SB 9- Ch 21

Select all correct descriptions of polygenic traits.

Alleles have additive affects on phenotype. Phenotypic variation appears continuous. Phenotype can be influenced by the environment.

Match each body system with how it is affected by the pleiotropic genetic disorder Marfan syndrome.

Cardiovascular---Mitral valve prolapse, aortic enlargement Integumentary---Stretch marks, dural ectasia Respiratory---Collapsed lungs Sensory---Lens dislocation Skeleton---Long, thin fingers, flat feet, loose joints

Select all examples of multifactorial traits in humans.

Cleft palate Cancers Allergies

An X-linked disorder that causes muscle degeneration due to the absence of a protein involved in calcium release is ______.

Duchenne muscular dystrophy

Studies of twins separated at birth can provide evidence for whether traits are susceptible to which of the following?

Environmental influences Genetic influences

Which is an example of polygenic inheritance in humans?

Human skin color

For a child with blood type O, select all possible blood types of the father.

O, A, B

People who have ______ copies of CGG repeats have "full mutation" and show the traits of fragile X syndrome.

Over 200

True or false: A male receives all of his X-linked alleles from his mother.

True

True or false: Fragile X syndrome is the most common proven cause of autism.

True

Sex-linked genes are found on sex chromosomes, but not on the 22 other pairs of chromosomes, which are called

autosomes

The offspring of crosses between parents that are heterozygous for skin pigmentation genes will have a distribution of phenotypes that resembles a ______-shaped curve.

bell

A genetic system in which alleles are equally expressed in a heterozygote is called ______.

codominance

Marfan syndrome is a pleiotropic disease, because a single gene defect affects ______ tissues that are present in a variety of organs.

connective

X-linked dominant disorders can be inherited from ______.

either or both parents

he main sign of hemophilia is ______.

excessive bleeding

In familial hypercholesterolemia, a person with one mutated allele and one normal allele has ______.

half the normal number of cholesterol receptors

Because Queen Victoria was a carrier of ______, this X-linked clotting disorder was introduced into several royal families in Europe.

hemophilia

Although males with Duchenne muscular dystrophy usually die before they are parents, the recessive allele remains in the population due to females that are ______.

heterozygous carriers

A child with wavy hair has a parent with straight hair and a parent with very curly hair. What genetic phenomenon explains this?

incomplete dominance

A genetic system in which a heterozygous individual displays a phenotype intermediate between that of an individual homozygotic for either allele is called

incomplete dominance

Humans that are heterozygous for familial hypercholesterolemia have intermediate plasma cholesterol levels. Familial hypercholesterolemia is an example of a(n) ______.

incompletely dominant trait

Traits controlled by polygenes that are influenced by the environment are called ______.

multifactorial traits

Marfan syndrome, in which a mutation in a gene leads to a weakened aorta, poor eyesight, and long limbs, is an example of ______.

pleiotropy

When one gene affects multiple, seemingly unrelated, traits it is called

pleiotropy

A plot of the height of a random human population reveals a bell-shaped curve or continuous variation, which shows that height is a(n) ______.

polygenic trait

In fragile X syndrome, between 59 and 200 copies of CGG repeats is considered ______.

premutation

Most sex-linked disorders are usually carried on ______.

the X chromosome

A male with a genotype XbY is red-green color blind because ______.

the Y chromosome does not carry an allele for that trait