General Genetics (Practical Session) BIO221 Lecturer Alshehri, Dokhnah Saeed Alshehri, Dikhnah Saeed

3 rd lab Incomplete dominance and Co-dominance (Lack Of Dominance ) Alshehri, Dikhnah Saeed

 The difference between co- dominance and incomplete dominance in genetics.  Some examples for both cases.  Some practical Exercises. Alshehri, Dikhnah Saeed

What is Co-dominance in Genetics? Co-dominance basically means existing together. This means when there are two alleles that share a co-dominant relationship, progeny will express both alleles. Read more at Buzzle: incomplete-dominance.html incomplete-dominance.html Alshehri, Dikhnah Saeed

if a black cat (C b Cb) is crossed with a brown cat (CrCr), the kittens (CbCr) will be either brown with black spots or stripes or black with brown spots or stripes, that is, tabby cat. This means both the colors are co-dominant in this case. Both alleles are completely expressed and the kittens show both colors at the same time. Alshehri, Dikhnah Saeed

What is Incomplete Dominance in Genetics? It is the expression of alleles that are neither dominant or recessive. These alleles mix together and result in expression of a physical trait that is a mixture of the two alleles. Read more at Buzzle: vs-incomplete-dominance.html vs-incomplete-dominance.html Alshehri, Dikhnah Saeed

when you cross a black mice (BB) with a white mice (WW), the progeny of these mice is gray in color (BW). The colors blend together and express the phenotype of both alleles. This type of dominance is similar to mixing paints. When you mix one color with another color, the result is a completely different color. Similarly, when one allele is mixed with another allele they blend together to give rise to a new phenotype. Alshehri, Dikhnah Saeed

 In Japanese four o'clock plants red (R) color is incompletely dominant over white (r) flowers, and the heterozygous condition (Rr) results in plants with pink flowers.  For each of the following breeding give phenotypic and genotypic ratios of the offspring. a) a red plant and a white plant. b) a red plant and a pink plant. c) a white plant and a pink plant. d) two pink plants. Alshehri, Dikhnah Saeed

 In some cats the gene for long tail shows incomplete dominance. Cats with long tails and cats with no tails are homozygous for their respective alleles. Cats with one long tail allele and one no tail allele mates and have short tails offspring.  For each of the following mate give phenotypic and genotypic ratios of the offspring. a) a long tail cat and a cat with no tail b) a long tail cat and a short tail cat c) a short tail cat and a cat with no tail d) two short tail cats. Alshehri, Dikhnah Saeed

 The L M and L N alleles at the MN blood group are co-dominance alleles. Give the expected genotypes and phenotypes (with their ratios) of progeny from the following crosses:  a) L M L M x L M L N  b) L M L N x L N L N Alshehri, Dikhnah Saeed

 In a case of disputed parentage, the mother of an illegitimate child is blood type N, the child MN, and one suspected father is N and the other MN.  How would you work out the case? Alshehri, Dikhnah Saeed