Chapter 21 Patterns and Genetic Inheritance

How many dominant alleles are typically needed to display a dominant phenotype?

1

How many traits are being considered in a monohybrid cross?

1

In a monohybrid cross, we can see a 3:1 phenotypic ratio in the offspring if there are a large number of matings observed; in a human monohybrid cross, we say that each child has a ______ to show the recessive trait.

1 in 4 chance

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

100%

What is the ratio of phenotypes expected in a cross between a dihybrid individual (WwEe) and a recessive individual (wwee)?

1:1:1:1

If there are four possible alleles for a specific gene, how many different alleles does each individual inherit?

2

If the first three children of a human monohybrid cross show the dominant trait, then a fourth child has a ______% chance of showing the recessive trait. Multiple choice question.

25%

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

f 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

Two parents are both heterozygous for unattached earlobes and short fingers (EeSs). How many of the children would be expected to show both dominant traits, unattached ear lobes and short fingers?

9/16

Which of these is an example of alleles?

A gene on a chromosome coding for brown eyes and a gene at the same locus of a homologue coding for blue eyes

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

AB, Ab, aB, ab

What could be the genotype for an individual who is a carrier of a recessive disorder?

Aa

Which of the following represents a monohybrid cross?

Aa x Aa

In a Punnett square what is written horizontally above the columns and vertically to the left of the rows?

Alleles of gametes

A male receives all of his X-linked alleles from his father.

False

Because females have two X chromosomes and males have only one, females exhibit more X-linked disorders than males do.

False

True or false: Because females have two X chromosomes and males have only one, females exhibit more X-linked disorders than males do.

False

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

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

Heterozygous

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

Homozygous dominant

An abnormal protein changes shape and accumulates inside neurons, eventually leading to neuron cell death, in what disease?

Huntington disease

______ alleles require two copies to be present in order to exert their effect.

Recessive

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

SF or sF

Traits determined by genes that are found on the X or Y chromosome are called

Sex-Linked

What is a gene locus?

The position of a gene on a chromosome.

True or false: If both parents are affected by an autosomal recessive disorder, all children will be affected.

True

Red-green color-blindness in humans is an X-linked, recessive trait. Which of the following genotypes represents a FEMALE with red-green color-blindness?

XbXb

The gene responsible for determining male gender is located on the

Y chromosome.

Alternate forms of a gene are called ____________

alleles

In codominance, the phenotype of a heterozygote is

an equal expression of both gene alleles.

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

autosomes

A person who is heterozygous for an autosomal recessive disorder and shows the dominant phenotype is called a

carrier

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

codominance.

all correct descriptions of Huntington disease.

degeneration of brain cells autosomal dominant inheritance increased trinucleotide repeats

An AaHh x AaHh cross is an example of a

dihybrid cross.

A ___________ allele masks the expression of an alternate form of that same gene.

dominant

If an individual inherits one dominant allele and one recessive allele, the phenotype shown will be

dominant.

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

genes

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

genotype.

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

A WwSs genotype is called dihybrid because the individual is ______ for two traits.

heterozygous

If a man with freckles (dominant trait) fathers a child with a woman without freckles, and they have a child without freckles, then the father's genotype regarding this trait is

heterozygous (Ff).

If a parent shows a dominant phenotype for a trait and has an offspring with the recessive phenotype, the genotype of the parent has to be

heterozygous.

If an individual has one recessive allele and one dominant allele, their genotype is

heterozygous.

An individual that inherits two copies of the same form of a gene from his or her two parents has a ______ genotype.

homozygous

An organism with a ____________ genotype carries two identical alleles for a given gene.

homozygous

If you received a dominant allele from your father and a dominant allele from your mother, your genotype for the trait would be

homozygous dominant.

If you received a recessive allele from your father and a recessive allele from your mother, your genotype for the trait would be

homozygous recessive

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; Dominant

The position of a gene on a chromosome is called its

locus

Because the allele for red-green color blindness is carried on the X chromosome and is recessive, the disorder is much more common in

males.

An Ff x Ff cross is an example of a

monohybrid cross.

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

phenotype

9:3:3:1 is the expected ______ ratio for a dihybrid cross.

phenotypic

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.

The best definition of phenotype is

the physical manifestation of a genetic trait.