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Remember: Chromosomes occur in pairs.
(homologous pairs)
Gen GANDA:
the different alleles of a gene occupy the same positions on each chromosome
The ABO
blood system
• This is a controlled by a tri-allelic gene
• It can generate 6 genotypes
• The alleles control the production of antigens on the surface of the red blood cells
• Two of the alleles are codominant to one another and both are dominant over the third
• Allele IA produces antigen A
• Allele IB produces antigen B
• Allele i produces no antigen
• About 30% of the genes are di-allelic, exist in two forms, (they have
two alleles)
• About 70% are mono-allelic, they only exist in one form and they
show no variation
• A very few are poly-allelic having more than two forms
GEN PADA MANUSIA:
Contoh: PADA MANUSIA, Sistim golongan darah ABO
In this case both A and B are dominant to O (recessive).
A and B are codominant (both expressed)
So... there are four human blood typesAA, AO A blood type
BB ,BO B blood type
AB AB blood type
or
OO O blood type
Genotypes Phenotypes (Blood
types)
IA IA A
IA IB AB
IAi A
IB IB B
IBi B
ii O
What if you lack both A and B sugars?You are an ‘O’!
multiple alleles: A, B and O
Sistem Golongan Darah A-B-O. (K. Landsteiner, 1868 –
1943)
Gen Asli I (Isoagglutinogen), :
1. Alelnya : Ia, Ib, I
2. Urutan dominan: Ia = Ib >i
Golongan
(Fenotip)
Genotip
A Ia Ia atau Ia i
B Ib Ib; atau Ib i
AB Ia Ib
O ii
Contoh: Gol A x Gol B
(Ia Ia; Ia I) x ( Ib Ib; Ib I)
1. Ia Ia x Ib Ib AB
2. Ia Ia x Ib I AB; A
3. Ia I x Ib I AB; B
4. Ia I x Ib I AB; A, B, O
Donor-recipient compatibility
Recipient
Type A B AB O
A
Donor B
AB
O
= Agglutination
= Safe transfusion
Note:
• Type O blood may be transfused into all the other types = the universal donor.
• Type AB blood can receive blood from all the other blood types = the universal recipient.
BASIC: ALEL DAN GEN GANDA
MonoHibrid pada Hewan:
Warna Rambut Hitam: (gen A):
AA (hitam) x aa (albino)
Aa (Hitam)
Gen A:
1 Kali mutasi : -- >alel a
Gen Ganda:
Bbrp kali mutasi---) bbrp alel: a1,a2,a3, dst
However, it is possible to have several
different allele possibilities for one gene.
Multiple alleles is when there are more than two
allele possibilities for a gene.
A L E L G A N D A
Pengertian:
Gen (virgin) kalau bermutasi membentuk Alel ( A -- a)
Banyak Gen mengalami mutasi berulang-ulang, menimbulkan
banyak macam alel (lebih dari 2, disebut alel Ganda)
Contoh: Gen pigmentasi bulu kelinci (Gen C, pigmentasi hitam),
memiliki 3 alel:
1. c : albino (tak ada pigmentasi)
2. cch: pigmentasi terang, bulu pigmentasi gelap pada ujung
(Chinchilla)
3. ch: pigmentasi bagian ujung-ujung tubuh, bagian lain putih
(H= himalaya)
Urutan dominasi alel : C>cch>ch>c
Certain types of rabbits…
…can either be brown, white, have a chinchilla pattern, or
have a himalayan pattern
C causes fully brown coat
cc causes albino (white)
cch causes a chinchilla pattern
ch causes a Himalayan pattern
The alleles are arranged in the following pattern
C > cch > ch > c
• Himalayan rabbit – color in certain parts of the body; dominant only to c; chc or chch
• Albino rabbit – no color – allele is recessive to all other alleles; cc
Full color rabbit – alleles are dominant to all others; CC, Ccch, Cch, or Cc
Chinchilla rabbit – partial defect in pigmentation
cch allele dominant to all other alleles except C; cchch, cchcch, or cchc
Kelinci Gelap:
CC, Cc, Ccch, Cch
Kelinci lebih terang; Chinchila:
cch cchh; cch, ch; ccchc
Kelinci Himalaya:
c h ch; ch,c
Kelinci Albino:
cc
P; Cch Cch X Ch Ch
F1: Cch Ch X Cch Ch
F2: Cch Cch
Cch Ch
Cch Ch
Ch Ch
P ; CC x Cch Cch
F1 : C Cch x c c
F2: Cc
Cch c
dominance
sex linkage
multiple alleles
d
Multiple alleles
Each gene locus can have more than 2 alleles.
An allele may be dominant to some alleles but recessive to others.
This situation produces more than 2 different phenotypes.
Each individual has 2 alleles present in their cells at any one time.
BB or Bb or
Bbl
blbl
bb or bbl
Multiple gene inheritance
Cat coat colour is the result of the inheritance of a large number of different genes.
Crossing Over dan Rekombinan
• Sometimes in meiosis, homologous chromosomes exchange parts in a process called crossing-over.
• New combinations are obtained, called the crossover products.
• Each synapsis is
made up of 2 pairs
of sister chromatids
• This matched set of
4 chromatids is
called a tetrad
MEIOSIS AND CROSSING OVER
Chromosomes are matched in
homologous pairs
Chromosomes
Centromere
Sister chromatids Figure 8.12
21 Apr 2002 16
Crossing Over Basics• Occurs at One or More Points Along
Adjacent Homologues
• Points contact each other
• DNA is Exchanged
• Menaikkan var.Genetik
http://waynesword.palomar.edu/images/cross3.jpg
• Crossing over is the exchange of
corresponding segments between two non-
sister chromatids of homologous chromosomes
• Genetic recombination results from crossing
over during prophase I of meiosis
– This increases variation further
Crossing over further increases
genetic variability
Recombination During Meiosis
Recombinant gametes
Two Loci Inheritance
Recombinant
21A A
B B
a a
b b
A a
B b3 4
a a
b b
A a
b b5 6
A a
B b
• How crossing over
leads to genetic
recombination
• Nonsister
chromatids break
in two at the same
spot
• The 2 broken
chromatids join
together in a new
way
Tetrad(homologous pair ofchromosomes in synapsis)
Breakage of homologous chromatids
Joining of homologous chromatids
Chiasma
Separation of homologouschromosomes at anaphase I
Separation of chromatids atanaphase II and completion of meiosis
Parental type of chromosome
Recombinant chromosome
Recombinant chromosome
Parental type of chromosome
Gametes of four genetic types
1
2
3
4
Coat-colorgenes
Eye-colorgenes
• A segment of one
chromatid has
changed places with
the equivalent
segment of its
nonsister homologue
• If there were no
crossing over meiosis
could only produce 2
types of gametes
Tetrad(homologous pair ofchromosomes in synapsis)
Breakage of homologous chromatids
Joining of homologous chromatids
Chiasma
Separation of homologouschromosomes at anaphase I
Separation of chromatids atanaphase II and completion of meiosis
Parental type of chromosome
Recombinant chromosome
Recombinant chromosome
Parental type of chromosome
Gametes of four genetic types
1
2
3
4
Coat-colorgenes
Eye-colorgenes