Mitosis and Meiosis Biology

interphase

phase before mitosis; growth of cell and preparation for division

prophase

chromatin condenses into chromosomes, nuclear envelope disappears, spindle fibers start to form

G1

growth and functioning

Synthesis

DNA replicates

G2

organelles replicate in preparation for division

metaphase

chromosomes line up in the middle of the cell

anaphase

the sister chromatids seperate into individual chromosomes and are moved apart

telophase

chromosomes return to chromatin; nuclear membranes form; cleavage furrow begins

cytokinesis

splitting of the cytoplasm

mitosis

splitting of the nucleus

sister chromatids

Replicated forms of a chromosome joined together by the centromere and eventually separated

centromere

area connecting sister chromatids

spindle fibers

microtubules that extend from the centrioles and guide chromosome movement

nucleus

organelle that initiates cell division

somatic cell

all human body cells; not the gametes

diploid

having two sets of chromosomes; all somatic cells

haploid

having one set of chromosomes; the gametes

gamete

sex cell; egg or sperm

zygote

fertilized egg

sexual

reproduction combining genetic info from two parents

asexual

reproduction by one parent as a result of cell division

cell plate

forms in plant cells to form new cell membrane and cell wall

meiosis

cell division producing gametes

homologous chromosomes

Pair of chromosomes that are the same size, same appearance and same genes.

germ cell

immature reproductive cell that gives rise to haploid gametes when it divides

tetrad

structure containing 4 chromatids that forms during meiosis, forms in prophase I when crossing over occurs

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

independent assortment

One of Mendel's principles that states that genes for different traits can segregate independently during the formation of gametes (line up independentely in metaphase I)

polar bodies

small haploid cells produced in XX individuals that do not participate in reproduction

ovum/egg

female gamete

Sperm

male gamete

Nondisjunction

Error in meiosis in which homologous chromosomes or (sister chromatids) fail to separate correctly

meiotic segregation

Distribution of chromosomes during gamete formation.

Monosomy

Chromosomal abnormality consisting of the absence of one chromosome from the normal diploid number

Trisomy

a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities.