Mitosis and meiosis (week 4)

prophase

mitotic spindles form from centrosomes, chromosomes condense into compacted form

mitotic spindles

structure of microtubules that seperates chromosomes

centrosomes

contains centrioles, where spindle fibers develop

prometaphase

nuclear envelope breaks down, spindle fibers attach to sister chromatids, motor proteins move chromosomes to the center of the cell

nuclear envelope

membrane that surrounds the nucleus

sister chromatids

two halves of the chromosame that are split apart

metaphase

chromosomes line up in the center of the cell

anaphase

mitotic spindles pull chromosomes apart, spindle fibers shorten to pull chromosomes to opposite poles

telophase

mitotic spindles disintegrate, new nuclear envelope developes around collections of chromatids, cytokenesis

chromosomes

condensed strands of DNA, counted by centromeres

homologous chromosomes (homologs)

set of chromosomes, one paternal and one maternal, paired up during meiosis

chiasma & crossing over

synapsed chromosomes that cross over each other, can exchange segments

gametes

cells used for sexual reproduction, produced by meiosis

somatic cells

non-reproductive cells of an organism

ploidy level

number of copies of a type of chromosome present

haploid number

number of unique types of chromosomes present in a cell (n)

nondisjunction

error in division of chromosomes or sister chromatids

aneuploidy

abnormal number of chromosomes in a cell due to loss or duplication

polyploidy

cells of an organism have more than 2 paired sets of chromosomes

heritable variation

genetic variation in reproduction

differential reproduction

selective breeding that favors certain traits

S-phase

period of DNA synthesis/replication

M-phase

period of cell division

G1

normal cell opperation, DNA uncondensed and unreplicated

G2

before M-phase, cell is preparing

Interphase

growth period of a cell, synthesizing resouces

centromere

region with kinetochore, represents number of chromosomes

chromosome

condensed DNA around a centromere

sister chromatid

identical copies of each other around in a replicated chromosome

synapsis

process of homologous chromosomes pairing up

kinetochore

proteins in centromere that move chromotids/chromosomes along spindle fibers

trisomy

n+1 gamete fused with normal gamete, 2n+1

monosomy

n-1 gamete fused with normal gamete, 2n-1

triploidy

diploid and haploid gamete fused, 3n, lethal in humans

meiosis

produces 4, genetically unique, haploid cells - gametes

mitsosis

produces 2, genetically identical, diploid cells - somatic cells