Exam 3 review

bio

A particular organism has 46 chromosomes in its karyotype. Which of the following statements is correct regarding this organism?

It produces gametes with 23 chromosomes.

In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?

length, centromere position, size and traits coded for by their genes

A particular organism has 46 chromosomes in its karyotype. Which of the following statements is correct regarding this organism?

It produces gametes with 23 chromosomes.

In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?

length, centromere position, size and traits coded for by their genes

A human female has chromosomes in each skin cell and chromosomes in each egg cell.

46, 23

Many organisms spend most of their life cycle in the diploid state. If meiosis produces haploid cells, how is the diploid number restored for these types of organisms?

by fertilization

Which of the following processes occurs in meiosis but not in mitosis?

synapsis of chromosomes

Which of the following processes occur during meiosis but not mitosis?

Diploid cells form haploid cells

When chiasmata can first be seen in cells using a microscope, which of the following processes has most likely occurred?

Prophase I

Which of the following statements is correct regarding the human X chromosomes?

It carries genes that determine an individual's biological sex.

Which of the following events happens at the conclusion of meiosis I?

Homologous chromosomes of a pair are separated from each other.

Which of the following statements describes the chromosomal makeup of each daughter cell after telophase of meiosis I?

The cells are haploid, and the chromosomes are each composed of two chromatids.

One of the purposes of meiosis is to .

reduce the chromosome number in each resulting cell by half

During which of the following phases of meiosis do homologous chromosomes separate?

anaphase I

Crossing over of chromosomes normally takes place during which of the following processes?

prophase I of meiosis I

Imagine that there are 25 different species of protists living in a tide pool. Some of these species reproduce both sexually and asexually, and some of them can reproduce only asexually. The pool gradually becomes infested with disease-causing viruses and bacteria. Which species are more likely to thrive in the changing environment?

The sexually reproducing species is likely to thrive.

A triploid cell contains three sets of homologous chromosomes. If a cell of a diploid species that normally has 42 chromosomes per cell is triploid, this cell would be expected to have which of the following sets of chromosomes?

63 chromosomes in 3 sets of 21 chromosomes

Which of the following processes might produce a human zygote with 45 chromosomes?

an error during anaphase of meiosis occurring in either an egg or sperm

Which of the following characteristics do homologous chromosomes exhibit?

They carry information for the same traits.

Which of the following statements defines a genome?

the complete set of an organism's genes and other DNA sequences

Which of the following statements correctly describes a karyotype?

It is an organized image of a cell's chromosomes.

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I?

The cells have half the number of chromosomes and one-fourth the amount of DNA.

During which of the following processes do sister chromatids separate from each other?

during both mitosis and meiosis II

Asexual reproduction occurs during which of the following processes?

Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm?

2

Which of the following statements describes a major difference between meiosis II and mitosis in a diploid animal?

Meiosis II occurs in a haploid cell, while mitosis occurs in diploid cells

During which of the following processes do homologous pairs of chromosomes align adjacent to one another at the metaphase plate of a cell?

metaphase I of meiosis

Which of the following processes occurs when homologous chromosomes cross over in meiosis I?

Corresponding segments of non-sister chromatids are exchanged.

The bulldog ant has a diploid number of two chromosomes. Therefore, following meiosis, each daughter cell will have a single chromosome. In addition to mutations, how might genetic diversity be generated in this species?

crossing over and random fertilization

If a cell has completed meiosis I and the first cytokinesis, and is just beginning meiosis II, which of the following is an appropriate description of its genetic contents?

It has half the amount of DNA as the cell that began meiosis.

Independent assortment of chromosomes is a result of which of the following processes?

the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I

In eukaryotes, genetic information is passed to the next generation by processes that include mitosis or meiosis. Which of the following explanations correctly identifies the process and supports the claim that heritable information is passed from one generation to another?

In asexual reproduction, a single individual is the sole parent and passes copies of its genes to its offspring without the fusion of gametes.

