ch8 bio

In many organisms, including humans, chromosomes are found in homologous pairs. Homologous chromosomes _____.

are identical in the arrangement of their genes, but some versions of the genes may differ between the chromosomes

Nondisjunction occurs when

members of a chromosome pair fail to separate.

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

nondisjunction

A cell that has a cell wall is undergoing cell division, and the following events are observed: the formation of a cell plate and the division of the cell into two daughter cells. What type of cell is being observed and what process(es) is it going through?

plant cell; telophase and cytokinesis of mitosis

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

possible combinations of characteristics.

The term binary fission is best applied to _____.

prokaryotes

Synapsis occurs during _____

prophase 1

Crossing over occurs during _____.

prophase I

The phase of mitosis during which the mitotic spindle begins to form is

prophase.

Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures called

sister chromatids.

The kinetochores are __________.

sites at which microtubules attach to chromosomes

During which phase of mitosis does the nuclear envelope re-form

telophase

DNA replication occurs in _____.

the S phase of interphase

Cancer is not usually inherited because

the chromosomal changes in cancer are usually confined to somatic cells.

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

47

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.

Asexual reproduction requires ________ individual(s), whereas sexual reproduction requires _______ individual(s).

1; 2

If a chromosome fragment breaks off and then reattaches to the original chromosome but in the reverse direction, the resulting chromosomal abnormality is called a(n)

inversion.

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

Plant cells have cell walls.

Which of the following statements regarding prokaryotes is false?

Prokaryotic chromosomes are more complex than those of eukaryotes.

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

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

Which of the following indicates Turner syndrome?

XO

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

The stage of mitosis during which the chromosomes move toward separate poles of the cell is _____.

anaphase

A cell replicates its entire chromosomal DNA only __________.

before it is about to divide

Karyotyping

can reveal alterations in chromosome number.

The diploid phase of the human life cycle begins with ____

fertilization

Which of the following is a feature of plant cell division that distinguishes it from animal cell division?

formation of a cell plate

The function of meiosis is to make __________.

four cells with a haploid number of chromosomes

Without crossing over,

genetic recombination could not occur.