Chapter 8 Assignment Questions

In theory, when a nondisjunction for chromosome 18 occurs during meiosis I, four gametes can be produced. If these gametes are fertilized with unaffected gametes from the second parent, what observations would you make concerning the resulting embryos?

Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18.

Sister chromatids are

joined together at a centromere

After fertilization, the resulting zygote begins to divide by __________.

mitosis

During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as _____.

nondisjunction

Which of the following features likely accounts for the difference between plant and animal cell cytokinesis?

plants cells have cell walls

Independent orientation of chromosomes at metaphase I results in an increase in the number of

possible combinations of characteristics.

Asexual reproduction _____.

produces offspring genetically identical to the parent

The term binary fission is best applied to _____.

prokaryotes

Many cancer drugs known as "antimitotics" target microtubules. What is the first stage of mitosis at which these drugs are likely to have an effect?

prophase

In meiosis II, _____.

sister chromatids separate

Each somatic cell in an individual with Down syndrome contains _____ chromosomes.

47

You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication?

In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.

How many generations does it take to develop a new plant species by polyploidy?

1

In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing __________ different gametes.

2^23

When observing a bird skin cell in G2 under a microscope, you count 160 total chromatids. How many chromosomes does a male chicken have in its sperm cells?

40

In a cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing __________ chromosomes.

5

Imagine that a human skin cell went through mitosis but did not undergo cytokinesis. How many chromosomes would be in the cell?

92

In this sample of cells, what stage of the cell cycle are most of the cells in?

G1

During binary fission, each copy of the duplicating chromosome moves to opposite ends of the cell. What does this achieve?

It ensures that each daughter cell receives one copy of the chromosome

Which of the following statements regarding mitosis and meiosis is false?

Meiosis provides for asexual reproduction.

Which of the following statements regarding the cell cycle control system is false?

The cell cycle control system operates independently of the growth factors.

What would be the immediate consequence of destroying a cell's centrosomes?

The mitotic spindle would not form.

You are observing a single cell under a microscope. You go home for the night, and the next day you see four cells. The four cells look similar, and when you stain them with a dye that binds to DNA they all appear to contain the same amount of DNA as the original cell. What likely happened overnight?

The single cell divided to form two new cells, and the two new cells each divided to form four total cells, all by asexual reproduction.

Which of the following occurs during mitosis?

Two daughter nuclei, one at each pole of the cell, are generated.

With the exception of identical twins, siblings who have the same two biological parents are likely to look similar, but not identical, to each other because they have

a similar but not identical combination of genes

If a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction, the resulting chromosomal abnormality is called

an inversion

After reading the paragraphs below, answer the questions that follow. Mr. and Mrs. Smith have three sons in elementary school. Two of their children are progressing normally, but their youngest son, Charles, has been much slower than his siblings in developing speech and language skills. His parents are concerned that he has a learning disability and decide to investigate further. Since some learning disabilities can be genetically based, their pediatrician recommends a chromosomal analysis. The results show that Charles has a trisomy of the sex chromosomes, diagnosed as XYY. A mistake during sperm formation resulted in an extra copy of the Y chromosome. The extra copy was passed on to Charles during fertilization. Most often, this chromosomal change causes no unusual physical features or medical problems, but those with trisomy of the sex chromosomes may have a higher-than-normal risk of delays in learning development. During which stage of meiosis could this mistake have occurred?

anaphase II

Strictly speaking, the phrase "like begets like" refers to

asexual repoduction only

A cell replicates its entire chromosomal DNA only __________.

before it is about to divide

Karyotyping

can reveal alterations in chromosome number

Which of the following occurs during interphase?

cell growth and duplication of the chromosomes

In the picture below, the chromosomal region where the nonsister chromatids are crossing over is called a(n) _____.

chiasma

A cleavage furrow forms in an animal cell during _____.

cytokinesis

The process by which the cytoplasm of a eukaryotic cell divides to produce two cells is called

cytokinesis

A cell is treated with a drug that prevents the formation of vesicles. Which of the following processes depends on the formation of vesicles and would therefore be blocked?

cytokinesis in a plant cell

Consider the photograph shown below. You can determine this is a plant cell rather than an animal cell because it has __________.

formed a cell plate

What is the typical result when a diploid cell undergoes meiosis?

four haploid cells

During asexual reproduction, yeast cells can produce _____.

