Exam 4

Question 1

In his transformation experiments, what did Griffith observe?

Answer 1

Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

Question 2

After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, 2) nonphosphorescent strain, you discover that some of the living cells are now phosphorescent.
Which observation(s) would provide the best evidence that the ability to phosphoresce is a
heritable trait?

Answer 2

phosphorescence in descendants of the living cells

Question 3

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately 3) what percentage of the nucleotides in this sample will be thymine?

Answer 3

8%

Question 4

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with 4) modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They
reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won’t this
experiment work?

Answer 4

Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not
distinguish between DNA and proteins.

Question 5

How does the enzyme telomerase meet the challenge of replicating the ends of linear 5) chromosomes?

Answer 5

It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.

Question 6

Why do histones bind tightly to DNA?

Answer 6

Histones are positively charged, and DNA is negatively charged.

Question 7

A new DNA strand elongates only in the 5 to 3 direction because______

Answer 7

DNA polymerase can add nucleotides only to the free 3

Question 8

The leading and the lagging strands differ in that _____.

Answer 8

the leading strand is synthesized in the same direction as the movement of the replication
fork, and the lagging strand is synthesized in the opposite direction

Question 9

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

Answer 9

It joins Okazaki fragments together.

Question 10

Which of the following would you expect of a eukaryote lacking telomerase?

Answer 10

a reduction in chromosome length in gametes

Question 11

A particular triplet of bases in the template strand of DNA is 5’ AGT 3’. The corresponding codon 11) for the mRNA transcribed is _____.

Answer 11

3 UCA 5

Question 12

The genetic code is essentially the same for all organisms. From this, one can logically assume 12) which of the following?

Answer 12

A gene from an organism can theoretically be expressed by any other organism.

Question 13

A possible sequence of nucleotides in the template strand of DNA that would code for the 13) polypeptide sequence phe-leu-ile-val would be _____.

Answer 13

3

Question 14

Refer to the figure above. What would the anticodon be for a tRNA that transports phenylalanine to 14) a ribosome?

Answer 14

AAA

Question 15

Codons are part of the molecular structure of _____.

Answer 15

mRNA

Question 16

A single base substitution mutation is least likely to be deleterious when the base change results in _____.

Answer 16

a codon that specifies the same amino acid as the original codon

Question 17

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG 17) start of translation, is likely to have the most serious effect on the polypeptide product?

Answer 17

a deletion of two nucleotides

Question 18

How does termination of translation take place?

Answer 18

A stop codon is reached.

Question 19

Translation requires _____.

Answer 19

mRNA, tRNA, and rRNA

Question 20

Picture question

Answer 20

picture question

Question 21

Which of the following is a protein produced by a regulatory gene?

Answer 21

repressor

Question 22

A mutation that inactivates a regulatory gene of a repressible operon in an E. coli cell would result 22) in _____.

Answer 22

continuous transcription of the structural gene controlled by that regulator

Question 23

For a repressible operon to be transcribed, which of the following must occur?

Answer 23

RNA polymerase must bind to the promoter, and the repressor must be inactive.

Question 24

At the beginning of this century there was a general announcement regarding the sequencing of the 24) human genome and the genomes of many other multicellular eukaryotes. Many people were
surprised that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for much of the DNA that is not coding for proteins?

Answer 24

non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function

Question 25

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments she succeeded in increasing acetlylation of histone tails. Which of the following results would she most likely see?

Answer 25

decreased chromatin condensation

Question 26

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. One way to detect alternative splicing of transcripts from a given gene is to _____.

Answer 26

compare the sequences of different mRNAs made from the given gene

Question 27

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _____.

Answer 27

sets of regulatory proteins

Question 28

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would be likely?

Answer 28

Beta galactosidase will not be produced.

Question 29

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. What would occur if the repressor of an inducible operon were mutated so that it could not bind the operator?

Answer 29

continuous transcription of the operon’s genes

Question 30

The fact that plants can be cloned from somatic cells demonstrates that _____.

Answer 30

differentiated cells retain all the genes of the zygote

Question 31

Catastrophism was Cuvier’s attempt to explain the existence of _____.

Answer 31

the fossil record

Question 32

During a study session about evolution, one of your fellow students remarks, “The giraffe stretched its neck while reaching for higher leaves; its offspring inherited longer necks as a result.” Which statement is most likely to be helpful in correcting this student’s misconception?

Answer 32

Characteristics acquired during an organism’s life are generally not passed on through genes.

Question 33

Picture Question

Answer 33

Picture Question

Question 34

The cow Bos primigenius (which is bred for meat and milk) has a smaller brain and larger eyes than closely related wild species of ungulates. These traits most likely arose by _____.

Answer 34

artificial selection, because changes in these traits co-occurred with human selection for high
milk output and high muscle content

Question 35

Which of these conditions are always true of populations evolving due to natural selection?
Condition 1: The population must vary in traits that are heritable.
Condition 2: Some heritable traits must increase reproductive success.
Condition 3: Individuals pass on most traits that they acquire during their lifetime.

Answer 35

Conditions 1 and 2

Question 36

After the drought of 1977, researchers hypothesized that on the Galápagos island Daphne Major, medium ground finches with large, deep beaks survived better than those with smaller beaks
because they could more easily crack and eat the tough Tribulus cistoides fruits. A tourist company
sets up reliable feeding stations with a variety of bird seeds (different types and sizes) so that
tourists can get a better look at the finches. Which of these events is now most likely to occur to finch beaks on this island?

Answer 36

increased variation in beak size and shape over time

Question 37

Darwin and Wallace were the first to propose _____.

Answer 37

natural selection as the mechanism of evolution

Question 38

Which of the following represents an idea that Darwin learned from the writings of Thomas Malthus?

Answer 38

Populations tend to increase at a faster rate than their food supply normally allows.

Question 39

Which of the following must exist in a population before natural selection can act upon that population?

Answer 39

genetic variation among individuals

Question 40

Currently, two extant elephant species (X and Y) are classified in the genus Loxodonta, and a third species (Z) is placed in the genus Elephas. Thus, which statement should be true?

Answer 40

Species X and Y share a greater number of homologies with each other than either does with species Z.