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CHAPTER 11: INTRODUCTION TO GENETICS
Standards B.1.8, B.1.21, B.1.28, B.1.29
Section 11.4: Meiosis
Section 11.4: Meiosis
ASEXUAL REPRODUCTION
SEXUAL REPRODUCTION
SO, Where does the baby get its genetic material?
Sexual Reproduction = 2 Parents
Section 11.4: Meiosis
IMPORTANT CONCEPT:
Because organisms get half of their chromosomes from mom and half from dad, the chromosomes from each parent MUST be divided in half before they can be passed on.
Section 11.4: Meiosis
Homologous Chromosomes A matching pair of chromosomes that have the
same genes. One of these chromosomes comes from MOM. The other chromosome comes from DAD.
Every animal has a unique # of chromosomes.
Humans have 46 chromosomes.(23 from MOM, 23 from DAD)
Section 11.4: Meiosis
Diploid Cell A cell that contains BOTH sets of
chromosomes (mom AND dad).(2 sets = diploid = 2N) All body cells!
Haploid Cell A cell that contains ONE set of chromosomes
(mom OR dad).(1 set = haploid = 1N) All sex cells!
Section 11.4: Meiosis
Meiosis The process of reduction division in which
the number of chromosomes in a cell is cut in half.
Homologous chromosomes are separated in the process.
mom!dad!
Section 11.4: Meiosis
There are TWO major divisions during meiosis.
Meiosis I Reduction Division Homologous chromosomes pair up to form
tetrads.
Section 11.4: Meiosis
Meiotic “Crossing Over” Crossing over: The exchange of alleles
between homologous pairs while in tetrads.
Chromosomes “trade” information! **Increases Diversity**
Section 11.4: Meiosis
There are TWO major divisions during meiosis.
Meiosis II This happens the SAME way as Mitosis!
During Meiosis II, the sister chromatids are pulled apart.
This results in 4 haploid daughter cells.
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
• This happens the SAME way as Mitosis!• During Meiosis II, the sister chromatids are pulled
apart, resulting in 4 haploid daughter cells.
Section 11.4: Meiosis
Results in 2 genetically identical diploid cells.Allows organisms to grow and replace parts.
Results in 4 genetically different haploid cells.Sex cell (gamete) production.
MITOSIS MEIOSIS