Genes, Mitosis, and Cytokinesis Chapter 9 (pgs ; )

DNA contains an organisms genome Genome = complete collection of that organism’s genetic information DNA code A & T; C & G

Deoxyribonucleic acid 4 bases Cytosine (C) Thymine (T) Adenine (A) Guanine (G) G C A T

Contains a phosphate, a sugar, and a nitrogen base = Nucleotide

The nucleotides form a chain

DNA contains an organisms genome Genome = DNA code A & T; C & G DNA is packaged into chromosomes

Sister Chromatid

Homologous chromosomes = 22 pairs of autosomes 1 pair of sex chromosomes XX = XY =

Cell division 1.Duplication of DNA = replication 2.Two identical strands that move to opposite sides of a cell = mitosis 3.Splitting of cellular material = cytokinesis

Mitosis Division in somatic cells Cell duplication For the replacement of cells because they have died, need more cells during certain points in life, etc..

The cell cycle Interphase consist of: G1 = gap 1 S = synthesis G2 = gap 2 Mitotic phase = mitosis and cytokinesis

Interphase DNA (chromatin) is extended Nucleus is visible

Mitosis - Prophase Beginning of mitosis Sister chromatids are joined together and seen as a chromosome Centrosomes start to move apart to opposite poles Formation of spindle fibers Nuclear envelope breaks down

Mitosis - Metaphase Attachment and alignment Chromosomes line up at the equator Spindle fibers from centrosome attach to the centromere of each chromosome Nuclear envelope has disappeared

Mitosis - Anaphase Separation Spindle fibers pull the sister chromatids apart to the opposite poles

Mitosis - Telophase Exit from mitosis Chromosomes begin to unwind Spindle fibers break down Nuclear envelope begins to from Beginnings of furrowing Nucleolus reappears

Mitosis - Cytokinesis Cell membrane pinches together Membranes on either side fuse Formation of two cells

Meiosis Chapter 10 (pgs )

Meiosis Division in the sex cells Egg and sperm (X and Y chromosomes) Fusion results in a zygote Egg = 23 chromosomes + Sperm = 23 chromosomes….fusion results in a 46 chromosome zygote! Meiosis I and Meiosis II

Formation of chromosomes Homologous chromosomes pair up Crossing-over Centrosomes move to opposite poles Formation of spindle fibers Meiosis I – Prophase I

Crossing-over Exchange of parts from non-sister chromatids Ex. Chromosome 6 from mom with chromosome 6 from dad

Spindle fibers from centrosome attach to the centromere of chromosome Homologous chromosomes move to the equator the cell Random alignment of chromosomes from the mother and from the father = Independent Assortment Nuclear envelope has disappeared Meiosis I – Metaphase I

Spindle fibers pull homologous chromosomes apart to the opposite poles Sister chromatids are still together Meiosis I – Anaphase I

Formation of two new daughter cells Each cell has 46 chromosomes Meiosis I – Telophase I and Cytokinesis

Meiosis II - Prophase II: Formation of chromosomes Centrosomes start to move apart to opposite poles Formation of spindle fibers Nuclear envelope breaks down

Metaphase II: Metaphase II Sister chromatids line up at the equator Spindle fibers from centrosome attach to the centromere of each chromosome Nuclear envelope has disappeared

Meiosis II - Anaphase II : Spindle fibers pull sister chromatids apart to opposite poles

Meiosis II - Telophase II and Cytokinesis Chromosomes begin to unwind Spindle fibers break down Nuclear envelope begins to from Beginnings of furrowing Nucleolus reappears Results in four new cells, each with 23 chromosomes

Mitosis vs. Meiosis Duplication of chromosome number Division into two new daughter cells Diploid cells = 2n or 46 chromosomes Halving of chromosome number Production of four gamate cells Haploid cells = 1n or 23 chromosomes