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?

Sperm Cell(Male)

Egg cell(Female)

The joining of a sperm cell with an egg cell is called fertilization.

How many chromosomes do we have in our cells?

• 46 chromosomes

• 23 pairs of chromosomes

Karyotype

OR

Why do we have 2 of each chromosome?

One from mom and one from dadEach pair of chromosomes are called:

Homologous Chromosomes

Homologous Chromosomes:

Have genes that code for the same trait, but may have different versions

of that trait

Eye Color

Hair Color

Mom DadB G

B R

Gene

Part of a chromosomethat codes fora 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

46X46X

Mitosis

Same amount as the parent

cell

Humans = 46

Do our sex cells have 46 chromosomes?

NO!!!

What would happen if our sex cells did have 46 chromosomes?

46 + 46 92

Egg Offspring

Sperm

The offspring would have 92 chromosomes

Sexual Reproduction:

23 + 23 46

Sperm

Egg Offspring

A fertilized egg cell is called a Zygote

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: -SPERM and EGG

• Sex cells should have 1/2 the normal number of chromosomes

Sex Cells (Gametes)

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

1 Diploid cell 4 Haploid Cells

What is the end result of meiosis?

46X

23X23X 23X 23X

Meiosis

4 cells with ½ the number of chromosomes

Where does meiosis occur?

Gonads – Ovaries and Testis

Why is meiosis important?

• Maintains the number of chromosomes from generation to generation

• Provides genetic variation

• .

Gametogenesis

Production of gametes (sperm & egg)

By meiotic cell division

Gameto = gametes

Genesis = creation

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.

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

Practice Problems: