Study Guide Answers: Genetics
1. Mendel self-pollinated different varieties of pea flowers for several generations to produce
true-breeding P generations. Then, he cross-pollinated P generation plants with contrasting
forms of a character and recorded the number of F1 plants expressing each trait. He also
self-pollinated F1 plants and recorded the number of F2 plants expressing each trait.
2. Mendel was the first to develop rules that accurately predict patterns of heredity.
3. Genes are pieces of DNA that code for a particular character. Alleles are the alternative
versions for each gene.
4. The Bb rabbit has a black coat and the bb rabbit has a brown coat.
5. They are 50% black and 50% brown. One parent who is heterozygous gives one dominant in
two crosses and give the recessive in the other two.
6. Cross Ff and Ff. 3:Freckles1: no freckles; 1FF:2Ff:1ff
7. Humans who inherit sex chromosomes from both mother and father are female. Humans
who inherit an X from the mother and a Y from the father are male. The SRY gene on the Y
chromosome appears to trigger testis development. In the absence of this gene, an
individual develops ovaries and is female. In grasshoppers and crickets, an individual with
one sex chromosome (XO) is male and one with two (XX) is female. Sperm cells with or
without sex chromosomes determine the sex of the offspring. In ants and bees, diploid
individuals are female and haploid are male.
8. The male receives from his mother an X chromosome with a mutated blood-clotting gene.
9. A genetic disorder results when a mutation is inherited and the mutation produces harmful
effects.
10. Many genetic tests detect conditions (Huntington’s disease) that are not yet treatable. Does
every afflicted individual need or want to know? If so, then what? Tests should always be
accompanied by counseling. Is this always the case? Are there enough counselors? What
about the “do yourself tests” from mail orders or online labs? A “bad” result might
stigmatize an individual. Could this person lose their job or be denied health or life
insurance? Will genetic testing only be available to those who can afford it?