Biology 8a

Tay-Sachs disease is an autosomal recessive disorder. Which of the following is the phenotypic ratio for the F1 generation resulting from a cross between two heterozygous carriers for Tay-Sachs?

1 Tay-Sachs: 3 normal

FH, Familial Hypercholesterolemia, is caused by a autosomal dominant gene. Inheritance of the gen leads to higher than normal blood cholesterol levels. Heterozygotes can experience cardiovascular disease in their 30's and 40's whereas homozygotes can experience it in their childhood years. What is the genotypic ratio of two heterozygotes who mate to have a child affected in some way by the disorder?

3 FH: 1 normal

Sickle-cell anemia is an inherited chronic blood disease caused by an autosomal recessive allele. Suppose a man who is homozygous recessive for the sickle-cell gene fathers a child by a woman who is a carrier for sickle-cell. What are the chances their children will exhibit the disease? (Note: A Punnett square may be useful.)

50 percent

What are the types of gametes that can be produced by an individual with the genotype AaBb?

AB, Ab, aB, ab

Consider the X-linked dominant disorder congenital generalized hypertrichosis (CGH). What can you determine about the potential offspring of a couple in which the father has CGH and the mother does NOT?

All daughters will have the disorder.

Red-green color blindness is a sex-linked recessive disorder. A carrier female marries a red-green color blind male. Which statement is false concerning their children?

All male children will be colorblind.

Why do your chromosomes come in pairs?

Because one member of each pair came from my mother and the other from my father.

Why are all the eggs in humans X and never Y?

Human females only have X genes to put into their eggs.

Which of the following statements about homologous chromosomes is FALSE?

They are all maternal in origin.

Nondisjunction with monosomy X

Turner syndrome

Down syndrome in humans is an example of

a change in the overall number of chromosomes

Alternate forms of a gene are called

alleles

In humans, X-linked genetic diseases

can be seen in both males and females.

Cri du chat syndrome results when a portion of chromosome 5 is missing. This is caused by which of the following structural changes to chromosomes?

deletion

Boys inherit sex-linked traits from their dad, not their mom.

false

The genotypic ratio between two heterozygotes for a monohybrid autosomal recessive trait is 3:1.

false

If mom's genotype is Bb, she is described as

heterozygous

A recessive trait will be observed in individuals that are ________ for that trait.

homozygous

Nondiscjunction with XX and normal Y

kinefelter syndrome

Genes located on the same chromosome tend to be inherited as a group. This is known as

linked genes

Which of the following is NOT a process that contributes to genetic variation in organisms?

mitosis

Nondisjunction with 1 less chromosome

monosomy

Nondisjunction with trisomy X.

mostly unaffected females

Nondisjunction with YY and normal X

mostly unaffected male

Failure of chromosomes to separate during meiosis

nondisjunction

translocation

part of a chromosome breaks off and attaches to another chromosome

Duplication

part of chromosome is copied

Deletion

part of chromosome is lost

inversion

part of chromosomes breaks off and reattaches backwards

Describing a person as having hemophilia is to indicate his or her

phenotype

The observable traits expressed by an organism are described as its

phenotype

The X chromosome in humans is

present in both human males and females.

Half of the gametes produced by an organism with the genotype Aa will receive the A allele, while half will receive the a allele. This is a demonstration of

segregation

Genetic mutations that are never passed to the next generation occur in

somatic cells

On chromosomes, a pair of linked genes will be found only on

the same chromosome

If two parents are heterozygous for an autosomal recessive disease,

they are both considered genetic carriers for the disease.

Nondisjunction with 1 extra chromosome

trisomy

Fathers determine the gender of children.

true

Most conditions of nondisjunction and chromosomal abnormalities typically ends in the premature death of the fetus.

true

The phenotypic ratio for 2 heterozygotes on an autosomal recessive trait is 3:1.

true

The phenotypic ratio for a dihybrid cross between 2 heterozygotes for both traits is 9:3:3:1.

true

There are very few lethal autosomal dominant traits in the population because most offspring would die before they are able to reproduce.

true