Chapter 29

Actual genetic makeup

genotype

Situation in which an individual has different alleles making up the genotype for a particular trait.

heterozygous

Situation in which an individual has identical alleles for a particular trait.

homozygous

An individual who is heterozygous for a particular trait, yet expresses both alleles of that trait, is demonstrating an example of ________.

incomplete dominance

The heterozygote has a phenotype intermediate between those of the homozygous dominant and homozygous recessive

incomplete dominance

The genotype of a normal man is ________.

XY

Using the information provided in this figure as an example, what is the genotype of a homozygous recessive offspring if A represents a dominant allele, and a represents a recessive allele?

aa

Genes for the same trait that have different expressions.

allele

Recessive alleles are best defined as ________.

an allele only expressed when the allele is homozygous

What advantage is gained because both paternal and maternal chromosomes present in some gametes?

an increase in variability in the offspring

Chromosomes regulating most body characteristics

autosomes

Suppose that a child received one of the purple chromosomes (top) from their father and one of the green ones (bottom) from their mother. Which of the following would be the correct phenotype for the child?

brown hair and brown eyes.

Dominant alleles are so called because under most circumstances they ________.

can suppress the expression of other alleles

How many alleles exist for a given gene?

each gene can have a different number of alleles

Y chromosomes contain far more genes than X chromosomes. T or F

false

What pattern of inheritance results from the effects of multiple genes at different chromosome locations to produce one overall phenotype?

polygene inheritance

Which of the following terms applies to a continuous phenotypic variation between two extremes?

polygenic inheritance

Genes not expressed unless they are present in homozygous condition.

recessive

Which of the following does not match the term to its correct definition/description?

recessive: gene expressed when present

Amy's hand was exposed to X-rays. A gene in a skin cell of her hand mutated. This mutant gene will ________.

replicate itself when the cell divides but will not be passed on to Amy's offspring

A chromosome pair that may be very different in size.

sex chromosomes

Inherited traits determined by genes on the X or Y chromosomes.

sex-linked inheritance

Which type of inheritance involves genes not located on autosomal chromosomes?

sex-linked inheritance

Alleles may code for alternative expressions of a genetic trait. T or F

true

Height in humans is determined by polygene inheritance T or F

true

The dominant gene is expressed when present; the recessive gene is expressed only in the absence of the dominant gene.

Dominant-recessive inheritance

Your genotype is a description of your combination of alleles for a given phenotype. T or F

True

An allele that can mask another allele is said to be __________.

dominant

The gene allele that suppresses or masks the expression of the other allele.

dominate

The genetic determination of blood type is based on __________ inheritance

multiple-allele

Inheritance of the ABO blood group type is an example of this type of inheritance.

multiple-allele inheritance

How many chromosomes are in a haploid human cell?

23

Using the information provided in this figure, what is the probability of heterozygous parents carrying the recessive allele for albinism producing an offspring who expresses the albino phenotype?

25%

Using the information provided in this figure, what is the probability of these parents producing a homozygous dominant offspring?

25%

Which statement is most correct?

Alleles are variations of the same gene.

Select the statement that best describes the difference between a gene and an allele.

Genes express a specific trait while alleles are variations of a particular gene that result in the variation we see in that trait.

Suppose that a child received one of the purple chromosomes (top) from their father and one of the green ones (bottom) from their mother. Which of the following would be the correct genotype for the child?

HhEe

Inheritance that results in continuous or qualitative phenotypic variations between two extremes; an example is skin color.

Polygenic inheriteance

Steven has the dominant tongue rolling phenotype but he does not know his genotype. His wife has the recessive non-tongue rolling trait. If their son cannot roll his tongue this means ________.

Steven has a heterozygous genotype

It is possible for a baby to have type O blood if neither parent is type O. T or F

True

The reason recessive genetic disorders are more frequent than dominant genetic disorders is that ________.

carriers are not eliminated by the disease before passing the defective alleles on to their offspring

Which event can directly produce one chromosome containing both maternal and paternal genes?

crossing-over only

Genes on the same chromosome are said to be __________.

linked

Which of the following is not a source of genetic variation?

mitosis of fertilized egg

Gene mutations in the X chromosome would tend to become visibly expressed ________.

more frequently in males