Genetics & Inheritance

If two individuals homozygous dominant for this trait have a child, what is the chance that the child will not be able to roll his tongue?

0%

"In humans, widow's peak is a dominant trait, and a straight hairline is a recessive trait." If an individual homozygous dominant for widow's peak has a child with an individual heterozygous for widow's peak, what is the chance that the child will have a widow's peak?

100%

A couple is planning to have a child. The female is a carrier for hemophilia; the male does not have hemophilia. What is the chance that a female child will never develop hemophilia?

100%

If an individual homozygous dominant for this trait has a child with a person who cannot roll his tongue, what is the chance that the child will have a heterozygous genotype?

100%

"In humans, the ability to roll the tongue is a dominant trait; the inability to roll the tongue is a recessive trait." If two individuals heterozygous for this trait have a child, what is the chance that the child will not be able to roll his tongue?

25%

Tay-Sachs disease is inherited as an autosomal recessive disease. A couple has learned that they are both heterozygous carriers of the Tay-Sachs recessive gene. What is the probability that they will have a child with Tay-Sachs disease?

25%

An individual with the genotype XXY would have ________ chromosomes and phenotypically would be a ________.

47; male

Cystic fibrosis is a genetic disorder that results from the inheritance of two recessive alleles. What is the chance that a child will inherit the disorder if one parent is heterozygous for this gene and one parent has cystic fibrosis?

50%

If an individual homozygous dominant for widow's peak has a child with an individual heterozygous for widow's peak, what is the chance that the child will have a homozygous dominant genotype?

50%

Red-green color blindness is an X-linked recessive disorder. Assume that mom is a carrier and dad is color blind. What is the chance that their son will inherit red-green color blindness?

50%

What is the probability that a woman who is a carrier for the red-green color-blindness allele and a man who is color blind will have a child who is NOT color blind?

50%

If an individual with type O blood marries an individual with type AB blood, what are the possible blood types of their children?

A and B

Which of the following statements is NOT true for a person who is heterozygous for sickle cell?

A person who is heterozygous for sickle cell tends to die at a younger age than a person with sickle-cell anemia does.

Consider the hypothetical X-linked recessive gene M. Suppose a woman expresses this gene. So does her husband. What are the chances that a child of theirs will NOT express this gene?

All of the children will express the trait.

Which of the following conditions is caused by "trisomy 21"?

Down syndrome

Alleles are alternative versions of chromosomes.

False

Genotype is determined by the interaction of phenotype and the environment.

False

Individuals with Klinefelter's syndrome (XXY) are phenotypically female, because they have two X chromosomes.

False

Women cannot inherit X-linked traits such as hemophilia and red-green color blindness.

False

The basic laws of genetic inheritance were described by ________.

Gregor Mendel

If a female inherits and expresses an X-linked recessive disorder, what must be true about her parents?

Her father has the disease.

Which of the following genetic disorders is caused by the inheritance of a dominant-lethal allele?

Huntington's disease

Based on what you know about two-trait inheritance, what can you say about the gametes produced by a female with the genotype AaDd that could NOT be possible?

One of her gametes might be AaDd.

Having a chin dimple (cleft chin) is dominant over having no chin dimple. Having long eyelashes is dominant over having short eyelashes. Jack and Jill are both heterozygous for a chin dimple and long eyelashes. What are the chances that their baby will have no chin dimple and short eyelashes?

The chances are about 1 in 16 that their child will have no chin dimple and short eyelashes.

What could be said of the genes for two different traits that always appear together?

These are "linked genes" on the same chromosome.

An unaffected man whose mother had sickle-cell anemia marries an unaffected woman whose father had sickle-cell anemia. Which of the following statements about their offspring is NOT true?

They must all have the sickle-cell trait.

Which of the following syndromes results in an individual with a nearly normal female phenotype and a tendency to develop mild mental retardation?

Trisomy-X syndrome

A pedigree chart is a tool used to follow the inheritance pattern of a trait through many generations.

True

Codominance occurs when both alleles in a genotype are expressed equally.

True

Human height, eye color, and hair color are examples of traits determined by polygenic inheritance.

