Meiosis

1
Meiosis

• LN 16

Science Content Standards Genetics
2b. Students know only certain cells in a
multicellular organism undergo meiosis.
2e. Students know why approximately half of an
individuals DNA sequence comes from each parent.
2
Genetics

• Heredity is passing traits from one generation to
  another.
• Genetics is the study of heredity and hereditary
  variation

3
What part of the cell carries genetic information?

• Chromosomes carry genetic information.
• They are located in the nucleus of cells.
• Chromosomes contain genes.
• Genes are a section of DNA that codes for
  different traits.
• Genes are passed from one generation to the next.

4
How many chromosomes are in human cells?

• Human body cells (somatic cells) have 46
  chromosomes.
• Diploid means to have two of each kind of
  chromosome. (2n)
• Chromosomes exist in pairs. One pair coming from
  mom the other from dad.
• Homologous chromosomes are paired chromosomes.
  They contain genes for the same trait.

Karyotype a way to organize chromosomes based
on size and type.
5
Sex cells are not like body cells.

• Sperm and egg cells are called gametes.
• Sperm and egg cells have half the number of
  chromosomes.
• Haploid mean to have one kind of each chromosome.
  (n)
• Gametes (sex cells) are produced by meiosis.

6
Meiosis

• Meiosis is a type of cell division where one body
  cell makes four gametes. Each gamete has half
  the number of chromosomes as a parents body
  cell.
• Meiosis only occurs in the reproductive organs
  (ovaries and testes in animals).
• Meiosis occurs in two parts, Meiosis I and
  Meiosis II.
• Each part contains steps that you might remember
  from Mitosis.
• Remember mitosis is the cellular division of body
  cells, where one cell makes an exact copy of
  itself.

7
The Steps of Meiosis I

• Meiosis I begins with a diploid cell and
  produces two cells.

8
The Steps of Meiosis II

• In meiosis II there are two cells undergoing the
  same process simultaneously. The end result of
  meiosis are 4 haploid cells.

9
Summary

• What will we be studying in the genetics unit?
• What are chromosomes and where are they located?
• How many chromosomes do humans have?
• Why do chromosomes exist in pairs?
• What is the difference between diploid and
  haploid?
• What is meiosis?
• What type of cells undergo meiosis?