Question 1

How many chromosomes are in a normal human cell?

Accepted Answer

A normal human cell contains 46 chromosomes, which are arranged in 23 pairs.

Question 2

Assume a phenotype is determined by one gene with a dominant allele and a recessive allele.If one parent is homozygous dominant (AA)and the other parent is homozygous recessive (aa),what genotype(s)might their offspring have?

Accepted Answer

The dominant allele (A) will always be expressed in the presence of the recessive allele (a). When one parent is homozygous dominant (AA) and the other parent is homozygous recessive (aa), all of the offspring will inherit one copy of the dominant allele and one copy of the recessive allele (Aa). They will all exhibit the dominant phenotype because it only takes one copy of the dominant allele to express the trait. Therefore, the only possible genotype for the offspring is Aa.

Question 3

What is an insertion mutation?

Accepted Answer

An insertion mutation is when a nucleotide is added to a gene sequence, which alters all subsequent codons. This can cause a frameshift mutation, where the reading frame of the mRNA is shifted and changes the amino acid sequence of the resulting protein.

Question 4

For the scenario in animation 11.9,what is the probability that an offspring will not have the disease?

Accepted Answer

Both parents are carriers of the disease (heterozygous), which means they each have a 50% chance of passing on the disease-causing allele to their offspring. Therefore, the probability of an offspring inheriting the disease-causing allele from one parent is 1/2 or 0.5. The probability that an offspring will not inherit the disease-causing allele from either parent is the product of the probabilities of not inheriting the allele from each parent, which is (1/2) x (1/2) = 1/4 or 0.25. The probability of an offspring not having the disease is the square of this probability, which is (1/4)^2 = 1/16. However, we are asked for the probability of an offspring not having the disease, which is the complement of the probability of having the disease. Therefore, the probability of an offspring not having the disease is 1 - 1/16 = 15/16 or 0.9375. This is closest to C) 12/16 or 0.75.

Question 5

What is the end result of meiosis?

Accepted Answer

The end result of meiosis is the production of haploid gametes, which have half the number of chromosomes as the parent cell. Therefore, the correct answer is D) haploid gametes.

Question 6

How would meiosis differ without independent assortment?

Accepted Answer

The answer of How would meiosis differ without independent assortment?
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Question 7

What information can be deduced from a pedigree? Select the TWO answers that are correct.

Accepted Answer

A pedigree can help determine the inheritance pattern of X-linked traits over generations and calculate the probability of a female being a carrier of an X-linked allele. It cannot determine the probability of a parent or grandparent being infertile, how autosomal traits contribute to X-linked traits, or the probability of paternity through Y-chromosome analysis.

Question 8

How do haploid gametes result in diploid offspring?

Accepted Answer

Haploid gametes (sperm and egg cells) fuse during fertilization to form a diploid zygote, which contains two sets of chromosomes (one from each parent). The zygote then grows and develops into a diploid offspring through mitosis, where the cells divide and replicate their chromosomes to maintain the diploid chromosome number. So, a haploid egg and a haploid sperm fuse to form a diploid zygote that grows by mitosis after fertilization. Choice E is the only option that correctly describes the process of how haploid gametes result in diploid offspring.

Question 9

Assume a phenotype is determined by one gene with a dominant allele and a recessive allele.If one parent is heterozygous and the other parent is homozygous dominant,what is the probability of producing a homozygous recessive offspring?

Accepted Answer

Given one parent is heterozygous (Aa) and the other is homozygous dominant (AA), all offspring will receive at least one dominant allele (A), making it impossible to produce a homozygous recessive (aa) offspring.

Question 10

Can males be carriers of an X-linked trait?

Accepted Answer

Males cannot be carriers of X-linked traits because they have only one X chromosome. If they inherit an X-linked trait, they will express it, not carry it without expression.

Question 11

For the scenario in animation 11.9,what is the probability that an offspring will have the less severe form of the disease?

Accepted Answer

The answer of For the scenario in animation 11.9,what is...

Question 12

How are proto-oncogenes and tumor suppressor genes different?

Accepted Answer

Proto-oncogenes promote cell division when a cell is ready, while tumor suppressor genes halt cell division when a DNA sequence needs correction or repair. This is the key difference between these two types of genes in their role in regulating cell growth and division.

Question 13

Why are X-linked traits more commonly expressed in males than in females? Select the TWO answers that are correct.

Accepted Answer

A) Males have only one X chromosome, so they do not have another copy of the gene to potentially mask the effects of a mutant allele.
C) Females have two X chromosomes, so one copy of the gene can mask the effects of a mutant allele on the other copy.

Question 14

Assume a phenotype is determined by one gene with a dominant allele and a recessive allele.If one parent is homozygous recessive and the other is heterozygous,what is the probability that an offspring will have the recessive phenotype?

Accepted Answer

The answer of Assume a phenotype is determined by one...

Question 15

A grandfather has an X-linked disease.His wife does not have the disease and she is not a carrier for it.What is the probability that their daughter's sons will have the disease?

Accepted Answer

Since the disease is X-linked and the grandfather has it, all of his daughters will be carriers because they receive his affected X chromosome. The wife does not have the disease or carry it, so she provides a normal X chromosome. Their daughters, being carriers, have a 50% chance of passing the affected X chromosome to their sons, who would then express the disease because males have only one X chromosome.

Question 16

What may happen when a mutation changes the amino acid sequence of a protein?

Accepted Answer

When the amino acid sequence of a protein is changed due to a mutation, the protein may become less effective, more effective, or altogether nonfunctional. This is because the specific sequence of amino acids in a protein determines its shape and function. Changing one amino acid can alter the entire structure and disrupt its ability to perform its intended function.

Question 17

Assume a phenotype is determined by one gene with a dominant allele and a recessive allele.If both parents are heterozygous,what is the probability of an offspring being a carrier of the recessive allele?

Accepted Answer

If both parents are heterozygous, they have a genotype of Aa. When they produce offspring, there is a 25% chance that the offspring will inherit aa genotype and be a carrier of the recessive allele. Therefore, the probability of an offspring being a carrier is 50%.

Question 18

What is the p53 gene and how can its mutation cause cancer?

Accepted Answer

The p53 gene is a tumor suppressor gene that plays a crucial role in regulating cell division and preventing the formation of cancer. Its mutation can cause cancer because it normally promotes apoptosis, or programmed cell death, in cells with damaged DNA or other abnormalities. Mutated p53 genes cannot induce apoptosis in rapidly dividing cells, which can lead to the formation and growth of tumors.

Question 19

How do meiosis I and meiosis II differ? Select the TWO answers that are correct.

Accepted Answer

Meiosis I is the reduction division and divides homologous chromosomes, whereas meiosis II is the equational division and divides sister chromatids. Meiosis I is preceded by DNA replication, whereas meiosis II is not preceded by replication. Option A is incorrect as meiosis I yields two haploid daughter cells, not four. Option C is incorrect as meiosis I yields haploid daughter cells, not diploid. Option E is incorrect as meiosis I and meiosis II can yield either egg or sperm cells in different organisms.

Question 20

How does recombination contribute to offspring diversity?

Accepted Answer

The answer of How does recombination contribute to offspring diversity?
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Quiz 33: A Range of Biology