Gametes & Fertilisation :
Gametes & Fertilisation Gamete mother cells DIPLOID DIPLOID Meiosis- reduction division resulting in variation Gametes HAPLOID HAPLOID Zygotes DIPLOID New combination of genetic material leading to variation
Meiosis :
Meiosis MEIOSIS is a form of nuclear division that produces two haploid gametes. During Meiosis genes are shuffled by:
The crossing over of pieces of chromosomes at points called chiasmata
The independent assortment of pairs of chromosomes at the equator of the cell
Meiosis :
Meiosis
Monohybrid Crosses :
Monohybrid Crosses MONOHYBRID CROSS: is a cross between individuals which show different features of only one gene. A GENE is a part of a chromosome controlling one characteristic. An ALLELE is different forms of a gene. Tall X Dwarf
P HH hh
F1 Hh
2nd cross Hh X Hh
F2 3:1 tall:dwarf
Dihybrid :
Dihybrid DIHYBRID CROSS: A cross between individuals which show different features of two genes. Round&Yellow wrinkled&green
P RRYY X rryy
F1 RrYy
2nd Cross RrYy X RrYy
F2 9:3:3:1 RY:Ry:rY:ry
Dihybrid Backcross :
Dihybrid Backcross BACKCROSSES/ TESTCROSSES: are used to discover the genotype of an organism. Flies produced in the F1 of a Dihybrid cross are back- crossed with the double recessive fly (ggll) If 50% are recombant & 50% are parental- 1:1:1:1 therefore crossing over and independent assortment has occurred and genes are not linked.