CHAPTER 12 BIO

Let Y = yellow and y = green, and R = round and r = wrinkled. You cross YYRR peas with yyrr peas. All of the F1 individuals are yellow and round with a genotype of YyRr. You then perform a F2 cross and get the expected 9:3:3:1 phenotypic ratio. Which of the following is the correct genotypic ratio for yellow, round F2 individuals?

1/16 YYRR, 2/16 YYRr, 2/16 YyRR, 4/16 YyRr

Achondroplasia is a common form of dwarfism caused by autosomal dominant mutation in the fibroblast growth factor receptor gene 3. If a person with achondroplasia married and had children with a person of normal height, what is the probability that both their first child and second child would have achondroplasia?

1/4

The phenotypic ratio for a testcross with a homozygous individual and a heterozygous individual is _______.

1:1

The genotypic ratio produced in the F2 generation is

1:2:1.

In white tigers, the absence of fur pigmentation is caused by a recessive allele. This allele also causes the tigers to be cross-eyed. If two tigers heterozygous for this allele mate and produce offspring, what percentage can be expected to be white and/or cross-eyed?

25% will be white and the same 25% will be cross-eyed.

Let P = purple flowers and p = white, and T = tall plants and t = dwarf. Of the 16 possible gamete combinations in the dihybrid cross, how many would be the phenotype white, tall?

3

In a typical Mendel experiment on pea-seed color, if the dominant yellow seed-bearing plant was crossed with the recessive green seed-bearing plant, the F2 generation will show what ratio of each kind?

3 yellow: 1 green

How many different types of gametes can be formed by plants with a genotype of PpYYrrTt?

4

Why would a genetic counselor need to know how to construct a human pedigree?

A genetic counselor provides individuals and potential parents with the probabilities of inheriting a . particular disease. An accurate pedigree is an essential part of establishing the correct probabilities.

14. Knight followed up on attempts of English farmers to improve varieties of agriculture with his studies on garden peas. When he crossed two true breeding varieties, he found out a number of things about an inherited trait. Which of the following about inherited traits is false?

An inherited trait is always present in every generation.

If you crossed flies heterozygous for the Cy allele, what surviving genotypes would you find in the F2 generation?

Cy+/Cy+ and Cy/Cy+

Mendel chose the garden pea for his work on inheritance for all of the following reasons except

He failed his examination for a teaching certificate.

Irene and William are having their first child. Irene knows her blood type is A, but William does not know his blood type. However, William knows that his mother and father were B. Their first child is a boy named Gregory. Gregory has type O blood. Of course, Irene and William do not understand how this happened. You could explain this to them using which of the following choices?

Irene's genotype is AO, and William's genotype is BO; thus, Gregory expresses the phenotype of O.

Height and eye colors are two examples of continuous variation in humans. Whereas in pea plants the tall allele is dominant over the short allele, there are no intermediate heights in peas. Which of the following is the best explanation for the differences described above?

Many genes, rather than one gene for a characteristic, control some variations in species.

The first detailed and quantitative studies on inheritance were carried out by an Austrian monk named ______.

Mendel

A person who has lost a large amount of blood but is still alive is found in a wrecked automobile under a highway bridge. Several people are helping the paramedics load the victim into the ambulance. After the ambulance has departed for the hospital, you overhear the following conversation from the persons who helped the paramedics. "I am certain that when that guy gets to the hospital, they will transfuse him with any blood that they have in the blood bank since he has lost so much blood." The other person says, "Yeah, I bet you're right!" Having had a biology course, you know which blood could be safely given to anyone. Select it below.

O

Let P = purple flowers and p = white, and T = tall plants and t = dwarf. What combinations of gametes could be produced by a heterozygote for both the traits?

PT, Pt, pT, pt

Mendel's observations that different pairs of genes assort independently of each other is known as Mendel's

Second Law of Heredity.

8. The Principle of ________ states that alternative alleles for a trait segregate from one another during gamete formation and remain distinct.

Segregation

Children born in areas where proper nutrition is not available to them do not always realize their full growth potential. These children have the genes for normal growth of bones. Which of the following statements can best explain this situation?

Since nutrition is necessary for proper development and is a part of the environment, it is a clear case . of environmental effect on the phenotype.

Mendel performed reciprocal crosses in which he used pollen from a white-flowered plant to fertilize a purple-flowered plant and pollen from a purple-flowered plant to fertilize a white-flowered plant. What did these reciprocal crosses demonstrate?

