Biology 1610 Ch 11 Learning curve and quiz

In mammals, females have two copies of the X chromosome, whereas males have only one copy. Dosage compensation (equalization of the numbers of each gene) is accomplished in mammals by:

females randomly inactivating one of the X chromosome in all cells

A human cell with a total of 23 chromosomes is

haploid

bivalents line up in a random orientation so that gametes inherit a random set of maternally and paternally derived chromosomes during which phase

metaphase I

Nondisjunction results when

pairs of chromosomes fail to separate during anaphase

genes that are paternally and maternally derived recombine so that the gametes have chromosomes that are different from the parents' chromosomes during which phase

prophase I

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

What is the function of histone proteins?

to package DNA in eukaryotic chromosomes

Evidence exists (especially in dinoflagellates) that mitosis evolved from binary fission. For example, in certain eukaryotic cells during mitosis, DNA is attached to the membrane of the nucleus (much like a circular chromosome of a bacterium is attached to the plasma membrane). True False

true

Tumor suppressors oppose oncogenes by:

-repairing mutations. -instructing defective cells to die. -blocking the action of an oncogene. -slowing cell division.

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: _____.

12; 12; 6; 6; 3

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

46

The prokaryotic protein FtsZ is evolutionarily related to eukaryotic tubulin. What does this mean? All of these choices are correct. The amino acid sequence for FtsZ is similar to tubulin. The overall protein structure of FtsZ is similar to tubulin. The two proteins evolved from a common ancestral protein. The gene sequence for FtsZ is similar to tubulin.

All

The second meiotic division resembles mitosis because -spindle microtubules attach from opposite directions to the centromere of each sister chromatid pair. -All of these choices are correct. -The second meiotic division is much like mitosis except it is starting with half the number of chromosomes after the reduction division in meiosis I. -Spindles form to facilitate the separation of sister chromatids, which decondense after telophase.chromosomes decondense during telophase II. -the daughter cells have the same number of chromosomes as the parent cell. -sister chromatids are separated during anaphase II to become the chromosomes of the daughter cells.

All

Which of the answer choices could be a proto-oncogene? All of these choices are correct. a gene encoding a cell-surface receptor a gene encoding a protein kinase a gene encoding a growth factor a gene encoding a G-protein

All

function of cyclins

Cyclins activate kinases that regulate passage of cell cycle checkpoints

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

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

The occurrence of nondisjunction during mitosis can result in the development of certain cancers; however, nondisjunction is often thought of in relation to meiosis and the development of certain trisomies True False

True

A gene associated with promoting normal cell division is called

a proto-oncogene

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

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

Non-sister chromatids are

copies of homologs but not fully identical chromosomes

A _____ is an enzyme that adds phosphate groups to other proteins. If this enzyme is only active when bound to a specific protein that fluctuates in concentration in synchrony with the cell cycle, then it is a _____

cyclin; cyclin-dependent kinase

An early observation in the study of the development of sea urchin embryos was that there were several proteins that appeared and then disappeared in synchrony with the pattern of rapidly repeating cell divisions. Because of this up-and-down pattern of abundance these proteins became known as:

cyclins

Meiosis _____ is sometimes called reductional division because _____

I; the number of chromosomes is reduced by half

Meiosis _____ is similar to mitosis in that _____ separate

II; sister chromatids

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

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

G0

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

At which stage of the cell cycle could you see sister chromatids with a microscope?

M

Which of the answer choices is a characteristic of meiotic cell division?

Meiotic cell division results in halving the number of chromosomes

Would genetic recombination result if crossing over occurred between sister chromatids?

No, because sister chromatids are genetically identical or nearly identical

A researcher is studying phases of the cell cycle in a population of cells during which there is an increase in the DNA content. This stage is most likely

S phase

A researcher is studying phases of the cell cycle in a population of cells during which there is an increase in the DNA content. This stage is most likely:

S phase

Which statement represents a misconception about sister chromatids?

Sister chromatids are formed when the prokaryotic circular chromosome attaches at the plasma membrane

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

The cells would be smaller than normal

Sexual reproduction results in an increase in genetic diversity because

The random orientation of bivalents assures that gametes receive a random mix of maternal and paternal homologs. This happens in the formation of eggs and sperm, so the zygote formed from their fusion creates a random mix from both parents. Recombination in prophase I mixes regions of maternal and paternal homologs to provide more genetic diversity.

Why are the X and Y chromosomes not considered homologous?

They do not carry the same set of genes

How do CDKs promote cell division?

They phosphorylate proteins that allow passage through cell cycle checkpoints.

The development of cancer requires both the _____ of an oncogene and the _____ of a tumor suppressor.

activation; inhibition

In which phase of mitosis do spindle microtubules shorten?

anaphase

During what step in meiosis do homologous chromosomes separate?

anaphase I

When do sister chromatids separate in meiosis?

anaphase II

Mitotic cell division is considered asexual because

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

Cell division is regulated by

signals that indicate that the cell has reached a sufficient size. signals about the nutritional status of the cell. growth factor signals. signals that indicate that DNA has been replicated.

During meiosis I

sister chromatids are not separated

Synapsis is best described as:

the pairing of homologous chromosomes in prophase I