Learning Objectives How Chromosomes and DNA are connected How Chromosomes and Genes are connected Know the 3 types of DNA point mutations The difference between Haploid and Diploid The different purposes for Mitosis and Meiosis and why they each end with different results

Chromosomes- eukaryotic cellular structures Chromosomes- eukaryotic cellular structures. Chromosomes are VERY compact strands of DNA. Chromosomes only appear just before cells divide. When not in chromosomes, DNA is uncoiled in the nucleus.

(before it copies itself) Chromosome Structure: “Sister” Chromotids Chromotid Original Copy Centromere Single Chromosome (before it copies itself) Double Chromosome

Homologous Chromosomes: in most animals the offspring will get a single “Chromosome” from EACH parent for most traits. So all genetic traits have 2 sets of instructions (1 from Mom, 1 from Dad). So both parents contribute to the genetic make-up of the offspring Both go to the offspring (these are NOT Sister Chromotids, they are HOMOLOGUS CHROMOSOMES) H W C h w c Mom’s Chromosome Dad’s Height (H or h) Weight (W or w) Hair Color (C or c)

Any Change in the nucleotide sequence of DNA Genetic Mutation: Any Change in the nucleotide sequence of DNA Point Mutations: A type of mutation that cause by an error at single base (a single point) in the DNA sequence. 1) Substitution: A G C T C normal 3) Deletion: A G C T C normal A G G T C mutation A G C C mutation 2) Insertion: A G C T C normal A G C A T C mutation

Mitosis: (how your body grows) -Where a cell divides to make two complete “daughter” cells. Mitosis occurs in a set pattern of phases that is part of “The Cell Cycle”. It never goes out of this set pattern (unless the cell is sick). Interphase Mitosis Cytokinesis Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Mitosis “I Prefer Milk and Tea Cold”

“I Prefer Milk and Tea Cold” Mitosis cont: “I Prefer Milk and Tea Cold” Interphase  Prophase  Metaphase  Anaphase  Telophase Cytokinesis  Back to Interphase … (after mitosis) In Mitosis, cells are dividing to make more cells within the organism. Mitosis is the process of how your body grows to adulthood and how your body repairs itself. 1 Parent Cell (2n) Daughter Cell (2n)

2 Daughter Cells (2n) Parent Cell (2n) https://www.cellsalive.com/mitosis_js.htm 2 Daughter Cells (2n) Parent Cell (2n)

4 Gametes (either sperm or egg) Meiosis: how your cells make gametes (gametes are sex cells sperm or eggs) 1 Parent Cell (2n) 4 Gametes (either sperm or egg) All are (n) 2n = “diploid” = 46 chromosomes (in regular human cells) N = “haploid” = 23 chromosomes (in human gametes) Mitosis used for Meiosis used for reproduction growth and repair (produces sperm & eggs)

Meiosis: how your cells make gametes (gametes are sex cells sperm or eggs) Meiosis: Stages in order Part 1 Meiosis I Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis Part 2 Meiosis II Prophase II Metaphase II Anaphase II Telophase II and Cytokinesis

1 Parent Cell (2n) 4 Gamete Cells (n) DNA replication Meiosis I Meiosis II 4 Gamete Cells (n)

This location is called CHIASMA Crossing Over: Exchanging of parts of chromatids. This ONLY happens in Meiosis I (Prophase I) This location is called CHIASMA (Synapsis)

Video 1 Animation 1

Unique aspects of Meiosis: Synapsis Crossing-over Reduction of number of Chromosomes