Connect HW 4: Meiosis and Crossing Over

In the fruit fly Drosophila, there is a dominant gene for normal wing shape and its recessive allele for dumpy wings. At another gene locus on the same chromosome, there is a dominant gene for tan body color and its recessive allele for ebony body color. A male that is homozygous for both dominant alleles is crossed with a female that is homozygous for both recessive alleles. What percentage of the F1 flies are expected to be heterozygous at both gene loci? ( Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5 )

100

In the fruit fly Drosophila, there is a dominant gene for normal wings and its recessive allele for vestigial wings. At another gene locus, there is a dominant gene for red eyes and its recessive allele for purple eyes. A female that was heterozygous at both gene loci was mated with a male that is homozygous for both recessive alleles. Knowing this, complete the sentences with the correct terms.

25% 50% 47% on the same chromosome crossing over

At an autosomal gene locus in humans, the allele for brown eyes is dominant over the allele for blue eyes. At another gene locus, located on the X chromosome, a recessive allele produces colorblindness while the dominant allele produces normal color vision. A heterozygous brown-eyed woman who is a carrier of colorblindness has children with a blue-eyed man who is not colorblind. The woman becomes pregnant and an ultrasound test shows that the child is a boy. What is the probability that he will be colorblind? ( Enter the probability as a percent. Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5 )

50

At an autosomal gene locus in humans, the allele for brown eyes is dominant over the allele for blue eyes. At another gene locus, located on the X chromosome, a recessive allele produces colorblindness while the dominant allele produces normal color vision. If a heterozygous brown-eyed woman who is a carrier of colorblindness has children with a blue-eyed man who is not colorblind, the probability that their first child will be a brown-eyed, colorblind male is 1 in __________.

8

Complete the sentences with the correct terms.

During meiosis, the process of nondisjunction produces gametes, and therefore offspring, that have extra or missing chromosomes. Having one or more extra or missing chromosomes is called aneuploidy. Humans that are missing a single autosome are called monosomics. Humans that have one extra autosome, in addition to the normal diploid number, are called trisomics. The developmental defects associated with three copies of chromosome 21 are referred to as Down syndrome. The developmental defects associated with a single X chromosome and no Y chromosome are referred to as Turner syndrome. The developmental defects associated with two X chromosomes and one Y chromosome are referred to as Kleinfelter syndrome. Female gametes with no sex chromosomes are produced when the two X chromosomes fail to separate during meiosis.

Which of the following can directly cause genetic disease? Check all that apply.

altering a single base pair in the DNA of an organism altering multiple base pairs in the DNA of an organism a mutation that alters a single amino acid within a protein a mutation that alters several amino acids within a protein a mutation that changes a gene coding for a normal protein into a gene coding for a defective protein or no protein at all a mutation that changes a gene coding for a normal protein into a gene coding for a defective protein or no protein at all loss of a small section of a chromosome one or more extra chromosomes one or more missing chromosomes