Biology Exam 3

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G₂?

16; 16

During which phase of mitosis do the chromatids become chromosomes?

anaphase

In eukaryotic cells, chromosomes are composed of _____.

DNA and proteins

Metaphase is characterized by _____.

aligning of chromosomes on the equator

Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have times more DNA than G₁ phase cells. The cells of this group are _____.

in the S phase of the cell cycle

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

32

The first gap in the cell cycle (G₁) corresponds to _____.

normal growth and cell function

The following questions are based on the accompanying figure.
In the figure above, G₁ is represented by which numbered part(s) of the cycle?

I or V

The following questions are based on the accompanying figure.
In the figure above, which number represents DNA synthesis?

II

What is the final result of mitosis in a human?

genetically identical 2n somatic cells

A given organism has 46 chromosomes in its karyotype. Therefore, we can conclude that it must _____.

have gametes with 23 chromosomes

After telophase I of meiosis, the chromosomal makeup of each daughter cell is _____.

haploid, and the chromosomes are each composed of two chromatids

Asexual reproduction occurs during _____.

mitosis 

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

meiosis I

For the following questions, match the key event of meiosis with the stages listed below.

 I.  Prophase I  V.  Prophase II
 II.  Metaphase I  VI.  Metaphase II
 III.  Anaphase I  VII.  Anaphase II
 IV.  Telophase I  VIII.  Telophase II


Homologous chromosomes are aligned at the equator of the spindle.

II

Homologous chromosomes _____.

carry information for the same traits

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

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

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

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

If meiosis produces haploid cells, how is the diploid number restored for those organisms that spend most of their life cycle in the diploid state?

fertilization

In meiosis, homologous chromosomes are separated during _____.

anaphase I

Independent assortment of chromosomes occurs during _____.

meiosis I only

Refer to the drawings in the figure below of a single pair of homologous chromosomes as they might appear during various stages of either mitosis or meiosis, and answer the following questions.

Which diagram represents anaphase II of meiosis?

V

Refer to the drawings in the figure below of a single pair of homologous chromosomes as they might appear during various stages of either mitosis or meiosis, and answer the following questions.


Which diagram represents anaphase I of meiosis?

I

Sister chromatids separate from each other during _____.

mitosis and meiosis II

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

two

The human X and Y chromosomes _____.

include genes that determine an individual's sex

What is 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.

Which of the following defines a genome?

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

Which of the following is true of a species that has a chromosome number of 2n = 16?

Each diploid cell has eight homologous pairs.

Which of these is a karyotype?

organized images of a cell's chromosomes

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

Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation, but both have one parent who is albino (without melanin pigmentation). What is the probability that their first child will be an albino?

1/4

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

8

Mendel accounted for the observation that traits that had disappeared in the F₁ generation reappeared in the F₂ generation by proposing that _____.

traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F₁

Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F₂ generation. The results were as follows: 6022 yellow and 2001 green (8023 total). The allele for green seeds has what relationship to the allele for yellow seeds?

recessive

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

anaphase I of meiosis

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?

different possible assortment of chromosomes into gametes

Use the figure and the following description to answer the question(s) below.

In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D 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, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.


Which of the boxes marked 1-4 correspond to plants with dark leaves?

1, 2, and 3

Use the figure and the following description to answer the question(s) below.

In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D 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, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.


Which of the boxes marked 1-4 correspond to plants with a heterozygous genotype?

2 and 3

Use the figure and the following description to answer the question(s) below.

In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D 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, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.


Which of the boxes marked 1-4 correspond to plants that will be true-breeding?

1 and 4 only

A man who carries an allele of an X-linked gene will pass it on to _____.

all of his daughters

A man who is an achondroplastic dwarf with 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. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind dwarfs?

none

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

Cinnabar eyes is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F₁ males will have cinnabar eyes?

100%

Genetic exchange between 2 homologous chromosomes is called

crossing over.

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

males are hemizygous for the X chromosome

Of the 23 pairs of human chromosomes, 22 pairs are homologous and are found in both males and females. These are called ________.

autosomes

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?  

X^NXⁿ and X^NY

What does a frequency of recombination of 50% indicate?

The two genes are likely to be located on different chromosomes.

When Thomas Hunt Morgan crossed his red-eyed F₁ generation 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 on the X chromosome.

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

8%

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 an analysis of the nucleotide composition of DNA, which of the following will be found?

A + C = G + T

In his transformation experiments, what did Griffith observe?

Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (¹⁵N) and then transferred them to a medium containing ¹⁴N. Which of the results in the figure above would be expected after one round of DNA replication in the presence of ¹⁴N?

D

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

DNA contains phosphorus, whereas protein does not.

Refer to the figure above. What bases will be added to the primer as DNA replication proceeds? The bases should appear in the new strand in the order that they will be added starting at the 3' end of the primer.

A, G, A, C, G, A, C

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?

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

Semiconservative replication involves a template. What is the template?

one strand of the DNA molecule

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.