Transcript Persilangan monofaktorial

Allelic relationship
Dominance Relationships
• In Mendel’s experiments, his traits showed
complete dominance; heterozygotes had
phenotypes similar to homozygotes with
two copies of the dominant allele
• In 1903, A. Garrod demonstrated that
human traits were transmitted according to
Mendel’s laws...
Alcaptonuria inherited as
Mendelian Trait
• inheritance pattern of 3:1 in affected families
(autosomal recessive)
• Garrod noted that affected individuals built up
homogentisic acid in their urine
Alkaptonuria
• Disebut juga “black urine disease” suatu penyakit menurun krn
kelainan genetis pada metabolisme phenylalanine and tyrosine.
• Autosomal recessive , karena defect pada enzim homogentisate
1,2-dioxygenase yg berperan dalam degradasi tyrosine, sehingga
dihasilkan tyrosine yg toksik disebut asam homogentisic (alkapton)
yg terakumulasi pd darah dan diekskresikan lewat urin.
• Asam homogentisic menyebabkan rusaknya kartilago (ochronosis,
leading to osteoarthritis) and heart valves as well as precipitating
as kidney stones.
• common in Slovakia and the Dominican Republic
Phenotype for alcaptonuria: individuals with the disease show
urine which blackens upon exposure to air
1. Dominan tak sempurna
(incommplete dominance)
• Not all traits show an inheritance pattern of
complete dominance
• In some instances, the phenotype of the
heterozygote (A_) can be distinguished from
that of the homozygote (AA)
• e.g.: inheritance of flower color in
snapdragons….
2. Dominansi tak sempurna
white
Phenotype
distinguished from
either parent
1:2:1 ratio
2. Alel kodominan
• Alel-alel tdk memiliki hubungan dominan dan
resesif.
• Misalnya gol darah M-N pd manusia
Genotipe
Golongan darah
(Fenotipe)
LMLM
M
LMLN
MN
LNLN
N
•A and B are “dominant” to O phenotype
•AB is codominant phenotype: both alleles expressed
3. Alel letal
• Perwujudan fenotipik suatu gen yg dapat
menyebabkan kematian sebelum kematangan
seksual
• Alel letal dominan (menyebabkan kemation
organisme baik pada homozigot maupun
heterozigot) kadang muncul akibat mutasi alel
wild type nya
• Tipe lain: alel letal homozigot resesif (sebagian
besar) .
Allel ganda
(Multiple allele)
• : terdapat lebih dari 2 allel pada satu lokus
gen.
• Ada hieraki dominansi antar allel, biasanya
huruf kapital digunakan untuk alel yg paling
dominan terhadap alel-alel lainnya dalam
suatu seri allel ganda, sedangkan huruf kecil
digunakan untuk menunjukkan alel resesif thd
semua alel dlm seri alel ganda tsb.
Genes and the immune system
• Poly-allelic alleles are usually associated
with tissue types
• These genes are so varied that they provide
us with our genetic finger print
• This is very important to our immune system
which must tell the difference between our
own cells (self) and invading disease causing
microbes (non-self)
© 2007 Paul Billiet ODWS
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
© 2007 Paul Billiet ODWS
The ABO blood system
Genotypes
Phenotypes (Blood types)
IA IA
IA IB
IAi
A
AB
A
IB IB
IBi
ii
B
B
O
Note:
• Blood types A and B have two possible genotypes –
homozygous and heterozygous.
• Blood types AB and O only have one genotype each.
© 2007 Paul Billiet ODWS
Blood types and transfusions
• Blood types vary and your immune system
recognises your own blood type as being
self
• Other blood types are recognised as nonself
• If a blood which is incompatible with your
body is transfused it will result in the
agglutination of the foreign red blood
cells
© 2007 Paul Billiet ODWS
Blood types and transfusions
• People who are Type A blood produce antibodies to
agglutinate cells which carry Type B antigens
They recognise them as non-self
• The opposite is true for people who are Type B
• Neither of these people will agglutinate blood cells
which are Type O
Type O cells do not carry any antigens for the ABO
system
© 2007 Paul Billiet ODWS
Donor-recipient compatibility
Recipient
Type
A
B
AB
O
A
Donor
B
AB
O
Note:
• Type O blood may be transfused into all the
= Agglutination
other types = the universal donor.
• Type AB blood can receive blood from all
= Safe transfusion
the other blood types = the universal
recipient.
© 2007 Paul Billiet ODWS
Contoh lain
• Warna bulu pada kelinci:
– C menghasilkan warna bulu penuh (abu-abu)
– cch menghasilkan warna bulu abu-abu keperakan
(chinchilia), jika heterozigot bersama dengan allel
yg lebih rendah dalam hierarki dominansi
menghasilkan bulu abu-abu muda
– ch menghasilkan warna bulu himalaya (putih
dengan tungkai warna hitam)
– c menghasilkan warna bulu albino (tidak
berpigmen)
Fenotipe
Genotipe yang mungkin
Abu-abu (warna CC, Ccch , Cch , Cc
penuh)
Chincilla
cchcch
Abu-abu muda
Cchch, cchc
Himalaya
chch , ch c
albino
cc