Chapter 13-Meiosis

C-13-Meiosis and Sexual Life Cycles

Inheritance or Heredity-the transmission of traits from one generation to the next

Variation- offspring differ somewhat in appearance from parents and siblings

Genetics- the scientific study of heredity.

The study of Genetics
(Levels)

Organism level- phenotype and symptoms of genetic disease

Cell and molecular level- here we look at the cell and the chromosomes and the genes (DNA) to see what has gone wrong

Remember-Genes (DNA)
Code For Proteins

And what do the proteins do?

Structural proteins

Transport proteins

Hormonal proteins

Contractile proteins

Antibody proteins

Enzyme proteins

Children acquire genes from parents by inheriting chromosomes in the egg and sperm

How many? 23+23

What do you actually inherit? Genes which are segments along the DNA molecule. The A, T, G and C

The Human Life Cycle

Fig-13.3

Karyotype

A method of organizing the chromosomes of a cell in relation to number, size and type

Meiosis

The method cells use to reduce the chromosome number from 46 to 23

Meiosis occurs in the ovaries and testes to form eggs and sperm

Meiosis has the same stages as mitosis but it occurs twice. In other words we have prophase, metaphase, anaphase and telophase-1 and prophase, metaphase, anaphase and telophase-2

Meiosis- an overview

Fig. 13.5

A Comparison of Mitosis and Meiosis

Mitosis

Prophase, metaphase, anaphase and telophase occur once

No crossing over

Two diploid cells are produced each with 46

For growth, repair and zygote development

Meiosis

All stages occur twice

Crossing over occurs

Four haploid cells are produced each with 23

For gamete(egg and sperm) production

Sources of Genetic Variability

Independent assortment of chromosomes during meiosis

Crossing over during meiosis

Random fertilization