##### Genetics Chapter 2.

Mendel performed many types of crosses, including those in which the same genotypes are crossed but the sexes of the parents are switched. These are known as

A) replicate crosses.

B) reciprocal crosses.

C) test crosses.

D) monohybrid crosses.

E) dihybrid crosses.

B.) Reciprocal crosses.

Crosses in which F1 plants heterozygous for a given allele are crossed to generate a 3:1 phenotypic ratio in the F2 generation are known as

- A) replicate crosses.
- B) reciprocal crosses.
- C) test crosses.
- D) monohybrid crosses.
- E) dihybrid crosses.

D.) Monohybrid Crosses

In peas, the round allele is dominant over the wrinkled allele. If a plant with round peas is crossed to a plant with wrinkled peas, all of the resulting plants have round peas. What is the genotype of the parents in this cross?

A) *RR × rr*

B) *RR × Rr*

C) *Rr × rr*

D) *Rr × Rr*

E) *rr × rr*

A.) *RR × rr*

In peas, the yellow allele is dominant over the green allele. If a plant with yellow peas is crossed to a plant with green peas, the resulting plants are 50% yellow and 50% green. What is the genotype of the parents in this cross?

A) *YY × yy *

B) *YY × Yy *

C) *Yy × yy *

D) *Yy × Yy *

E) *yy × yy *

C.) *Yy × yy*

Assuming independent assortment, what phenotypic ratio would you expect to see if an individual with the genotype RrGg is self-crossed?

A) 1:3

B) 9:3:3:1

C) 1:2:1

D) 1:3:2:1

E) 3:1

B) 9:3:3:1

What genotypic ratio would you expect to see among the progeny of a monohybrid cross?

A) 1:3

B) 9:3:3:1

C) 1:2:1

D) 1:3:2:1

E) 3:1

C) 1:2:1

A couple has four children. What is the probability that they would have four boys?

A) 1/2

B) 1/4

C) 1/8

D) 1/16

E) 1/32

D) 1/16

Humans have a gene, "T," that is involved in muscle formation of the tongue. Individuals with the one allele can roll their tongues, while individuals with the other allele cannot. If both parents can roll their tongues, but their child cannot, what can be said about the mode of inheritance?

A) Tongue rolling is dominant.

B) Tongue rolling is recessive.

C) The parents were both homozygous, but the child was heterozygous.

D) Tongue rolling is dominant, and both parents were heterozygous (Tt).

E) Tongue rolling is recessive, and both parents were heterozygous (Tt).

D) Tongue rolling is dominant, and both parents were heterozygous (Tt).

In peas, axial (*A*) flower position is dominant to terminal
(*a*), tall (*L*) is dominant to short (*l*), and
yellow (*Y*) is dominant to green (*y*). If a plant that
is heterozygous for all three traits is allowed to self-fertilize, how
many of the offspring would be dominant for all three traits?

A) 3/64

B) 9/64

C) 27/64

D) 32/64

E) 64/64

C) 27/64

In peas, axial (*A*) flower position is dominant to terminal
(*a*), and tall (*L*) is dominant to short (*l*).
If a plant that is heterozygous for both traits is allowed to
self-fertilize, how many of the offspring would also be heterozygous
for both traits?

A) 9/16

B) 4/16

C) 3/16

D) 2/16

E) 1/16

B) 4/16

The law of segregation states that the F2 progeny of F1 heterozygous plants will exhibit

A) a 3:1 phenotypic ratio.

B) a 9:3:3:1 phenotypic ratio.

C) a 1:2:1 genotypic ratio.

D) a 9:3:3:1 phenotypic ratio and 1:2:1 genotypic ratio.

E) both a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio.

E) both a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio.

The law of independent assortment would predict that the F2 progeny of F1 heterozygous plants will exhibit a

A) 3:1 phenotypic ratio.

B) 9:3:3:1 phenotypic ratio.

C) 1:2:1 genotypic ratio.

