Mendel and Meiosis Gregor Mendel 1822 1884 In

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Mendel and Meiosis

Mendel and Meiosis

Gregor Mendel 1822 -1884 • In his younger years Mendel taught high school math,

Gregor Mendel 1822 -1884 • In his younger years Mendel taught high school math, physics and Greek in Brno, Czech Republic. • He was a monk and eventually became the abbot of his monastery • In his spare time he did experiments with pea plants to see how they passed on their traits. • The study of inheritance was popular in the mid 1800’s. People bred dogs for hunting and farm animals for milk/food, and pigeons for fun.

Mendel’s Research 1. He studied patterns of inheritance by breeding pea plants by the

Mendel’s Research 1. He studied patterns of inheritance by breeding pea plants by the thousands and counting and doing the statistics. 2. Pure traits were developed by self fertilization of plants for several generations. 3. If the offspring looked like the parents it was a Pure Line.

Monohybrid Cross • If two pure lines are crossed , then the offspring are

Monohybrid Cross • If two pure lines are crossed , then the offspring are called Hybrids. • Mendel could control his crosses and planned them carefully to study one trait at a time. • This is called a monohybrid cross. • Mendel chose traits that could be seen in only two forms. • Eg Tall and short

Terminology P 1 = Parent generation F 1 = First filial generation (the kids)

Terminology P 1 = Parent generation F 1 = First filial generation (the kids) F 2 = Second filial generation (the grand kids) F 1 Every time he crossed a pure red with a pure white the was always red, so he called Red Dominant (R). • Every time he crossed 2 F 1 reds the F 2 generation had a 3 : 1 ratio red : white • The white was just hiding so he called it recessive (r) • From this ratio Mendel deduced. . • •

Mendel's Law of Segregation • A trait is determines by 2 factors. • 1

Mendel's Law of Segregation • A trait is determines by 2 factors. • 1 from the mother and 1 from the father. • Some how these factors must be separated in making the gametes.

? What Mendel didn’t know? ? ? How did it work ? ? ?

? What Mendel didn’t know? ? ? How did it work ? ? ?

Meiosis What Mendel didn’t know or • The normal human cell has 2 sets

Meiosis What Mendel didn’t know or • The normal human cell has 2 sets of each chromosome. (2 n) We call these cells diploid. • They are called homologous pairs. • There is a special kind of cell division that makes eggs and sperm (Gametes) • It reduces the number of chromosomes (n) by half by separating the homologous pairs. We call these cells haploid.

Meiosis has 2 sets of cell division Division 1 The homologous pairs line up

Meiosis has 2 sets of cell division Division 1 The homologous pairs line up At the equator and get separated. This is called the reduction division. It reduces the # of chromosomes by ½ 2 n n Division 2 The chromatid pairs line up at the equator and get separated. The end result is 4 cells with ½ the chromosomes.

Spermatogenesis and oogenesis sperms and eggs • In order to best spread genes to

Spermatogenesis and oogenesis sperms and eggs • In order to best spread genes to the next generation the most successful strategy for the male is to produce lots of sperm, 4 from each meiotic division. • The female, however, has to provide a nourishing environment for the developing embryo. It sacrifices 3 gametes and puts all the cytoplasm into one egg. That’s why the egg is the biggest cell in your body.

Meiosis creates 4 sperm but only 1 egg

Meiosis creates 4 sperm but only 1 egg

To recap • Humans have 46 chromosomes in each cell • The 1 st

To recap • Humans have 46 chromosomes in each cell • The 1 st meiotic division separates the homologous pairs reducing the # to 23 • The 2 nd division separates the chromatid pairs and makes 4 cells ( 4 equal sperm or 1 egg and 3 polar bodies.

What cells under go this process in animals? • In females meiosis occurs in

What cells under go this process in animals? • In females meiosis occurs in the ovary usually before you are born. The eggs star maturing and hatch out 1 per month between puberty and menopause. • In males meiosis occurs in the testes continually from puberty on. • These are called you sex cells.

Somatic cells • All the other cells in you body are called somatic cells

Somatic cells • All the other cells in you body are called somatic cells (skin , liver, nerves, heart etc. ) • Somatic cells are always diploid, 2 n. • They undergo Mitosis. • If an organism reproduces by mitosis this is called asexual reproduction • Eg. regeneration, budding, cloning, parthenogenesis, and reproduction in single celled organisms

Sexual reproduction is the life cycle between diploid (2 n) and haploid (n) cells

Sexual reproduction is the life cycle between diploid (2 n) and haploid (n) cells or organisms

Fertilization is the opposite of meiosis

Fertilization is the opposite of meiosis

You’ve now learned two different kinds of cell division Mitosis • Occurs in the

You’ve now learned two different kinds of cell division Mitosis • Occurs in the somatic cells. • Only one division. • Chromatid pairs are separated. • Produces 2 identical daughter cells. • 2 Daughter cells are diploid (2 n). • Used for growth, repair, and asexual reproduction. Meiosis • Occurs in ovaries and testes. • Two sets of divisions • Homologous pairs are separated. • Produces 4 cells that are similar but not identical. • 4 daughter cells are haploid (n) • Used to produces gametes (eggs and sperm) for sexual reproduction.

Meiosis and fertilization is the machinery behind Mendel • • Mendel didn’t know any

Meiosis and fertilization is the machinery behind Mendel • • Mendel didn’t know any of this. Yet he figured out how it must work Just by using careful planning. Controlled experiments Scientific method And math / statistics Ta Da!

Next time How to screw up a good system in order to get some

Next time How to screw up a good system in order to get some variation on a theme. • • Cross overs Linkages Sex linked and limited Polygenic inheritance and. . . • Mutations