CELL DIVISION - MITOSIS AND MEIOSIS

what r the 2 types of cell division

mitosis - body cells

meiosis - gametes

the purpose of mitosis is

to make 2 identical body cells for growth and repair

what r the main phases of the cell cycle

interphase and mitosis

what happens during G1 phase of interphase

cell grows and performs normal functions

what happens during S phase of itnerphase

DNA is replicated, sister chromatids are formed

what happens during g2 phase of interphase

cell grows more

copies organelles

prepares for division

what happens during prophase

DNA condenses into chromosomes

spindle fibers form

nuclear envelop breaks down

nucleolus disappears

what happens during metaphase of mitosis

chromosomes line up in middle of cell - metaphase plate

what happens during anaphase

sister chromatids to opposite sides of cell

what happens durint telophase

2 new nuclei form around DNA

what is the final result of mitosis

2 genetically identical daughter cells

what is purpose of meiosis

produce 4 genetically different haploid gametes - sperm or egg

what is difference between diploid and haploid

diploid = 46 chromosomes

haploid = 23

what r homologous chromosomes

homologous chromosomes - one from mom and one from dad

have same genes, possibly different alleles

what r sister chromatids

identical copies of a chromosome connected at a centromere

what happens in prophase 1 of meiosis

chromosome condenses

homologous chromosomes pair to form tetrads

crossing over occurs

nuclear membrane breaks down

spindle forms

homologous chromosomes pair to form

tetrads

what is crossing over

non-sister chromatids swap dna - increases genetic variation

what happens in metaphse 1

tetrads (homologous pairs) line up at metaphase plate

what happens in anaphase I

homologous chromosomes are pulled to opposite sides, sister chromatids stay together

what happens in telophase I and cytokinesis

chromosomes arrive at poles

nuclear membrane reforms

cytoplasm divides into 2 haploid cells

still duplicated as sister chromatids

what is main purpose of meiosis

separate sister chromatids - just like mitosis

how many chromosomes does each gamete have after meiosis

23 - haploid

final result of meiosis II

4 haploid cells - each with 23 chromosomes each