practice test chapter 9

Which of the following statements best describes the concept of blending inheritance, and why is it considered an outdated explanation for genetic inheritance?

Blending inheritance suggests that offspring inherit traits by averaging the characteristics of both parents, and this theory fails to account for the re-emergence of traits in later generations, which Mendelian genetics explains.

Which plants in a typical Mendelian monohybrid cross figure must all be heterozygous?

The purple-flowered plants in the F1 generation.

Mendel conducted his most memorable experiments on:

peas.

In cats, polydactyly (extra toes) is due to a dominant allele P. Jake has 28 toes and Lucy (18 toes) is normal. All 16 of their kittens have extra toes. What is Jake's genotype?

PP

In pea plants, tall (T) is dominant over short (t). Two heterozygous tall plants are crossed. What is the expected phenotypic ratio of tall to short offspring?

3 tall : 1 short

The alleles of a gene are found at:

the same locus on homologous chromosomes.

In cattle, spotted coat is dominant to even coat, short horns are dominant to long horns, and the traits assort independently. In a cross of two individuals heterozygous for both traits, what proportion of offspring are expected to have long horns?

1/4

In pea plants, tall stems (T) are dominant to short (t), and purple flowers (P) are dominant to white (p). Two TtPp plants are crossed. What is the probability their offspring will have short stems and white flowers?

1/16

In cats, black (B) is dominant to brown (b) and striped (S) is dominant to marbled (s). A black, striped cat of unknown genotype is crossed with a brown, marbled cat (bbss), and all offspring are black and striped. What is the genotype of the black, striped cat?

BBSS

What is the probability that a couple's first child is female and the second child is male?

25%

Suppose a platypus with genotype EEFfGGHh reproduces with one of genotype EeFfGGHh. What is the probability of a baby platypus (puggle) with genotype EeFFGGhh?

1/32

In a pedigree for an autosomal dominant trait (H), Libby is affected and has one affected parent and one unaffected parent. What is Libby’s genotype?

Hh

In an autosomal recessive form of deafness (d), two hearing carriers (Dd × Dd) have children. Which statement is NOT true?

If the first two children from Dd parents are deaf, there is no risk that their next child will also be deaf.

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

incompletely dominant to the allele for white flowers.

A homozygous orange-beaked finch is crossed with a homozygous ivory-beaked finch and all offspring have pale ivory-orange beaks. This pattern is an example of:

incomplete dominance.

Blood group O is referred to as the universal donor because type O red blood cells:

have neither Carbohydrate A nor Carbohydrate B on their surface.

Justin has type A blood and both his parents are type AB. Brittany has type B blood and both her parents are type AB. What are the chances that their son Theodore has type A blood?

0%

A single allele that controls more than one character is said to be:

pleiotropic.

The multiple symptoms of sickle-cell disease (anemia, pain, organ damage, etc.) are best explained by:

the pleiotropic effects of the sickle-cell allele.

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

polygenic inheritance.

Two parents of mixed ethnicity have twins, one with very light skin and one with very dark skin. This is because of:

the polygenic nature of skin color genes.

Which statement about the determination of height in humans is true?

Height is determined by variations in more than a hundred genes as well as environmental conditions.

Many traits are affected, in varying degrees, by both genetic and environmental factors.

True

Mendel’s law of has its physical basis in the orientation of homologous chromosome pairs in metaphase I of meiosis, while Mendel’s law of has its physical basis in the separation of homologous chromosomes in anaphase I.

independent assortment; segregation

Linked genes are on and generally .

the same chromosome; do not follow the laws of independent assortment.

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

crossing over.

You determine recombination frequencies between genes X and Y (11.5%), Y and Z (13%), and X and Z (25%). What is a possible sequence of these genes on the chromosome?

X-Y-Z

Which statement about sex determination in the animal kingdom is true?

In some animals, sex chromosomes determine sex and, in some animals, environmental factors such as temperature determine sex.

A human karyotype shows 22 pairs of equal-length chromosomes plus one pair where one chromosome is longer than the other. What can you conclude?

The organism that this cell came from is likely a male.

In fruit flies, red eyes are X-linked dominant and white eyes are X-linked recessive. A white-eyed female is mated with a red-eyed male. What offspring are expected?

All females will be red-eyed, and all males will be white-eyed.

Recessive X-linked traits are more likely expressed in males because:

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