D) 9:3:3:1 phenotypic ratio and 1:2:1 genotypic ratio.

E) 3:1 phenotypic ratio and 1:2:1 genotypic ratio.

B) 9:3:3:1 phenotypic ratio.

What phenotypic ratio would you expect as a result of a test cross between a dihybrid organism and one that is homozygous recessive for alleles at two independent loci?

A) 3:1

B) 1:2:1

C) 1:1:1:1

D) 9:3:3:1

E) 9:4:2:1

C) 1:1:1:1

How many possible gametes can be produced by a short plant with
yellow, round peas with a heterozygous genotype (*YyRrSs*)?

A) 3

B) 6

C) 8

D) 10

E) 12

C) 8

By convention, when the difference between the *observed
*experimental outcomes and the *expected* outcome is less
than 5 percent (< 0.05), the experimental results are considered to be

A) within normal expected range.

B) statistically significantly and different from the expected outcome.

C) not significant.

D) less than one standard deviation from the mean.

E) equal to the mean.

B) statistically significantly and different from the expected outcome.

The statistical interpretation of a chi-square value is determined by identifying the

A) mean.

B) degrees of freedom.

C) average.

D) *P* value.

E) joint probability.

D) *P* value.

The P value is a quantitative expression of the probability that the
results of another experiment of the same size and structure will
*deviate as much or more from expected results by chance*.
The greater the difference between observed and expected results of an experiment,

A) the lower the χ2 value and the lower the *P *value.

B) the greater the χ2 value and the greater the *P* value.

C) the greater the χ2 value and the lower the *P* value.

D) the lower the χ2 value and the greater the *P* value.

E) the greater the χ2 value; but the* P* value is unaffected.

C) the greater the χ2 value and the lower the *P* value.

The statistical interpretation of a chi-square value is determined by
identifying the *P* value for each experiment, and the
*P* value is dependent on the number of degrees of freedom (df)
in the experiment being examined. For the coin flip experiment, the df
value is equal to 1. What would be the df value for the example about
rolling a 1 in a single roll of a die?

A) 1

B) 2

C) 3

D) 4

E) 5

E) 5

The genes responsible for some of the traits that Mendel observed
have been recently identified and have helped in determining how
molecular variation produces morphologic variation in pea plants.
Allelic variation in the *Sbe1* gene, which produces starch-branching enzyme 1, is responsible for which
trait in peas?

A) round and wrinkled pea shape

B) yellow and green pea color

C) purple and white flowers

D) tall and short plant height

E) axial and terminal flower position

A) round and wrinkled pea shape

In 1997, a gene called *Le* was discovered by two research
groups led by David Martin and Diane Lester. Allelic variation in the
*Le* gene, which controls elongation of the plant stem between
branches, is responsible for which trait in peas?

A) inflated and constricted pod shape

B) yellow and green pod color

C) purple and white flowers

D) tall and short plant height

E) axial and terminal flower position

D) tall and short plant height

Mendel performed numerous controlled genetic crosses to obtain strains that consistently produced a single phenotype without variation. What are these strains that consistently produce the same phenotype called?

Answer: pure-breeding or true-breeding strains

In a test cross, a pure-breeding plant is crossed with a plant
suspected to be heterozygous (*Aa*). What is the genotype of
the pure-breeding plant?

Answer: *aa*

Why did Mendel cut off the nascent anthers during the process of artificial cross-fertilization?

Answer: to prevent self-fertilization or to prevent uncontrolled crosses

What simple type of cross that looks at the inheritance of only one trait could be used to illustrate Mendel's law of segregation?

Answer: monohybrid cross

If an affected individual is born to parents who are unaffected, what is the likely mode of inheritance?

Answer: autosomal recessive

What type of cross would be used to illustrate Mendel's law of independent assortment?

Answer: dihybrid cross (or test cross)

A cross between a short pea plant and a tall pea plant results in a
1:1 genotypic *and* phenotypic ratio in the offspring. What are
the genotypes of the parent plants?

