BIOL 1001 Lecture Notes - Lecture 12: Balancing Selection, Stabilizing Selection, Directional Selection

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31 Jan 2018

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In negative frequency-dependant selection, the frequency of a morph is always negatively correlated with its fitness. Its good to have a trait that"s rare. Higher chance of being eaten, lower fitness. The frequency of genotypes of a know gene can be calculated using the hardy-weinberg equation is false because the hardy equation can work if natural selection is not acting on it. If alleles are inherited together, they usually inherit the same thing (linkage) Different genes can be doing different things. Discrete character: either/or characters with distinct phenotype categories (traits) Population has a variation as ^, it is said to be a qualitative variation and it is a polymorphism; existence of qualitative variation in a population. Height, ski(cid:374) colour etc do(cid:374)"t have disti(cid:374)ct phe(cid:374)otypes; these are polyge(cid:374)ic characters because they have more than one gene involved. Width of a curve describes amount of variation in the population.

Related Questions

1. A) Explain how changes in the environment drive evolutionary change. B) Provide and explain an example

2. A) Explain how the Hardy-Weinberg equation allows us to find evidence of evolution. B) Could processes other than Natural Selection result in deviation from the Hardy-Weinberg equilibrium? List and explain each one: C) define what the process is and D) the effect it has on the allele frequency.

3. A gene that is responsible for multiple traits (pleiotropy), for example the same allele causes sickle-cell anemia and provides resistance to malaria. Would a gene that controls these two traits respond equally to natural selection favoring malaria resistance as a non-pleitropic gene that only controls malaria resistance? Explain your answer.

4. A) Explain how lack of genetic variation limits evolution and provide an example. B) Explain how epistasis limits evolution and provide an example

Questions 5-6 are based on the following:

Letâs say you are studying a population of Japanese four oâclock plants. In these plants, the allele for red color flower shows incomplete dominance over the allele for white flowers. This is very convenient for this experiment because you can distinguish the heterozygous (pink flowers) from the homozygous dominant (red flowers). For your experiment, you produced a large number of plants, 25% had red flowers, 25% had white flowers and 50% had pink flowers. You transplanted them into different habitats and left some in the lab (using the same proportions in all the habitats). You waited a few years, while plants reproduce for a few generations and then you go back and resample the populations youâve transplanted.

5. In the lab you ensured that all individuals receive all requirements to grow and reproduce and mate randomly. A) What do you expect the distribution of the phenotypes after a few generations breeding in the lab? B) Is the lab population in Hardy-Weinberg equilibrium? Yes/No, explain

6. In habitat A, you find that you only have red flowering plants and white flowering plants but there are no pink flowering plants. A) Is the population in habitat A in Hardy-Weinberg equilibrium? Yes/No, explain. B) Which one(s) of the five agents of evolutionary change could be responsible for these results? Explain. C) What type(s) of selection (stabilizing, disruptive, directional, oscillating, etc...) could be responsible for the results in habitat A? Explain

plumdonkey701

Please do not answer unless you plan on answering all parts of the question. Thank you very much. I really appreciate your help.

1a. (2 pts) Pandas use their thumb to strip off bamboo leaves, a main staple of their diet. A panda would be much better off with a human thumb, which is much more versatile than the pandaâs. Why then does the panda have an inferior thumb?

b. (2 pts) Why do some species of blind cave-dwelling fish have eyes? A million years into the future, do you expect these blind cave fish still have eyes? Why or why not?

c. (2 pts) In some fictional breeds of dog, tail length is correlated with eye color (long tailed animals typically have brown eyes; short tailed one have black eyes). I notice in feral populations of these dogs and individuals tend to mate assortatively on the basis tail length. If I examine the genetic underpinnings of eye color, should I expect to find this variation to be in Hardy-Weinberg Equilibrium?

d. (2 pts) Why is blending inheritance antithetical to the theory of natural selection?

e. (2 pts) Mendelian traits are discrete, discontinuous, but most of the variation â think, human height â we see in nature is continuous. How is it possible to reconcile these two observations?

f. (3 pts) In most cases in which the genetic basis of industrial melanism has been analyzed, the melanic colour pattern has been found to be due to a single dominant allele. In one study of a polluted area around Birmingham, UK, Kettlewell observed a frequency of 87% melanic Biston betularia. Assume that the population is now in Hardy-Weinberg Equilibrium and estimate the frequency of the dominant allele leading to melanism in this population, and the proportion of melanics that are heterozygous.

g. (2 pts) As populations crash in response to hunting and environmental degradation, endangered species are in danger of inbreeding. Explain why this is a problem.

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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BIOL 1001 Lecture Notes - Lecture 12: Balancing Selection, Stabilizing Selection, Directional Selection

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