THESE SLIDES ARE BASED ON MEIOSIS 1 AND 2

1. Genetics
MEIOSIS
GRADE 12
LIFE SIENCES

2. WHAT IS GENETICS?
• Genetics is a study in biology that was established by a famous
scientist named Gregor Mendel
• This is a study about how traits are inherited though the
interaction of genes.

3. CHROMOSOMES
• In humans somatic cell (body cells) have 23 pairs of
chromosomes
• 22 pairs of these have the same size and genetic
composition and are known as Autosomes
• and the last pair are the sex chromosomes and are
known as Gonosomes

4. HOMOLOGOUS CHROMOSOMES
• The gonosomes (X and Y) are different both in size and
genetic composition.
• Autosomes are arranged in homologous pairs, which
means they have the same length, centromere position and
gene location(locus).
• Different versions of genes may be found at the same
locus on both maternal and partenal chromosomes

5. HOMOLOGOUS PAIR

6. MEIOSIS
Meiosis is a type of cell division that produces haploid gametes
(sperm and egg cells) from diploid cells, during fertilization the two
haploid gametes fuse together forming a diploid (2n) zygote.

7. MEIOSIS 1
INTERPHASE 1
• The cell accumulates energy
• DNA is replicated for duplication of
chromosomes
• Structure of the cell remains the same.

8. MEIOSIS1
PROPHASE 1
• Chromatin network coils forming chromosomes
• Chromosomes lay next to one another by synapsis
forming a tetrad to allow crossing over to occur
to ensure genetic variation
• Nuclear membrane and nucleolus disappear
• Centrioli move to opposite poles forming spindle fiblres in between them.

9. MEIOSIS1
METAPHASE 1
• Centrioli have reached the poles
• Homologous pairs of chromosomes align on the
equatorial region of the cell
• Each homologous pair is attached to one spindle
fiber
• Chromosomes attache to spindle fibre by means of a kinetochore of centomere

10. MEIOSIS1
ANAPHASE 1
• Centrioli on poles contract
• Homologous chromosomes are pulled to
opposite poles

11. MEIOSIS1
TELOPHASE 1
• Nuclear membrane and nucleolus reappear.
• Number of chromosomes is now haploid(n)
on each chromosome
• Cell invagination occurs forming a cleavage
furrow to form two n cells

12. MEIOSIS II
PROPHASE II
• Now the two cells from telophase 1 have a
haipliod (n) number of chromosomes.
• Nuclear membrane and nucleolus re-disappear
• Cetrioli begin moving to poles forming spindle
fibres in both cells.

13. MEIOSIS II
• Individual duplicated chromosomes align at
the equator
• One individual deplicated chromosome is
attached on one spindle fiber

14. MEIOSISII
ANAPHASE II
• Centrioli on the poles contract
• Duplicated chromosomes split in half as well
as the centromere
• Daughter chromosomes are pulled to the poles

15. MEIOSIS II
TELOPHASE II
• Nuclear membrane and nucleolus are formed
• Centrosome is formed
• Daughter chromosomes have reached the poles
• They uncoil forming chromatin
• Cell invagination occurs in each cell
• We end up with four cells

16. REFERENCE LIST
Reece, J.B, Urry, L.A. ,Wasserman, S.A. , Minorsky, P.V. , Jackson, R.B. (2008).
Cambell Biology. Pearson Education: San Francisco
Anonymous. (2013). Zygote pictures. [Online], Available:
www.canstockphoto.com Accessed 06 March 2014