Answer: *Ss* × *ss* (heterozygous × homozygous recessive)

What is the probability of rolling one six-sided die and obtaining a 1 or a 2?

Answer: 1/6 + 1/6 = 2/6 = 1/3

What is the probability of rolling one six-sided die and obtaining any number but 6?

Answer: 1 - 1/6 = 5/6

What is the probability of rolling two six-sided dice and obtaining two 4s?

Answer: 1/6 × 1/6 = 1/36

What is the probability of rolling two six-sided dice and obtaining at least one 3?

Answer: (1/6) + (5/6)(1/6) = 6/36 + 5/36 = 11/36

What is the probability of rolling two six-sided dice and obtaining an odd number on at least one die?

Answer: 9/36 + 9/36 + 9/36 = 27/36 = 3/4

Prob. of rolling odd number the 1st roll only = 3/6 (odd) × 3/6 (even) = 9/36

Prob. of rolling odd number the 2nd roll only = 3/6 (even) × 3/6 (odd) = 9/36

Prob. of rolling odd number both rolls = 3/6 (odd) × 3/6 (odd) = 9/36

Prob. of any one of these three possible scenarios = addition rule

When calculating the probability of a given genotype in a trihybrid cross, you can generate a Punnett square. Which of the rules of probability can be used to calculate the joint probability of simultaneous inheritance of multiple alleles?

Answer: the product rule

In a cross between individuals who are both heterozygous (carriers) for a recessive disease such as albinism, you would like to determine the risk of one or more children to inherit the recessive phenotype. Which of the rules of probability can be used to calculate the probability of a particular combination of events that each have two alternative outcomes?

Answer: binomial probability

You have self-fertilized a plant with round seed that is heterozygous, and you want to determine what proportion of the offspring will be not only dominant, but true-breeding. Which of the rules of probability can be used to calculate the probability of obtaining a particular outcome when specific information about that outcome modifies the probability calculation?

Answer: conditional probability

In a dihybrid cross, you want to calculate the probability that an F2 progeny of the cross will inherit both dominant phenotypes. Which of the rules of probability can be used to calculate the probability of obtaining that combination of alleles?

Answer: the product rule

The statistical value obtained from the chi-square analysis refers to the probability that the deviations of between the observed numbers and the expected numbers are caused by what?

Answer: random chance

A normal distribution curve contains all the possible experimental outcomes in graph form. The tall central segment of the curve represents the outcomes with the highest probability of occurrence. The average outcome, represented by the center of the data distribution, is known as what?

Answer: the mean (µ)

The probability of experimental outcomes gets smaller toward the farthest left and right portions of the curve. The probability of a given observation compared to all possible outcomes is known as what?

Answer: the standard deviation (σ)

Geneticists must be able to compare the outcomes they obtain in their experiments to the outcomes that might be expected to occur. Which test would they use to confirm that the difference between observed and expected can be attributed to chance?

Answer: chi-square test

One key to Mendel's success was choosing to observe ________ traits, which exhibit one of two possible phenotypes.

Answer: dichotomous

The hereditary particles that are passed from one generation are
called *alleles* in modern terminology. This term had not been
invented in Mendel's time; instead, he determined that two
"________" (alleles) were present for each trait in a plant
and together determined the phenotype of the trait.

Answer: elementen

A ratio of 9:3:3:1 is expected among the F2 progeny of a dihybrid cross as a result of ________ of alleles at two loci.

Answer: independent assortment

Binomial expansion is a complex genetic calculation requiring
repetition and precision in the use of the product rule and the sum
rule. A shortcut called ________ eliminates the need for these
repetitive calculations and can be used for any number of expansions
between 0 and the *n*th power to yield the size of each
possible class and the total number of classes possible.

Answer: Pascal's triangle

The *P* value is dependent on the number of ________, which is
equal to the number of independent variables in an experiment.

Answer: degrees of freedom (df)