2. Mendel's Laws of Inheritance

Describe Mendel's conclusions about how traits are passed from generation to generation.

Compare and contrast the terms in each of the following pairs:

A polymorphic trait and a polymorphic gene

Give the information requested.

Progeny of the cross Rt/rT×rt/rt

Give the information requested.

The gametes produced by an organism with the genotype Rt/rT

Draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written.

DFg/DFG

Draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written.

aBc/abC

Draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written.

AB/ab

Reciprocal crosses of experimental animals or plants sometimes give different results in the F₁. What are two possible genetic explanations? How would you distinguish between these two possibilities (i.e., what crosses would you perform, and what would the results tell you)?

Write a short essay that correlates Mendel's four postulates with what is now known about genes, alleles, and homologous chromosomes.

For the retinal cancer retinoblastoma, the inheritance of one mutated copy of RB1 from one of the parents is often referred to as a mutation that produces a 'dominant predisposition to cancer.' This means that the first mutation does not produce cancer but makes it very likely that cancer will develop.

What is the genotype of a normal cell in the retina in a person who has sporadic retinoblastoma? What is the normal cell genotype if the person has hereditary retinoblastoma? Explain the reason for the difference between the genotypes.

For the retinal cancer retinoblastoma, the inheritance of one mutated copy of RB1 from one of the parents is often referred to as a mutation that produces a 'dominant predisposition to cancer.' This means that the first mutation does not produce cancer but makes it very likely that cancer will develop.

Using RB1⁺ for the normal wild-type allele and RB1⁻ for the mutant allele, identify the genotype of a cell in a retinoblastoma tumor.

Which of Mendel's postulates are illustrated by the pedigree that you constructed in Problem 3? List and define these postulates.

What advantages were provided by Mendel's choice of the garden pea in his experiments?

An organism has alleles R₁ and R₂ on one pair of homologous chromosomes, and it has alleles T₁ and T₂ on another pair. Diagram these pairs of homologs at the end of metaphase I, the end of telophase I, and the end of telophase II, and show how meiosis in this organism produces gametes in expected Mendelian proportions. Assume no crossover between homologous chromosomes.

Which of Mendel's postulates can only be demonstrated in crosses involving at least two pairs of traits? State the postulate.