Question 1

What is occurring when the phenotype is influenced primarily but not exclusively by the dominant gene?

Accepted Answer

Incomplete dominance occurs when the phenotype is influenced by both alleles but not to the extent that one is completely dominant over the other, resulting in a blend or intermediate phenotype.

Question 2

Sickle-cell anemia is a defense against what disease?

Accepted Answer

Sickle-cell anemia is an inherited blood disorder where the shape of the red blood cells is abnormal, causing them to stick together and block small blood vessels. It is commonly found in regions where malaria is endemic. The sickle-shaped cells are not as easily infected by the malaria parasite, providing a survival advantage to people carrying the sickle-cell trait in areas where malaria is prevalent. Therefore, sickle-cell anemia can be seen as a defense against malaria.

Question 3

Which of the two sex chromosomes is significantly smaller and contains approximately 30% less genetic material?

Accepted Answer

The Y chromosome is significantly smaller than the X chromosome and contains approximately 30% less genetic material. This is due to its lack of homologous recombination during meiosis, leading to a higher rate of mutations and deletions over time. The X chromosome, on the other hand, is one of the largest chromosomes in the human genome and contains a wide range of genes involved in many biological functions.

Question 4

Why are males more likely to have X-linked inherited disorders?

Accepted Answer

Males only have one X chromosome and one Y chromosome, while females have two X chromosomes. If the X chromosome contains a recessive gene for a disorder, a male has no second X chromosome with a dominant gene to mask the expression of the disorder. Females are less likely to have X-linked inherited disorders because the healthy X chromosome can mask the expression of the recessive gene on the other X chromosome. Thus, males are more likely to be affected by X-linked inherited disorders. Option B is incorrect because the immaturity of boys at birth has no relation to X-linked inherited disorders. Option C is also incorrect because androgen is merely a hormone and cannot cause inherited disorders to occur. Similarly, option D is incorrect because the Y chromosome carries very few genes, and its absence or malfunction is unlikely to cause inherited disorders.

Question 5

While having a conversation with a friend who is pregnant, she says that because she is "carrying high" she will have a girl.Based on the textbook, which of the following statements are you thinking?

Accepted Answer

There is no scientific evidence to support the belief that "carrying high" indicates the gender of the baby. It is a common myth or folklore that has not been proven by research studies. Therefore, it is not statistically correct to assume that a woman carrying high will have a girl.

Question 6

Which statement accurately reflects sex ratios of boys to girls across the world?

Accepted Answer

The natural human sex ratio at birth is approximately 105 boys to 100 girls. This ratio is a biological constant observed globally, although slight variations can occur due to natural and societal factors.

Question 7

Which of the following is an example of an incomplete dominant inheritance?

Accepted Answer

In sickle-cell anemia, the inheritance pattern is incomplete dominant. This means that individuals who inherit one copy of the sickle cell gene have some symptoms of the disease but are not as severely affected as those who inherit two copies of the gene. This is different from dominant inheritance, where the presence of one copy of the gene is enough to cause the disease, and recessive inheritance, where individuals need to inherit two copies of the gene to have the disease. Down syndrome, Fragile X, and HIV are not examples of incomplete dominant inheritance.

Question 8

What happens during fertilization that determines the sex of the offspring?

Accepted Answer

The egg or ovum contains the X chromosome and the sperm cells carry either the X or the Y chromosome. The sperm cell that fertilizes the egg and contributes either an X or a Y chromosome determines the sex of the offspring. If the sperm cell carries an X chromosome, the offspring will be female (XX), and if it carries a Y chromosome, the offspring will be male (XY). Therefore, choice A is the correct answer.

Question 9

How would you create an individual who will definitely have blue eyes?

Accepted Answer

Blue eyes are a recessive trait, meaning that an individual must inherit two copies of the recessive gene to have blue eyes. Therefore, ensuring that they have one pair of recessive genes for blue eyes is the only way to create an individual who will definitely have blue eyes. Option A is incorrect because having one dominant gene for brown eyes will result in brown eyes being expressed, as the dominant gene will always be expressed over the recessive gene. Option C is incorrect because having a pair of alleles for eye color does not guarantee that the individual will have blue eyes, as the alleles could code for brown or green eyes. Option D is also incorrect because green eyes are a completely separate trait from blue eyes, meaning that having one recessive gene for blue eyes and one dominant gene for green eyes would result in green eyes being expressed, not blue.

