Chapter 7

Question 1

T or F: since protein contains large amounts of sulfur and DNA contains large amount of phosphorus, an experiment was conducted where bacteriophages developed in a phosphorus environment and sulfur environment - in the phosphorus environment, DNA was radioactively marked and in the sulfur environment, the phage protein coat was marked.

Answer 1

True

Question 2

In the sulfur/phosphorus bacteriophage experiment, how did researchers know that something (DNA) was transferred to the bacteria after shaking off the phage protein coat? Also, how did the researchers know that DNA was actually transferred, as opposed to something else?

Answer 2

In the experiment where only protein was labeled, when the bacteria was plated, plaques formed
In the experiment where only DNA was labeled, they put plates on film and the radiation made dots on the film

Question 3

The most common 3D form of DNA is the __________ which has a major and minor groove that’s recognized by protein

Answer 3

B-form

Question 4

Explain the Meselson-Stahl Experiment

Answer 4

To determine if DNA replication was conservative, semi-conservative, or dispersive, 15N (heavy) and 14N (light) growth mediums were used to measure weight of DNA strands after two generations.
Generation 0: all heavy
Generation 1: all intermediate (rejects conservative)
Generation 2: half light, half intermediate (rejects dispersive)
Conclusion: DNA replicates semi-conservatively

Question 5

In eukaryotes, each chromosome typically has multiple _________________ (ori) while each replicon of bacteria only has typically one. Semiconservative DNA replication occurs _____________.

Answer 5

origins of replication, bidirectionally

Question 6

Explain the roles of each protein in the Replisome

Answer 6

1) DNA topoisomerase: relaxes supercoiling
2) Helicase: unwinds the double helix
3) SSB: prevents reannealing of separated strands
4) Primase: adds RNA primers
5) DNA polymerase III: synthesizes daughter strand on both leading and lagging strand
6) DNA polymerase I: removes and replaces RNA primer nucleotides
7) DNA ligase: joins DNA together

Question 7

T or F: when there is a DNA polymerase error and an incorrect nucleotide, exonuclease cleaves the nucleotide and replication continues - this is DNA proofreading

Answer 7

True

Question 8

The mutation rate is typically ________________ base pairs, which is low. Humans inherit about _____ new mutations each generation, mostly coming from our ________.

Answer 8

1 out of every 1 billion, 60, father

Question 9

What are the pros and cons of sex?

Answer 9

Pros: male parental care, sexual selection removes bad alleles, recombination
Cons: the twofold cost of sex, may disrupt advantageous combinations of alleles, STDs

Question 10

What is the advantage of recombination?

Answer 10

Offspring have a combination of traits that are different from parents and there are more phenotypic values to choose from for natural selection

Question 11

Describe Muller’s ratchet, Hill-Robertson effects, Genetic hitchhiking, and background selection

Answer 11

Muller’s Ratchet: the best chromosome is lost due to genetic drift
Hill-Robertson: when beneficial and deleterious mutations are linked, this slows the fixation of the good and slows the removal of the bad
Genetic Hitchhiking: deleterious mutations rise to high frequency since they’re linked to advantageous mutations
Background Selection: beneficial mutations are removed since they are linked to deleterious mutations

Question 12

What are two reasons why genetic recombination is useful?

Answer 12

1) can separate good mutations from bad mutations
2) can unite multiple advantageous mutations that appeared in different individuals

Question 13

DNA replication at the ends of linear chromosomes requires an RNA primer so consequently, after a replication cycle, chromosomes become slightly shorter. The ________________ is the number of times (roughly ____ - ____) a normal, differentiated somatic cell can undergo cell division before undergoing programmed cell death.

Answer 13

Hayflick Limit, 50 - 70 cell divisions

Question 14

What are disorders associated with low telomerase activity?

Answer 14

dyskeratosis congenita, aplastic anemia, pulmonary fibrosis, cancer

Question 15

A ribonucleoprotein is an enzymatic complex that includes _________ and _______________. Examples include ___________, ___________, and components of the ______________

Answer 15

protein, ribonucleic acid, telomerase, ribosomes, spliceosome

Question 16

Telomeres are….

Answer 16

repetitive sequences at the ends of linear chromosomes that ensure a portion of the chromosome can be lost without harm to the organism

Question 17

Telomerase is usually active only in germ cells and stem cells. Why wouldn’t evolution favor all cells to have a high-level of telomerase activity to ensure chromosomal integrity and cell longevity

Answer 17

Most cancers have high telomerase activity so apoptosis of old cells may be favored to reduce the incidence of cancer

Question 18

PCR requires…

Answer 18

1) DNA template
2) supply of the four DNA nucleotides
3) Taq polymerase (can withstand high heat)
4) DNA primers
5) buffer solution

Question 19

The three main steps of PCR is __________________, __________________, and _____________________. The main limitations of PCR are that you need to know something about the sequence to design primers and PCR only works for _______________.

Answer 19

denaturation of DNA, primer annealing, primer extension, small fragments

Question 20

Sanger Sequencing

Answer 20

a method of DNA sequencing that involves electrophoresis and involves producing partial products for all four nucleotides and piecing them together for the final sequence