LO: SWBAT explain how gametes are formed. DN: What are gametes? Where are the gametes formed? HW: HW Packet #1-4 (whole packet due Monday)

What is Sexual Reproduction? It involves the joining of two cells to begin the development of a new individual. These special cells are called: Sex Cells (Gametes)

What are the names of these sex cells? Egg cell (Female) Sperm Cell (Male) The joining of a sperm cell with an egg cell is called fertilization.

How many chromosomes do we have in our cells? OR 23 pairs of chromosomes Karyotype

Why do we have 2 of each chromosome? One from mom and one from dad Each pair of chromosomes are called: Homologous Chromosomes

Homologous Chromosomes: Eye Color Hair Color Mom Dad B G R Gene Part of a chromosome that codes for a trait Have genes that code for the same trait, but may have different versions of that trait

How are chromatids different than homologous chromosomes? Chromatids are exact copies of each other Homologous chromosomes same size chromosomes genes for the same trait, can have different versions of that trait

How many chromosomes do the offspring have after mitosis? 46X Same amount as the parent cell Humans = 46 Mitosis 46X 46X

Do our sex cells have 46 chromosomes? NO!!!

What would happen if our sex cells did have 46 chromosomes? 92 + Offspring Egg Sperm The offspring would have 92 chromosomes

Sexual Reproduction: 23 23 46 + Offspring Egg A fertilized egg cell is called a Zygote Sperm Characteristics of Sexual Reproduction: 1) Is the creation of a new individual from parents. 2 2) Offspring are not genetically to the parents. identical

Sex Cells (Gametes) Sex Cells: -SPERM and EGG Sex cells should have 1/2 the normal number of chromosomes

Chromosome Number Diploid cells: (2n) normal number of chromosomes (Body Cells) Haploid cells: (n) ½ the normal number of chromosomes (Sex Cells)

Meiosis The process by which sex cells are produced with half the number of chromosomes.

Meiosis is 2 Cell Divisions 1st Cell Division 2nd Cell Division 4 Haploid Cells 1 Diploid cell

What is the end result of meiosis? 46X 4 cells with ½ the number of chromosomes Meiosis 23X 23X 23X 23X

Where does meiosis occur? Gonads – Ovaries and Testis

Why is meiosis important? Maintains the number of chromosomes from generation to generation Provides genetic variation .

Crossing over – Prophase I Synapsis – homologous chromosomes pair up Crossing over – chromosomes overlap and exchange of genes.

Production of gametes (sperm & egg) By meiotic cell division Gametogenesis Gameto = gametes Genesis = creation Production of gametes (sperm & egg) By meiotic cell division

Creation of an ovum or egg cell by meiotic cell division in the ovary. Oogenesis Creation of an ovum or egg cell by meiotic cell division in the ovary.

How many eggs are produced? There is an unequal sharing of cytoplasm 1 egg & 3 non functional polar bodies

Egg vs. Polar Bodies The egg is very large, has most of the cytoplasm, which will provide nutrients for the offspring.

Creation of sperm cells by meiotic cell division in the testes. Spermatogenesis Creation of sperm cells by meiotic cell division in the testes.

How many sperm are produced by spermatogenesis? 4 equal sized sperms with flagella for swimming.

Spermatogenesis vs. Oogenesis

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