why do we have sex

1
Jim Wiggins
why do we have sex???
R. Höhn
Les Clarke
http//www.swmed.edu/home_pages/chlamy/1998chlamy.
html
2
cartoon of a human cell the chromosomes are
made up of 6 billion DNA nucleotides (As Cs
Gs and Ts), and every human cell that has
nuclei has the same number of chromosomes...excep
t for sperm eggs!
3
humans have 46 chromosomes, including the two
that determine male female
http//morgan.rutgers.edu
4
whats an extra chromosome here or there??
http//www.dsa-uk.com
http//www.genecrc.org/site/lc/lc2e.htm
Dr. Sebastiano Bianca
5
TRUE OR FALSE ?
the chromosome number 1 that you got from your
mother is identical to the chromosome number 1
that you got from your father?
FALSE!! they are slightly different
when your cells divide into two daughter cells,
your mothers chromosome number 1 goes into one
of the daughter cells and your fathers
chromosome number 1 goes into the other
FALSE!! all of your cells (except the eggs and
sperm and a few other special cells) get TWO
chromosome number 1s - one originally came from
your mother, the other came from your father
BUT HOW???
6
REPLICATION chromosomes making photocopies of
themselves before the cells divide in two
our cells do it!
bacteria do it!
D. J. Daniels' Glendale High Biology Page
McGraw-Hill
7
OK, so thats how cells divide but we have a
problem when eggs and sperm fuse to form an
embryo, how come this embryo doesnt have 2x too
many chromosomes??
8
eggs and sperm have a special kind of cell
division where the daughter cells (grand-daughter
cells to be exact) end up with HALF the normal
number of chromosomes
chromosomes find your partners!
replication
cell division 1 partners, go to opposite sides
of the room!
separate the twins!
cell division 2
9
differences between eggs and sperm
10
sea urchin sperm surrounding an egg
Chicago Loyola University, Biol Dept
Dr. J. Hardin