Ch 14 - Mendel and the Gene Idea

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How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?

Cross the green-pod plant with a yellow-pod plant.


Suppose that the botanist carried out the test cross described in Parts A and B and determined that the original green-pod plant was heterozygous (Gg). Which of Mendel’s findings does her test cross illustrate?

law of segregation


During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur?

meiosis I, anaphase


What is the difference between heterozygous and homozygous individuals?

All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.


When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.

gametes, progeny


True or false? The same phenotype can be produced by more than one genotype.



A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)?



A dominant phenotype is indeed expressed if the individual is homozygous dominant for that trait, but the dominant phenotype is also expressed if the individual is heterozygous for the trait. In fact, heterozygous expression is the definition of dominant.



If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?



Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?

The offspring would be in a 3:1 ratio of normally pigmented mice to albino mice.

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What is the genotype of the parent with orange eyes and white skin? (Note: orange eyes are recessive.)

This result of the cross indicates that both orange eyes and white skin are recessive.


Black eyes are dominant to orange eyes, and green skin is dominant to white skin. Sam, a MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. Carole is a MendAlien with orange eyes and white skin. If Sam and Carole were to mate, the predicted phenotypic ratio of their offspring would be _____.

1 black eyes, green skin : 1 black eyes, white skin : 1 orange eyes, green skin : 1 orange eyes, white skin

Sam's genotype is BbGg, and Carole's genotype is bbgg.


In order to determine the genotype of a MendAlien with black eyes and green skin, you would cross this individual with a(n) _____ individual.



A cross between an individual with orange eyes and green skin and an individual with black eyes and white skin is an example of a _____ cross.



A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.

both parents are heterozygous for both genes

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The observed distribution of alleles into gametes is an illustration of _____.

Mendel's laws of segregation and independent assortment


An individual heterozygous for eye color, skin color, and number of eyes mates with an individual who is homozygous recessive for all three characters; what would be the expected phenotypic ratio of their offspring? [Hint: B = black eyes, b = orange eyes; G = green skin, g = white skin; C = two eyes, c = one eye]

1 black eyes, green skin, two eyes : 1 black eyes, green skin, one eye : 1 black eyes, white skin, two eyes : 1 black eyes, white skin, one eye : 1 orange eyes, green skin, two eyes : 1 orange eyes, green skin, one eye : 1 orange eyes, white skin, two eyes : 1 orange eyes, white skin, one eye


A BbGg x bbgg cross yields a phenotypic ratio of approximately 5 black eyes, green skin : 5 orange eyes, white skin : 1 black eyes, white skin : 1 orange eyes, green skin. Which of the following best explains these results?

Mendel's law of independent assortment is being violated.

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In the following cross the genotype of the female parent is BbGg. What is the genotype of the male parent? [Hint: B = black eyes, b = orange eyes, G = green skin, g = white skin]



In a situation in which genes assort independently, what is the ratio of the gametes produced by an AaBB individual?

1 AB : 1 aB


What process is responsible for the independent assortment of alleles?



How do cells acquire homologous chromosome pairs that carry the alleles that are independently assorted?

Fusion of gametes

During fertilization, gametes bring together homologous chromosomes to generate a diploid individual.


Which of the following statements most accurately describes the process of independent assortment?

Alleles of different genes segregate from one another in a random manner.


The principle of independent assortment is best illustrated by events that take place during metaphase I, during which nonhomologous chromosomes segregate independently of each other.

this is correct


How many genetically unique types of gametes could be produced by an individual with the genotype RrYY?



Which of the following parental genotypes would yield a 1:1:1:1 phenotypic ratio in the offspring?

AaBb, aabb


In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations?

P ... F1 ... F2

Mendel started with true-breeding P generation plants, and in a typical experiment generated two subsequent generations, called F1 and F2.


Which of the following is true about a plant with the genotype AABbcc?

It is homozygous at two loci.

An organism having a pair of identical alleles at a given locus is said to be homozygous for that locus. Here, the plant is homozygous at loci A and C.


What is an allele?

alternative version of a gene


Mendel's second law of independent assortment has its basis in which of the following events of meiosis I?

alignment of tetrads at the equator


Mendel worked _____.

in a monastery

Mendel was a monk who worked in his monastery garden.


Consider pea plants with the genotypes GgTt and ggtt . These plants can each produce how many type(s) of gametes?

four ... one


Two organisms with genotype AaBbCcDdEE mate. These loci are all independent. What fraction of the offspring will have the same genotype as the parents?



Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently.

Among the F2 offspring, what is the probability of plants with white axial flowers?



Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.

These results indicate which of the following?

Epistasis is involved.


Drosophila (fruit flies) usually have long wings (+) but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg).

If flies that are heterozygous for both the bent wing gene and the vestigial wing gene are mated, what is the probability of offspring with bent wings only?