Chapter 21: Genetic Inheritance

If two parents are not affected by an autosomal dominant disorder, then what percent of their children will be affected?

0

Because it is an autosomal recessive disorder, how many copies of the mutated CFTR allele do cystic fibrosis patients have?

2

How many copies of a damaged allele must be present for a recessive genetic disease to be expressed?

2

If there are three possible alleles for a specific gene, how many different possible genotypes exist in the population for this gene (assume none are lethal)?

6

If two heterozygous parents are both affected by an autosomal dominant disorder, then what percent of their children will be affected?

75

SS x Ss

One-trait cross between one homozygous individual and one heterozygous individual

EE x ee

One-trait cross between two homozygous individuals

EeSs x EESS

Two-trait cross between one individual who is heterozygous for both traits and one individual who is homozygous for both traits

In this pedigree for color blindness, the female indicated by the arrow is

a carrier.

What are all the genotypic possibilities for the gametes of a parent that is homozygous recessive for two genes (aabb)?

ab

Tay-Sachs disease is NOT sex-linked and so therefore is termed a(n) __________ recessive disorder.

autosomal

How is sickle-cell disease inherited?

autosomal recessive

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

autosomes

X-linked dominant disorders can be inherited from

either or both parents.

Select all correct descriptions of autosomal dominant disorders.

heterozygotes have an affected phenotype. two unaffected parents will not have children with an affected phenotype. both males and females are affected with equal frequency.

In a one-trait cross, if one parents is homozygous dominant and the other is homozygous recessive, what will the genotype of their offspring be?

heterozygous

the position of a gene on a chromosome is called its

locus or loci

A defect in the production of a connective tissue protein causes ________ syndrome, which causes long limbs and fingers, a caved-in chest, and dislocated lenses of the eye.

marfan

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

pleiotropy

the best definition of a phenotype is

the physical manifestation of a genetic trait

What is a gene locus?

the position of a gene on a chromosome

Men will inherit X-linked dominant disorders from

their mother.

humans normally inherit _____ allele(s) for each gene

two

If the picture shows all the possible gametes of a parent, what is the genotype of the parent with respect to these two traits?

FfSs

One of the children in a family has freckles and long fingers and another child in the family has no freckles and short fingers. If the mother has a no freckles and long fingers, what is the genotype of the father with respect to these two traits?

FfSs

Which of the following are classified as human sex chromosomes?

Y and X

Even though it affects lysosomes, which are present in nearly every cell, Tay-Sachs disease mainly affects the

brain

The specific genes or combination of alleles for a trait is called an individual's

genotype

In a one-trait cross, if both parents are homozygous dominant, what will the genotype of their offspring be?

homozygous dominant

For each gene, an individual inherits ______ allele(s) with ______ being contained in the sperm and ______ being contained in the egg.

two ; one ; one

How many copies of a mutated allele need to be inherited for an autosomal dominant genetic disorder to be displayed?

1

The faulty gene (CFTR) associated with cystic fibrosis is carried by about how many Caucasians in the United States?

1 in 30

If two parents are both affected by an autosomal recessive disorder, what percent of their children will also have the disorder?

100%

What are all the genotypic possibilities for the gametes of a parent that is heterozygous for two genes (AaBb)?

AB, Ab, aB, ab

A male is heterozygous for short fingers (Ss) and homozygous for freckles (FF). Determine the possible alleles present in his sperm.

SF or sF

True or false: X-linked recessive disorders are often passed from grandfather to grandson.

True

EEWw x eeww

Two-trait cross between one individual who is homozygous for one trait and heterozygous for the other, and an individual who is homozygous recessive for both traits

What pattern of inheritance is shown in the picture?

X-linked recessive

Cystic fibrosis is a relatively common autosomal recessive disease that causes thick mucus to build up mainly in which two areas of the body?

bronchial tubes pancreatic ducts

All combinations of alleles are possible in the gametes because the ______ align independently during meiosis.

chromosomes

Marfan syndrome is an autosomal dominant disorder in which the gene coding for what specific protein is mutated?

fibrillin

An individual's genotype is the specific ____ an individual has for a trait

genes

Several inheritance patterns differ from one trait crosses, in which one gene effects one trait. If multiple genes govern a trait it is said to follow an inheritance pattern called _______. If one gene affects many traits, it follows an inheritance pattern called _______.

multiple-allele; pleiotropy

In a one-trait cross, the inheritance of __________ set(s) of alleles is being examined, and in two-trait crosses, the inheritance of __________ set(s) of alleles is being examined.

one ; two

The physical appearance of a trait in an individual is the ______, although in some cases traits are not easily observable.

phenotype

Select all correct descriptions of polygenic traits.

phenotype can be influenced by the environment. phenotypic variation appears continuous. alleles have additive affects on phenotype.

Traits that are governed by multiple sets of alleles that result in a continuous variation of phenotypes (bell-shaped curve) are called ______ traits.

polygenic

A girl is homozygous for long fingers (ss) and homozygous for no freckles (ff). Determine the possible alleles present in her eggs.

sf only

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

the Y chromosome does not carry an allele for that trait.

Which of the following are ways that a mutation for a genetic disorder can be passed to a child? Select all that apply.

the mutation is present in all of the parent's cells. The mutation occurs during the formation of sperm or eggs.

Because it is an autosomal recessive disease, in order for a person to have sickle-cell disease,

they must inherit a recessive allele from each parent.

In the offspring of a cross between two heterozygotes, ______ phenotype(s) are possible when the trait displays incomplete dominance, and ______ phenotype(s) are possible when the trait displays simple dominance.

three ; two