of packing during the course of the cell cycle

A

Chromatin

62
Q

At __________, most of the chromatin is compacted into a 30-nm fiber, which is folded further in some areas by looping

A

interphase

63
Q

This condensed chromatin is called __________; the more dispersed, less compacted chromatin is called __________

A

heterochromatin
euchromatin

64
Q

Dense packing of the heterochromatin makes it largely __________ to the machinery responsible for transcribing genetic information

A

inaccessible

65
Q

Complementary base pairing of DNA is the basis for __________, the base pairing of one strand of a nucleic acid to another, complementary sequence

A

nucleic acid hybridization

66
Q

__________ forms the foundation of virtually every technique used in __________, the direct manipulation of genes for practical purposes

A

nucleic acid hybridization
genetic engineering

Biology 151 (20 decks)

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