Biology 1201A Lecture Notes - Lecture 14: Zygosity, Allele Frequency, Heterozygote Advantage

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16 Nov 2015

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November 11 + 16, 2015: selection in which the heterozygous phenotype has the highest fitness, ultimately better to be heterozygous, what has to be true about inheritance patterns is: must be incomplete dominance or codominance. There is another allele for sickle allele, what happens within it is a consequence that the red blood cells are not shaped the ways it should. Heterozygote advantage, will have higher fitness so it must be greater than 0. 5. So it will be a value of 1. 0 because the others are set in relativity to the highest fitness. Allele: f(r) = f(s) = 0. 5 *approximately. Genotype wrr = wss: rr = 0. 23, rs = 0. 58. Homozygous r individuals are experiencing more death due to the wolves. 80% of the red pigs will end up dying due to wolves. The red spotted ss will die a little bit of the wolves, because their fitness is less than 1 but higher than the homozygous r.

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Part 1 - Mendelian Genetics Review

Match the example with the type of inheritance.

A) Complete dominance B) Incomplete dominance C) Codominance

_______Pea shape in garden pea plants: The W gene encodes for an enzyme that synthesizes starch granules in peas. The w gene encodes for a dysfunctional enzyme that will not synthesize the starch granules. The presence of starch granules makes the seeds round, and the absence of the starch granules results in wrinkled seeds. Heterozygotes have only half as many starch granules, yet that is enough to make the seeds round.

_______Piebald (white) spotting in cats: Cats homozygous for the s allele do not have any white spots. Cats with the S allele are completely white. Cats that are heterozygous (Ss) are about 50% white.

________ Sickle-cell anemia in humans: Heterozygotes have one copy of the wild-type hemoglobin and one copy of the mutant hemoglobin. Phenotypically, heterozygotes have about half the number of sickled red blood cells as
homozygotes do.

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Questions 4-6. Sickle cell disease:
Sickle cell disease (sickle cell anemia) is a relatively common disorder in individuals of

African descent and affects approximately 1 in 500 African-Americans. Due to a mutation in an autosomal gene for hemoglobin, the homozygous recessive genotype leads to red blood cells that are relatively stiff and sticky, and deform into a sickle shape as they lose oxygen. This leads to problems in the spleen, and anemia.

There are hundreds of different hemoglobin alleles. Individuals heterozygous for the sickle cell allele and one non-sickle cell allele usually do not experience major complications or even noticeable symptoms. A genetic test is available to diagnose carriers.

James does not have sickle cell disease, neither does his mother or father, but his sister does. His wife Natasha does not have sickle cell disease, and neither of her parents does either. Natasha also has a sister who has sickle cell anemia and two brothers without the disease.

5.) If James and Natasha have a child, what is the probability that the child would be a homozygote for the recessive allele and have sickle cell disease? You may draw the Punnet square but please solve the problem using probability calculations, then explain your reasoning in 2-5 complete sentences.

cyanalligator893

Q1. What are alleles?Different forms of the same gene.Different genes.The different characteristics of an organism.Genes found only in humans.Q2. If you add up the frequency of homozygotes + the frequency of heterozygotes for one gene (i.e. at one locus) in a population, what number do you get?Q3. People who are heterozygous for the sickle-cell allele:Are susceptible to malaria but not sickle-cell anemia.Are susceptible to sickle-cell anemia but not malaria.Are not susceptible to either sickle-cell anemia or malaria.Are susceptible to both sickle-cecell anemia and malaria.Q4. In the case study in this lab, which genotype is represented by "2pq" in the Hardy-Weinberg equation?Homozygous HbAHomozygous HbSHeterozygous HbA/HbSNo specific genotypeQ5. Suppose that, in an isolated village, the proportion of individuals that have sickle-cell anemia is 0.1 (or 1 of every 10 people). What proportion of the population should be sickle-cell carriers, according to Hardy-Weinberg expectations?Q6. When you simulated the elimination of malaria at the beginning of the lab, once the allele frequencies stabilized, what was the frequency of the HbA allele?Q7. When you investigated regional differences, what was the frequency (over many generations) of the HbS allele in the village in the "slightly wet" part of Africa?Q8. What is the number of deaths due to sickle-cell anemia in a region without mosquitoes expected to be?Very lowVery highModerateRelated to the frequency of malaria allelesQ9. As long as there are multiple alleles of a gene in a population, why will the frequencies of the alleles always change over time?Because natural selection changes all allele frequencies in populations over time.Because genetic drift causes random fluctuations of allele frequencies in populations.Because diseases will eliminate some of the alleles, generating fluctuations in their frequencies.Because allele frequencies fluctuate before the alleles eventually become fixed.Q10. Imagine a huge population with a gene that has ten functionally equivalent, neutral alleles. A small but genetically representative group of individuals from the big population is transported to an island, forming a small population. Which of the statements below best describes what will likely happen over time, and why?Because natural selection doesn't act on neutral alleles, the frequencies in the two populations should remain the same over time.Genetic drift will cause one allele to first become fixed in the island population, and later to become fixed in the original, large population.Genetic drift will result in the allele frequencies of the two populations diverging over time, with alleles being lost sooner in the island population.The allele frequencies of the two populations will change similarly due to a combination of genetic drift natural selection.

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Biology 1201A Lecture Notes - Lecture 14: Zygosity, Allele Frequency, Heterozygote Advantage

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