BIO Exam 3 Ch.11

At the start of mitosis, how many sister chromatids are present in a human cell?

46

In human cells, at the end of mitosis and after cytokinesis, how many chromatids have moved into each daughter cell?

46

centrosome

A compact structure that is the microtubule organizing center for animal cells.

Centromere

A constriction that physically holds sister chromatids together; the site of the attachment of the spindle fibers that move the chromosome in cell division.

Why don't plant cells use a contractile ring to divide their daughter cells?

A contractile ring can't "pinch" a cell wall.

cyclin-dependent kinase

A kinase that is always present within the cell but active only when bound to the appropriate cyclin.

cyclins

A regulatory protein whose levels rise and fall with each round of the cell cycle.

Muscle cells in the mammalian heart are multinucleate, meaning that multiple nuclei are present in the cytoplasm of individual large cells. Predict what is different about the cell cycle in a muscle cell.

Cytokinesis does not occur.

S phase

DNA replication occurs

Which statement is true regarding binary fission?

DNA replication of the circular bacterial chromosome during binary fission is a bidirectional process, starting at one point but progressing in opposite directions.

If you analyze the sequences of the two copies of any of the chromosomes shown in the karyotype, there would be slight sequence differences. What could account for the small differences between a few of the homologous chromosomes?

Each homologous chromosome in a pair is from a different parent.

first-division nondisjunction

Failure of chromosome separation in meiosis I - homologous chromosomes fail to separate and all of the resulting gametes have an extra or missing chromosome

A cell that is not actively dividing is in what phase of the cell cycle?

G0

3 phases of interphase

G1, S, G2 -Thus, G1 is a time of preparation for S-phase DNA synthesis, and G2 is a time of preparation for M-phase mitosis and cytokinesis.

Meiosis _____ is sometimes called reductional division because _____.

I; the number of chromosomes is reduced by half

binary diffusion

cells of bacteria or archaeons divide to form two daughter cells.

First Stage of Mitosis: Prophase

characterized: appearance of visible chromosomes - chromosomes condense - centromeres radiate microtubules and migrate to opposite poles

What characteristics do you expect to observe with a microscope if you investigate the division of mitochondria and chloroplasts in eukaryotic cells?

circular DNA attached to the plasma membrane and binary fission

A protein that has regular up-and-down pattern of abundance during the cell cycle and that triggers progress of the cell cycle by activating kinases is called a:

cyclin

G1 phase

gap phase in which the size and protein content of the cell increase and specific regulatory proteins are made and activated in preparation for S-phase DNA synthesis. -between the end of M phase and the start of S phase -during G1, regulatory proteins, such as kinases, are made. These proteins activate enzymes that synthesize DNA

A human cell with a total of 23 chromosomes is:

haploid

What are three ways in which meiosis I differs from mitosis?

homologous chromosomes pair, undergo crossing over, and segregate from each other. in mitosis, centromeres divide and sister chromatids separate

In a human cell at the end of prophase I, how many chromatids, centromeres, and bivalents are present?

in human cells: - 92 chromatids - 46 centromeres - 23 bivalents

Cell cycle: two phases

m phase and interphase

Metaphase I

meiotic spindle is completed and the bivalents move to lie on an imaginary plane cutting transversely across the spindle.

How is cell division similar and different in prokaryotic cells and eukaryotic cells?

prokaryotic - binary diffusion eukaryotic - mitotic cell division: cell replicate their chromosomes in the nucleus. Nuclear envelop dissolves and each pair of is separated. once the two full sets of chromosomes are separate, a nuclear envelop forms around each one. Cell goes into cytokenisis, where it is split into two new daughter cells. similarities - one parent cell gives rise totwo daughter cells, and two daughter cells are identical to each other and the parent cell. Difference 1. size and shape of genetic material - bacteria have a single circular chromosome - eukaryotic cells has one or more linear chromosomes 2. DNA of prokary. is attached to the plasma membrane, allowing separation of DNA into daughter cells by cell growth. Eukaryotic cells. chromosomes are not attached to cell or nuclear membrane

In which phase of mitosis do chromosomes condense?

prophase

tumor suppressor

proteins whose normal activities inhibit cell division

Reproduction by mitotic cell division:

results in two daughter cells that are genetically identical.

Interphase

second stage of cell cycle - time between two successive M phases

Several years ago, a man noticed a small mole on his wrist. Years later, the mole grew in size and the man was diagnosed as having metastatic melanoma. This was likely the result of:

several mutations affecting proto-oncogenes and/or tumor suppressor genes.

second-division nondisjunction

sister chromatids fail to separate, giving rise to gametes with an extra chromosome, a missing chromosome, and normal numbers of chromosomes.

Karyotype

standard arrangement of chromosomes, showing the number and shapes of the chromosomes representative of a species.

Mitotic cell division is considered asexual because:

the daughter cells receive DNA from one parent cell, and the daughter cells are genetically identical.

Prometaphase I

the nuclear envelope breaks down and the meiotic spindles attach to kinetochores on chromosomes

kinetochore

the protein complexes on a chromatid where spindle fibers attach.

Anaphase I

the two homologous chromosomes of each bivalent separate as they are pulled in opposite directions two homologous chromosomes of each bivalent separate as they are pulled in opposite directions, but the sister chromatids remained joined at the centromere.

What is the function of histone proteins?

to package DNA in eukaryotic chromosomes

The protein p53 is an example of:

tumor suppresor

Diploid

two complete sets of chromosomes.

sister chromatids

two copies of a chromosome produced by DNA replication.

Trisomy of the X chromosome has little effect on the health, whereas trisomy of any of the autosomes has significant detrimental developmental effects. What could account for this difference in effect of trisomy between the X chromosome and any of the autosomes?

