Question 1

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

Accepted Answer

Incomplete dominance is when the heterozygous phenotype is intermediate between the homozygous dominant and homozygous recessive phenotypes. Sickle-cell anemia is an example of incomplete dominance. Codominant alleles are when both alleles are expressed equally in the phenotype. Blood type is an example of codominant alleles, as both A and B antigens are expressed on the surface of red blood cells in the AB blood type. The other answer choices are not examples of incomplete dominance or codominance.

Question 2

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 3

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

Accepted Answer

At the molecular level, a mutation is an alteration in the DNA that typically occurs during mitosis or meiosis. A small number of mutations are viable-the mutated cell survives. In mitotic cell division, if a viable mutation occurs early in development, it will then be passed along to all the cells replicated in subsequent divisions of that cell. When mutation occurs during meiosis, on the other hand, it is incorporated into the genetic code passed along to offspring in the sperm or ova. Genetic and Chromosomal Disorders

Question 4

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 5

If the gene for blue eyes is recessive, and if John's mother and father both have blue eyes, we know that John:

Accepted Answer

Normally, recessive traits are only expressed when a person has inherited two recessive genes. In this example, one should assume that both the mother and father, having blue eyes, have two recessive genes. It follows that each would have had to contribute a recessive gene, resulting in John being homozygous on the eye color trait.

Question 6

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 during meiosis that results in the random segregation of homologous chromosomes, which leads to genetic diversity in the offspring. During this process, the chromosomes line up randomly at the metaphase plate, and chance determines which chromosome of a pair will end up in each gamete. This random segregation is independent of the segregation of other chromosome pairs, leading to different combinations of genetic traits in the gametes.

Question 7

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

Crossing over is the process in which genetic material is exchanged between chromosomes during meiosis. This exchange results in new combinations of alleles, which are called recombinant alleles.

Question 8

Dr. 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 9

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 are expressed equally in the heterozygous state. In this case, the A and B alleles are codominant and produce a phenotype with both A and B antigens on the surface of red blood cells. The O allele is recessive to both A and B alleles, resulting in the O phenotype when homozygous (OO). Dominance and incomplete dominance do not account for the expression of both alleles in a heterozygous individual.

Question 10

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 11

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 12

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 13

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 14

According to the text, genetic mutations are:

Accepted Answer

The text states that genetic mutations are "quite common" and that "it is estimated that every person carries at least one or two genetic mutations." This suggests that genetic mutations are not rare occurrences. The text does not mention an age requirement for mutations to occur, and it also notes that mutations can be positive or negative in their effects on an individual's survival.

Question 15

Mr. 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 16

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 17

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 18

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 19

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 20

Dr. 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.

Quiz 2: Heredity and Environment

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

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?