End of Chapter Questions

Question 0

Write the genotypes of all recombinant and nonrecombinant progeny expected from the following 3 pt cross.
m+p+s+/mps x mps/mps

Answer 0

m+p+s+ m+ps mp+s mp+s+ m+p+s mps+ m+ps+ mp+s mps / mps mps mps mps mps mps mps mps

Question 1

How does a genetic map differ from a physical map?

Answer 1

Genetic maps are based on rates of recombination; physical maps are based on physical distances.

Question 2

A three point test cross is carried out between three linked genes. The resulting nonrecombinant progeny are s+r+c+ and src. The double crossover progeny are src+ and s+r+c. Which is the middle locus?

Answer 2

The c locus

Question 3

In analyzing the results of a 3-pt test cross, a student determines that the interference is -0.23. What does this negative interference value indicate?

Answer 3

More double crossovers took place than expected on the basis of single-crossover frequencies.

Question 4

Chromosome duplications often result in abnormal phenotypes because

Answer 4

Developmental processes depend on the relative amounts of proteins encoded by different genes

Question 5

What is pseudodominance and how is it produced by a chromosome deletion?

Answer 5

Pseudodominance is the expression of a recessive mutation. It is produced when the dominant wild-type allele in a heterozygous individual is absent due to a deletion on one chromosome.

Question 6

A dicentric chromosome is produced when crossing over takes place in an individual heterozygous for which type of chromosome rearrangement?

Answer 6

Paracentric inversion

Question 8

A DNA molecule 300 bp long has 20 complete rotations. This DNA is

Answer 8

Negatively supercoiled

Question 9

Bacterial DNA

Answer 9

is not complexed to histone proteins and is circular

Question 10

Neutralizing their positive charge would have which effect on the histone proteins?

Answer 10

They would separate from the DNA

Question 11

How many copies of the H2B histone would be found in chromatin containing 50 nucleosomes?

Answer 11

100

Question 12

Which is a characteristic of DNA sequences at the telomeres?

Answer 12

All of the above

• guanine and adenine nucleotides
• repeated sequences
• one strand protrudes beyond the other

Question 13

What is the outcome of a Robertsonian translocation?

Answer 13

One metacentric chromosome and one chromosome with two very short arms.

Question 14

How does an incorporated error differ from a replicated error?

Answer 14

An incorporated error is due to a change that takes place DNA. This change may be corrected by a DNA repair pathway. However, if the error has been replicated, it is permanent and cannot be detected.

Question 15

Base analogs are mutagenic because of which characteristic?

Answer 15

They are similar in structure to the normal bases

Question 16

Mismatch repair in E. coli distinguishes between old and new strands of DNA on the basis of

Answer 16

Methyl groups on the old strand

Question 17

How do direct repair mechanisms differ from mismatch repair and base-excision repair?

Answer 17

Direct repair return an altered base to its correct structure without removing and replacing nucleotides. Mismatch and base-excision repair remove and replace nucleotides.

Question 18

Why are defects in DNA repair often associated with increases in cancer?

Answer 18

Cancer arises from mutations in DNA

Question 19

DNA fragments that are 500 bp, 1000 bp and 2000 bp in length are separated by gel electrophoresis. Which fragment will migrate the fastest?

Answer 19

500 bp fragment

Question 20

In the dideoxy sequencing reaction, what terminates DNA synthesis at a particular base?

Answer 20

The absence of a 3’-OH group on the ddNTP prevents the addition of another nucleotide.

Question 21

A geneticist interested in immune function induces random mutations in a number of specific genes in mice and then determines which of the resulting mutant mice have impaired immune function. This is an example of

Answer 21

Reverse genetics

Question 22

What is the advantage of using the neo gene to disrupt the function of a gene in knockout mice?

Answer 22

The neo gene provides a selectable marker for finding cells that contain the disabled gene.

Question 23

How are microsatellites detected?

Answer 23

By using PCR with primers that flank the region containing tandem repeats.