Biology 1001A Lecture Notes - Lecture 20: Inbreeding, Heterozygote Advantage, Allele Frequency

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emeraldcattle11

7 May 2018

School

Western University

Department

Biology

Course

Biology 1001A

Professor

Beth Mac Dougall- Shackleton

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Use HW principle to infer evolutionary mechanisms.

1.) In a pond of 100 fish: 16 are black (genotype BB), 48 are gray (Bb) and 36 are white (bb), what can

you reasonably conclude about selection at this locus?

A. Selection probably favours b allele

B. Selection probably favours heterozygotes

C. Selection is probably not occurring

Is population in HWE?  p = 0.4, q = 0.6 (0.42 = expeted geotpe feue of BB…)

Observed and Expected correspond so population is in HWE, so selection is not occurring

2.) In a flock of 100 birds, 5 have red feathers (Genotype RR), 90 have purple feathers, (Rr) and 5 have

blue feathers (rr). Which of the following is most likely?

A. f(r)= f(R), so selection is not operating on feather colour (red herring, just because allele

frequencies are equal to 0.5 and 0.5 does not mean selection is not occurring  this situation

ould ou i heteozgote adatage (o dissoiatie atig fo feathe olou ut e do’t

worry about that b/c it is not selection), the only way to see if selection is not happening is to

see if the population is in HWE or not. (Selection acts on phenotypes, not genotypes/alleles!)

B. The population is extremely inbred

C. selection at this locus favours heterozygotes

Population is not in HWE and there are much more observed heterozygotes than expected so

heterozygote advantage is most likely happening

3.) In a cave of 100 bats, 81 have long claws (CC) 18 have short claws (Cc) and one has no claws (cc).

Which explanation is most likely?

A. The bat without claws is a mutant

B. The bat without claws has immigrated from another population

C. Long-clawed bats have the highest relative fitness (seletio is’t happeig eause pop. is i

HWE)

D. All genotypes have equal relative fitness (If the hae the sae elatie fitess should’t the

number of individuals with each genotype be the same?  No! because expected genotype

frequencies - number of individuals with each genotype - depends on the allele frequencies of

original population, not the relative fitness of the genotype) (i.e. just because a population has

an equal relative fitness does not mean that each genotype/phenotype occurs in the same

number of individuals)

Population is in HWE. (selection is not happening, so all genotypes have equal relative fitness).

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Document Summary

P = 0. 4, q = 0. 6 (0. 42 = expe(cid:272)ted ge(cid:374)ot(cid:455)pe f(cid:396)e(cid:395)ue(cid:374)(cid:272)(cid:455) of bb ) Observed and expected correspond so population is in hwe, so selection is not occurring. In a flock of 100 birds, 5 have red feathers (genotype rr), 90 have purple feathers, (rr) and 5 have blue feathers (rr). Population is not in hwe and there are much more observed heterozygotes than expected so heterozygote advantage is most likely happening. In a cave of 100 bats, 81 have long claws (cc) 18 have short claws (cc) and one has no claws (cc). Which explanation is most likely: the bat without claws is a mutant, the bat without claws has immigrated from another population, long-clawed bats have the highest relative fitness (sele(cid:272)tio(cid:374) is(cid:374)"t happe(cid:374)i(cid:374)g (cid:271)e(cid:272)ause pop. is i(cid:374) Population is in hwe. (selection is not happening, so all genotypes have equal relative fitness).

Related Questions

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 Frankâs roses are pink? (Assume HWE.)
A. 18
B. 21
C. 42
D. 84
âE. 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
ââE. 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

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Biology 1001A Lecture Notes - Lecture 20: Inbreeding, Heterozygote Advantage, Allele Frequency

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