The reciprocal crosses demonstrated that each parent made an equal contribution to the offspring.

Mendel's first law encompasses all of the following except

all genes found in an individual are not separable into gametes.

Early geneticists demonstrated all of the following about inherited traits except

all traits breed true.

Alternate forms of the same gene are called ______.

alleles

Based on the inheritance pattern, the secretor trait is

autosomal dominant.

An individual possessing both kinds of alleles of two different traits is called

dihybrid.

Individuals carrying two "factors" for most traits are

diploid.

In a heterozygous individual the allele being expressed is

dominant

As a genetic counselor, you are constructing a human pedigree for a particular disease. You note that every generation shows the trait, suggesting that it is

dominant.

Mendel referred to the trait that was expressed in the hybrid, F1 or first filial generation as

dominant.

Based on the inheritance pattern of the secretor trait, a secretor can have a genotype of

either Se/Se or Se/se.

Sometimes one gene pair will interact so as to control the expression of a second gene pair in an interaction called

epistasis.

You can use a Punnet square to do all of the following except

establish a pedigree.

In modern terminology, Mendel's factors are equivalent to _____.

genes

The totality of the alleles present in an organism.

genotype

The allelic make up of an individual is referred to as its

genotype.

One of the general principles of biology that was accepted before much was known about genetics was that

heredity occurs within species, and species "breed true."

A diploid individual carrying two different alleles on its homologous chromosomes.

heterozygote

When Mendel crossed two purple-flowered pea plants with each other, he obtained a phenotypic ratio of 3:1 (purple-flowered pea plants to white-flowered pea plants). His results are consistent with which of the following sets of parents?

heterozygous purple pea plant and heterozygous purple pea plant

When the two haploid gametes contain two different alleles of a given gene, the resulting offspring is called

heterozygous.

A diploid individual whose two copies of a given gene are the same.

homozygote

A diploid organism that has two identical alleles for the same trait is called _______ for that particular trait.

homozygous

Mendel's experiments had all of the following characteristics except

hybrid plants were self-pollinated for several generations.

Mendel's understanding of the inheritance of traits in peas, expressed in modern language, included all of the following except

if a given allele is present, its effects will be seen in the individual.

Let R = red pigment and r = no pigment. In carnations, RR offspring make a lot of red pigment, rr offspring make no pigment and Rr offspring make a small amount of red pigment, thus appearing pink. Pink carnations are therefore an example of

incomplete dominance.

As the new technician in a lab that studies coat color in rodents, you are assigned the task of counting and recording the coat color of the F2 progeny of a dihybrid cross. Your results are: 18 agouti mice, 6 black mice, 8 albino mice. Based on this data, you conclude that coat color in rodents

involves an epistatic interaction.

A single gene has 3 or more alternative forms. These are called

multiple alleles.

ABO blood group expression is an example of

multiple alleles.

Mendel used the garden ___ plant for his studies on inheritance.

pea

The ________ of an organism is the physical appearance resulting from the expression of the genes present.

phenotype

The observable expression of the genes present.

phenotype

The observable outward manifestation of the genes of an individual is referred to as its

phenotype.

If an individual allele has more than one effect on the phenotype it is said to be

pleiotropic.

Let P = purple flowers and p = white, and T = tall plants and t = dwarf. What would be the appearance of a plant with the genotype PpTt?

purple flowers, tall

A gene for a particular trait that is only expressed in the presence of another gene of the same kind is called a(n)

recessive gene.

An allele that is present but unexpressed is

recessive.

Mendel invented the ____ cross to determine whether an individual with an unknown genotype was homozygous or heterozygous for a trait.

test

What is the name of the cross that involves the mating of a hybrid F1 plant with a homozygous recessive plant for the same trait?

test cross

When Mendel crossed dark purple-flowered pea plants with white-flowered pea plants, he never got any pea plants with light purple flowers. This was counter to the

theory of blending inheritance.

One of the main reasons genes assort independent of one another is that

they are on different chromosomes.

Traits that breed _______ can be passed onto future generations without alteration.

true

Yellow-seeded plants might be homozygous or heterozygous. We could find out which by crossing these plants with

true breeding green-seeded plants.

If you crossed flies heterozygous for the Cy allele, what phenotypes would you find in the F1 generation?

wild type and curly wings