X-Linked Inheritance and Phenotypic Outcomes in Fruit Flies

The video explains X-linked inheritance, focusing on how genes on the X chromosome are passed from parents to offspring. It covers the basics of sex chromosomes in humans and fruit flies, the concept of hemizygosity in males, and the different combinations of offspring based on parental chromosomes. The video uses fruit flies to illustrate how different alleles affect phenotypes, employing Punnett squares to predict outcomes. It introduces criss-cross inheritance, where male and female phenotypes switch across generations, and provides rules of thumb for understanding X-linked inheritance patterns.

What is the primary difference in chromosome composition between male and female organisms in terms of X-linked genes?

• Males have two X chromosomes.

• Females have two X chromosomes, while males have one X and one Y chromosome.

• Males have two Y chromosomes.

• Females have one X and one Y chromosome.

In fruit flies, what phenotype does the dominant W plus allele produce?

• Green eyes

• Blue eyes

• Red eyes

• White eyes

What is the phenotype of a male fruit fly with a recessive W allele on his X chromosome?

• Blue eyes

• White eyes

• Red eyes

• Green eyes

In a cross between a heterozygous red-eyed female and a red-eyed male, what is the expected phenotype of all female offspring?

• All will have blue eyes.

• All will have white eyes.

• All will have red eyes.

• Half will have red eyes, half will have white eyes.

In the same cross, what is the expected phenotype distribution among male offspring?

• Half will have red eyes, half will have white eyes.

• All will have white eyes.

• All will have red eyes.

• All will have blue eyes.

What is criss-cross inheritance?

• When male and female phenotypes remain the same across generations.

• When only male phenotypes change across generations.

• When male and female phenotypes switch from one generation to the next.

• When only female phenotypes change across generations.

In a cross between a white-eyed female and a red-eyed male, what is the expected phenotype of all male offspring?

• Half will have red eyes, half will have white eyes.

• All will have white eyes.

• All will have red eyes.

• All will have blue eyes.

What determines the genotype of male offspring in X-linked inheritance?

• The genotype of the male parent.

• The genotype of the female parent.

• The environment.

• Random chance.

If a male parent has a dominant phenotype, what will be the phenotype of all his female offspring?

• All will have a mixed phenotype.

• Half will have the dominant phenotype, half will have the recessive phenotype.

• All will have the dominant phenotype.

• All will have the recessive phenotype.

What happens if the female parent is heterozygous in terms of male offspring phenotype?

• Half of the male offspring will have the dominant phenotype, and half will have the recessive phenotype.

• All male offspring will have the recessive phenotype.

• All male offspring will have the dominant phenotype.

• All male offspring will have a mixed phenotype.