Exam 1

Give the complementary sequence (the other strand) for the following DNA sequence: AAG CTG ATC GAC

. TTC GAC TAG CTG

Examine the pedigree below. What is the most likely mode of inheritance?

Autosomal recessive

The following diagram shows a cell, chromosomes, and spindle fibers attached. What process is this cell undergoing?

Metaphase I of meiosis

If a woman has red-green colorblindness (an X-linked recessive trait), her father must have also had the disorder.

True

An allele for purple fur color in muppets (P) is dominant to an allele for white fur color (p). Heterozygotes for purple exhibit 50% penetrance. The following cross is carried out: P/p x p/p. What proportion of the progeny will be purple?

0.25

James is a 52-year-old man with hemophilia, a sex-linked recessive condition. His daughter, Susan, who has normal blood clotting, is married to Fred who also has hemophilia. Susan and Fred are expecting their first child and an ultrasound shows that the fetus is male. What is the approximate probability that their new son will have hemophilia?

1/2

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2. If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring?

1/4 bitter fruit, yellow spots; 1/4 bitter fruit, no spots; 1/4 sweet fruit, yellow spots; and 1/4 sweet fruit, no spots

If a typical somatic cell (non-sex) of a mammal has 32 chromosomes, how many chromosomes are expected in each gamete of that organism?

16

Suppose that a diploid cell contains 8 chromosomes (2n = 8). How many different combinations in the gametes are possible?

16

A new muntjac species that you are studying has 9 different chromosomes. Like all mammals, the muntjac is diploid. How many chromosomes would you expect to see in a normal somatic (non-gamete) cell from this organism?

18

If you have a fly with the genotype A/a; B/b, and you cross it with a homozygous recessive individual, what phenotypic ratio would you expect in the progeny?

1:1:1:1

What would be the phenotypic ratio produced by a cross between A/a; B/b and a/a; b/b?

1:1:1:1

A male has Klinefelter syndrome with the chromosome constitution of XXXY. How many Barr bodies should be found in the nuclei of cells of this individual?

2

In a certain species of plant, flowers occur in three colors: blue, pink, and white. A pure-breeding pink plant is mated with a pure-breeding white plant. All of the F1 are blue. When the blue F1 plants are selfed, the F2 plants occur in the ratio 9 blue : 3 pink : 4 white. How many gene pairs control the flower color phenotype?

2

If adenine makes up 30% of the bases in a certain DNA sample, what percentage of the bases must be guanine?

20%

In Mendel's peas, yellow seeds are dominant to green. A pure-breeding yellow plant is crossed with a pure-breeding green plant. All of the offspring are yellow. If one of these yellow offspring is crossed with a green plant, what will be the expected proportion of plants with green seeds in the next generation?

50%

A mother with blood type AB has a child with blood type B. Give all possible blood types for the father of this child.

A, B, AB, O

A mother with blood type B has a child with blood type O. Give all possible blood types for the father of this child.

A, B, O

About 70% of Americans perceive a bitter taste from the chemical phenylthiocarbamide (PTC). The ability to taste this chemical results from a dominant allele (T) and not being able to taste PTC is the result of having two recessive alleles (t). Albinism is also a single locus trait with normal pigment being dominant (A) and the lack of pigment being recessive (a). A normally pigmented woman who cannot taste PTC has a father who is an albino taster. She marries a normally pigmented man, who is homozygous at the albinism locus, and who is a taster but who has a mother that does not taste PTC. Which of the following choices list ONLY possible genotypes of their children (all listed are possible)?

A/A; T/t --- A/a; T/t --- A/a; t/t

The pedigree below shows the transmission of an autosomal recessive trait. What is the genotype of individual II-3?

A/a

Which of the following crosses would produce a 1:1 ratio of phenotypes in the next generation?

Aa × aa

In horses, the black coat color is due to a dominant allele B, and the chestnut coat color is due to a recessive allele b. The trotting gait is due to a dominant allele T, and the pacing gait to the recessive allele t. What gametes will be produced by a homozygous black pacer?

All B; t

tRNAs play a key role in protein synthesis. One end of a tRNA contains a(n) _________, and a(n) ________ is attached to the other end.

Anticodon, amino acid

In dogs, black coat color (B) is dominant over brown (b), and solid coat color (S) is dominant over white spotted coat (s). A cross between a black, solid female and a black, solid male produces only puppies with black, solid coats. This same female was then mated with a brown, spotted male. Half of the offspring from this cross were black and solid, and half of the offspring were black and spotted. What is the genotype of the female?

B/B; S/s

When T.H. Morgan crossed the mutant male fruit fly with white eyes to normal females with red eyes, he found in the F1 offspring mostly _____.

Both males and females with red eyes

Two children, a brother and his sister, are born with an autosomal recessive condition. They are believed to be the first two individuals in their extended family to have this disorder. What are the most likely genotypes for their parents?

Both parents are likely heterozygous for the disorder.