Question 10

__________ are more affected by X-linked inherited disorders while __________ are generally carriers of X-linked disorders.

Accepted Answer

Males are more affected by X-linked inherited disorders because they have only one X chromosome, so a single recessive gene on that X chromosome will result in the disorder. Females, having two X chromosomes, are more often carriers of X-linked disorders; a single recessive gene on one of their X chromosomes may not cause the disorder due to the presence of a normal allele on the other X chromosome.

Question 11

According to ancient Chinese folklore, how can one predict whether a pregnant woman is having a boy?

Accepted Answer

The answer of According to ancient Chinese folklore, how can...

Question 12

The chromosomes that determine whether a fetus will be male or female are known as the __________.

Accepted Answer

Sex chromosomes are responsible for determining an individual's biological sex. In humans, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). Therefore, the sex chromosomes are the best answer to the question, as gender chromosomes, male chromosomes, and female chromosomes are not accurate or commonly used terminology.

Question 13

Jill's mother and father both have brown eyes, yet she has blue eyes.She has come to believe that she is not her parents' actual biological daughter.What would you tell her?

Accepted Answer

Brown eyes are dominant over blue eyes, but if both parents carry a recessive gene for blue eyes, they can still pass it on to their child. Therefore, it is possible for Jill to have blue eyes even if both her parents have brown eyes.

Question 14

For a recessive gene to be expressed in the phenotype, it must be paired with a __________.

Accepted Answer

For a recessive gene to be expressed in the phenotype, it must be paired with another recessive gene. If paired with a dominant gene, the dominant gene's trait will be expressed instead.

Question 15

A person with an XY pairing of chromosomes is a(n) __________, whereas a person with an XX pairing of chromosomes is a(n) __________.

Accepted Answer

The presence of XY chromosomes typically indicates a male, while XX chromosomes usually indicate a female. Therefore, option A is the correct choice.

Question 16

What recessive disorder results in non-normal-shaped blood cells that clog blood vessels and cause pain, increased susceptibility to disease, and early death, particularly among Africans and African American populations?

Accepted Answer

Sickle-cell anemia is a recessive genetic disorder that results in the production of abnormal-shaped red blood cells that can clog vessels and limit blood flow. This condition causes acute pain, increased risk of infections, and may lead to organ damage and early death. It is prevalent in populations of African and African American ancestry. Tay-Sachs is a recessive disorder that affects the nervous system and typically presents in infancy. Trisomy-21 refers to Down syndrome, a genetic condition caused by an extra copy of chromosome 21. Malaria is a disease caused by a parasitic infection and is not a genetic disorder.

Question 17

According to ancient Mayan folklore, how can one predict whether they are having a girl?

Accepted Answer

According to ancient Mayan folklore, if the mother's age and the month of conception are both even or odd, she is likely to be having a girl. This prediction method is called the Mayan gender chart or Mayan gender predictor.

Question 18

Which type of inheritance influences characteristics such as height, weight, skin color, intelligence, personality, and disease susceptibility?

Accepted Answer

Polygenic inheritance involves the interaction of multiple genes in determining a single trait, and is responsible for variation in characteristics such as height, weight, skin color, intelligence, personality, and disease susceptibility. The other options refer to specific modes of inheritance that do not encompass such a wide range of traits.

Question 19

Single gene pairs play a crucial role in development.However, it is more common that developmental outcomes occur because of the interaction of multiple genes.This is known as ___________.

Accepted Answer

Polygenic inheritance refers to the phenomenon where multiple genes interact to produce a particular trait or developmental outcome. This is in contrast to single gene dominance, where only one gene is responsible for a particular trait. Bimodal inheritance is not a recognized term in genetics, and while inheritability is important in genetics, it does not specifically refer to the interaction of multiple genes.

Question 20

Your older brother has a friend who was angry with his wife because they have two sons and he wanted to have a daughter.He thought that she was responsible for having two boys rather than a boy and a girl.What would you tell your brother?

Accepted Answer

The sex of the offspring is determined by the sperm, which carries either an X or a Y chromosome. The ovum provides an X chromosome. Therefore, it is not anyone's "fault" whether a couple has a boy or a girl.

Quiz 2: Genetics and Prenatal Development