BIO WEEK 6

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]

BBGg

True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.

False

Imagine a human disorder that is inherited as a dominant, X-linked trait. How would the frequency of this disorder vary between males and females?

Females would display the disorder with greater frequency than males

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

According to Mendel's law of independent assortment, the alleles for seed color and seed shape are transmitted into gametes in ______________

all possible combinations

Alleles are ______.

alternative or different forms of a gene

What is an allele?

an alternative version of a gene

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

bbgg

What is the genotype of the parent with orange eyes and white skin?

bbgg

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

both parents are heterozygous for both genes

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

cross the green-pod with a yellow-pod plant

Which of the following events causes recombination between linked genes to occur?

crossovers between the genes results in chromosomal exchange

Alleles are _____.

different forms of the same gene that will be present on homologous chromosomes

A cross between two individuals with black eyes and green skin which results in an individual with orange eyes and white skin is an example of a _____ cross.

dihybrid

What is the source of the extra chromosome 21 in an individual with Down syndrome?

duplication of the chromosome NOT: nondisjunction in the father only

Consider pea plants with the genotypes GgTt and ggtt. How many types of gametes can be produced by each of these two plants?

four ... one

At fertilization, two gametes come together. The resulting F2 generation exhibits _______ different phenotypes in the ratio of __________

four; 9 to 3 to 3 to 1

Is this disorder (Pseudohypertrophic muscular dystrophy) caused by a dominant or recessive allele?

recessive

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?

that the parents were both heterozygous for a single trait

In crossing an individual that is homozygous for a completely dominant allele with a heterozygous individual, what is the chance of getting an offspring with the homozygous phenotype?

100%

Match the phenotypes on the labels at left to the genotypes listed below.

- AaBbcc: albino - AaBBCC: agouti black - Aabbcc: albino - AAbbCc: Agouti brown - aaBbCc: solid color, black - AABBcc: albino

Indicate the genotypes by dragging the correct label to the appropriate location

(see image)

What is the probability that a daughter of this mating will be hemophiliac?

0

A woman with red-green color blindness marries a man with normal vision. Thinking only about their daughters, what is the probability that a daughter will be color blind?

0%

In crossing an individual that is homozygous for a completely dominant allele with a heterozygous individual, what is the chance of getting an offspring with the homozygous recessive phenotype?

0%

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

1 AB : 1 aB

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

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?

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

In a particular plant, leaf color is controlled by gene locus D. Plants with at least one D allele have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in the figure above, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the boxes marked 1 - 4 correspond(s) to plants with dark leaves?

1, 2, and 3

If the couple has four sons, what is the probability that all four will be born with hemophilia?

1/16

A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits. Remember that extra digits is a dominant trait. What fraction of this couple's children would be expected to have extra digits?

1/2

Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt × BBtt will be expected to have black fur and long tails?

1/2

What is the probability that a son will be a homophiliac?

1/2

A woman with red-green color blindness marries a man with normal vision. If they have a son or sons, what is the probability that the son or sons will be color blind?

100%

If a blood type O person has children with another blood type O person, ____ of the children will have a recessive allele.

100%

Gregor Mendel crossed two homozygous parents, a tall pea plant and a short pea plant to produce offspring. The allele for "tall" is dominant to the allele for "short." After further study, Mendel was able to infer that the F1 offspring had been:

100% heterozygous

Gregor Mendel crossed two homozygous parents, a tall pea plant and a short pea plant to produce offspring. The allele for "tall" is dominant to the allele for "short." Mendel observed that the F1 offspring were:

100% tall

Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies. How many genes must be responsible for these coat colors in Labrador retrievers?

2

Suppose you mate two mice with the genotypes AYaBb x AYaBb . Considering only the live-born offspring, what would be the expected frequency of mice with yellow fur? (For help getting started, see Hint 1.) Express your answer as a fraction using the slash symbol and no spaces (for example, 1/16).

2/3

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?

25

Gregor Mendel crossed two homozygous parents, a tall pea plant and a short pea plant to produce offspring. He then crossed the F1 offspring with each other to produce a second generation of offspring. The allele for "tall" is dominant to the allele for "short." Mendel observed that the second-generation offspring were:

25% tall and 75% short

If a person with type B blood has children with a person possessing type B blood, how many different Punnett squares that could be made to show all of the possible combinations of paternal gametes?

3

What would be the expected frequency of agouti brown offspring in the litter?