Genetic variation leads to genetic diversity contributes to the evolution of populations of organisms. Which of the following statements best represents the connection between reproduction and evolution?

Sexual reproduction increases genetic variation because random mutations can be shuffled between organisms.

Which of the following statements is correct in describing the terms monohybrid cross and dihybrid cross?

A dihybrid cross involves organisms that are heterozygous for two traits that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one trait being studied.

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of meiosis?

anaphase I of meiosis

Why did all of the F1 offspring of Mendel's classic pea crosses always look like one of the two parental varieties?

One allele was dominant

Albinism (lack of dark pigmentation, i.e., coloration), is a recessive trait. A man and woman both show normal pigmentation, but both have one parent who has albinism (lacks dark pigmentation). What is the probability that their first child will have albinism?

1/4

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 result of "blending."

What is the probability of producing the genotype AABBCC in a cross of individuals who both possess this genotype: AaBbCc?

1/64

Which of the following statements best describes the addition rule of probability?

If there is more than one way that a particular result can occur, the chance of that result is the sum of the probabilities of that result.

A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have the normal number of digits (five fingers on each hand and five toes on each foot.) Having extra digits is caused by a dominant allele. The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits?

1/2

Which of the following inheritance patterns describes the ability of a single allele to have multiple phenotypic effects?

pleiotropy

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

environmental factors such as soil pH affect the phenotype

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. If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F1 will be expected to exhibit which of the following phenotypes?

purple and long

Mendel continued some of his experiments into the F2 or F3generation in order to .

observe whether or not a recessive trait would reappear

Which of the following statements correctly describes how Mendel accounted for the observation that traits had disappeared in the F1 generation and then reappeared in the F2 generation?

Traits can be dominant or recessive, and the recessive traits were "hidden" by the dominant ones in the F1.

What type of allele produces its effects in only homozygous individuals?

recessive

According to the law of segregation:

pairs of alleles separate during the formation of gametes

The physical manifestation of an organism's genes is its

phenotype

The results of a test cross reveal that all the offspring resemble the parent being tested. This parent must be:

homozygous

A Mendelian test cross is used to determine whether:

an individual is homozygous or heterozygous.

If you cross pea plants that are heterozygous for purple flowers and yellow seeds (PpYy), and you examine 800 offspring for flower and seed color, about how many do you expect to have white flowers and green seeds?

50

All of the following statements about genotypes and phenotypes are true EXCEPT:

matings between individuals with dominant phenotypes cannot produce offspring with recessive phenotypes.

If, in a heterozygous individual, only one allele is expressed in the phenotype, that allele is:

dominant

Skin color in a certain species of fish is inherited by a single gene with four different alleles. How many different types of gametes would be possible in this organism?

4

Given the following genotypes for two parents, AABBCc × AabbCc, assume that all traits exhibit simple dominance and independent assortment. What proportion of the offspring of this cross will be expected to phenotypically resemble the parent with the genotype AABBCc?

3/4

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

alignment of pairs of homologous duplicated chromosomes along the middle of the cell

In crossing a homozygous recessive with a heterozygote, what is the chance of getting a homozygous recessive phenotype in the F1 generation?

50%

Which of the following calculations requires the use of the addition rule of probability?

Calculate the probability of a child having sickle-cell anemia OR cystic fibrosis (both autosomal recessive disorders) if parents are each heterozygous for both.

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

8

Which of the following statements about independent assortment or segregation is correct?

The law of independent assortment describes how alleles of two or more genes are inherited.

Phenylketonuria is an inherited disease caused by a recessive autosomal allele. If a woman and her husband are both carriers, what is the probability that their first child will be a phenotypically normal girl?

3/8

In mice and many other mammals, one gene controls production of fur color pigment (black or brown), and another gene determines whether the pigment is deposited in the fur. A mouse could have the genotype for coloration that produces black pigment, but if it has a genotype for the pigment deposition gene that prevents that pigment from being deposited in the fur, the mouse is white. This is an example of:

epistasis

Albinism results from a recessive allele. Which of the following describes the expected offspring from a normally pigmented male with an albino father and an albino wife?

