Inheritance：練習題

Which of the following describes an alternative form of a gene that occupies the same relative position on a pair of homologous chromosomes?

A cross is performed between two heterozygous tall pea plants (Tt). What is the expected phenotypic ratio of tall to short plants in the offspring?

A plant is homozygous for the dominant allele for tallness (T). If it is crossed with a short plant (tt), what is the expected phenotype of the \(F_{1}\) generation?

If a man with blood group O (genotype ii) and a woman who is homozygous for blood group A (genotype \(I^{A}I^{A}\)) have children, what is the probability that a child will have blood group A?

Which term describes the physical appearance or observable trait of an organism resulting from its genetic makeup?

State the sex chromosomes present in a normal human male body cell and state the sex chromosomes present in a normal human female body cell.

In pea plants, the allele for tall stems (\(T\)) is dominant over the allele for short stems (\(t\)).
State the expected phenotypic ratio of the offspring resulting from a genetic cross between a heterozygous tall pea plant (\(Tt\)) and a short pea plant (\(tt\)).

In a monohybrid cross between two heterozygous fruit flies with red eyes, the expected ratio of red-eyed to brown-eyed offspring is \(3:1\). However, when a scientist counts \(200\) actual offspring, the observed ratio is slightly different.
Explain why the observed ratio of phenotypes often differs from the expected theoretical ratio.

Genetic variation and mutations contribute to the diversity and health of a population.

(a) Distinguish between continuous variation and discontinuous variation, providing one example of each.

(b) Define mutation and name one environmental factor that can increase the rate of mutation in human cells.

In pea plants, the allele for tall height (T) is dominant over the allele for dwarf height (t).

(a) Define the terms phenotype and genotype.

(b) A heterozygous tall plant is crossed with a dwarf plant. Using a genetic diagram, predict the expected ratio of phenotypes in the offspring.