Learning Target: Mitosis v. Meiosis I Can…Compare and contrast key points between the process of mitosis and the process of meiosis to explain why there are two processes for cellular division I Will… Describe the characteristics of somatic and gamete cells Distinguish between autosome and sex chromosomes List examples of when mitosis and meiosis would occur

10.4 In sexually reproducing organisms, each offspring contains a mix of characteristics inherited from both parents. D 36 Explain how meiosis contributes to the genetic variability of organisms. What makes you… YOU?!!

Two major groups of cells in the body: Somatic cells –Body cells e.g. skin cells, bone cells, muscle cells etc… Diploid – (2n) 2 copies of each chromosome DNA from these cells IS NOT passed on to offspring Germ/Gamete cells – Located in reproductive organs (Gonads); the ovaries and testes Develops into gametes (sex cells) Egg Sperm Haploid – (n) 1 copy of each chromosome DNA from these cells IS passed on to offspring

Each species has a characteristic number of chromosomes per cell Every body cell has an identical set of chromosomes (DNA Replication) Exception – mutation (change in nucleotide sequence) Cells are different because of different genes are expressed NOT because of containing different genes

Species chromosome number is not related to the complexity of an organism but… Important that the number remains constant for reproducing Change in number in animals is usually harmful or fatal Yeast 32 Fruit Fly 8 Fern >1200 Human 46

46 chromosomes in 23 pairs Half from mom ♀ Half from dad ♂ Autosomes – chromosome pairs #1 – 22 Contain genes not related to sex characteristics (gender) Chromosome pair # 23 – Sex Chromosomes Two versions Y – Smallest chromosome with fewest genes X – Larger also contains genes unrelated to sex characteristics

22 pairs of autosome chromosomes 1 pair of sex chromosomes XY = Male ♂ XX = Female ♀

Homologous chromosomes – two chromosomes with same length, shape and genes (not necessarily the same version) Alleles – different versions of gene

Mitosis Produces 2 genetically identical cells Diploid (2n) Occurs throughout lifetime Asexual reproduction Meiosis Produces 4 genetically unique cells Haploid (n) Occurs only when producing egg/sperm Sexual reproduction

Sexual reproduction – Fusion of gametes Offspring is mixture of parents’ genetics Fertilization – nuclei of egg and sperm fuse and form one nucleus

Reproduction Asexual V. Sexual Benefit: Quick No need to find mate Disadvantages: No genetic diversity = clone Benefit: Increases genetic diversity of species Disadvantages: Need to find a mate

Learning Check √ Intro to Meiosis 1.List two types of somatic cells. A.________________ B.________________ 2.List two types of gamete cells. A.________________ B.________________ 3.Explain the difference between diploid and haploid cells.