Allo some : ✗ & Y Chromosomes
16.1 -
Role Of Meiosis Autosomes : Pairs 1- 22
somatic cells
→
mitosis → asexual repro , grown , repair , increase in cell numbers
Meiosis Production of gametes
in
sexually reproducing organisms
→
↳
genetic variation
sister chromatid
✗
"" " " " ° " "° " " " " °" " "" " ° "
=
"" "" " "
↳ 2 sets diploid ( 2n )
(
=
1 set =
haploid (n)
produced [
centromere
gametes are occurs in me gametes of d
from GERM CELLS [ sexually reproducing organisms :
egg /0rem , sperm ,
pollen
the haploid number is the number of chromosomes in one set
u ,
n complete
kinetochore -
disc-shaped Of chromosomes .
protein where spindle fibers
attached to . humans =
n =
23 2h =
46
,
onion 8 2h 16
=
n =
,
=
REDUCTION DIVISION In sexual reproduction ,
two
gametes
To keep the
fuse to form a
zygote .
-46 '
(4×23)
number of chromosomes +
ploidy to be
2h '
n
constant for one species .
92 Chromatids → ( 46 ✗ 2) Chromatids → (23×4) Chromatids
9 9
if diploid 12h1 parents were used 12h -12h =
4h )
DI DI will not be continued Therefore
species
= .
DI t 1) It =
PMATXZ 2h
parents must make so nth :
n ,
=
NORMAL DIPLOID NUMBER RESTORED
•
homologous chromosomes •
[ mother p
father
since in fertilisation nth =
2h somatic cells must have 1 ✗ maternal set and I ✗ paternal set
,
sgY§
Pair 23 =
Pair of sex chromosomes
Each pair : some
genes in the same position ( loci ) on the chromosome
:
not necessarily the same forms of allele
of the gene
:
some length and overall size
:
centromere et same
position
:
one chromosome of maternal origin , one chromosome at
paternal
:
some bending
:
come tgt + pair up at Prophase I