BIOL1003 Lecture Notes - Lecture 7: Lactase Persistence, Genetic Drift, Myxoma Virus

1. If an individual has a genotype of Bb, what types of gametes (sperm/egg) could they produce?
A) B
B) b
C) B or b
D) Bb, BB, bb
E) Bb

2. Which of the following statements is true about phenotypic plasticity, i.e., phenotype variation that is the result of genotype by environment interactions?
A. Phenotypic plasticity is only favored when the parental environment is a good predictor of the offspring environment
B. Since the trait expression of a genotype varies across environments, it cannot respond to selection
C. A variable environment is required for phenotypic plasticity to be selected for
D. A single trait can only ever be plastic or non-plastic within a species
E. Phenotypic plasticity can only occur within a single generation, never across generations

3. With large numbers of genes contributing to variation for a phenotypic trait (e.g. height in humans), the population approaches what kind of distribution for that trait?
A. Mendelian
B. Exponential
C. Binomial
D. Normal
E. Continuous

4. A classic example of phenotypic plasticity is caste determination in social insects. Whether a female ant becomes a worker, soldier, or queen is determined by the food she is fed. Would you say this this an example of G, E, or GxE?

5. In an infinite population, the frequency of the A allele is 0.3 and the frequency of the a allele is 0.7. What is the frequency of heterozygotes?
A. .10
B. .21
C. .30
D. .42
E. .70

6. Blue eyes are a recessive trait caused by an autosomal allele. If there are 180 people with blue eyes in a population of 500 people, what is the frequency of the brown-eye allele? (Assume HWE)
A. .36
B. .40
C. .50
D. .60
E. .64

7. Imagine flower color in diploid roses is determined by a single gene with two alleles, white and red, which are co-dominant so that heterozygotes are pink. Frank is colorblind and can only discriminate between white and colored roses, and knows that his population has 18 white roses and 182 non-white roses. How many of Frank’s roses are pink? (Assume HWE.)
A. 18
B. 21
C. 42
D. 84
​E. 100

8. Imagine flower color in diploid roses is determined by a single gene with two alleles, white and red, which are co-dominant. If Eva's population has 250 white roses, 500 pink roses, and 250 red roses, what is true about this population?

A. It is not in Hardy-Weinberg equilibrium
B. It is under balancing selection
C. It is connected to another population by migration
D. It is in Hardy-Weinberg equilibrium
​​E. White is a recessive lethal

9. 9% of a population is unable to taste the compound PTC, which is a recessive trait. Assuming HWE, if two carriers of the non-tasting allele had a baby what is the probability that it would be unable to taste PTC?
A. 0.09
B. 0.25
C. 0.30
D. 0.50
E. 0.70

10. (Adapted from: Christensen, A. C. (2000). Cats as an aid to teaching genetics. Genetics, 155(3), 999-1004.) ss cats have no white fur, Ss cats generally have <50% white fur, and SS cats generally have >50% white fur (cats who are 100% white are scored as dominant white and can't be scored for piebald spotting). The S allele is incompletely dominant, but variably expressed, so there is a more-or-less continuous gradient of white pigmentation in populations. You and your friends score all non-white cats up for adoption: http://www.adoptapet.com/cat-adoption/search/50/miles/48824 and find there are 160 with >50% white fur, 350 with <50% white fur, and 490 with no white fur. Which of the following statements is definitely true:

A. The population is in Hardy-Weinberg equilibrium
B. The population is not in Hardy-Weinberg equilibrium
C. There is selection acting on the population
D. It is impossible to know if the population is in Hardy-Weinberg equilibrium
E. Fur color is not a heritable trait and therefore cannot evolve

Evolution naturally produces better features: stronger muscles,teeth and minds. Killing the weakest, evolution wipes defectivegenes out of populations.

The mutations are necessary for advance. However, they arerandom and, thus, mostly negative. Right? How does the natureeliminate them from the population?

I see that one mechanism is polygamy: male have higher mutationrates. They tend to reproduce as much as possible. Female havelower mutation rates, they couple with only with best men andcontribute much more to their offsprings. So, men generate as muchrandom solutions as possible, whereas the role of female is toconserve the best of them. This means that the most of the male(bad mutations) die unreproduced. This eliminates the bad mutationsand favours the progress of good qualities. The higher animalsstarted to form harems and tournaments over their ownership. Thisfurther fosters the elimination of weak men and profileration ofstrong genes. However, human monogamy has disabled this selectionmechanism. Best men are dedicated to only one woman. Other womencannot mix their genes with other good genes from previousgenerations. They are forced to look at the low quality men, whocarry degenerate mutations. Might be it is monogamy that makes ushuman but it implies that all genes reproduce.

Yet 100 years ago it was not a big deal since we still hadanother filter: our grandfathers were born in families that hadnormally 10 children (I am speaking about Russia) and only 2-3survived until reproduction (the population increased reallyslowly). I bet that those who survived had really good health:thanks to the bad health and immense selection pressure, thenegative mutants are eliminated immediately and populationmaintains a perfect genome (aka biologic health). Killing moreweakest in the current generation improves the health of nextgenerations.

However everything has changed during the 20th century. Theadvances in economy and medicine have almost eliminated theselection. The selection pressure has relaxed to essentially zeroso that everybody survives and leaves the same amount of offspring(and some scientists are even concerned that degradatoryindividuals leave more offsprings than the prosperous ones). Wehave even eliminated the infant mortality. We use baby incubatorsso that the people with the weakest health could survive andreproduce as normal and we are proud of it. It may sound strangebut the mutation rate has not changed at all. Does it mean that thehuman genome is in danger?

I see the situation like you have inherited a perfect mechanismand decided not recovering it from the inevitably adverse action ofentropy, that degrades it constantly. There is a constant chance,d, that every good gene is affected by a mutation. It is afraction of healthy genes that will fail passing to the nextgeneration. This will leave only (1-d) genes healthy inthe next generation. The fraction of healthy genes will melt like1, (1-d), (1-d)