50% normal; 50% albino

When Thomas Hunt Morgan crossed his red-eyed F1generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

The gene involved is located on the X chromosome.

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their 20s. How likely is it for a woman to have this condition?

One-half of the daughters of an affected father and a carrier mother could have this condition.

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is the inheritance of this trait sex-linked or autosomal?

recessive, sex-linked

A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color blind marries a color-blind male. What is the probability that this couple's first son will be color blind?

1/2

Which of the following statements correctly describes the meaning of the chromosome theory of inheritance as expressed in the early 20th century?

Mendelian genes are at specific loci on the chromosome and, in turn, segregate during meiosis.

Use the following information to answer the question.

In a Drosophila experiment, a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F1s were phenotypically wild type. However, adult flies of the F2 generation (resulting from matings of the F1s) had the characteristics shown in the figure. How is the mutant allele for yellow body inherited?

It is recessive.

Which of the following statements regarding gene linkage is correct?

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

Which of the following phrases correctly defines what one map unit is?

a 1% frequency of recombination between two genes

Why are males more often affected by sex-linked traits than females?

Males only have one X chromosome so they cannot be carriers.

In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophilawere determined as shown in the figure. For example, the recombination frequency between vg and b is 19%. Based on this information, what is the order of these genes on a chromosome map?

b-rb-cn-vg

Which of the following statements correctly describes the reason that closely linked genes are typically inherited together?

They are located close together on the same chromosome.

If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, how will this affect the gametes at the completion of meiosis?

One-quarter of the gametes descended from cell X will be n+ 1, one-quarter will be n - 1, and half will be n.

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?

One of the gametes in the mother most likely underwent nondisjunction during meiosis.

In cats, black fur color is determined by an X-linked allele; the other allele at this locus determines 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

Inheritance patterns cannot always be explained by Mendel's models of inheritance. If a pair of homologous chromosomes fails to separate during meiosis I, select the choice that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n)?

n + 1; n + 1; n - 1; n - 1

A color-blind boy has a mother with normal vision and a color-blind father. From which parent did he get the color-blind gene?

mother

A man who is a dwarf with achondroplasia and normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind with achondroplasia?

none

The SRY gene is best described as ____

a gene present on the Y chromosome that triggers male development

In humans, the sex of the offspring is determined by the:

sex chromosome carried by the sperm cell

Traits controlled by sex-linked recessive genes are expressed more often in males because:

the male has only one gene for the trait

A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following statements describes her expected phenotype?

healthy female of slightly above-average height

Sex determination in mammals is due to the SRY gene found on the Y chromosome. Which of the following situations could allow a person with an XX karyotype to develop a male phenotype?

translocation of SRY to an X chromosome

Which of the following statements would explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?

The two genes are closely linked on the same chromosome

A human sperm cell possesses autosomes and:

either an X or a Y chromosome

During meiosis, a defect occurs in a cell that results in the failure of spindle microtubules binding at the kinetochores. Which of the following statements describes the most likely result of such a defect?

The resulting cells will not receive the correct number of chromosomes in the gametes, a condition known as aneuploidy.

Color blindness is more common in men than in women because:

men have only one X chromosome.

A disorder caused by nondisjunction of chromosome 21, resulting in a trisomy 21 child, is:

Down syndrome

Which of the following conditions causes may cause infertility in a human?

XXY

Hershey and Chase set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell?

DNA

In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the polymer?

the 3' OH

Which of the following statements accurately describes the differences between DNA replication in prokaryotes and DNA replication in eukaryotes?

Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

What is meant by the description "antiparallel" regarding the two strands that make up the DNA double helix?

The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

DNA in both daughter cells would be radioactive.

In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?

DNA polymerase III