10. Consider the simplified scenario for genetic determinants ofheight in humans, where there are three genes (A/B/C) with varyingnumbers of alleles (3/3/2) affecting height, and with differenteffects in males and females. (Assume additive contributions, thusthe effect of having genotype A1A2 is +0.1†+ +0.2†= +0.3â€).Average height for men and women is 69†and 64â€.
Gene | Allele | Male(effect | Female(effect |
A | 1 | +0.1 | +0.1 |
| 2 | +0.2 | +0.2 |
| 3 | 41.3 | 41.5 |
B | 1 | +0.5 | +.3 |
| 2 | 40.4 | 40.2 |
| 3 | 40.1 | 40.1 |
C | 1 | 42 | +1.5 |
| 2 | +0.1 | 0 |
| | | |
What is the expected height for a male with genotypeA2A2B1B3C1C2 (3 points)?
11. Consider a cross between two heterozygotes.
What is the probability that their first offspring has recessivephenotype? (2 points)
What is the probability that their first offspring has recessivephenotype and the second offspring also has the recessivephenotype? (2 points)
What is the probability that out of their first offspring, onehas dominant phenotype and one has recessive phenotype? (2points)
15. The gene for petal color in a flower has incompletedominance, so that individuals with two A1 alleles (A1A1) areblack, individuals with two A2 alleles (A2A2) are white, andindividuals with one of each allele (A1A2) are mottled.
In a cross between two black flowers, what is the probability ofgetting a mottled offspring? (2 points)
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In a cross between a black flower and a mottled flower, what isthe probability of getting a black offspring? (2 points)
In a cross between two mottled flowers, if there are twooffspring, what is the probability of getting one black offspringand one mottled offspring? (2 points)
In a cross between two mottled flowers, if there are twooffspring, what is the probability of getting one white offspringand one mottled offspring? (2 points)
In a cross between two mottled flowers, if there are nineoffspring, what is the probability of getting exactly three mottledoffspring? (2 points)
16. Two individuals that are heterozygous for a recessiveautosomal trait have an offspring with dominant phenotype. What isthe probability that that offspring is a carrier (heterozygote?) (3points)
If that offspring has an offspring with an individual with therecessive condition, what is the chance their offspring has thecondition? (2 points)
17. Most randomly occurring mutations that occur in humans donot have an effect on phenotype. Why is this? (4 points)
18. Imagine that coronavirus has a 0.002% incidence in thepopulation. A test for the virus has a 0.001% false positive rateand no false negative rate (false positive rate means the chancethat if an uninfected individual takes the test the test willfalsely identify them as infected). If a random person takes thetest and gets a positive result, what is the chance that they areinfected? (Show your work to earn partial credit) (4 points)
Now consider the case in the future, where the incidence of thevirus has increased to 1%. Now if a random person takes the testand gets a positive result, what is the chance that they areinfected? (2 points)
19. Your colleague is studying long toes in the California vole(Microtus californicus). She proposes that this trait is due to toan X-linked dominant allele.
You go for a hike in Oakland, and notice that very few of theCalifornia voles you see have the long toe trait. Does this affectyour colleague’s hypothesis? How? Why? (2 points)
You go for a walk in Golden Gate Park, and notice that, amongCalifornia voles in the Golden Gate population, females are muchless likely than males to have the long toe trait. Does this affectyour colleague’s hypothesis? How? Why? (2 points)
20. You are a genetic counseler. A mother and father with a sonand a daughter come to see you. The mother and the father both havea very rare condition that no one has ever studied, but neithertheir son or their daugther does. Karyotype analysis shows that themother and the daugther are XX and the father and the son are XY.You think about it and realize that this pattern cannot be due to anumber of simple inheritance patterns. Explain why:
Why can’t it be an autosomal dominant condition? (2 points) Whycan’t it be Y-linked condition? (2 points)
Why can’t it be an X-linked dominant condition? (2 points) Whycan’t it be an X-linked recessive condition? (2 points) Why can’tit be a mitochondrial condition? (2 points)
