3.6 - 3.7 Mammalian gametes and fertilisation

Fertilisation

• fusion of the nuclei from a male gamete and a female gamete to form a zygote.

When are gametes formed?

During meiosis

What number of chromosomes does each gamete have?

Haploid number - 23 chromosomes

(One copy of each chromosome)

Adaptations of Sperm Cell

• Flagellum

• Many mitochondria in middle piece

• Acrosome

Adaptations of Egg Cell

• Much larger

• Follicle cells

• Zona pellucida

Adaptations of Sperm Cell: Flagellum

• Allows sperm to swim to egg cell

Adaptations of Sperm Cell: Many mitochondria

• provide energy for movement (swimming)

Adaptations of Sperm Cell: Acrosome

• Contains digestive enzymes to break down the protective the zona pellucida

• Sperm cells must penetrate this layer in order to fertilise the egg

Adaptations of Egg Cell: Much larger

• Internal space contains food to nourish a growing embryo

Adaptations of Egg Cell: Follicle

• Follicle cells form a protective coating

Adaptations of Egg Cell: Zona pellucida

• forms an impenetrable barrier after fertilisation

• prevents other sperm nuclei from entering the egg

How does a zygote divide?

By mitosis

What type of cells are produced from mitosis?

Diploid cells

What type of cells are produced from meiosis?

Genetically different haploid cells