End of Chapter Questions Flashcards
Write the genotypes of all recombinant and nonrecombinant progeny expected from the following 3 pt cross.
m+p+s+/mps x mps/mps
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
How does a genetic map differ from a physical map?
Genetic maps are based on rates of recombination; physical maps are based on physical distances.
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?
The c locus
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?
More double crossovers took place than expected on the basis of single-crossover frequencies.
Chromosome duplications often result in abnormal phenotypes because
Developmental processes depend on the relative amounts of proteins encoded by different genes
What is pseudodominance and how is it produced by a chromosome deletion?
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.
A dicentric chromosome is produced when crossing over takes place in an individual heterozygous for which type of chromosome rearrangement?
Paracentric inversion
A DNA molecule 300 bp long has 20 complete rotations. This DNA is
Negatively supercoiled
Bacterial DNA
is not complexed to histone proteins and is circular
Neutralizing their positive charge would have which effect on the histone proteins?
They would separate from the DNA
How many copies of the H2B histone would be found in chromatin containing 50 nucleosomes?
100
Which is a characteristic of DNA sequences at the telomeres?
All of the above
- guanine and adenine nucleotides
- repeated sequences
- one strand protrudes beyond the other
What is the outcome of a Robertsonian translocation?
One metacentric chromosome and one chromosome with two very short arms.
How does an incorporated error differ from a replicated error?
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.
Base analogs are mutagenic because of which characteristic?
They are similar in structure to the normal bases
Mismatch repair in E. coli distinguishes between old and new strands of DNA on the basis of
Methyl groups on the old strand
How do direct repair mechanisms differ from mismatch repair and base-excision repair?
Direct repair return an altered base to its correct structure without removing and replacing nucleotides. Mismatch and base-excision repair remove and replace nucleotides.
Why are defects in DNA repair often associated with increases in cancer?
Cancer arises from mutations in DNA
DNA fragments that are 500 bp, 1000 bp and 2000 bp in length are separated by gel electrophoresis. Which fragment will migrate the fastest?
500 bp fragment
In the dideoxy sequencing reaction, what terminates DNA synthesis at a particular base?
The absence of a 3’-OH group on the ddNTP prevents the addition of another nucleotide.
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
Reverse genetics
What is the advantage of using the neo gene to disrupt the function of a gene in knockout mice?
The neo gene provides a selectable marker for finding cells that contain the disabled gene.
How are microsatellites detected?
By using PCR with primers that flank the region containing tandem repeats.
