Question

Questions 9-12 deal with SSR loci in Sam's genome. Remember that SSRs (simple sequence repeats) are tandem (next to each other) repeats of short sequences (a few bp). Such tandem repeats are located at specific sites scattered throughout the genome. Individuals vary in the number of repeats at each site sites can have up to 100 repeats. Each locus with the same repeats is called an SSR ocus DNA was extracted from Sam's white blood cells and cut with a restriction enzyme that cuts outside of the repeat region. The DNA fragments were separated by size by gel electrophoresis, blotted to a membrane, and hybridized with a probe (shown below) that can base pair with the repeat DNA present in each SSR locus. This particular SSR is located at a specific site on 5 different chromosomes (chromosomes 3, 5, 9, 13, and 21) SSR locus (each box is a repeat): restriction sites: probe: What is the maximum number of bands you would expect to see in Sam's DNA? Put a number in the box. (Remember that a probe to the repeat DNA will hybridize to all SSR loci in the genome that have that repeat.) Question 10 0.5 pts How many of Sam's SSR bands would you expect to be inherited by his child? Put a number in the box

Answer 1

Q9. Ans: 5

Explanation: The SSR is located at the specific site on 5 different chromosomes. So, the probe can hybridize with these bands. Hence, 5 bands could be expected.

Q10. Ans: 5

Explanation: As, 5 SSR sites are present in 5 different chromosomes, these 5 chromosomes, hence 5 probes could be inherited by his child, as all are in different chromosomes, provided, he is homozygous for these sites.

Q11. Ans: 1

Explanation: As only one SSR is found in chromosome 3, the probe will hybridize outside this region. And only one band would be expected.

Q12. Ans: 1

Explanation: As, one SSR site is present in chromosome 3, this chromosome, hence one probe could be inherited by his child, provided, he is homozygous for this chromosome.

Q13. Ans: That site may vary between individuals.

Q14. Ans: 9

Explanation: There are 5 restriction sites present in this DNA. They can yield 10 different fragments. Among them 9 can hybridize with the probe.