3/16

A particular disease is caused by the allele R, which is completely dominant to the normal recessive allele r. Consider a couple where one parent has the genotype Rr, and the other parent has the genotype rr. What is the chance that their first child will develop the disease?

50%

Domesticated cattle show a genetic defect known as "rabbit hock" in which the knee of the back leg is malformed slightly. The gene controlling this trait is sex-linked and recessive. Now, suppose a bull with the normal phenotype mates with a cow that is heterozygous for rabbit hock. Through amniocentesis testing we know that the cow is about to give birth to a male offspring. What is the chance of producing a normal son?

50%

In humans, strait thumbs are caused by the dominant allele T, whereas, individuals who are tt have thumbs that curve backwards (hitchhiker's thumb). Consider a family in which one parent has straight thumbs. That parents has the heterozygous genotype for the condition. The other parent exhibits the hitchhiker's phenotype. What is the probability that a child of the parents will have hitchhiker's thumb?

50%

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

50%

Tallness (T) in snapdragons is dominant to dwarfness (t), and red (C^R) flower color is not dominant to white (C^W). The heterozygous condition results in pink (C^R C^W) flower color. If snapdragons are heterozygous for height as well as for flower color, a mating between them will result in what ratio?

6:3:3:2:1:1

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

8

In a cross between two mice that are heterozygous for agouti, black, color, and piebaldism, what is the probability that offspring will have solid black fur along with large patches of white fur?

9/256

Which of the following statements correctly describes a dihybrid cross?

A dihybrid cross involves organisms that are heterozygous for two characters

Which of the following statements correctly describes a monohybrid cross?

A monohybrid cross involves organisms that are heterozygous for one character

Which of the following statements is true? In other words, four of the statements are false. Pick the true statement.

ANSWER: - only incomplete dominance can result in three different phenotypes when a trait is caused by a single gene with two alleles - recessive alleles are less common in a population than dominant alleles - for a particular gene the dominant allele may be either more or less common than the recessive allele - type O blood is the most common phenotype observed in almost all human populations - the concepts of pleiotropy, epistasis, and polygenic inheritance all require the presence of two different genes to affect the phenotype of a trait

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

Why is this disorder almost never seen in girls?

For a girl to have the disorder, she would have to inherit recessive alleles from both parents. This would be very rare since males with the recessive allele on their X chromosome die in their early teens

A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

HT

Select the correct explanation for the fact that a carrier of a recessive genetic disorder does not have the disorder

In a recessive disorder, only a single functioning allele is necessary to determine a normal phenotype

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

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

Mendel's laws of segregation and independent assortment

A woman is heterozygous for red-green color blindness, a sex-linked trait. Her husband has normal color vision. Imagine that they have a child. What percentage of their children will have normal vision?

NOT: 50%

In pea plants, the allele for purple flowers is dominant to the allele for white flowers. In a cross between a purple-flowered plant and a white-flowered plant, all 73 of the offspring had purple flowers. Which cross would provide such results?

PP x pp

In pea plants, the allele for purple flowers (P) is dominant to the allele for white flowers (p). In a cross between a purple-flowered plant and a white-flowered plant, 38 of the offspring plants had purple flowers and 41 of the offspring plants had white flowers. Which cross would provide such results?

Pp x pp

You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?

Red shows incomplete dominance over white

SRY is best described in which of the following ways?

SRY is a gene region located on the Y chromosomes that triggers male development

Which of the following is true of an X-linked gene but not of a Y-linked gene?

The gene is present in both males and females

(Pseudohypertrophic muscular dystrophy) Is its inheritence sex-linked or autosomal?

The inheritance of the disorder is sex-linked because it is seen only in boys

In humans, what determines the sex of offspring and why?

The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome

Select the correct statement(s) about sex determination in animals.

The mechanism of sex determination varies with different animal species.

Each chromosome in this homologous pair possesses a different allele for flower color. Which statement about this homologous pair of chromosome is correct?

