Questions

Question 1

A mother and father are both heterozygous (Ff) for a trait that, when homozygous recessive (ff), causes death in the first trimester of pregnancy. This couple has one child, a son. Their son grows up and marries a woman. The woman he marries is also heterozygous for this same trait. They decide to do an amniocentesis for genetic screening at 21 weeks of pregnancy. What is the probability that this screening will find that this fetus does not carry any recessive alleles for this trait? Give your answer as a percentage, rounded to three significant figures. Just enter the number, nothing else.

Please explain how you arrived at your answer to the previous question.

Question 2

The polymerase chain reaction (PCR) amplifies a nucleotide sequence between two PCR primers. You want to generate a knock-in of a marker at a specific locus on the genome using homologous recombination. You designed a knock-in vector with 5' and 3' homology arms of 50 bp each with a 350 bp knock-in sequence in between. In the targeted genomic region, there is a distance of 100 bp between the two homologous regions. To identify the cell that contains the correct DNA fragment knocked in, you designed a PCR reaction with primers flanking the homologous regions, which generated a 1000-bp product in intact cells. Please calculate the expected size of the PCR product from the region with a successful knock-in. Give your answer in base pairs, and round to the nearest whole number. Just enter the number, nothing else.

Please explain how you arrived at your answer to the previous question.

Question 3

Kevin and his two brothers have a disease that causes the degeneration of retinal ganglion cells and their axons, leading to loss of central vision. Kevin's physician decides to do a genetic investigation, and the results show that there is a 3460 (G-to-A) point mutation in a gene. Kevin then undergoes an expensive genetic correction process via retroviral insertion to resolve this point mutation in every diploid cell in his body, which also corrects 50% of all haploid cells in his body. Kevin then fathers three young children with two different mothers, both of whom started wearing glasses at a young age. What is the probability that Kevin will pass his genetic defect to any of his three children? Give your answer as a percentage, rounded to the nearest whole number. Just enter the number, nothing else.

_Note: It will help to first identify Kevin's condition.

Please explain how you arrived at your answer to the previous question.

Question 4

Suppose there is only one pair of alleles that control the eye color in Nifflers. Eyes can be white, grey, red, blue, and purple. Red and blue are each caused by a dominant allele. Purple eyes occur when combining red and blue alleles. Grey and white eyes are due to recessive alleles. In a distantly related species, grey is found to be dominant over white; however, it is observed that white-eyed and grey-eyed Nifflers cannot be bred together, as the young all die in utero.

_The number of different alleles for this gene is the minimum possible number consistent with the information above. How many possible combinations of alleles are there for this gene in an adult Niffler? Round your answer to the nearest whole number. Just enter the number, nothing else.

Please explain how you arrived at your answer to the previous question.

Question 5

A dog breeder is attempting to retain desirable traits in the offspring of the next mating pair. Soft fur (S), green eyes (G), and happy temperament (H) are the desired traits and are dominant to coarse fur (s), brown eyes (g), and grumpy temperament (h), respectively. All three loci are known to assort independently. In a cross of Ss Gg HH with SS Gg Hh, what proportion of the offspring will have a minimum of two of the three desired traits? Give your answer as a percentage, rounded to the nearest whole number. Just enter the number, nothing else.