12 The Chromosomal Basis of Inheritance

Question 1

What name is given to the most common phenotype in a natural population?

Answer 1

wild type

Question 2

In humans, what determines the sex of offspring and why?

Answer 2

The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome.

Question 3

Which of the following is true of an X-linked gene, but not of a Y-linked gene?

Answer 3

The gene is present in both males and females.

All cells have at least one functional X chromosome

Question 4

What is a nondisjunction?

Answer 4

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell

Question 5

When can nondisjunction occur? Choose the best answer.
All three answers are correct.
In meiosis, when homologous chromosomes fail to separate
In mitosis, when sister chromatids fail to separate
In meiosis, when sister chromatids fail to separate

Answer 5

All three answers are correct
Nondisjunction errors can occur in meiosis I, when homologous chromosomes fail to separate, or in either mitosis or meiosis II, when sister chromatids fail to separate.

Question 6

Which syndrome is characterized by the XO chromosome abnormality?

Answer 6

Turner syndrome

Turner syndrome is characterized by a chromosome pattern of XO, or one X chromosome and no Y chromosome.

Question 7

Of the following chromosomal abnormalities, which type is most likely to be viable in humans?
 1 Monosomy
 2 Triploidy
 3 Haploidy
 4 Trisomy

Answer 7

Trisomy