Question

an individual that has an allele for a autosomal recessive disorder but does not display the disorder is called a ____. a. mutate b. carrier c. drone d. hologram value: 10 if you cross a carrier individual for marfans syndrome with a homozygous normal individual, what is the chance of getting offspring with marfans syndrome (autosomal recessive)? a. 0 % b. 25% c. 50% d. 75% e. 100% value: 10 if you cross two carriers for marfans syndrome, what is the chance of getting offspring with marfans syndrome? a. 0 b. 25% c. 50% d. 75% e. 100%

Explanation:

1. An individual with an allele for an autosomal - recessive disorder but no symptoms is called a carrier. A carrier has one normal allele and one mutant allele.
2. Let the allele for Marfans Syndrome be represented by 'a' and the normal allele by 'A'. A carrier has the genotype 'Aa' and a homozygous normal individual has the genotype 'AA'. When Aa x AA is crossed, the possible genotypes of the offspring are AA and Aa. None of the offspring will have the 'aa' genotype (the genotype for Marfans Syndrome), so the probability is 0%.
3. When two carriers (Aa x Aa) are crossed, using a Punnett - square, the possible genotypes of the offspring are AA:Aa:aa in a ratio of 1:2:1. The 'aa' genotype represents the offspring with Marfans Syndrome, so the probability is 25%.

Answer:

1. b. Carrier
2. a. 0%
3. b. 25%