Chapter 8 Cellular Reproduction: Cells from Cells

trisomy 21

Down syndrome- there are three number 21 chromosomes, making 47 chromosomes in total. It affects about 1 in every 700 children.

sister chromatids

Each chromosome consists of two copies called ________ _________ which contain identical genes. They are joined tightly by a centromere. Before a cell begins the division process, the DNA molecule of each chromosome is copied through DNA replication and new histone protein molecules attatch as needed.

centromere

The narrow "waist" where sister chromatids are joined tightly together.

gametes

egg and sperm- production involves the process of meiosis and only occurs in the reproductive organs.

crossing over

exchange of corresponding segments of non-sister chromatids of homologous chromosomes, which occurs during prophase I of meiosis. With this exchange, gametes arise with chromosomes that are partly from the mother and partly from the father.

chromatin

fibers composed of roughly equal amounts of DNA and protein molecules- make up chromosomes

diploid organisms

humans (+many other animals and plants) are considered __________ _______________ because all body cells contain pairs of homologous chromosomes (come in matching sets).

histones

proteins used to package DNA in eukaryotes

cytokinesis

stage where the cytoplasm (along with all other organelles) is divided into two.

Roles of cell division

1) replaces damaged or lost cells 2) growth 3) allows for reproduction

autosomes

22 pairs (44 chromosomes in total) of matching chromosomes. You inherited one chromosome of each pair from your mother and the other from your father. (1-22)

haploid cell

a cell that only has ONE member of each pair of homologous chromosomes (i.e. sex cells). To visualize, imagine you closet containing only one shoe from each pair. For humans, the ________ _____ number is 23.

zygote

a fertilized egg- diploid, with two sets of chromosomes (one set from each parent).

G1 phase

a gap phase before the s phase in interphase where each chromosome is single and the cell performs its normal functions

S phase

a period during interphase when chromosome duplication occurs. Stands for DNA synthesis

fertilization

a process in the human life cycle where a haploid sperm cell from dad fuses with a haploid egg cell from mom

parthenogenesis

a rare form of asexual reproduction- the production of offspring by a female without the involvement of a male.

interphase

a time when a cell goes about is usual business, performing its normal functions within the cell. Most of the cell cycle is spent in this phase (90% of the time). During this phase, a cell performs its normal functions, doubles everything in its cytoplasm, chromosome duplication, and grows in size.

somatic cell

a typical body cell and has 46 chromosomes- every single cell except sperm/egg cells

sex chromosomes

chromosomes that determine a person's sex. Males have one X chromosome and one Y chromosome, whereas females have two X chromosomes.

nucleosomes

consist of DNA wound around several histone molecules. The combination of DNA and histones has the appearance of beads on a string. Each "bead" is a _____________.

cell control system

system that directs the sequential events of the cell cycle. Consists of specialized proteins within the cell. The proteins integrate info from the environment and from other body cells and "stop" and "go-ahead" signals at certain key points during the cell cycle. Cancer cells do not normally respond to this system and divide excessively.

prophase

the first phase of mitosis where 1) chromatin fibers coil. Each chromosome exists as two identical sister chromatids joined at the centromere. 2) In the cytoplasm, the mitotic spindle beings to form. 3) Late in ________, the nuclear envelope breaks into pieces. 4) The spindle tracks attach to the centromeres and move the chromosomes toward the center of the cell

telophase

the fourth and final phase of mitosis. This phase begins when the two groups of chromosomes have reached opposite ends of the cell. It is the reverse of prophase: nuclear envelopes form, the chromosome uncoil, and the spindle disappears. Cytokinesis usually occurs with this phase. In animal cells, a cleavage furrow pinches the cell in two, producing two daughter cells.

G2 phase

the gap phase (occurs after DNA replication during the S phase) where each chromosome in the cell consists of two identical sister chromatids and the cell prepares to divide.

nondisjunction

the members of a chromosome pair fail to separate at anaphase, producing gametes with abnormal numbers of chromosomes. Can occur during meiosis I and meoisis 2. When a normal sperm fertilizes an egg cell with an extra chromosome, the result is a zygote with a total of 2n + 1 chromosomes. Because mitosis duplicates the chromosomes as they are, the abnormality will be passed to all embryonic cells. If the organism survives, it will have an abnormal karyotype and probably a medical disorder caused by the abnormal number of genes.

cell cycle

the ordered sequence of events that extend from the time a cell is formed from a dividing parent cell to its own division in two daughter cells.

mitotic phase

the part of the cell cycle when the cell is actually dividing. Includes two overlapping stages: mitosis and cytokinesis. The combination of mitosis and cytokinesis produces two genetically identical daughter cells, each fully equipped with a nucleus, cytoplasm, organelles, and plasma membrane.

meiosis

the process of cell division that produces haploid gametes in diploid organisms, resembles mitosis, but with two differences 1) In _________, a cell that has duplicated its chromosomes undergoes 2 consecutive divisions (_________ 1 & _________ 2). Because one duplication of the chromosome is followed by two divisions, each of the 4 daughter cells resulting from _________ has a haploid set of chromosomes. 2) The second difference is the exchange of genetic material between homologous chromosomes. This exchange, called crossing over, occurs during the first prophase of __________.

cell division

the process of cellular reproduction where two "daughter" cells that result are genetically identical to each other and to the original "parent cell". Before the parent cell splits, it duplicates its chromosomes. Then, during this process, each daughter cell receives one identical set of chromosomes from the parent cell.

metaphase

the second phase of mitosis where the mitotic spindle is now fully formed. 1) The centromeres of all the chromosomes line up between two poles of the spindle. 2) For each chromosome, the tracks of the mitotic spindle attached to the two sister chromatids pull toward opposite poles. (This tug of war keeps the chromosomes in the middle of the cell.)

life cycle

the sequence of stages in a multicellular organism leading from the adults of one generation to the adults of the next

mitosis

the stage where the nucleus and its contents divide evenly into two daughter nuclei

chromosomes

the structures that contain most of the cell's DNA - a detailed instruction manual on how to run a cell

anaphase

the third phase of mitosis where 1) the sister chromatids of each chromosome separate (each is now considered a full-fledged daughter chromosome). 2) The chromosomes move toward opposite poles of the cell as the spindle tracks shorten. Simultaneously, the tracks not attached to chromosomes lengthen, pushing the poles father apart and elongating the cell.

homologous chromosomes

the two chromosomes of a matching pair that carry genes controlling the SAME inherited characteristics. A pair of this type of chromosomes has two nearly identical chromosomes, each of which consists of two identical sister chromatids after chromosome duplication. Humans have 46 chromosomes

karotype

to produce a _________, a technician can break open a human cell in metaphase of mitosis, stain the chromosomes with dyes, take a picture with the aid of a microscope, and arrange the chromosomes in matching pairs by size.

asexual reproduction

type of reproduction that does not involve fertilization of an egg by a sperm. (Ex. single-celled organisms like amoebas, or multicellular organisms like sea stars)

sexual reproduction

type of reproduction that requires fertilization of an egg by a sperm

cytokinesis

usually, begins during telophase, divides the cytoplasm, and is different in plant and animal cells. In animal cells,this process is known as cleavage and begins with the appearance of a cleavage furrow. In plant cells, vesicles containing cell wall material collect at the middle of the cell and then fuse forming a cell plate. The cell plate grows outward, accumulating more cell wall material as more vesicles join it. Eventually, the membrane of the cell plate fuses with the plasma membrane, and the cell plate's contents join the parental cell wall.