CELL TYPES CHROMOSOMES Somatic cells are body cells

CELL TYPES & CHROMOSOMES

Somatic cells are body cells Gametes are sex cells (egg & sperm)

Humans body cells have 46 chromosomes or 23 pairs. maternal paternal

Is this individual a male or female? xy…. male What are these chromosomes called? Sex chromosomes

Is this individual a male or female? xx…female

Similar chromosomes are called: Homologous chromosomes

Homologous chromosomes How are they similar? Allele for short allele for tall Allele for brown hair Allele for black hair Allele for brown eyes Allele for curly hair Allele for straight hair They contain alleles for the same trait.

Somatic cells/body cells are diploid. Diploid cells (2 n) have homologous pairs.

A Diploid Cell 2 n A e E The chromosomes are in pairs… homologous pairs. a b B What type of cell is this? Gamete or somatic cell paternal maternal

Gametes/sex cells are haploid. Egg and sperm are gametes. Haploid cells (n) have one set of chromosomes.

A Haploid Cell Haploid = half Half the chromosomes. n There is one set of chromosomes. What type of cell is this? Gamete or somatic cell

Diploid cell Which cell is diploid? 2 n

Haploid cell n Which cell is haploid?

Sexual reproduction involves the union of egg and sperm offspring are genetically unique

Fertilization - - - fusion of egg and sperm

Fertilization Egg + sperm n + n = 2 n 23 + 23 = 46 = zygote

Making Gametes MEIOSIS & CYTOKINESIS

Why do cells undergo meiosis? To make gametes, egg and sperm. In which organs? ovaries and testes

Body Cells vs Two sets of chromosomes Gametes One set of chromosomes Homologous pairs 2 n n

MEIOSIS gametes 2 n One diploid cell n n four haploid cells

Meiosis halves the number of chromosomes forms four haploid cells, (n) forms gametes --- egg & sperm

MEIOSIS There are eight phases in meiosis: 1. prophase I 2. metaphase I 3. anaphase I 4. telophase I 5. prophase II 6. metaphase II 7. anaphase II 8. telophase II Meiosis I - - Homologous chromosomes separate Meiosis II - - Sister chromatids separate