These homologous chromosomes represent a maternal and a paternal chromosome

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

Traits are inherited in discrete units and are not the results of the "blending" of traits

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

True

This means that the F1 generation makes gametes with the following genotypes:

YR, Yr, yR, yr

The resulting offspring - the F1 generation - have genotype _______

YyRr

Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height?

a combination of polygenic inheritance and environmental factors

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

gametes, progeny

Consider two parents, one with blood type B and other with genotype I^A I^A. The parent with blood type B is heterozygous. The maximum number of different genotypes, and the maximum number of different phenotypes of the offspring would be ___.

genotypes = 2, and phenotypes = 2

Consider a Punnett square of the cross: ww x Ww. The allele for white flowers (W) is completely dominant to the allele for red flowers (w). The offspring of this cross would have ______ genotypes and the phenotypes of the offspring would be _______.

genotypes = 2, and phenotypes with 50% white, 50% red

Predict genotypic and phenotypic ratios for this cross:

genotypic ratio of 1 Ii : 1 ii and a phenotypic ratio of 1 inflated : 1 constricted

With the exception of X and Y chromosomes, each chromosome is present in two copies in a diploid cell, one maternal copy and one paternal copy. What is the correct term for these pairs of chromosomes?

homologous chromosomes

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. True-breeding red-flowered long radishes are crossed with true-breeding white flowered radishes. All of the F1 offspring are purple-flowered and long radishes. The flower color trait in radishes is an example of which of the following types of inheritance?

incomplete dominance

Which of the following terms is not relevant to understanding the genetics of the ABO blood group?

incomplete dominance

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

Males are more often affected by sex-linked traits than females because

males are hemizygous for the X chromosome

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

In cottontail rabbits, brown fur (B) is dominant to white fur (w). Two brown-furred cottontail rabbits were joined in blessed wedlock and began to reproduce like, well, rabbits. What is the most likely outcome?

more of the offspring will have brown fur than white fur.

Homologous chromosomes _____.

more than one choice is correct - are present in two copies in a diploid cell, one inherited from the mother and one inherited from the father - overlap at a point known as the chiasmata in meiosis, forming some recombinant chromosomes in the process - carry the same genes - are inherited from both parents

In geraniums, R is the dominant allele for red flowers and r is the recessive allele for white flowers. S is the dominant allele for short plants and s is the recessive allele for tall plants. Which of the following statements about the phenotypes of offspring from a cross between two individuals that are both heterozygous for the flower color gene and plant height gene is correct?

more than one of the choices is correct - three-fourths of the offspring would have red flowers and one-fourth of the offspring would be tall. - none of the choices are correct - the offspring will have the following ratio: 1 white flowers and tall, 9 red flowers and short, 3 red flowers and tall, and 3 white flowers and short - one-half of the offspring would have pink flowers and one-half of the offspring would be tall

Characters in humans such as a person's red and white blood cell counts vary quite a bit depending on such factors as altitude and physical activity. Traits like this are referred to as:

multifactorial

A man who is a dwarf due to achondroplasia and has normal vision marries a color-blind woman of normal height. The man's father was 6 feet tall, and both the woman's parents were of average height. Achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. How many of the couple's daughters might be expected to be color-blind dwarfs?

none

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

none

Gregor Mendel crossed two homozygous parents, a tall pea plant and a short pea plant to produce offspring. He then crossed the F1 offspring with each other to produce a second generation of offspring. The allele for "tall" is dominant to the allele for "short." Mendel observed that the second-generation offspring were:

none of the choices are correct: - 100% heterozygous - 25% tall, 50% medium, 25% short - 100% short - none of the choices are correct

Which of the following describes the ability of a single gene to have multiple phenotypic effects?

pleiotropy

In Mendelian inheritance, one or a few genes have a large, visible effect on the phenotype. However, most traits and characteristics of all organisms do not follow this simple pattern. These are called non-Mendelian traits. Which of the following terms is most relevant to the concept of Mendelian traits and least relevant to the concept of non-Mendelian traits?

polygenic

Look at the Punnett square, which shows the predicted offspring of the F2 generation from a cross between a plant with yellow-round seeds (YYRR) and a plant with green-wrinkled seeds (yyrr). Select the correct statement about wrinkled yellow seeds in the F2 generation.

the chance that an individual taken at random from the F2 generation produces wrinkled seeds is 25% and the chance that the same individual produces yellow seeds is 75%

Which of the following statements correctly describes gene linkage?

the closer two genes are on a chromosome, the lower the probability that a crossover will occur between them

What is the reason that closely linked genes are typically inherited together?

the likelihood of crossing over between these two genes in prophase I is low NOT: chromosomes are unbreakable

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?

tortoiseshell females; black males

A tall, purple-flowered pea plant is allowed to self pollinate. 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?

ttpp

In humans, wavy hair occurs in heterozygous offspring of people with straight hair and curly hair. Which of the following crosses would produce offspring with the ratio of 1 straight : 2 wavy : 1 curly?

wavy x wavy

In the P generation, a true-breeding pea plant with genotype YYRR is crossed with a true-breeding plant with genotype ___________

yyrr