bio chapter 9 questions

Martian invaders come to Earth to conduct tests on human biology students. A Martian tells you that, in his species, n = 62. Assuming their chromosomes are like human chromosomes, he then asks you how many chromosomes are present in each cell of his finger. How do you reply?

124. [The Martian gave you the haploid number. The cells of his finger are likely diploid (containing pairs of chromosomes), so they have twice the haploid number (2 x 62 = 124).]

What is the most important difference between asexual reproduction and sexual reproduction?

Asexually produced cells are genetically identical (excluding mutational events). Sexually produced cells are genetically unique.

DNA is compacted and condensed in order to make it easier to proceed through the cell cycle. What is the correct sequence from loosely compacted DNA to highly condensed DNA?

DNA double helix, histone, nucleosome, chromatin, chromosome

The first step of bacterial replication is _____.

DNA replication

Which of the following statements about the daughter cells of prokaryotic fission is true?

Daughter cells are clones of each other.

Which of these phases encompasses all of the stages of mitosis?

E

True or false. Mitosis takes place during M phase of the cell cycle, which is longer than interphase.

False. (Mitosis does indeed take place during M phase, but M phase is shorter than interphase; cells spend most of their time in interphase.)

Which of the following is the correct sequence of stages in the mitotic cell cycle that produces a differentiated cell? (D = cell differentiation)

G1, S, G2, M, D

During what stage of the cell cycle will a cell release Cdks to initiate the events for cell division?

G2. (The release of Cdks in G2 is what causes the cell to progress to mitotic cell division.)

How do the genes in DNA control cell function?

Genes carry the instructions for making proteins.

The chromosomes line up in the center of the cell during which phase of mitosis?

Metaphase.

The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?

Prophase. (Prophase is the first phase of mitosis, when the centrosomes begin moving toward opposite poles and the nuclear envelope breaks up.)

Centrioles duplicate during the cell cycle. Given your knowledge of the cell cycle, when would you guess that the duplication of centrioles occurs?

S phase. (Soon after the cell makes the decision to divide, the centrioles are duplicated along with the chromosomes during the S phase.)

What is the function of the telomere?

Telomeres prevent the ends of chromosomes from being damaged.

The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?

Telophase

How do cells fit long pieces of DNA into a compartment as small as the nucleus?

The DNA is wrapped around histones.

Which statement below would be accurate in describing the DNA of a prokaryotic organism?

The DNA of a prokaryotic cell is contained in a single, circular chromosome about a millimeter in circumference.

Compare the cells of a woman's leg muscle to the cells of a baby growing inside her womb. What is the most important difference between them?

The chromosomes in the cells of the woman's leg muscle are genetically identical to the rest of her body. The baby's cells contain only half of the mother's chromosomes and the other half come from the father.

What must happen before a cell can begin mitosis?

The chromosomes must be duplicated. (Before mitosis can begin, the chromosomes, or genetic material, must be copied, which occurs during interphase.)

Which cellular structure contributes to the biggest difference between mitosis in plants and mitosis in animals?

cell wall

Which specific structure must separate during anaphase in order for sister chromatids to begin moving toward opposite poles?

centromeres. (The centromere is the point of attachment between the two sister chromatids. During the anaphase stage, the centromeres will "split" and allow the sister chromatids to physically separate from each other.)

A(n) _____ consists of a very long DNA molecule associated with many proteins. During the cell cycle, this structure is duplicated and the copies are distributed to separate cells.

chromosome

Prokaryotic fission would NOT occur if which of the following items or processes were missing or not completed properly?

chromosome duplication

Which of the following is produced in response to growth factors binding to surface receptors?

cyclins

At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________.

cytokinesis

_____ is the stage of the cell cycle when the cytoplasm and organelles divide into two daughter cells and move apart.

cytokinesis

During which stage of mitosis is the nuclear membrane broken into fragments?

early prophase

_____ is a carcinogen that promotes colon cancer.

fat. (A diet high in fat increases the risk of both colon and breast cancer.)

The proteins that coil with DNA producing the "beads on a string," or nucleosomes, are called which of the following?

histones. (These are specialized proteins that the DNA will wrap around to assist in the compacting)

Nucleoli are present during _____.

interphase

_____ is the stage of the cell cycle between cell divisions, in which the cell acquires nutrients, grows, and duplicates its chromosomes.

interphase

During _____ the cell grows and replicates both its organelles and its chromosomes.

interphase.

