Question 1

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

Accepted Answer

A recessive gene will only be expressed in the phenotype if it is paired with another recessive gene, as it requires two copies of the gene for its expression to be visible. If paired with a dominant gene, the dominant gene will be expressed instead. An expressed gene or a controller gene may or may not be involved in the expression of the recessive gene, as it depends on the specific genetic interactions involved.

Question 2

Each form of a gene that is contained within a chromosome is referred to as a ____.

Accepted Answer

An allele is each form of a gene that is contained within a chromosome. Dominant and recessive genes refer to how those alleles are expressed, while single gene is too general of a term.

Question 3

Characteristics such as height,weight,and skin color are made up of a ____.

Accepted Answer

Characteristics such as height, weight, and skin color are controlled by multiple genes, not just one. Polygenic inheritance is responsible for traits that are influenced by multiple genes. Height, weight, and skin color are all examples of polygenic inheritance. Homogenetic inheritance and heterogenetic inheritance are not well-defined terms in genetics. Dominant-recessive inheritance refers to a single gene that controls a trait with one version being dominant over the other.

Question 4

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

It is possible for both parents to carry the recessive gene for blue eyes, and if both pass it on to their child, then she can have blue eyes even though her parents have brown eyes. This is a classic example of a Punnett Square experiment, where the outcome shows that two brown-eyed parents can have a blue-eyed child if they both carry a recessive gene for blue eyes.

Question 5

On every pair of chromosomes there are how many forms of each gene?

Accepted Answer

On every pair of chromosomes, there are two forms of each gene, one inherited from each parent. These two forms of a gene are called alleles.

Question 6

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.

Question 7

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 interaction of multiple genes in the development of a trait or characteristic. This is in contrast to single gene pairs, which can also have a significant impact on development but are less common sources of complex traits. In polygenic inheritance, the contributions of multiple genes can be additive, resulting in gradual changes in the phenotype, or they can interact in more complex ways, such as through epistasis or gene-environment interactions.

Question 8

A person with an XY pairing of chromosomes is a ____,whereas a person with an XX pairing of chromosomes is a ____.

Accepted Answer

A person with an XY pairing of chromosomes is male and a person with an XX pairing of chromosomes is female.

Question 9

If the gene for curly hair is dominant and the gene for straight hair is recessive,from a dominant-recessive pairing,which of the following would be an individual's phenotype?

Accepted Answer

If the gene for curly hair is dominant and the gene for straight hair is recessive, an individual's phenotype will depend on whether they inherit one or two copies of the dominant curly hair gene. If they inherit at least one dominant curly hair gene, they will have curly hair (even if they also inherit a recessive straight hair gene). Therefore, the correct answer is B) curly hair.

Question 10

If a fetus has the sex chromosomes XX,its genotype is ____.

Accepted Answer

The XX genotype is characteristic of females, while the XY genotype is characteristic of males. Therefore, if a fetus has XX sex chromosomes, it is genetically female. Choice B (male) is incorrect. Choice C (undetermined) is incorrect because the sex of the fetus can be determined by the presence of the sex chromosomes. Choice D (dimorphic) is incorrect because this term refers to the presence of two distinct forms or types, and is not applicable in this context.

Question 11

All ova,a female reproductive egg,are ____.

Accepted Answer

All ova contain an X chromosome. During fertilization, the sex of the offspring is determined by the sperm, which can carry either an X or a Y chromosome.

Question 12

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

Accepted Answer

The chromosomes that determine if a fetus will be male or female are known as sex chromosomes. In humans, females have two X sex chromosomes (XX) while males have one X and one Y sex chromosome (XY). The presence of the Y chromosome determines male development while the absence results in female development.

Question 13

If the fetus has the sex chromosomes XY,its genotype is _____.

Accepted Answer

The XY sex chromosomes indicate that the fetus is male. The X and Y chromosomes determine the sex of the individual, with XX indicating female and XY indicating male. Therefore, the genotype of the fetus is male. Option A is incorrect because the absence of a Y chromosome means the fetus is not female. C and D are also incorrect as the sex is determined by the presence or absence of the Y chromosome, and the term "dimorphic" refers to two distinct forms, which is not applicable in this case.

Question 14

Of the following,which best describes the Y chromosome?

Accepted Answer

The Y chromosome contains about 30% less genetic material than the X chromosome. This is because the Y chromosome carries fewer genes than the X chromosome. However, the Y chromosome is still important in determining the sex of the child as it carries the SRY gene which triggers the development of male characteristics.

Question 15

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. Therefore, it is not the wife's fault that they have two sons and not a daughter. The husband's anger towards his wife is unjustified and misplaced.

Question 16

All eggs contain which sex chromosome?

Accepted Answer

All eggs contain one X chromosome, regardless of the individual's genetic sex. The determination of the individual's sex is made by the sperm that fertilizes the egg, which can contribute either an X or a Y chromosome.

Question 17

Thomas's biological mother and father are both gifted athletes.He was adopted by a couple who had no interest in him being involved in sports.Although Thomas likely inherited athletic ability,it was never expressed in his _____.

Accepted Answer

Thomas's phenotype refers to the observable characteristics of an individual, including their athletic ability. While he may have inherited athletic ability in his genotype and genes, it was never expressed in his observable traits, or phenotype, due to his upbringing and lack of involvement in sports. Alleles refer to the different forms of a gene that can exist, while genes and genotype refer to an individual's complete set of heritable traits.

Question 18

What happens that determines the sex of the offspring?

Accepted Answer

The eggs or ovum contain the X chromosome and the sperm cells carry either the X or the Y. The sperm cell that is involved in fertilization determines the sex of the offspring.

Question 19

What type of gene,if it is present,will be expressed in the phenotype?

Accepted Answer

In genetics, a dominant gene is one that is expressed in the phenotype even if only one copy of the gene is present. This means that if an individual inherits one copy of a dominant gene from a parent, they will exhibit the trait associated with that gene. In contrast, a recessive gene is only expressed in the phenotype if an individual inherits two copies of the gene (one from each parent). Therefore, if we are looking for a gene that will be expressed in the phenotype, the best choice is a dominant gene.

Question 20

If having more than five fingers occurs because of a dominant gene,what needs to happen for a person to have more than five fingers?

Accepted Answer

The presence of more than five fingers occurs due to a dominant gene. This means that a person must inherit at least one copy of the dominant gene in order to have more than five fingers.

Quiz 2: Genetics and Prenatal Development