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