Chapter 11 QUIZ

How do the two alleles of the CFTR gene in a lung cell differ?

They are inherited from different parents.

Which statement is true of a single human liver cell?

The number of chromosomes in this liver cell is referred to as diploid. There are 46 chromosomes present. There is one allele on each chromosome. There are two alleles for each gene.

Which statement is true of a single human gamete?

There is one allele per trait on each chromosome.

What is the genotype of a person with cystic fibrosis?

The genotype includes two mutant CFTR genes, one each on the homologous chromosomes for chromosome 7.

A diploid cell of baker’s yeast has 32 chromosomes. How many chromosomes are in each of its haploid spores?

16

In diploid organisms, having two homologues of each chromosome can be beneficial if one allele of a gene encodes a nonfunctional protein. Can haploid organisms avoid the negative effects of nonfunctional alleles?

No, because there is only one allele for the gene in each cell, and the nonfunctional allele has no other allele to mask it.

Why is it possible for two healthy parents to give birth to a child with a genetic defect such as cystic fibrosis?

CF is only evident in individuals with two mutant alleles; a healthy parent could carry both a defective allele and a normal allele.

A human female has _____ chromosomes in each skin cell and _____ chromosomes in each egg.

46; 23

A woman is heterozygous for the CF-associated gene (the alleles are represented here by the letters A and a. Assuming that meiosis occurs normally, which answer choice represents eggs that she can produce?

A or a

Which phrase accurately describes meiosis?

contains two rounds of division (meiosis I and meiosis II) takes one diploid cell to make four haploid cells ends with four gametes that are not the same genetically

Meiosis differs from mitosis in the _____.

number of chromosomes in each ending cell

One of the purposes of meiosis is to _____.

reduce the chromosome number in each resulting cell by half

Besides recombination, what other event in meiosis increases the genetic diversity of the gametes?

the random line-up and separation of maternal and paternal chromosomes

An alien has 82 total chromosomes in each of its body cells. The chromosomes are paired, making 41 pairs. If the alien’s gametes undergo meiosis, what are the number and arrangement (paired or not) of chromosomes in one of its gametes?

41 unpaired chromosomes

If meiosis were to fail and a cell skipped meiosis I, so that meiosis II was the only meiotic division, how would you describe the resulting cells?

diploid cells with 23 pairs of chromosomes

Children often have many of the phenotypes of their parents because _____.

they inherit half of their genetic material from each parent

Women can inherit alleles of a gene called BRCA1 that puts them at higher risk for breast cancer. The alleles associated with elevated cancer risk are dominant. Of the genotypes listed below, which carries the lowest genetic risk of developing breast cancer?

bb

In order for a child to develop cystic fibrosis _____.

a sperm carrying a CF allele must fertilize an egg that also has that allele

Assume that Emily (who has CF, a recessive disease (aa)) decides to have children with a man who does not have CF and who has no family history of CF. What combination of gametes can each of them produce, and what is the probability that they will have a child who is a carrier for CF?

Emily: aa, man: AA; 100% probability

Phenylketonuria is considered to be an inborn error of metabolism. It is a recessive genetic condition in which the enzyme that breaks down the amino acid phenylalanine is defective or missing. Testing of all newborns allows this condition to be detected at birth. A special diet that severely minimizes phenylalanine (e.g., by avoiding diet sodas and most usual sources of protein) can treat the condition.
In this scenario, two carriers of both cystic fibrosis and phenylketonuria have a child.
What is the probability that the child will have both cystic fibrosis and phenylketonuria?

6.25%

Phenylketonuria is considered to be an inborn error of metabolism. It is a recessive genetic condition in which the enzyme that breaks down the amino acid phenylalanine is defective or missing. Testing of all newborns allows this condition to be detected at birth. A special diet that severely minimizes phenylalanine (e.g., by avoiding diet sodas and most usual sources of protein) can treat the condition.
In this scenario, two carriers of both cystic fibrosis and phenylketonuria have a child.
What is the probability that the child will have cystic fibrosis and be a carrier for phenylketonuria?

12.5%

What does it mean to say that a person has a heterozygous genotype for a disease and no disease phenotype?

It means that the person does not show symptoms of the disease if the disease allele is recessive.