Question 1

Color blindness and hemophilia are examples of

Accepted Answer

Color blindness and hemophilia are both examples of sex-linked inheritance because the genes for these conditions are located on the X chromosome. Since males only have one X chromosome, they are more likely to express these conditions if they inherit the affected gene than females, who have two X chromosomes.

Question 2

Most complex human characteristics, such as personality and intelligence, are inherited via

Accepted Answer

Complex human characteristics, such as personality and intelligence, are typically not controlled by a single gene pair or sex-linked inheritance. Rather, they are influenced by multiple genes interacting with each other and the environment, which is known as polygenic inheritance. This is why these traits often display a bell curve distribution, where most people fall in the middle range with fewer individuals at the extremes. Mutations can contribute to genetic variation, but they are not the sole cause of these complex traits.

Question 3

What might make a physician suspect that the person from whom she has just drawn blood has sickle-cell disease?

Accepted Answer

Sickled red blood cells are characteristic of sickle-cell disease. These cells are not round, but instead take on a crescent or sickle shape.

Question 4

Which disorder is the result of a chromosomal abnormality?

Accepted Answer

Down syndrome is caused by an extra copy of chromosome 21 (trisomy 21), which is a chromosomal abnormality. Hemophilia, sickle-cell disease, and malaria are caused by genetic mutations but not chromosomal abnormalities.

Question 5

As a hemophiliac, Charles has a deficiency in his blood's ability to

Accepted Answer

Hemophilia is a genetic disorder that affects the blood's ability to clot properly, leading to bleeding and bruising. Therefore, the correct choice is B, which states that Charles has a deficiency in his blood's ability to clot. The other options, such as forming the desired round shape, generating white cells, and fighting infections, do not relate to the symptoms of hemophilia.

Question 6

Sickle-cell disease likely arose as a mutation that was passed along because it protected individuals from

Accepted Answer

Sickle-cell disease is caused by a mutation in the HBB gene that codes for the beta-globin subunit of hemoglobin. While having two copies of the mutation (homozygous) causes sickle-cell disease, carrying only one copy (heterozygous) can confer some protection against malaria. This is because the sickle-shaped red blood cells are less hospitable to the malaria parasite, reducing the severity of the infection.

Question 7

The key characteristic of polygenetic traits is that they ALWAYS involve

Accepted Answer

Polygenetic traits involve multiple pairs of genes, which means they are controlled by more than one gene. This is different from single gene traits, which are controlled by only one gene.

Note: A is not the best choice because polygenetic traits do not necessarily involve mutations. B and D are not the best choices because polygenetic traits do not necessarily have anything to do with sex cells or recessive genes.

Question 8

As it suddenly appeared in the bloodline of the royal family of Europe, hemophilia is best explained in terms of

Accepted Answer

The answer of As it suddenly appeared in the bloodline...

Question 9

A human trait is influenced by a single pair of genes, with "T" representing the dominant gene and "t" representing the recessive gene. Joe (genotype Tt) and Meg (genotype Tt) decide to have children. According to the principles of Mendelian heredity, what percentage of their children would exhibit the trait?

Accepted Answer

According to Mendelian genetics, the possible genotypes for their children are TT, Tt, Tt, and tt. Three out of these four combinations (TT, Tt, Tt) will exhibit the dominant trait, resulting in 75% of the children showing the trait.

Question 10

Marcia has just given birth to a baby girl. She is concerned because she is a carrier for hemophilia. Which of the following is true?

Accepted Answer

Hemophilia is an X-linked recessive disorder, meaning that it is usually transmitted to male offspring from their carrier mother. Female carriers of hemophilia have a 50% chance of passing on the affected X chromosome to their male offspring, but typically do not show symptoms themselves. However, there is still a small chance of passing on the affected X chromosome to their female offspring as well. Therefore, while Marcia should still be concerned, the likelihood of her daughter inheriting hemophilia is lower than if she had a son.

Question 11

If green eyes are dominant and designated as "G" and gray eyes are recessive and designated as "g," probability would predict that if a couple each with a "Gg" eye color genotype had four children, _____ would have gray eyes.

Accepted Answer

The probability of each child having gray eyes is 25%. Therefore, the probability of having one child with gray eyes is 25%.

Question 12

Michael is color blind. Whose genes caused this to happen?

Accepted Answer

Color blindness is often inherited in an X-linked recessive pattern. Since males have only one X chromosome, they inherit color blindness from their mother's genes.

Question 13

When looking at the unusual protrusion sticking out of a newborn's head, Dr. Natas says, "I am sure that the growth is due to some sudden change in the structure of the genes that was not passed on by the parents." This means that Dr. Natas suspects that the growth is due to

Accepted Answer

Dr. Natas's statement suggests that the growth is due to a mutation, which is a sudden change in the genetic material that can result in new traits or abnormalities. This is the most likely explanation for an unusual protrusion that was not passed on by the parents' genes.

Question 14

Children who have one dark-skinned parent and one light-skinned parent can have a skin tone that is somewhere between their mother's skin color and their father's skin color. This is an example of

Accepted Answer

This is an example of incomplete dominance because neither parent's trait is completely dominant and the offspring's phenotype is a blend of the two.

Question 15

Olive has very red eyes, while her husband Skye has very blue eyes. Interestingly, their son's eyes are best described as purple. The eye color of their child best exemplifies the concept of

Accepted Answer

Incomplete dominance refers to a situation where neither allele is completely dominant over the other, resulting in a blending of traits. In this case, it appears that the red and blue alleles have blended to produce a new phenotype (purple) in their offspring's eyes. This is different from codominance, where both alleles are expressed equally in the phenotype, and polygenic inheritance, which involves the contribution of many genes to a single trait. There is no indication of mutation being involved in this scenario.

Question 16

The fact that type AB blood appears to be the result of a compromise between genes for type A and type B blood provides a good example of

Accepted Answer

Type AB blood is the result of codominance, meaning that both the A and B alleles are expressed equally in the phenotype. This is different from incomplete dominance, where a heterozygous individual exhibits an intermediate phenotype, and polygenic inheritance, which involves the influence of multiple genes on a single trait. Mutation may play a role in the evolution of blood types, but it is not directly related to the appearance of type AB blood.

Question 17

Who is LEAST likely to have a chromosomal abnormality?

Accepted Answer

Humans typically have 23 pairs of chromosomes, so Dick, with 23 pairs, is least likely to have a chromosomal abnormality.

Question 18

Incomplete dominance occurs when

Accepted Answer

In incomplete dominance, neither gene is completely dominant or recessive, so there is a compromise between the two effects. For example, in snapdragons, the red and white genes are incompletely dominant, so when a plant has one red gene and one white gene, it appears pink because there is a compromise between the effects of the two genes.

Question 19

A sex-linked characteristic most likely involves a problem with the _____ chromosome.

Accepted Answer

Sex-linked traits are typically carried on the X chromosome. This means that males, who only have one X chromosome, are more likely to be affected by sex-linked traits since they don't have a second X chromosome to compensate for a faulty gene on the first X chromosome. Females, who have two X chromosomes, are less likely to be affected since they have a backup copy of the X chromosome.

Question 20

Which is the best example of codominance?

Accepted Answer

Codominance occurs when both alleles in a gene pair are fully expressed, resulting in offspring with a phenotype that shows both parental traits distinctly, like a flower with both yellow and blue colors.

Quiz 3: Genes, Environment, and Development