Quizs Ch 15 Part II Gene Linkage & X-inactivation

An abnormal female with an extra X chromosome has what genotype and how many barr bodies?

• XX, 1 barr body

• XXX, 2 barr bodies

• XXY, 1 barr body

• XXXX, 3 barr bodies

What is the result of crossing-over during meiosis?

• Crossing-over increases genetic diversity.

• Crossing-over decreases genetic diversity.

• Crossing-over has no effect on genetic diversity.

• Crossing-over results in identical genetic material.

Determining if two genes are linked

• By using experimental data from genetic crosses to calculate the recombination frequency.

• By analyzing the physical distance between the genes on a chromosome.

• By observing the phenotypic ratios in the offspring of a cross.

• By performing a test cross with a homozygous recessive individual.

Use of recombination frequency

• To determine the age of fossils

• To make Gene Maps

• To measure genetic diversity

• To identify dominant traits

Some of the color alleles in cats are X-linked. Study the image. Why does the tortoise shell pattern vary between female cats?

• Because x-inactivation is random, leading to different X chromosomes being inactivated in different female cats.

• Because male cats do not have the tortoise shell pattern due to their XY chromosome configuration.

• Because the tortoise shell pattern is influenced by environmental factors rather than genetic ones.

• Because female cats have a single X chromosome, which determines their color pattern.

Gene assortment on chromosomes

• Genes on different chromosomes assort independently, while genes on the same chromosome are linked and inherited together.

• All genes assort independently regardless of their chromosomal location.

• Genes on the same chromosome always assort independently.

• Genes on different chromosomes are always inherited together.

How would you use an actual genetic cross to determine if gene Y and gene R are linked to the same chromosome or if they are located on different chromosomes?

• Perform a cross and count the offspring; if the ratio matches 1:1:1:1, the genes are likely unlinked.

• Assume that genes Y and R are on the same chromosome without testing.

• Use a Punnett square to predict the offspring ratios without performing any crosses.

• Count the number of dominant traits in the offspring to determine linkage.

If two genes are found on the same chromosome, are they linked forever?

• Yes, they are linked forever without exception.

• No, they are not linked forever. Crossing-over during meiosis can separate genes.

• They are linked only if they are close together on the chromosome.

• They can be separated by mutations in the DNA sequence.

The data shows that genes for body color and wing shape are linked.

• Genes for body color and wing shape are independent of each other.

• Genes for body color and wing shape are linked based on the data provided (the actual genetic outcome does not match the predicted phenotypic ratio from the punnett square).

• Genes for body color and wing shape have no correlation in genetic studies.

• Genes for body color and wing shape are only linked in certain environmental conditions.

A normal male has what genotype and how many barr bodies?

• XX, 1 barr body

• XY, 0 barr bodies

• XY, 1 barr body

• XXY, 0 barr bodies