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# lecture answers - Name Class unique number Practice...

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Unformatted text preview: Name Class unique number Practice Problems on Allele Frequencies and Population Genetics 1. lfthe alleles for a certain trait (single locus, simple dominance) had frequencies of p = 0.7 and q = 0.3, then (a) what is the frequency of homozygous recessive individuals? q2 = .91 . (b) What is the frequency of heterozygous individuals? 2pq = , Lia . (c) If this trait was determined for ngL individuals randomly chosen from the population, how many would show the recessive trait? 5i (.11;- L, Eye 2591;: gob ‘ . 3 _ ‘ l in pa 2, Within a population of butterflies, the color brown (B) is dominant over the color white (b), and 25% of all butterflies are white. Given this simple information, calculate the following: (a) the percentage of butterflies in the population that are heterozygous (b) the frequency of homozygous dominant individuals. ‘-.’\T: z r ~._‘-. , bu D, i " , ,S‘Fp‘w ii 3. In a population of mice, 4% (0.04) of the individuals are albino (phenotype showing simple recessive trait, so their genotype is aa), and the rest are all agouti brown (phenotype showing the dominant trait A). (a) what is the frequency of the agouti allele A? .. '3’! (allele frequency) (b) what is the frequency of the white allele 3’? t 3 (allele frequency) (c) what proportion of those mice are heterozygotes (Aa)? oBZ. (genotype frequency) (d) what proportion of those mice are homozygous dominant? .mLI (genotype frequency) (e) In a sample of 50 mice taken from this population, how many mice would be expected to show the dominant trait? 53’ (number of individuals showing A trait) 7 z i \ . . u? a * IN ’\ ’ C.,\ —-. ‘, _. 'A‘ If} — - J \‘1 :\: Q \‘ t: u x- H a t c I: /‘ i: ._ . - e JO “ C“ ‘ l; _ ,‘t ’J’: 4. [source KSU] Sickle-cell anemia is due to a recessive allele, alternative form of hemoglobin. Normal homozygous individuals (88) have normal blood cells that are easily infected with the malarial parasite, and many die from the parasite. Individuals homozygous for the sickle—cell trait (ss) have red blood cells that readily collapse (“sickle”) when deoxygenated. Although malaria cannot grow in these red blood cells, individuals often die from sickle cell anemia. Individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but generally not enough to cause disease. In addition, malaria parasites cannot survive well Within the red blood cells. Thus, heterozygotes tend to survive better than either of the homozygous conditions in regions with malaria. If 9% of an African population is born with a severe form of sickle—cell anemia (ss), what percentage of the population will be more resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene? .3 7 , i 3 a 13:, .: f‘ 3 ~ tuft“ : L-(Wg 5}: ‘.\ Al.) x — V n 5. Cystic fibrosis (of) is the most common lethal gene in people of Caucasian descent, particularly those of northern European ancestry. One in 2000 Caucasian live births is a baby with cystic fibrosis (50, the frequency of homozygous recessives is 1/2000 2 0.0005. Cf is due to a recessive allele, which produces a nonfunctional chloride ion channel regulatory protein and a deadly accumulation of mucous in multiple organs including the |ungs.(a) If 100 people were randomly selected from a population having that frequency of cystic fibrosis, how many people in the group would be heterozygous carriers of the cystic fibrosis gene? (q = square root of 1/2000 = 0.022, so What is p?) Ci“ 2F: LCJ) A /s m .ij of “ x , WA ‘ 5’ Lt *1. a >10 \ _ ‘ d. \: Eye0\5\ K» “ LW* 7 e , ...
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