Chapter 8

Binary fission

“dividing in half”, part of asexual reproduction when cell divides equally.

parts of chromosome

chromatid, centromere, kinetochore, sister chromatds

Chromatid

one of the two identical halves of a chromosome that has been replicated in preparation for cell division

Centromere

The region of the chromosome to which the spindle fiber is attached during cell division

Kinetachore

proteins, attachment point for spindle fibers

Sister chromatids

Chromosomes as it readies to divide

Cell cycle

leading up to mitosis

G1

Growing phase (interphase)

S phase

DNA is replicated (interphase)

G2

Organelles get copied/made. Last minute prep. (interphase)

Phases of mitosis

Prophase, metaphase, anaphase, telophase

Prophase

• Chromatin condenses into distinct chromosomes

• chromosomes begin to migrate to opposite poles

• Nuclear membrane and nucleolus begins to dissolve

• Beginning to see spindle fibers elongate

Prometaphase

• Nuclear membrane is dissolved

• spindle fibers connected with kinetochores

• chromosomes begin moving

Metaphase

• Spindle fibers align chromosomes in the middle of the cell

Anaphase

• paired chromosomes separate , moving to opposite ends of cell

Telophase

• Cytokinesis overlaps to begin

• Chromosomes have arrived at opposite poles

• spindle fibers have dissolved

• starting to see formation of nuclear membrane

• Chromosomes begin to turn into chromatin

Cytokinesis

• NOT PART OF CELL DIVISION

• division of cytoplasm

Cytokinesis in animal cell

• cleavage furrow forms

• splits off into 2 daughter cells with the same # of chromosomes

Cleavage furrow

• Used in animal cell cytokinesis

• Marks spot for division

Plant cell cytokinesis

• Square

• Cell plate used to divide cytoplasm and form cell wall

• 2 daughter cells form with same chromosome number

Cell plate

Used to divide cytoplasm in a plant cell

interphase

• Cell growth and prep for cell divison

• dna is replicated

• centrosomes form with asters

centrosome

pair of centrioles made from microtubules

anchorage dependence

cells must have surface to grow on

density dependent inhibition

cells continue to divide until they sense that a cell is next to them, then they stop.

cancer

An uncontrolled growth and spread of abnormal cells

tumor

mass of cells that grows more rapidly than surrounding tissue

malignant

very dangerous and harmful

benign

harmless and non-cancerous

metastasis

process where cancer spreads from one area of the body to a different area of the body

meiosis

produces the sex cells (egg and sperm) gametes

reduction division

human 46

egg 23

sperm 23

Diploid number

full amount of chromosomes

haploid number

n

½ of full chromosome number

prior to meiosis I

cells grow/interphase and DNA is duplicated

Prophase I

• synapsis

• crossing over

• chiasmata

synapsis

pairing up of homologous chromosomes

tetrad

two homologous chromosomes, each containing two sister chromatids

crossing over

• exchange of gene segments

• insures variety

chiasmata

overlapping of chromosome “arms”

Interphase (meiosis)

• longest phase in cell cycle

• cells enlarge and get ready to divide

Prophase I

• Chromatin condences, chromosomes form

• homologous pairs form

• spindle fibers elongates

• nuclear membrane breaks down

• synapsis occurs to form tetrad

• chiasmata (overlap)

• crossing over (exchange)

Metaphase I

• Homologous pairs move to the center of cell

Anaphase I

• Homologous pairs seperate, move to opposite poles

Telophase I

• nuclear membrane begins to reform

• spindle fibers disappear

• start to see pinching of cytoplasm

• each “cell” contains one member of homologous pair

Interkinesis

• phase between meiosis I and II

• cells divide, cytoplasm divides

• results in 2 haploid cells

• phases same as mitosis and end in 4 haploid cells

• no interphase

spermatogenesis

4 sperm

Oogenesis

1 egg, 3 polar bodies (disintegrate)