Question 1

The AB blood type is an example of a condition that results from:

Accepted Answer

The AB blood type is an example of codominance, where both alleles for A and B blood types are expressed equally in an individual's phenotype. This means that both alleles are dominant and there is no recessive allele present. Incomplete dominance occurs when neither allele is completely dominant and the heterozygous phenotype is an intermediate blend of both alleles. Therefore, option B is not a correct choice. Dominance and recessive alleles require the presence of at least one dominant or recessive allele to determine the phenotype, which is not the case in codominance.

Question 2

Suppose that a disease is inherited. Your mother has the disease, your father does not, and you have a very minor case of the disease which lies somewhere in between your mother's and father's situation. In this case, we would know that the alleles that determine this trait:

Accepted Answer

Codominance refers to a situation in which neither allele is dominant over the
other. When codominant traits are inherited, the result is a phenotype that is a blend.

Question 3

Ramley states that intelligence is determined by the action of hundreds of different genes. She has just defined intelligence as a _________ trait.

Accepted Answer

Polygenic inheritance is defined as the inheritance of a trait that is determined by multiple genes.

Question 4

A mother and a father have four children (biological not adopted). All four children have blue eyes. Assuming that brown eyes is a dominant trait and blue eyes is a recessive trait, which of the following statements must be true?

Accepted Answer

For a recessive trait to be expressed, a child must inherit two recessive alleles. Thus, for a child to have blue eyes, both parents must have at least one recessive allele (i.e., allele for blue eyes).

Question 5

About what percent of the DNA molecule is made up of protein-coding genes:

Accepted Answer

While the exact percentage varies between species, in humans, protein-coding genes make up only about 2% of the entire DNA molecule. The vast majority of the remaining DNA is non-coding, and its function is still not fully understood.

Question 6

Martin is worried that, if he has a child, the child might be "unlucky" and get the "bad half" of his chromosome pairs. Mr. Martin's worry would technically be referred to as an issue involving:

Accepted Answer

Independent assortment refers to the final stage of meiotic division, in which chance determines which half of the chromosome pairs will go into which sperm or ovum.

Question 7

Sickle-cell anemia is a genetic disorder that is best considered an example of:

Accepted Answer

The answer of Sickle-cell anemia is a genetic disorder that...

Question 8

Suppose that Shelly's mother has brown eyes and her father has blue eyes. Shelly has brown eyes. In this example we would ______ Shelly's phenotype for eye color and would _________ Shelly's genotype for eye color.

Accepted Answer

In genetics, the phenotype refers to those traits that are expressed in the individual. Thus, we know the phenotype: Shelly has brown eyes. The genotype refers to the genetic code of a given individual. Because the gene for brown eyes is dominant, Shelly would have brown eyes whether she inherited a recessive gene from her father and a dominant gene from her mother or whether she inherited dominant genes from both parents. Thus, we cannot determine Shelly's genotype from the information provided.

Question 9

Suppose that hair color is a single-gene trait and that dark hair is dominant and blonde hair is recessive. Also, suppose that Terry's mother has dark hair and his father has blonde hair. If Terry has blonde hair, we would ______ Terry's phenotype for hair color and would ________ Terry's genotype for hair color.

Accepted Answer

In genetics, the phenotype refers to those traits that are expressed in the individual. Thus, we know the phenotype: Terry has blonde hair. The genotype refers to the genetic code of a given individual. Because blonde hair is recessive, we can determine Terry's genotype: he would have to have inherited recessive genes from both his parents.

Question 10

The term "polygenic inheritance" refers to which of the following?

Accepted Answer

In polygenic inheritance, the inheritance of a trait is determined by multiple genes.

Question 11

Assume that eye color is a single gene trait and that brown eyes is a dominant allele and blue eyes is a recessive allele. If Harry's mother and father both have brown eyes and are both heterozygous on this trait, what is the probably that he will have brown eyes, too?

