Biology

1. A plant with red flowers is crossed with a white-flowered plant of the same species. All the seeds, when grown, produce plants with red flowers. Assuming that the flower color is controlled by a single pair of alleles, which allele is dominant and which is recessive?

2. How does inbreeding increase the incidence of recessive disorders in a population?

3. In cats, the allele (S) for short fur is dominant to the allele (s) for long fur. What is the phenotype of a cat with the genotype Ss?

4. The genetic disorder phenylketonuria (PKU) is caused by a recessive allele (n). The family tree below shows the incidence of the disease over three generations. What are the chances that Peter is the carrier of the PKU allele that resulted in his having an affected son?

5. In cats, the allele (S) for short fur is dominant to the allele (s) for long fur. In an Ss genotype, which allele is expressed in the phenotype?

6. When a particular gene is said to be ‘sex-linked’, on which chromosome is that gene usually present?

7. In cats, the allele (S) for short fur is dominant to the allele (s) for long fur. Which of the following genotypes is (i) heterozygous (ii) homozygous dominant? SS, Ss, ss

8. Why does an individual always have only two alleles for a given gene?

9. The genetic disorder phenylketonuria (PKU) is caused by a recessive allele (n). The family tree below shows the incidence of the disease over three generations. What is the genotype of Jane’s husband?

10. In cats, the allele (S) for short fur is dominant to the allele (s) for long fur. What is the genotype of a true-breeding, long-furred cat?

11. The genetic disorder phenylketonuria (PKU) is caused by a recessive allele (n). The family tree below shows the incidence of the disease over three generations.

What are the genotypes of the grandparents?