Overview Forces responsible for genetic variation mutation de novo mutation rates constant among populations intrinsic error rate in DNA polymerase founder effect if one member of a small community carries a triat, as the population expands there will be a higher frequency of that trait in the new community than there is in the general population Ex.) Pennsylvania Amish and Ellis-van Creveld syndrome genetic drift a dramatic change in allele frequency based on chance small populations are more vulnerable to genetic drift natural selection ↑ in allelic frequency that ↑ species fitness ↓ in allelic frequency that ↓ species fitness some genes ↑ species fitness as heterozygote but ↓ species fitness as a homozygote ex.) sickle cell trait lowers malarial infections, while sickle cell anemia is detrimental bottleneck Even when fitness is equal for all phenotypes, a population bottleneck can result in disrupted allelic frequencies or loss of a genotype all together by chance gene flow transfer of alleles from one population to another Hardy-Weinberg equilibrium states that genotype and allele frequencies remain constant through generations disease prevalence equation p2+ 2pq + q2 = 1 where p = frequency of allele A where q = frequency of allele B p2 = frequency of homozygous individuals for allele A q2 = frequency of homozygous individuals for allele B 2pq = frequency of heterozygotes requirements for validity large population random mating the genotypic frequencies of the population will remain stable from generation to generation assumptions no mutation no selection for any of the genotypes at the locus no migration other notes prevalence of an X-linked recessive disease in males = q prevalence of an X-linked recessive disease in females = q2 possible to assume in most cases that p = 1 as the wild-type allele is approximately 1
QUESTIONS 1 of 6 1 2 3 4 5 6 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.BC.14.27) A 21-year-old female presents to the clinic requesting prenatal counseling. She was born with a disease that has led her to have recurrent upper respiratory infections throughout her life requiring antibiotic prophylaxis and chest physiotherapy as well as pancreatic enzyme replacement therapy. She marries a man (without this disease phenotype) from a population where the prevalence of this disease is 1/100. What is the chance that their child will have the disease of interest? QID: 107015 Type & Select Correct Answer 1 9/100 41% (16/39) 2 1/10 21% (8/39) 3 18/100 18% (7/39) 4 81/100 8% (3/39) 5 9/10 8% (3/39) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (M1.BC.14.27) Red-green color blindness, an X-linked recessive disorder, has an incidence of 1/200 in males in a certain population. What is the probability of a phenotypically normal male and female having a child with red-green color blindness? QID: 107024 Type & Select Correct Answer 1 1/200 19% (50/260) 2 199/200 5% (14/260) 3 1/100 15% (39/260) 4 1/400 47% (123/260) 5 99/100 7% (19/260) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic
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