Accepted Answer

Heterozygous refers to the arrangement in which the two alleles for a simple dominant-recessive trait differ. One possibility is that Harry could inherit a recessive allele from his father and a recessive allele from his mother, which would result in blue eyes. Alternatively, he could inherit a recessive allele from his father and a dominant allele from his mother, a dominant allele from his father and a recessive allele from his mother, or dominant alleles from both parents - all circumstances that would result in Harry having brown eyes.

Question 12

Suppose that eye color is a single gene trait and that brown eyes is a dominant allele and blue eyes is a recessive allele. If Mark has brown eyes, we would know:

Accepted Answer

In genetics, the phenotype refers to those traits that are expressed in the individual. Thus, we know the phenotype: Mark has brown eyes.

Question 13

Sometimes in meiosis, genetic material from the mother and father is exchanged between chromosomes. This process is called and the alleles that carry the combination of both parents' genes are called alleles.

Accepted Answer

The process of genetic material exchange between chromosomes in meiosis is called crossing over. The alleles that result from this exchange are called recombinant alleles.

Question 14

The last stage of meiotic division, in which chance determines which half of each chromosome pair will go into which sperm or ovum, involves the process called:

Accepted Answer

Independent assortment is the process in meiosis during which homologous chromosome pairs are separated from each other randomly. This means that each resulting sperm or egg might end up with the paternal or maternal chromosome for each pair, leading to genetic diversity in the offspring.

Question 15

According to the text, genetic mutations are:

Accepted Answer

The text states that genetic mutations are "quite common" and can occur in "about 1 in every 100 to 200 genes."

Question 16

An example of a trait that results from incomplete dominance is ________; a trait that results from codominant alleles is __________:

Accepted Answer

Incomplete dominance refers to a situation where the phenotype of a heterozygous individual is intermediate between the two homozygous individuals. Sickle-cell anemia is an example of incomplete dominance because individuals who are heterozygous for the sickle cell allele have some sickle-shaped red blood cells, but not as many as individuals who are homozygous for the sickle cell allele. Blood type, on the other hand, is an example of codominance because both alleles are expressed equally in the heterozygous individual, resulting in a new phenotype. For example, individuals with AB blood type have both A and B antigens on their red blood cells.

Question 17

Gage argues that hereditary and environmental forces can never be understood separately, since they are continually influencing each other. This statement is best considered to reflect the concept of:

Accepted Answer

The central concept of gene-environment interactions is that genetic and environmental forces are in constant interaction with each other: genes influence the environments we select and environmental events can influence how genes are expressed.

Question 18

Color blindness is a sex-linked trait. As such, if a child is color blind, we can be assured that the child's genotype includes:

Accepted Answer

Sex-linked traits are those that are determined by genes on the 23rd chromosome pair. If a normally recessive allele appears on the male's X chromosome, there often is no allele on the Y chromosome to offset it, and the recessive trait will be expressed as the individual's phenotype. In contrast, in females, the recessive trait will be expressed only if it occurs on both X chromosomes. Regardless of whether the child is male or female, the mother must contribute a recessive gene on the X chromosome in order for the trait to be expressed.

Question 19

The blood clotting disease, hemophilia, occurs much more frequently in males because it is caused by a recessive gene carried on the sex chromosomes. As such, it would be referred to as:

Accepted Answer

Sex-linked traits are, by definition, those that are determined by genes on the 23rd chromosome pair (the sex chromosomes). Sex-linked traits are not, by definition, heterozygous or homozygous. If a normally recessive allele appears on the male's X chromosome, there often is no allele on the Y chromosome to offset it, and the recessive trait will be expressed as the individual's phenotype. In contrast, in females, the recessive trait will be expressed only if it occurs on both X chromosomes.

Question 20

If all cells in a person's body have a particular mutation present, we can conclude that the mutation most likely occurred:

Accepted Answer

The answer of If all cells in a person's body...

Quiz 2: Heredity and Environment