What word is used to describe the exact position of a gene on a chromosome?

locus

_____ is the second phase of mitosis, in which chromosomes line up along the equator of the cells. This phase is followed by anaphase, when sister chromatids separate.

metaphase

The equatorial plate of the mitotic spindle is formed during what stage?

metaphase. (During metaphase, the spindle apparatus becomes well-defined and the chromosomes get arranged at the equatorial plate.)

The overall process of nuclear division is known as _____.

mitosis

Compare prokaryotic cells to eukaryotic cells. Which difference between these two cell types affects cell division the most?

one chromosome vs. many chromosomes. (The complexity of mitosis (and meiosis) is based mostly off of the need to assure that each cell gets one copy of each chromosome. Prokaryotes have only one chromosome to copy and sort.)

Spindle fibers attach to kinetochores during _____.

prometaphase

Chromosomes become visible during _____.

prophase

_____ is the first phase of mitosis, in which chromosomes condense and spindle microtubules begin to form.

prophase

Cytokinesis often, but not always, accompanies _____.

telophase

_____ is the final stage of mitosis, in which spindle fibers disappear and cytokinesis occurs.

telophase

Which phase of mitosis comes last during cell division?

telophase. (Cytokinesis is part of M-phase, but not part of mitosis. M-phase consists of nuclear division (mitosis) and cytoplasmic division (cytokinesis). Telophase is part of mitosis, so it's in M-phase too.)

What is different concerning the DNA in bacterial cells as opposed to eukaryotic cells?

the amount of DNA present; whether the DNA is housed in a nucleus or not; whether the DNA is linear or circular

During _____ both the contents of the nucleus and the cytoplasm are divided.

the mitotic phase. (The mitotic phase encompasses both mitosis and cytokinesis.)

In mitosis, the number of chromosome sets in daughter cells is which of the following?

the same as in parent cell.

How many major checkpoints are there in mitosis that regulate the progress of the cell cycle?

three. (They are at the juncture of G1 to S, at the juncture of G2 to mitosis and between metaphase and anaphase.)

During prophase a homologous pair of chromosomes consists of _____.

two chromosomes and four chromatids

A certain species of animal has six pairs of chromosomes. How many DNA molecules are present in the nuclei of these animals during G2 phase?

24. (DNA replication is completed during S phase, which occurs prior to G2 phase. Since each chromosome (12) is replicated, there are 24 DNA molecules in the nucleus during G2 phase.)

Which of the following checkpoints does NOT occur late in G1?

A check that chromosome replication has been successfully completed. (Chromosome replication does not occur until after G1; this checkpoint is a G2 checkpoint.)

The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?

Anaphase.

Which of the following events occurs during prophase?

The spindle microtubules form.

What do the three major checkpoints for cell division have in common?

They all focus on DNA and chromosomes. (All three checkpoints focus on the readiness of the cell based on DNA replication and sorting of the chromosomes.)

Stem cells have two important characteristics: self-renewal and the ability to differentiate into a variety of cell types ("wildcards"). Which of the statements below would NOT be a valid characteristic of stem cells?

When a stem cell divides, both resulting daughter cells become stem cells, thus continuing the line. (This is not a correct statement for stems cells. When a stem cell divides, usually one daughter remains a stem cell, thus continuing the line while the other daughter eventually differentiates.)

Which of these is NOT a carcinogen? UV light fat testosterone cigarette smoke

all of the above are carcinogens

Centromeres divide and sister chromatids become full-fledged chromosomes during _____.

anaphase

Match the terms with the appropriate stages in the answer: migration, shortening and thickening, cytokinesis, prophase.

anaphase, prophase, telophase, centrioles forming

There are three major checkpoints that regulate progress of the cell cycle. Which of the following would NOT be one of the valid checkpoints in mitosis? -at the juncture of G2 to mitosis -at the juncture of G1 to G2 -at the juncture of G1 to S -between metaphase and anaphase

at the juncture of G1 to G2

In the process known as _____, a bacterium or other single-celled organism divides in half, producing two identical offspring.

binary fission

Bacteria divide by:

binary fission.