Mastering Genetics Chapter 3 HW

You would like to know whether the progeny of a pair of mated fruit flies are distributed among the resulting four phenotypic classes in a 1:1:1:1 ratio. You perform a chi-square test and obtain a p value of 0.04. Assuming you have done the test correctly

observed and expected counts are too large to be attributed to chance.

The larger the number of total individual counts in a chi-square test, the higher the degrees of freedom (df).

False

The expected ratio of phenotypes among the progeny of a test cross is 1:1:1:1. Out of 200 total resulting progeny, 48 occur in one of the four phenotypic classes. Given this information, which of the following must also be true?

The value of observed - expected for this cell = -2.

Independent assortment explains _______.

why a collection of meiotic products that includes gametes of genotype Ab will also include gametes of genotype AB in roughly the same proportion

Independent assortment occurs only in cells that are heterozygous for two genes (AaBb) and not in cells that are completely homozygous (AABB or aabb).

False

Which of the following genotypes represents a gamete produced by a failure to segregate during meiosis in a cell of genotype AaBbCC?

AaBC

Which of Mendel's postulates can only be demonstrated in crosses involving at least two pairs of traits?

independent assortment

Which of the following would be true of a plant heterozygous for a single gene controlling flower color?

If crossed with another heterozygous plant, the majority of progeny will have the dominant flower color.

The 3:1 phenotypic ratio observed among progeny of an F1 X F1 cross requires random union of gametes.

true

Of the methods listed below, which would be the best way to determine which of two alleles of a gene is dominant to the other?

Observe the relevant phenotype in the progeny that result from a cross between individuals from two different pure-breeding lines

In an individual that is heterozygous for a particular trait, the recessive allele is not expressed.

True

Round (R) seed shape is dominant to wrinkled (r) seed shape in pea plants. If an RR plant is crossed with an rr plant, what is the frequency of phenotypes in the F2 generation?

3 round seeds, 1 wrinkled seed

If the first three F2 offspring grown from the cross described above are round, what is the probability that the next F2 offspring will be wrinkled?

25%

Which two genotypes in an individual would be expressed as the same phenotype in a diploid organism?

homozygous dominant and heterozygous

The offspring of the P1 generation is known as the _______ generation.

F1

Mendel's unit factors in pairs are most accurately known to be _______

two alleles on paternal and maternal homologs

A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percentage of their remaining offspring would be expected to have normal pigmentation?

75%

Polydactyly is expressed when an individual has extra fingers and/or toes. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. Having extra digits is caused by a dominant allele. The co

1/2

Tightly curled or wooly hair is caused by a dominant gene in humans. If a heterozygous curly-haired person marries a person with straight hair, what percentage of their offspring would be expected to have straight hair?

50% straight

The fundamental Mendelian process that involves the separation of contrasting genetic elements at the same locus would be called ________.

segregation

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a). Two parents with normal pigmentation have an albino child.
What is the probability that their next child will be albino?
What is the probability that their next child

1/4
1/8
1/64

Assuming a typical monohybrid cross in which one allele is completely dominant to the other, what ratio is expected if the F1s are crossed?

3:1

In studies of human genetics, usually a single individual brings the condition to the attention of a scientist or physician. When pedigrees are developed to illustrate transmission of the trait, what term does one use to refer to this individual?

proband

The autosomal (not X-linked) gene for brachydactyly, short fingers, is dominant to normal finger length. Assume that a female with brachydactyly in the heterozygous condition is married to a man with normal fingers.
What is the probability that their firs

1/2
1/4
1/4

The law of independent assortment states that one gene in a pair is always dominant to the other.

false

If a yellow pea plant with round seeds that has the genotype GgWw is crossed to itself, what proportion of the offspring will be green with round seeds?

3/16

The following phenotypic ratios are determined for a trihybrid cross in which the gametes assort independently:
A 1 : A 2 = � : �
B 1 : B 2 = � : �
C 1 : C 2 = � : �
What is the probability that the F2 offspring will have the phenotype A 1 B 1 C 1?

3/64

Which of the following phenomena is a consequence of Independent Assortment?

The phenotypic ratio among phenotypes produced from an F1 X F1 dihybrid cross is 9:3:3:

The 9:3:3:1 ratio exhibited in the F2 generation of a dihybrid cross is a genotypic ratio.

false

A pea plant is heterozygous for two genes; one controlling height, one controlling color. The genotype is written PpTt. Based on the Law of Independent Assortment, approximately what proportion of the pollen produced by this plant should have the genotype

1/4

A 9:3:3:1 phenotypic ratio is expected from a dihybrid testcross

false

How many kinds of gametes will be expected from an individual with the genotype PpCcTTRr?

8 gametes

A gene can have a maximum of two alleles.

false

A couple has two boys and is expecting a third child. The probability that the third child will be a boy is �.

true

What is the probability of a family with six children having three boys and three girls?

20/64

If three differently colored dice are rolled at the same time, what is the probability that a 6 will be the outcome on each one?

1/216

Chi-square analysis can help us to decide whether _______

our observations of an event differ from our expectations

The Chi-square test involves a statistical comparison between measured (observed) and predicted (expected) values. One generally determines degrees of freedom as ________.

one less than the number of classes being compared

Which term describes the individual in a pedigree whose phenotype was first brought to the attention of a medical researcher?

Proband

Which of the following statements about autosomal recessive traits is true?

If neither parent expresses the trait, but the offspring does, both parents must be heterozygous for the trait

What is the most likely mode of transmission for a trait that is not expressed in parents but is expressed by one half of the sons?

Rare X-linked recessive

Assume that a Chi-square test provided a probability value of 0.02. Should the null hypothesis be accepted?

no