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 32Fruit 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.