Meiosis & Sexual Reproduction. Sexual Reproduction. Involves: Meiosis Gamete production Fertilization Produces genetic variation among offspring. Sexual Reproduction Shuffles Alleles. offspring inherit new combinations of alleles, leading to variations in traits
Meiosis, like mitosis, is preceded by chromosome duplication…
…but, in meiosis the cell divides twice to form four daughter cells.
INTERPHASE PROPHASE I METAPHASE I ANAPHASE I
Sister chromatids remain attached
Microtubulesattached to kinetochore
Centrosomes (with centriole pairs)
Sites of crossing over
Figure 8.14 (Part 1)
Crossing over increases genetic variability.
Genetic recombination results from crossing over during prophase I of meiosis and increases variation still further.
TELOPHASE IAND CYTOKINESIS
TELOPHASE IIAND CYTOKINESIS
PROPHASE II METAPHASE II ANAPHASE II
Haploid daughter cellsforming
Figure 8.14 (Part 2)
is the union of two haploid gametes; one from each parent.
Ex: in humans the egg and sperm each contain 23 chromosomes so after fertilization a zygote will have 46 chromosomes.