Mitosis and Meiosis Asexual v. Sexual Reproduction CELL DIVISION Mitosis and Meiosis Asexual v. Sexual Reproduction

Cell Division “process where 1 cell splits into 2” Replaces somatic (body) cells in multicellular organisms Allows for multicelullar growth Allows for asexual reproduction in plants

Chromosome – rod shaped structure made up DNA and protein a. held together by centromere - holds chromatids together until they separate during division b. only found during cell division

Chromosome Number Human/animal chromosomes – sex chromosomes and autosomes Humans have 46 chromosomes in somatic cells Karyotype – used to examine an individual’s chromosomes

Nondisjuntion Mutation “failure of chromosome to separate from it’s homologue during meiosis” One extra or one less chromosome at chromosome location Monosomy v. Trisomy

Examples of Nondisjunction Disorders Down Syndrome (Trisomy 21) 1. extra chromosome 21 2. Symptoms – muscle weakness, large forehead, large tongue, heart defects, short stature

Klinefelters Syndrome 1. male with extra X chromosome (XXY) 2. Symptoms: infertile, some feminine characteristics, undersized testicles Turners Syndrome 1. single X chromosomes (XO) 2. female appearance, infertile due to not maturing sexually

Karyotypes of Individuals with Genetic Disorders

Detecting Genetic Disorders Genetic Screening 1. examining a person’s DNA 2. Karyotype Ways to get a cell sample 1. amniocentesis 2. chorionic villi sampling Finding deformities 1. ultrasound

Haploid Diploid Reproductive cells (sperm and egg) Somatic cells (body-all other cells) ½ the # of chromosomes (23) Has ALL chromosomes (46) half the DNA Has ALL DNA N = haploid 2N = diploid

Haploid/Diploid Problems Haploid → Diploid = sex cell → body cell ( x by 2) Diploid → Haploid = body cell → sex cell ( ÷ by 2) Diploid → Diploid = body cell → body cell Haploid → Haploid = sex cell → sex cell

Practice Problems Dogs have 42 chromosomes in their diploid cells. How many are in their haploid cells? If there are 23 chromosomes in a sperm cell, how many would be in the skin cell? If there are 46 chromosomes in a nerve cell, how many would be in a blood cell? If there are 23 chromosomes in a sperm cell, how many would be in a human ovum (egg)

Cell Division in Prokaryotes Binary Fision – two identical cells are produced from one cell * division in bacteria

Budding:

Cell Division in Eukaryotes Mitosis Meiosis Asexual Reproduction Sexual Reproduction Division of diploid cells (somatic cells) Division of haploid cells (reproductive cells) Results in 2 identical daughter cells Results in 4 haploid daughter cells 1 division 2 divisions

Cell Cycle “series of events leading to cell division”

Mitosis Asexual Reproduction Diploid cells split into 2 identical diploid cells Allows body cells to be replaced and cells to GROW

Phases of Mitosis 1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Cytokinesis

Meiosis “sexual reproduction” Fusing of 2 haploid gametes to form 1 diploid zygote

Stages 2 divisions a. Meiosis I

b. Meiosis II

Sources of Genetic Variation Crossing – over Fertilization Independent Assortment