What are the structures in a cell that group genes together, are composed of chromatin (DNA and protein), and become visible under a light microscope during mitosis?

Chromosomes

Deafness in humans is often an autosomal recessive phenotype. However, it can be caused by mutations in a number of different genes. If two individuals with autosomal recessive deafness have a child together, and the child has normal hearing, what genetic phenomenon is this an example of?

Complementation

Which type of dominance occurs when the heterozygote has the same phenotype as one of the homozygotes?

Complete dominance

Meiosis results in diploid cells.

False

Which of the following statements is FALSE?

Generally, chromosomes of eukaryotes are circular.

If the pedigree below is for an autosomal recessive characteristic, which individuals are definitely heterozygous?

I-1, I-2, II-4, II-5, III-1

A new mutation in Drosophila, called peach, is found and causes a peach-like body color. A peach male is crossed to a homozygous wild-type female and the offspring consists of peach females and normal males. If a heterozygous peach female is crossed to a normal male, the offspring consists of 1/4 peach females, 1/4 normal females, 1/4 peach males, and 1/4 normal males. What is the MOST likely mode of inheritance for peach?

It is X-linked and dominant.

Which of the following theories of inheritance is no longer accepted as TRUE?

None of the provided theories is currently considered true.

The ability to roll up your tongue on the sides (T, tongue rolling) is dominant to the inability to roll your tongue (t). A woman who can roll her tongue has a child with a man who cannot roll his tongue. The child has his father's phenotype. What is the mother's genotype?

T/t

Achondroplasia is a common cause of dwarfism in humans. All individuals with achondroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with achondroplasia mate, the offspring occur in a ratio of 2 achondroplasia : 1 normal. What is the MOST likely explanation for these observations?

The allele that causes achondroplasia is a recessive lethal allele.

Which of the following statements is FALSE concerning prokaryotic cells?

They lack genetic information.

Homologous chromosomes always (barring a rare mutation) contain the same genes.

True

Mitosis results in two daughter cells that are identical to the starting cell.

True

The phenotype of the heterozygote determines if a given mutant allele is dominant, recessive, or incompletely dominant.

True

If a human trait is never passed from father to son, it is likely that this trait is:

X-linked

Another form of deafness is caused by a rare autosomal recessive gene. As in the previous question, a deaf man and a deaf woman with this form of deafness marry and have lots of children. Would you expect all of the children to be deaf, assuming Mendelian phenotype ratios?

Yes

Is it better to have a large sample size in genetic crosses?

Yes, larger sample sizes can produce phenotypic ratios closer to expected ratios.

Leber hereditary optic neuropathy (LHON) is a human disease that exhibits cytoplasmic inheritance. It is characterized by rapid loss of vision in both eyes, resulting from the death of cells in the optic nerve. A teenager loses vision in both eyes and is later diagnosed with LHON. How did this individual MOST likely inherit the mutant DNA responsible for this condition?

a mitochondrial gene from the mother

A form of a gene that has a slightly different sequence than other forms of the same gene but encodes the same type of an RNA or protein is called a(n):

allele.

Sister chromatids separate in which stage?

anaphase of mitosis and anaphase II of meiosis

The ability to curl one's tongue into a U-shape is a genetic trait. Curlers always have at least one curler parent but noncurlers can have one or both parents who are curlers. Using C and c to symbolize the alleles that control this trait, what is the genotype of a noncurler?

c/c

In Drosophila melanogaster, the level of expression of genes on the X chromosome in males is doubled.What phenomenon is this an example of?

dosage compensation

Freckles are caused by a dominant allele. A man has freckles but one of his parents does not have freckles. What is the man's genotype?

heterozygous

The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. What is the woman's genotype?

heterozygous

Chromatin is made up of DNA and _____.

histone proteins

Which of the following would serve the LEAST well as a model for understanding basic mechanisms of inheritance?

humans

A Barr body is a(n):

inactivated X chromosome, visible in the nucleus of a cell that is from a female mammal with normal chromosomes.

The process of _____ produces cells with half the number of chromosomes (relative to the original state).

meiosis

A measurable or observable trait or characteristic is called a:

phenotype.

Hair color is determined in Labrador retrievers by alleles at the B and E loci. A dominant allele B encodes black pigment, whereas a recessive allele b encodes brown pigment. Alleles at a second locus affect the deposition of the pigment in the shaft of the hair; dominant allele E allows dark pigment (black or brown) to be deposited, whereas recessive allele e prevents the deposition of dark pigment, causing the hair to be yellow. What type of gene interaction does this represent?

recessive epistasis

In pedigree analysis, the proband is:

the individual having the trait or disorder from whom the pedigree is initiated.

Which of the following are NOT prokaryotes?

viruses

With regard to the ABO blood types in humans, determine the possible blood types and proportions of offspring of the following parents:Female parent: Blood type A, whose father was blood type BMale parent: Blood type B, whose mother was blood type O

¼ A, ¼ B, ¼ AB, ¼ O