True

If alleles for the same gene are different in the same person, that individual is genotypically heterozygous for the trait.

True

In codominance, both phenotypes are expressed in heterozygotes; but in incomplete dominance, the heterozygotes exhibit a phenotype that is intermediate between the two homozygotes.

True

In incomplete dominance, the phenotype of the heterozygous genotype is intermediate between the phenotype of either homozygous genotype.

True

In the human male, genotype and phenotype associated with the genes on the X chromosome are determined by the one X chromosome he inherits from his mother.

True

Polygenic inheritance depends on gene products from multiple genes.

True

The Y chromosome contains a gene that leads to the development of testes and testosterone in a developing embryo.

True

What is tyrosinase?

Tyrosinase is an enzyme that facilitates the conversion of tyrosine to melanin.

Which of the following genotypes results in a female phenotype?

X

What can we say about the frequency of X-linked recessive traits?

X-linked recessive traits are more common in males than in females.

If a piece of chromosome breaks off during mitosis or meiosis and does not reattach, the event is called

a deletion.

Which of the following parental genotypes would produce offspring in a 1:1:1:1 phenotypic ratio?

aaBb x Aabb

"The color of the four-o'clock flower is as follows: homozygous dominantred homozygous recessivewhite" The flower color in this plant is inherited by incomplete dominance. If a flower homozygous dominant for flower color is crossed with a white flower, the color of the offspring flowers will be expected to be

all pink.

What is the term for a normally occurring variation of the same gene (e.g., brown and blue eye color)?

allele

Variations of homologous genes that result in differences in structure and function are

alleles

Hemophilia is an X-linked recessive disorder. A daughter can be afflicted with hemophilia if she inherits ________.

an Xh allele from her father and her mother

If flower color of the offspring was 25% white and 75% red, and flower color were inherited by complete dominance, the parents genotypes must be

both heterozygous.

If one possesses one allele for blood group A antigen and one allele for blood group B, he will have type AB blood, distinctly different from both A and B. This type of inheritance is called ________.

codominance

A homozygous trait can be ________.

either dominant or recessive

The law of segregation states that

genes separate from each other during gamete formation so that each sperm and egg receive only one allele from each pair.

A female is diagnosed with hemophilia, a condition caused by an X-linked recessive gene. While checking her medical history, the doctor will most likely discover that ________.

her father had hemophilia but her mother did not have the disorder

An individual who possesses two different alleles for a particular gene is referred to as ________.

heterozygous

An example of a genotype is

homozygous dominant.

If both alleles of a particular gene are identical, the person is said to be

homozygous.

The offspring resulting from a cross between a nearly white horse (cc) and a chestnut-colored horse (CC) are of an intermediate color (between white and chestnut). Which of the following patterns of inheritance best explains this?

incomplete dominance

When a heterozygous genotype results in a phenotype that is intermediate between the two homozygous conditions, this type of inheritance is referred to as ________.

incomplete dominance

In polygenic inheritance,

multiple alleles and genes contribute to a phenotype.

Failure of sister chromatids to separate properly is called

nondisjunction.

A couple has a daughter who is color-blind. The mother is not color-blind, but the father is. What is the genotype of the mother for this trait?

one dominant allele, one recessive allele

The inheritance of phenotypic traits that depend on many genes is called ________.

polygenic inheritance

The Punnett square is a useful tool for

predicting the ratios of possible genotypes of a particular combination of alleles.

Polygenic traits display phenotypes that

represent a continuous range within the population.

Which of the following is true regarding Klinefelter syndrome?

sterility and shows mild mental impairment

The trend toward increased height and weight due to improved nutrition in certain human populations is an example of the effect of ________ on phenotypes.

the environment

A phenotypic trait is considered sex-linked when

the genes for the phenotype occur on X or Y chromosomes.

Alterations in chormosome number can occur with any chromosome, but most alterations are not seen in human populations because

they are lethal during fetal development.

When a piece of chromosome breaks off and reattaches at another site on the same or another chromosome, this is called

translocation.

A person born with Edward's syndrome have a genotypic condition identified as

trisomy 18.

X-linked recessive disorders are more commonly expressed in males than in females because males have only one copy of the X chromosome.

true