2. INTRODUCTION TO MEOISIS
SOMATIC CELLS HAVE 23 HOMOLOGOUS CHROMOSOMES
HALF FROM THE FATHER: PATERNAL
HALF FROM THE MOTHER: MATERNAL
SEX CHROMOSOMES ARE KNOWN AS GONOSOMES OR X
AND Y
X AND Y DIFFER IN GENETIC COMPOSITION AND IN SIZE
3.
4. HOMOLOGOUS CHROMOSOMES
HOMOLOGOS CHROMOSOMES ARE SIMILAR IN LENGTH, CENTROMERE
POSITION AND GENETIC LOCATION (LOCUS)
DIFFERENT VERSIONS OF A GENE ARE CALLED ALLELES AND CAN BE
FOUND IN THE SAME LOCUS ON PATERNAL AND MATERNAL
CHROMOSOMES
5. WHAT IS MEOISIS
ALL HUMANS AND MOST PLANTS HAVE DIPLOID (2n)
CHROMOSOMES
MEOISIS IS THE HALVING OF THE NUMBER OF
CHROMOSOMES TO HAPLOID (n)
MEOISIS OCCURS IN THE SEX ORGANS TO PRODUCE
GAMETES THAT WILL MATURE INTO AN EGG CELL OR A
SPERM CELL
FERTILIZATION IS THE FUSION OF GAMETES
6.
7. INTERPHASE ONE
IN THE CELL THERE IS A BUILD UP OF ENERGY
DNA REPLICATION STARTS
9. CROSSING OVER
CROSSING OVER IS THE PROCESS WHEREBY THE
HOMOLOGOUS CHROMOSOMES TOUCH AT POINTS
CALLED CHIASMATA
THIS INCREASES THE GENETIC VARIATION OF THE
GAMETES
10. METAPHASE 1
CENTRIOLI REACH POLES
SPINDLE FIBRES FORM BETWEEN THEM
HOMOLOGOUS CHROMOSOMES REACH POLES
EQUOTORIAL PLANES ATTACHED TO SPINDLE
FIBRES
KINETOCHORE OF CENTROMERE ATTACH TO
SPINDLE FIBRES
11. ANAPHASE 1
DUPLICATED CHROMOSOMES MOVE TO ONE PART OF
THE CELL
SPINDLE FIBRES AND CENTRIOLI CONTRACT
12. TELOPHASE 1
THE CYTOPLASM WILL FORM AN INVAGINATION
AND UNGERGO CYTOKENISIS
THE NUCLEOMEMBRANE AND NUCLEOLUS
REAPPEAR
TWO DAUGHTER CHROMOSOMES FORM THAT
ARE HAPLOID
13. PROPHASE 2
NUCLEAR MEMBRANE AND NUCLEOLUS DISAPPEAR
CENTRIOLI MOVES TOWARDS THE POLES
