Achromatopsia in Canis Lupus Familiaris - Essay Example

Achromatopsia is caused by mutations in certain genes. Two common genes that undergo mutation to result in achromatopsia are CNGB3 and CNGA3. Four chromosomes might have changes responsible for achromatopsia. These chromosomes are chromosome 14, chromosome 8q21-q22, chromosome 2q11, and chromosome 10q24.

     A mutation that causes this disorder was discovered through a comparative positional cloning approach. The locus of the disorder is in a region of chromosome CFA29. The homologous region on the human genome has the gene for cyclic nucleotide-gated channel beta subunit. The mutation causes the same disorders in human beings. The mode of inheritance for this disorder is autosomal recessive. Some chromosomal information is lost or deleted through the process of converting DNA to amino acids (Parker, 2004).

Part II, punnet square

      A scientist known as Punnet 1993 discovered the trait of the blue egg. This trait was mapped on chromosome GGA1 to a region from 67.3-69.1. The dongxiang chicken breed was used to discover this trait. Using analysis of linkage on the candidate region on information from 146 F2 hens that originate from cross-breeding between homozygous blue and homozygous non-blue birds of the Dongxiang breed, scientists refined the location to 120 kb region from 67296991 bp to 67416784 bp located on chromosome 1along the chicken genome.

       The location that was refined by scientists is made up of four positional candidate genes. Just a single gene out of the four genes is responsible for the blue shell trait. This gene is SLCO1B3. It is expressed in the shell glands in the uterus of chickens with a blue shell trait but it is not expressed in shell glands within the uterus of non-blue-shelled hens. Through the process of converting DNA to proteins, a gene responsible for this trait was inserted within the amino acid sequence in the protein structure. The process of sequencing uncovered causal mutation to be a~4.2, (that is a retroviral), EAV-HP in the fifth flanking region of SLCO1B3. A survey for genotyping that consisted of 38 hens from different breeds in which blue eggshell segregates indicated a total correlation of the presence or absence of the insertion mutation with the blue egg-shell genotype. The same insertion mutation was also reported in other chicken breeds in different parts of the world. This trait comes because of autosomal dominant inheritance. A gene for this trait is located in somatic cells. A single mutated gene from one parent is enough for the offspring to acquire a trait that is responsible for the blue egg trait.