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 A IA IB IB IB B IBi ii 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 non-self 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 Type A B AB O Donor 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. = Agglutination = Safe transfusion © 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 penuh) CC, Ccch , Cch , Cc Chincilla cchcch Abu-abu muda Cchch, cchc Himalaya chch , ch c albino cc