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Biology quiz chapter 8

The vast majority of people afflicted with recessive disorders are born to parents who were

not affected at all by the disease.

All the offspring of a cross between a red-flowered plant and a white-flowered plant have pink flowers. This means that the allele for red flowers is ________ to the allele for white flowers.

incompletely dominant

Genes located close together on the same chromosomes are referred to as ________ genes and generally ________.

linked . . . do not sort independently during meiosis

All the offspring of a cross between a black-eyed mendelien and an orange-eyed mendelien have black eyes. This means that the allele for black eyes is ________ the allele for orange eyes.

dominant to

The phenotypic ratio resulting from a dihybrid cross showing independent assortment is expected to be

9:3:3:1.

How is sex determined in most ants and bees?

by the number of chromosomes

Mendel's law of independent assortment states that

each pair of alleles segregates independently of the other pairs of alleles during gamete formation.

Which of the following statements regarding genetic testing is false?

Most human genetic diseases are treatable if caught early.

Which of the following statements regarding genotypes and phenotypes is false?

An allele that is fully expressed is referred to as recessive.

The individual features of all organisms are the result of

genetics and the environment

Sex-linked conditions are more common in men than in women because

men need to inherit only one copy of the recessive allele for the condition to be fully expressed.

The expression of both alleles for a trait in a heterozygous individual illustrates

codominance.

A person with AB blood illustrates the principle of

codominance.

Which of the following terms refers to a situation where a single phenotypic character is determined by the additive effects of two or more genes?

polygenic inheritance

Imagine that beak color in a finch species is controlled by a single gene. You mate a finch homozygous for orange (pigmented) beak with a finch homozygous for ivory (unpigmented) beak and get numerous offspring, all of which have a pale, ivory-orange beak. This pattern of color expression is most likely to be an example of

incomplete dominance.

A color-blind woman marries a man who is not color-blind. All of their sons, but none of their daughters, are color-blind. Which of the following statements correctly explains these results?

The gene for color vision is linked to the X chromosome.

Dr. Smith's parents have normal hearing. However, Dr. Smith has an inherited form of deafness. Deafness is a recessive trait that is associated with the abnormal allele d. The normal allele at this locus, associated with normal hearing, is D. Dr. Smith's parents could have which of the following genotypes?

Dd and Dd

Which of the following statements regarding sickle-cell disease is false?

Sickle-cell disease causes white blood cells to be sickle-shaped.

Research since Mendel's time has established that the law of the segregation of genes during gamete formation

applies to all sexually reproducing organisms.

If A is dominant to a and B is dominant to b, what is the expected phenotypic ratio of the cross: AaBb × AaBb?

9:3:3:1

A carrier of a genetic disorder who does not show symptoms is most likely to be ________ to transmit it to offspring.

heterozygous for the trait and able

The mechanism that "breaks" the linkage between linked genes is

crossing over

A testcross is

a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest.

All the offspring of a cross between a black-eyed mendelien and an orange-eyed mendelien have black eyes. What is the expected phenotypic ratio of a cross between two orange-eyed mendeliens?

0 black-eyed:1 orange-eyed

Any gene located on a sex chromosome

. is called a sex-linked gene.

The alleles of a gene are found at ________ chromosomes.

the same locus on homologous

Sickle-cell disease is an example of

codominance and pleiotropy.

A monohybrid cross is

a breeding experiment in which the parental varieties differ in only one character.

Recessive X-linked traits are more likely to be expressed in a male fruit fly than a female fruit fly because

the male's phenotype results entirely from his single X-linked gene.

Imagine that we mate two black Labrador dogs with normal vision and find that three of the puppies are like the parents, but one puppy is chocolate with normal vision and another is black with PRA (progressive retinal atrophy, a serious disease of vision). We can conclude that

the alleles for color and vision segregate independently during gamete formation.

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