Summary IEB Grade 12 Life science: chromosomes and meiosis
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Course
Life Sciences
Institution
12
Book
Life Sciences
These notes are summarised from the Mind Action Series Gr 12 Life Sciences Text books . This includes Chromosomes, meiosis 1 and 2 , aneuploidy syndromes with diagrams and illustration.
aµµ
- Pairs are same size , shape & same
genes
at same place ,
but the alleles for each trait may not be the same Cfhhf
of Somatic Gametic
→ DNA each chromosome replicates into two identical chromatids joined via centromere
during Interphase of mitosis
-
. ⇐
daughter • me, • *
genetic material .
Chromosomes
number
What is meant by chromosome
Each specie specific
. has a number
of chromosomes in somatic cells
- Similarities in DNA of chromosomes shows relationships ,
not the number
meiosis
what is meiosis
to
gametes
-
cell division in reproductive organs produce
' Chromosomes reduced from 2h parents to one set n in each daughter chromosomes halved centromere
-
-
-
-
allelic
of
=
= pair =
haploid of
=
set chromosomes genes
-
gametes are = one
.
During sexu.at reproduction a male haploid gamete fuses with female haploid gamete during fertilization forming
=
diploid zygote
Where does meiosis take place
In animals & Ovaries
Testis
haploid
. :
sperm
haploid
4 cells
egg cells
n
diploid germand epithelial cell
n
'
spermatogenesis formation of sperm cells in testis somatic → A cseuomiatnic
cell in
test is
4 replication ovaries
→ n n ←
- oo
genesis formation of egg cells Cova) in ovaries diploid germanoil epithelial cell
fertilization
Sporangia
.
In Plant diploid
-
formation of spores
.
:
2h
zygote
.
.
. Micro
sporangia pollen sac in male anthers
f mitosis 1
Zygote
-
megasporangia ovules in female ovaries
① 2
Embryo
The process of meiosis
f mitosis 3 Foetus
§§§2n
2h embryo
. DNA
of parent cells replicated in Interphase
'
repeated
Meiosis I = reduction division two haploid cells
mitotic
division
four haploid
'
Mieosis I =
Copying division -
cells
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