BSC CH 10 Part 2

Select all of the following that are true about linked genes.

-inherited together -located on the same chromosome -do not assort independently

True or false: In the inheritance of X-linked disorders, males can be carriers of the disorder.

False

Select all of the following that are true about autosomal recessive inheritance of a human disorder.

Heterozygous individuals are called carriers. Both parents of an affected individual carry at least one copy of the disease-causing allele.

What describes X inactivation in humans?

One X chromosome in each cell is turned off in XX females.

What type of gene expression was present in the seven traits Mendel studied?

One allele was completely dominant over the other.

What describes an inheritance pattern called epistasis?

One gene affects the expression of another gene.

Select the true statement about genes and chromosomes.

The number of genes in a cell exceeds the number of chromosomes.

In Morgan's studies, why did males display the white-eye trait more often than females?

The white-eye allele is on the X chromosome, and males do not have another X to mask the white-eye allele.

What occurs early in embryonic development of female mammals to prevent "double dosing" of proteins from X chromosomes?

X inactivation

Referring to Morgan's experiments with red-eyed and white-eyed fruit flies, match each genotype to its correct phenotype. Instructions

XRY --> red-eyed male XRXR --> red-eyed female XrY --> white-eyed male XrXr --> white-eyed female

Typically, the sex chromosomes of a human female are

XX

What chromosomes typically make up the sex chromosomes in a human male?

XY

For X-linked recessive disorders, males who inherit a recessive allele from the mother will be

affected by the condition.

In a type of gene expression called ______, two different alleles are both expressed fully in the phenotype of the offspring.

codominance

Two different alleles of a heterozygous genotype are both fully expressed to produce the phenotype in a type of expression called

codominance

To construct linkage maps, scientists estimate the distance between genes on the same chromosome based on the ______, as indicated by the percentage of recombinant offspring.

crossover frequency

An example of a(n) ______ cross is the mating of two rats that both have the genotype Ff Tt for fur color and tail length to examine which of two fur colors and tail lengths their offspring will have.

dihybrid

What type of cross is a mating between two individuals that are both heterozygous for the same two genes?

dihybrid cross

Siamese cats and Himilayan rabbits have light-colored bodies but darker-colored paws, ears, and tail due to an enzyme whose activity varies with temperature. This is an example of

environmental effects.

When one gene's products affect the expression of another gene, this is called

epistasis

When one gene's products affect the expression of another gene, this is called

epistasis.

True or false: For some of the traits Mendel studied, alleles were incompletely dominant or codominant.

false

In a gene expression pattern called _______ dominance, the heterozygote has an intermediate phenotype between the homozygotes.

incomplete

The pink snapdragon flowers in the picture are an example of

incomplete dominance.

Mendel's ______ states that the segregation of alleles for one gene does not influence the segregation of alleles for another gene during gamete formation.

law of independent assortment

What are collections of genes that are commonly inherited together?

linkage groups

Using the frequency of crossing between genes V and W, what can be created, as shown in the picture?

linkage map

Fill in the blank question. Genes that are located on the same chromosome and inherited together are called _________ genes.

linked

The bottom panel of the picture shows the offspring genotypes that resulted from Morgan's cross between a male fruit fly heterozygous for two genes (AaBb) and a female fruit fly that was homozygous recessive for the same two genes (aabb). What accounts for the 5:1:1:5 genotypic ratio in the offspring that differs from the ratio Mendel would have predicted?

linked genes

After Mendel's work, biologists determined that a single chromosome carries

many genes

Linkage groups are sets of genes transmitted

on the same chromosome

A type of gene expression called pleiotropy occurs when

one gene has multiple effects on the phenotype.

A chart showing the presence and absence of phenotypes in multiple generations of a family is called a

pedigree.

In ______, one gene encodes a protein that is important in many biochemical pathways or that affects many parts of the body.

pleiotropy

Human eye color is controlled by multiple enzymes encoded by multiple genes; therefore, human eye color is an ______ trait.

polygenic

If the phenotype reflects the activities of more than one gene, it is called a ______ trait.

polygenic

The _______ rule states that the chance of two independent events occurring is equal to the product of the individual chances that each event will occur.

product

If a couple that are both heterozygous carriers of the cystic fibrosis allele have children, the chance that both their first and their second child are carriers is 0.5 x 0.5, or 25%, as determined by the

product rule

Genes that are located on the X or Y chromosome are said to be ______ and often are expressed in one sex more than the other.

sex-linked

Red-green color blindness and hemophilia are examples of ______, which are controlled by alleles on the sex chromosomes.

sex-linked genes

Presence of the phenotype of an autosomal recessive disorder in one generation and then absence of the phenotype in the next generation likely means

the allele is present in heterozygotes that are carrying the disorder.

The law of independent assortment deduced by Mendel states that

the assortment of alleles for one gene does not influence how the alleles for a second gene assort during gamete formation.

The effect of temperature or nutrition on the expression of genes are examples of how ______ can alter the phenotype.

the environment

When Morgan crossed a male fruit fly that was heterozygous for two genes (AaBb) with a female fruit fly that was homozygous recessive for the same two genes (aabb), most of the offspring were either homozygous recessive or heterozygous for both genes, indicating that

the genes for these traits are linked.