Mastering Biology Chapter 8

The exchange of parts between nonhomologous chromosomes is called ________________________.

reciprocal translocation (Reciprocal translocation is the exchange of genetic material between nonhomologous chromosomes.

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing ____ chromosomes.

16 (16 is half of 32)

Normal human gametes carry _____ chromosomes.

23 (This is the number of chromosomes in a single set of human chromosomes.)

The first step of bacterial replication is _______________.

DNA replication (The DNA must be copied in order to proceed.)

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. (Unfortunately, these trisomies do occur and are commonly observed in spontaneously aborted embryos and fetuses.)

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. (A nondisjunction that occurs in the first meiotic division will result in one daughter cell having two copies of chromosome 18. This will be trisomic upon fertilization. The other daughter cell will have no copies of chromosome 18 and will contain a single copy of chromosome 18 upon fertilization, a condition known as monosomy.)

Mature human neuron (nerve) cells and muscle cells

are permanently in a state of nondivision.

Which of the following is true of a species that has a chromosome number of 2n = 16? a. The species has 16 sets of chromosomes per cell. b. Each diploid cell has eight homologous pairs. c. A gamete from this species has four chromosomes. d. The species is diploid with 32 chromosomes per cell.

b. Each diploid cell has eight homologous pairs.

A cell replicates its entire chromosomal DNA only ________________.

before it is about to divide (This ensures that genetic material can be appropriately distributed to each of the daughter cells.)

Bacteria divide by

binary fission

Meiosis differs from mitosis in that _____________ only occurs in meiosis.

crossing over (Crossing over, the exchange of corresponding segments between nonsister chromatids of homologous chromosomes, only occurs during meiosis.)

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

interphase

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

interphase

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.

Gametes are produced by _______.

meiosis (Meiosis produces haploid gametes from a diploid parental cell.)

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

nondisjunction (In nondisjunction, chromosomes fail to separate properly at meiosis.)

To initiate a signal transduction pathway, a signal binds to a receptor protein usually located in the

plasma membrane

Asexual reproduction ___________________.

produces offspring genetically identical to the parent (Only one individual makes a genetic contribution to the offspring.)

Adrenaline is a "fight-or-flight" hormone and is released when danger threatens or in an emergency. It binds to a protein receptor, which causes a number of reactions to occur inside the cell. Enzymes are produced that perform a number of functions, including release of sugar into the bloodstream. What function does adrenaline play in this pathway?

signal molecule (Adrenaline binds to the surface of the cell; it is not internalized. Adrenaline is released by the adrenal glands. It binds to the surface of many cells, including kidney and liver cells, and initiates a signal transduction pathway that assists with the fight-or-flight responses.)

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, and 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.)

Mitosis results in the formation of how many cells; meiosis results in the formation of how many cells?

two diploid cells ... four haploid cells (In mitosis a cell that has doubled its genetic material divides to produce two diploid daughter cells. In meiosis a cell that has doubled its genetic material undergoes two rounds of division, producing four haploid cells.)