Chapter 9 and 10 - Chromosomes, mitosis, and Meiosis

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Heredity

involves the transfer of genetic information from parent to offspring-" like begets like."

Genetics

branch of biology concerned with heredity.

Chromatin

long stretched out threads of DNA.

Chromosome

chromatin eventually thickens into distinct rods. These form when cell prepares to divide during anaphase of mitosis, made of protein, DNA, and some rRNA- chromatids are called chromosmes after they seperatte in anaphase.

Gene

unit of inherited information in DNA, a sequenceof nitrogenous bases containing information to produce a secific RNA molecule- which codes for a specitic protein.

Mitosis

process of nuclear division of the cytoplasm.

cytokinesis

division of the cytoplasm.

mother cell

the cell that divides.

daughter cells

the 2 new cells formed from the division of the mother cell.

mother cell

before mitosis can occur the mother cell must double (replicate) her DNA. This so each daughter cell will have the same amount of DNA as the parent cell. After DNA riplication, the chromantin thickens to form paired chromatids joined together by thier shared centromere. The centromere holds the two chromatids together until they are pulled apart in anaphase to become chromosomes.

chromosomes

organisms of different species have a characteristic number of chromsomes in each somatic cell (body cell). Humans have 46 chromosomes or 23 pairs.

homologous chromosomes-

a pair of chromosomes governing the same trait. The gene for eye color, for example, is found on the same chromosomee both parents.The gene is therefore homologous.

diploid

(2n) 2 of each type of chromosome (body cells).

haploid

(n) gametes (sperm or egg) 1/2 the chromosomes number. When two haploid cell join (sperm + egg)- fertilization, diploid number is restored (2n).

cell cycle

period from the beginning of one cell division to the beginning of the next division:

G1 (first gap phase) 20%

cells grow and assemble substances necessary for DNA synthesis.

S (synthesis phase)-

DNA synthesis. (50%).

G2- (second gap phase)

cell prepares to divide by making and stockpiling certain materials (20%).

Mitosis

actual cell division (10%)

Interphase

formerly called resting stage: lasts several hours to years ( not actually a phase of mitosis.

Interphase

cell increase in size.

Interphase

amount of chromatin doubles in preparation for mitosis.

Prophase

Longest phase of mitosis

Prophase

nucleous disappears, nuclear membrane disappears, centrioleles move toward opposite poles and microtules (spindle fibers) form near the centrioles.

Prophase

**plants don't have centrioles**

Prophase

centrioles are hollow cylinders composed of 9 microtubules.

Prophase

when the nuclear membrane disappears, the chromatids have free access to the cytoplasm and attach to the spindle fibers by their centromere.

Metaphase

shortest phase
chromatids pairs move to center of the cell, the equator
each chromatid pair is attached by its centromere to spindle fibers.

Anaphase

centromeres split in half
spindle fibers pull the chromatids apart to opposite poles-
chromatids are now called chromosomes
each chromatid pair becomes 2 identical chromosomes
cytoplam divison begins (cytokinesis)

Late Anaphase

in plants: cell plate is laid down, dividing the cytoplasm

Late Anaphase

in animals: cleavage furrow forms and cell pinches into 2 parts.

Telophase

opposite of prophase
spindle fiber disappear
centrioles replicate
chromosomes return to chromatin stage
nuclear membrane reforms around each set of chromosomes
nucleolus reappears in each nucleus.

Telephase

continued pinching of cell membrane results in 2 duaghter cells. Cells return to interphase and the cycle begins again.

mitosis

ensures that each daughter cell receives exactly the same number and kind of chromosomes the parent has (somatic cell)

meiosis

reduces the number of chromosomes so that each daughter cell has one half the number of the parent (in sex cell only)

Stages of meiosis

two nuclear and cell division producing 4 cells

meiosis 1

reduction division
1.spermatogonia
2. primary spermatocyte
3. secondary spermatocyte

meiosis II

equatorial division
4. spermatids
5. mature sperm cells

meiosis

4 daughter cells produced has haploid (n) number of chromosomes.

meiosis

occur in sex cells ex. testes, ovaries

mitosis

occurs in somatic cells
only one nuclear and cell division ( cytokinesis)
2 daugter cells has the diploid (sn) number of chromosomes

after mitosis

the daughter cells contain an identical complement of chromosomes as the parent cell.

animals

gamete (sex cells) formation ( gametogenesis) takes place in specialized cells.

Spermatogenesis

in male- testes(gonads)-sperm(gamete)
sperm smaller than eggs
sperm mobile (can swim)
sperm are formed in a coiled mass of seminferous tubles that make up the testis.

Spermatogenesis

in humans, Sperm is produce all year long.

Spermatogenesis

in animals, sperm is produced durning spring and summer breeding season.

Spermatogenesis

1.acrosome- produces enzmes that help to penetrate the egg
2. nucleu- contains the genes from the male
3. tail- used when swimming toward the egg. Tails falls off when sperm penetrates the egg.

Oogenesis

is the production of ova, or egg in the ovary.

Oogenesis

in females- ovaries(gonads)- egg (gamete

Oogenesis

fetal life oogonia are formed by mitosis.
each surrounded by follicle
third month fetal deevelopment, oogonia develop in oocytes
cells in prophase for 13 years or so (puberty)
an egg that ovulated at age 47 has been in prophase for 47 years.

pinocytosis

"cell drinking", the process of liquid material being taken in.

isotonic

Having the same solute concentration as another solution.

hypertonic

describes a solution whose solute concentration is higher than the solute concentration inside a cell

hypotonic

(of a solution) having a lower osmotic pressure than a comparison solution

telephase

Nucelus forms; Chromosomes decondense; Spindles breakdown

first meiotic division

The division that separates the tetrads so that each daughter cell gets two copies of one of the two homologous chromosomes.

second meiotic division

new cells will have a haploid number of chromosomes; in females, only one of the daughter cells becomes a functional gamete; not preceded by chromosomal replication; chromosomes align, separate, and move to opposite poles, and are surrounded by a reformed nuclear membrane

tetrad

structure containing 4 chromatids that form during meiosis

crossing- over

exchange of genetic material between homologous chromosomes during prophase I of meiosis

spermatogenesis

the process by which male gametes form

oogenesis

the production, growth, and maturation of an egg, or ovum

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