31) What is nondisjunction?

A) failure of sperm and egg to fuse in fertilization

B) failure of cells to divide by cytokinesis in meiosis

C) failure of chromosomes to duplicate before mitosis or meiosis

D) failure of homologous chromosomes or sister chromatids to separate in meiosis

E) an extra duplication of the chromosomes before mitosis or meiosis

32) In humans, aneuploidy is fairly common yet goes largely unrecognized as a genetic problem. This is because:

A) it produces autosomal recessive individuals who don’t always express the disorder.

B) its effects are usually hidden.

C) it actually produces healthy individuals.

D) it often results in miscarriage of embryos.

33) Down syndrome in humans is caused by:

A) an extra X chromosome.

B) an extra y chromosome.

C) three copies of chromosome 21.

D) three copies of chromosome 13.

E) a single copy of chromosome 21.

34) Aneuploid human embryos are least likely to survive except those involving:

A) chromosome 1, 2, 3, X, Y.

B) chromosome 1, 2, 3, 4, 5.

C) chromosome 13, 18, 21, X, Y.

D) chromosome 6, 7, 8, 9, 10.

E) chromosome 11, 12, 14, 15.

35) If a diploid cell from an organism has 46 chromosomes, how many chromosomes are likely to be found in a gamete that is the result of nondisjunction?

A) 46 or 92

B) 23 or 22

C) 21 or 22

D) 22 or 24

E) 24 or 25

36) A woman is missing one of her X chromosomes. With which of the following conditions would she be diagnosed?

A) Turner syndrome

B) polyploidy

C) a chromosomal deletion

D) Klinefelter syndrome

E) cancer

37) A person with the genotype XO is mainly female, phenotypically. A person with the genotype XXY is mainly male. What can you conclude about the Y chromosome?

A) It has the same genes as X, just different alleles.

B) It has the same genes as X, in different orientation.

C) A Y chromosome confers maleness, regardless of the number of X chromosomes.

D) The only genes it carries are for female development.

E) A human cannot survive without a Y chromosome.

38) If a zygote has the genotype XYY, how many total chromosomes were in the sperm before it fused with the egg?

A) 20

B) 21

C) 22

D) 23

E) 24

39) Nondisjunction of the X chromosomes may occur during formation of gametes and produce two kinds of eggs. If normal sperm fertilizes these two kinds of eggs, which of the following pairs of genotypes are possible?

A) XX and XY

B) XXY and XO

C) XYY and XO

D) XYY and YO

40) Which condition or disease is caused by aneuploidy?

A) sickle-cell anemia

B) hemophilia

C) malaria

D) color blindness

E) Down syndrome