genetically identical offspring

At the conclusion of meiosis I, the daughter cells are _____.

haploid and the sister chromatids are joined

At a chiasma, two ________ are attached to each other.

homologous or nonsister chromatids

Eukaryotic cells spend most of their cell cycle in which phase?

interphase

Which of the following shows mitosis in the correct chronological order?

prophase, prometaphase, metaphase, anaphase, telophase

Which of the following helps maintain the structure of chromosomes and control the activity of genes?

proteins

One version of a gene may encode __________, whereas a different version of the same gene may encode __________.

red eyes;white eyes

Prior to mitosis and after S phase, each chromosome of a eukaryotic cell consists of a pair of identical structures called

sister chromatids

Within one chromosome, what is the relationship between the sequence of bases in DNA of one sister chromatid compared to the other?

the sequences are identical

Mitosis and cytokinesis result in the formation of __________; meiosis and cytokinesis result in the formation of __________.

two diploid cells : four haploid cells

Homologous chromosomes possess the same genes arranged in the same order but may possess different __________ of some of these genes.

versions

A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA in one of the grasshopper daughter cells?

100 units

After reading the paragraphs below, answer the question that follows. A technique called flow cytometry is used by scientists and researchers to count or sort cells based on specific properties. By labeling cellular DNA with a fluorescent dye, flow cytometry can sort cells based on the amount of DNA present, thereby making it possible to distinguish between cells that are in different stages of the cell cycle. Flow cytometry is especially useful to the medical community because it can help with the diagnosis of certain types of cancers. Below is a typical set of data that you might obtain when running a flow cytometry experiment using a sample of healthy skin cells. Use this figure to help you answer the following question. The figure shows the result of flow cytometry analysis. It shows the number of cells as a function of fluorescence. Peak A is very high and narrow. Then goes peak B: it is wide but low. And then goes peak C, which is narrow and low but higher than peak B. If you used flow cytometry to sort a sample of cancerous cells that have been treated with a drug to prevent them from replicating their DNA, what peaks would you expect to see on the resulting flow cytometry data set?

A only

Oncologists (medical doctors who treat cancer patients) routinely take biopsies (samples) of tissue from patients to determine whether the tissue is cancerous or not. What would be the best technique to use to determine whether cells from the tissue sample are cancerous?

Add cells from the tissue sample to a cell culture dish and compare their growth against a sample of noncancerous cells from the patient.

Which of the following statements regarding Down syndrome is false?

Down syndrome is least likely to be seen in the infants of mothers over 40.

A skin cell of a red fox has 34 chromosomes. You look at the cell under a microscope and see that it has 34 chromosomes and one nucleus. Several hours later, you look at the same cell again and see that it has double the amount of DNA and one nucleus. A little while later, you see that it has 68 chromosomes and two nuclei. What stage of the cell cycle was this cell in when you viewed it at each time point

First view: G1; second view: G2; third view: telophase

In anaphase I, __________.

Homologous chrmosomes move to the oppisite poles of the cell.

Below are three statements. Classify them as examples of independent orientation, crossing over, or random fertilization. I: The formation of a zygote from an egg and a sperm is an unpredictable event. II: Random combinations of paternal and maternal chromosomes end up in gametes. III: An allele on the paternal chromosome 18 ends up on the maternal chromosome 18.

I: random fertilization; II: independent orientation; III: crossing over

The likelihood of death within twenty years of a diagnosis for DCIS (ductal carcinoma in situ, a type of breast cancer) is only 3.3%. Does this mean that every individual diagnosed with DCIS has a 3.3% chance of death within twenty years from the disease?

No. Individuals within certain risk groups (such as women under age 40) have a risk notably higher than 3.3%, whereas individuals not in these risk groups have a lower risk on average.

Jacobsen syndrome, which can cause heart defects, intellectual deficiencies, and bleeding disorders, is caused by a deletion of the terminal end of chromosome 11. What method could you use to determine whether an individual has Jacobsen syndrome?

Perform a karyotype using a person's white blood cells.

Which of the following statements regarding sexual and asexual reproduction is true?

Sexual reproduction is more likely to increase genetic variation than is asexual reproduction.

Which of the following statements regarding mitosis and meiosis is true?

Sister chromatids separate during anaphase of mitosis and anaphase II of meiosis

Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not?

Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.