chapter 8 The cellular basis of reproduction and inheritance

Question 1

The period of cell growth when the cell synthesizes new molecules and organelles. During late G2, the cell has doubled much of its original contents and the cytoplasm now contains two centromeres. Within the nucleus, the chromosomes are duplicated, but they cannot be distinguished individually because they are still in the form of loosely packed chromatin

Answer 1

Interphase

Question 2

changes occur in both the nucleus and the cytoplasm. Within the nucleus, the chromatin fibers become more tightly coiled and folded, forming discrete chromosomes that can be seen with the light microscope. Each duplicated chromosome appears as two identical sister chromatids joined together along their lengths. In the cytoplasm, the mitotic spindle begins to for as microtubules rapidly grow out from the centromeres, which begin to move away from each other.

Answer 2

prophase

Question 3

The mitotic spindle if fully formed with its poles at opposite ends of the cell. The chromosomes line up on ______ plate, an imaginary plane equidstant between the two poles of the spindle. The centromeres of all the chromosomes are lined up on the _____ plate. For each chromosome, the kinetochores of the two sister chromatids are attached to microtubules from opposite poles.

Answer 3

metaphase

Question 4

begins when the two centromeres of each chromosome come apart, separating the sister chromatids. Motor proteins of the kinetochores, powered by ATP, “walk” the newly separated daughter chromosomes centromere-first along the microtubules toward opposite poles of the cell. As this happens, the spindle microtubules attached to the kinetochores shorten. However, the spindle microtubules not attached to chromosomes lengthen. Poles are moved farther apart, elongating the cell. At the end of this, two poles of the cell have equal collections of chromosomes.

Answer 4

Anaphase

Question 5

cell elongation that started in anaphase continues. Daughter nuclei appear at the poles of the cell as nuclear envelopes form chromosome and spindle structure, this is roughly the reverse of prophase. By the end of this, the chromatin fibers uncoil, and the mitotic spindle disappears. Mitosis, the division of one nucleus into two genetically identical daughter nuclei, is finished.

Answer 5

Telophase

Question 6

the division of the cytoplasm, usually occurs simultaneously with telophase, with two daughter cells completely separating soon after the end of mitosis. In animal cells, a cleavage furrow forms and the cell pinches into two.

Answer 6

cytokinesis

Question 7

True or false. Does cytokinesis overlaps with telophase

Answer 7

true they do overlap

Question 8

Where are stiff cell wall found?

Answer 8

in plant but not in animal cells

Question 9

name the characteristics below and where they belong
-cytokinesis occurs by cleavage
first sign of cleavage in animal cells is appearance of cleavage furrow, a shallow groove in the cell surface

Answer 9

animal cells

Question 10

What are the same proteins responsible for muscle contraction?

Answer 10

actin and myosin

Question 11

When the ring microfilaments interact with myosin, what happens?

Answer 11

the ring contracts

Question 12

vesicles fuse, forming a membranous disk

Answer 12

cell plate

Question 13

what happens when cell plate fuses with plasma membrane and join the parental cell wall?

Answer 13

result in two daughter cells, bounded by its own plasma membrane and cell wall

Question 14

a typical body cell in a human is called a

Answer 14

somatic cell

Question 15

chromosomes other than sex chromosomes are called

Answer 15

autosomes

Question 16

almost every chromosome has a twin that resembles it in length, centromere position, and staining pattern. These two chromosomes of such matching pair is called

Answer 16

homologous chromosomes

Question 17

is the sequence of generation to generation stages in the history of an organism, from fertilization to the production of its own offspring

Answer 17

life cycle

Question 18

what are the only cells that are not produced by mitosis?

Answer 18

gametes

Question 19

this is made of different from of cell division called meiosis this occurs only in reproductive organs

Answer 19

gametes

Question 20

Is it true that meiosis reduces the chromosome as the parent cell, meiosis reduces the chromosome number by half

Answer 20

yes it is true

Question 21

this is the type of cell division that produces haploid gametes in diploid organisms

Answer 21

meiosis

Question 22

fertilization and meiosis alter in sexual life cycles why?

Answer 22

this maintain a constant number of chromosomes in each species from one generation to next.

Question 23

what is the important difference in mitosis and meiosis II ?

Answer 23

meiosis II with a haploid cell containing a single set of still-duplicated chromosomes.

Question 24

what are the two sources of genetic variability in the gametes and zygotes of sexually reproducing organisms?

Answer 24

1) independent assortment and random fertilization

Question 25

the sites of crossing over appear as X shaped regions each site is called

Answer 25

chiasma

Question 26

one that carry DNA for two different parents

Answer 26

recombinant chromosomes