biology chapter 9

If a homozygous dominant is crossed with a homozygous recessive for a given trait, the offspring will be ____

all of the dominant phenotype

Which of the following is used to define a phenotypic characteristic resulting from the expression of two or more genes?

polygenic inheritance

Tay Sachs disease runs in Rebecca’s family. When she looked at her family pedigree, she saw a shaded circle. This represented ____

a female with Tay Sachs

Human males are much more likely than human females to have the recessive condition hemophilia (a failure of the blood to clot properly). This is the case because __________.

the gene for hemophilia is sex-linked

Assume tall (T) is dominant to dwarf (t). If a homozygous dominant individual is crossed with a homozygous dwarf, the offspring will __

all be tall

A genetic disorder that causes red blood cells to assume an unusual shape and produce abnormal hemoglobin proteins is _____.

sickle-cell disease

Flower color in snapdragons is an example of incomplete dominance. If a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with a pink-flowered plant, the progeny plants will be _______

25% red, 50% pink, and 25% white

Cystic fibrosis can be inherited even if neither parent has the disease. This is because the disease __

is caused by a recessive allele

The most common phenotype in a natural population is referred to as the _

wild type

An allele is __

an alternative version of a gene

A single allele that controls more than one character is ___

pleiotropic

The physical traits of an organism are called its __

phenotype

Which of the following matings can produce a child with blood type AB? The letters refer to blood types (phenotypes).

A x B

Phenylketonuria (PKU) is an autosomal recessive disorder. Using P and p to represent the alleles, what is the genotype of a phenylketonuric person?

pp

Why is it that men are responsible for the gender of their children?

Unlike women, who only contribute an X chromosome, men contribute either an X or a Y chromosome.

In a certain plant, the alleles A, B, and C are dominant to the alleles a, b, and c. A plant with the genotype AABbcc will have the same phenotype as the plant with the genotype __

AaBBcc

A man who has type B blood and a woman who has type A blood could have children of which of the following phenotypes?

A, B, AB, or O

Pea plants are tall if they have the genotype TT or Tt, and they are short if they have the genotype tt. A tall plant is mated with a short plant. Half the offspring are tall, and half are short. This allows us to conclude that the tall plant is ___

heterozygous

Huntington’s disease is due to an autosomal dominant allele. If a heterozygous male marries a normal female, what percentage of the offspring will have Huntington’s?

50%

If two genes are linked ____

they are on the same chromosome

In Mendel’s monohybrid cross of purple-flowered and white-flowered peas, all members of the F1 generation were of the _____ phenotype because their genotype was _____ for the flower-color gene.

purple-flowered … heterozygous

The scientific study of heredity is called

genetics

Which of the following statements is correct?

Offspring of two different true-breeding varieties are called hybrids.

The physical traits of an organism are called its

phenotype

A plant with the genotype AABbcc is __________.

homozygous for two different genes

GgTt pea plants can produce _____ type(s) of gamete(s), but a ggtt plant can produce _____ type(s) of gamete(s

four … one

Which of the following is a true statement?

A testcross is a mating between an individual with a dominant phenotype (but unknown genotype) and a homozygous recessive individual.

In a dihybrid cross, what is the probability of getting the genotype aa when you cross genotypes Aa and aa?

1/2

The most common lethal genetic disease in the United States is _

cystic fibrosis

An important technique that helps provide insight into interesting genetic questions at the molecular level, such as reasons for hairless dogs, is called __

DNA sequencing

You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered snapdragon. All of the F1 are pink. What can you say about the alleles for the parental traits?

Red and white show incomplete dominance.

Incomplete dominance is a condition in plants and people where _______

offspring have an appearance in between the phenotypes of the two parents

The ABO blood group in humans is an example of __________ producing four phenotypes

multiple alleles

Which of the following is used to define a phenotypic characteristic resulting from the expression of two or more genes?

polygenic inheritance

Although our environment can affect our phenotypic characters, __________.

the effects of our environment are not passed on to the next generation

Linked genes are genes that ________

are on the same chromosome

Assume you were studying two characteristics of peas and when you crossed heterozygous F1 individuals you did not see the 9:3:3:1 ratio predicted for a dihybrid cross. You later found that these two characteristics were on the same chromosome. With this information, how would you explain the results

The genes are linked and are inherited together.

The percentage of recombinant phenotypes resulting from fertilization involving recombinant gametes is called __

recombination frequency

In general, the frequency with which crossing over occurs between two linked genes depends on ____

how far apart they are on the chromosome

Using recombination data, it is possible to determine the location of genes on a chromosome. The result is _

a linkage map

The sex chromosomes in humans that make an individual a male are _

X and Y

In humans, the __________ determines the sex of the offspring because _________

male … the male can contribute either an X or a Y chromosome

A gene that is located on a sex chromosome (X or Y chromosome) is ____

A sex-linked gene

Human males are much more likely than human females to have the recessive condition hemophilia (a failure of the blood to clot properly). This is the case because

the gene for hemophilia is sex-linked

Modern advances in __________ have provided important insights into the evolutionary history of life on Earth.

technology