The X chromosomes undergo X inactivation and thereby correct for the copy number difference. Autosomes do not undergo dosage compensation (the equalization of the numbers of each gene).

What would happen to the daughter cells if the G2 phase of the parent cell is shortened?

The cells would be smaller than normal.

At which checkpoint would a cell become arrested if a chromosome was not properly aligned in the spindle?

at a checkpoint early in the mitotic phase

The microtubules that form the mitotic spindle extend out from the centrosome. Where would you expect to find the plus (fast-assembling) end of a spindle microtubule?

away from the centrosome and toward the kinetochore

Anaphase(mitosis)

- The sister chromatids separate - each chromatid is a full-fledged chromosome. - The spindle microtubules attached to the kinetochores gradually shorten, pulling the newly separated chromosomes to the opposite poles of the cell.

Proto-oncogenes:

- are the normal forms of genes that can mutate to cause cell division to be hyperactive. - can encode growth factors, cell surface receptors, or members of a signal transduction pathway. - can be mutated by cigarette smoke to become triggers for cancer.

Which cellular conditions promote progression of the cell cycle?

- the expression and synthesis of cyclin proteins - binding of cyclins to CDKs - the accumulation of cyclins - the activation of CDKs

What two processes during meiosis result in genetically unique daughter cells?

1. Crossing Over: - occurs at random positions along chromosomes and creates unique combos of genetic differences that may be present in the maternal and paternal chromosomes 2. Random Alignment of the homologous chromosomes on the spindle in metaphase I, so each nucleus receives a random combination of maternal and paternal homologs.

What are three examples of checkpoints that the cell monitors before proceeding through the cell cycle?

1. checkpoint for spindle attachment to chromosomes, which is active before anaphase and ensures that all chromosomes are attached to spindle 2. the DNA damage checkpoint. active in the G1 phase and checks DNA damage 3. the DNA replication checkpoint, - active in G2, makes sure DNA is replicated

It is estimated that a human cell in G1 phase of the cell cycle contains 6 picograms of DNA in its nucleus. If you measure the DNA content at various stages of mitosis and meiosis, what amounts of DNA can be expected in nuclei at the following stages? prophase mitosis: _____; prophase I meiosis: _____; prophase II meiosis: _____; telophase mitosis: _____; telophase meiosis II: _____. (All amounts are in picograms (10-12 g.) Please choose the correct answer from the following choices, and then select the submit answer button.

12; 12; 6; 6; 3

checkpoint

One of multiple regulatory mechanisms that coordinate the temporal sequence of events in the cell cycle.

Suppose you are observing some cells with a microscope, and you see a cell that appears to be dividing. You can see that as the cell starts to pinch in half, the DNA seems to be attached to the plasma membrane via a membrane protein. On further analysis, you find that this organism's DNA is circular - that is, it consists of a closed loop. What can you conclude about this organism and its mode of cell division?

It is a prokaryote that is dividing by binary fission.

Why would a compound that interferes with bacterial cell wall synthesis be useful for treating a bacterial infection?

It would limit growth of the bacterial population through cell division.

Haploid

a cell with one complete set of chromosomes.

Suppose a research team does a detailed analysis of the DNA sequence of all three copies of chromosome 21 from an individual with trisomy 21 (Down syndrome). They discover that two of the three chromosomes are essentially identical in sequence, whereas the third chromosome has a significant number of sequence differences. Which of the answer choices is consistent with this observation?

The extra chromosome 21 resulted from second-division nondisjunction in one of the parents' gametes.

G0 phase

The gap phase in which cells pause in the cell cycle between M phase and S phase; it may last for periods ranging from days to more than a year.

G2 phase

The gap phase in which the size and protein content of the cell increase in preparation for M-phase mitosis and cytokinesis. -between the end of S phase and the start of M phase -In G2, both the size and protein content of the cell increase.

3 major checkpoints

The presence of damaged DNA arrests the cell at the end of G1 before DNA synthesis, the presence of unreplicated DNA arrests the cell at the end of G2 before the cell enters mitosis, and abnormalities in chromosome attachment to the spindle arrest the cell in early mitosis.

telophase I

The stage of meiosis I in which the chromosomes uncoil slightly, a nuclear envelope briefly reappears, and in many species the cytoplasm divides, producing two separate cells.

Prometaphase

The stage of mitosis in which the nuclear envelope breaks down and the microtubules of the mitotic spindle attach to chromosomes.

M phase

The stage of the cell cycle consisting of mitosis and cytokinesis, in which the parent cell divides into two daughter cells. (1) mitosis, the separation of the chromosomes into two nuclei, and (2) cytokinesis, the division of the cell itself into two separate cells.

How do new cyclin proteins appear in the cytoplasm?

They are made through protein synthesis.

Why are the X and Y chromosomes not considered homologous?

They do not carry the same set of genes.

What do you predict would be the consequence of a mutation in FtsZ that disrupts the function of the protein it encodes?

block cell division(specifically cytokensis)

How does meiosis generate genetic diversity?

both crossing over at prophase I and random alignment of homologs at metaphase I

A zygote is:

diploid cell formed by the fusion of two gametes. - two sets of chromosomes one from each parent

Nondisjunction

failure of a pair of chromosomes to separate normally during anaphase of cell division - results in extra or missing chromosomes

Nondisjunction can only occur in the sex chromosomes and not the autosomes.

false

Which of the answer choices is part of the process of binary fission in prokaryotes?

formation of a new cell wall

mitotic spindle

forms in cytosol - microtubules that pull the chromosomes into separate daughter cells.