chapter 8 The cellular basis of reproduction and inheritance Flashcards
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
Interphase
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.
prophase
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.
metaphase
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.
Anaphase
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.
Telophase
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.
cytokinesis
True or false. Does cytokinesis overlaps with telophase
true they do overlap
Where are stiff cell wall found?
in plant but not in animal cells
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
animal cells
What are the same proteins responsible for muscle contraction?
actin and myosin
When the ring microfilaments interact with myosin, what happens?
the ring contracts
vesicles fuse, forming a membranous disk
cell plate
what happens when cell plate fuses with plasma membrane and join the parental cell wall?
result in two daughter cells, bounded by its own plasma membrane and cell wall
a typical body cell in a human is called a
somatic cell
chromosomes other than sex chromosomes are called
autosomes
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
homologous chromosomes
is the sequence of generation to generation stages in the history of an organism, from fertilization to the production of its own offspring
life cycle
what are the only cells that are not produced by mitosis?
gametes
this is made of different from of cell division called meiosis this occurs only in reproductive organs
gametes
Is it true that meiosis reduces the chromosome as the parent cell, meiosis reduces the chromosome number by half
yes it is true
this is the type of cell division that produces haploid gametes in diploid organisms
meiosis
fertilization and meiosis alter in sexual life cycles why?
this maintain a constant number of chromosomes in each species from one generation to next.
what is the important difference in mitosis and meiosis II ?
meiosis II with a haploid cell containing a single set of still-duplicated chromosomes.
what are the two sources of genetic variability in the gametes and zygotes of sexually reproducing organisms?
1) independent assortment and random fertilization
