2. Mendel's Laws of Inheritance

An experienced goldfish breeder receives two unusual male goldfish. One is black rather than gold, and the other has a single tail fin rather than a split tail fin. The breeder crosses the black male to a female that is gold. All the F₁ are gold. She also crosses the single-finned male to a female with a split tail fin. All the F₁ have a split tail fin. She then crosses the black male to F₁ gold females and, separately, crosses the single-finned male to F₁ split-finned females. The results of the crosses are shown below.

   Black male x F₁ gold female:
        Gold                 32
        Black                34
   Single-finned male x F₁ split-finned female:
        Split fin              41
        Single fin           39

What do the results of these crosses suggest about the inheritance of color and tail fin shape in goldfish?

Which of the following Mendel's postulates states that alleles separate in the formation of gametes?

Breeding two pure-lines of yellow-seeded flowers will always produce yellow-seeded offspring

What is the official genetics term for the second generation of offspring?

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

a polymorphic trait and a polymorphic gene

For parts (a), (b), and (c) of this problem, 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. For parts (d) and (e), give the information requested.

progeny of the cross Rt/rT×rt/rt

For parts (a), (b), and (c) of this problem, 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. For parts (d) and (e), give the information requested.

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

For parts (a), (b), and (c) of this problem, 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. For parts (d) and (e), give the information requested.

DFg/DFG

For parts (a), (b), and (c) of this problem, 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. For parts (d) and (e), give the information requested.

aBc/abC

For parts (a), (b), and (c) of this problem, 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. For parts (d) and (e), give the information requested.

AB/ab

Reciprocal crosses of experimental animals or plants sometimes give different results in the . 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)?

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.