Download Genetic Diversity and Differentiation

Genetic Diversity and
Differentiation
Genetic Diversity
• The amount of genetic
variation in a species or
population
– The more different gene
combinations, the
greater the genetic
diversity
• Increased in Meiosis by:
– Crossing over
– Independent Assortment
Crossing Over
• Parts of homologous
chromatids cross over in
Prophase I
– Pieces (genes) break off &
switch places
• **IMPORTANT - Crossing
over = genes switching
Independent Assortment of
Chromosomes
• Anaphase I - homologous
chromosome separate
randomly
• **IMPORTANT –
Independent Assortment
= Chromosomes mix
• Increases the possible
combinations of genes in
each gamete, which
increases genetic
variation
Meiosis Errors
• Nondisjunction
– Chromosomes do not
always separate correctly
– Results in an abnormal
number of chromosomes
in the gametes &
ultimately the zygote
Formation of Gametes
• Spermatogenesis =
formation of sperm cells
– Each of the four haploid
cells created by meiosis
develops into a mature
sperm cell
• Oogenesis = formation of
egg cells (ova)
– Only one of the four
haploid cells created by
meiosis develops into a
mature egg cell (ovum)
• Remaining 3 cells are called
polar bodies
Asexual & Sexual Reproduction
• Asexual Reproduction
– No meiosis or union of gametes
– Offspring are genetically identical to
parents; no variation.
– Examples: binary fission (done by
bacteria), budding (living sponges,
anemones, flatworms)
• Sexual Reproduction
– Has meiosis and gamete union
– Offspring are genetically different
from parents
– Increases genetic variation among
individuals - they are NOT genetically
identical
– ***Advantage: enables species to
adapt rapidly to changing
environmental conditions
Differentiation
• You started from one cell
• Mitosis divides that cell
into ~ 2 trillion
– Each with the same copies
of the DNA in that first
• Cells become specialized
for specific functions
– Not all of the DNA makes all
of the proteins possible
– Cells will make specific
proteins based upon where
they are located in the
organism