A F Question 3. Some neurons in the brain produce a neurotransmitter known as dopamine. Parkinson's disease occurs when the neurons that produce dopamine die. A person with the disease may experience difficulty in coordinating movement. In seen as tremors, shaking, in different parts of the body. Parkinson's disease typically occurs in people older than 55 years. Younger people with these symptoms are said to have early onset Parkinson's disease, EOPD. Recessive mutations in a gene known as pink one, located on chromosome one, and autosome, are believed to be one cause of EOPD. A person with this form of EOPD has a homozygous recessive genotype. Dear for discussion and illustration, please look. What is the difference between dominant and recessive mutations? In case of recessive mutation. One mutant allele is unable to be expressed in heterozygous individual as in person one. So it has no effect on the phenotype. In case of dominant mutation. The mutation has an effect in both homozygous and heterozygous individuals, person three and four. Question letter A. Draw a genetic diagram of a cross between two individuals who are heterozygous at the pink one gene locus. Simples used. Ecapital for healthy allele. E small for mutant allele or EOPD allele. Heterozygous individuals means they are carrier. So their genotypes are. Ecapital E small. The parents gametes are. Ecapital E small. Ecapital and E small. The offspring phenotype are. Ecapital Ecapital. Ecapital E small. Ecapital E small. And. E small E small. The phenotype ratio. Three normal. To one diseased. Question B. Pink one codes for a protein kinase enzyme that is important in a functioning of mitochondria in neurons. Most recessive pink one mutations are based substitutions which lead to the production of a non-functioning protein kinase enzyme. Explain how a base substitution mutation can lead to the production of a non-functioning protein kinase. Dear, for discussion and illustration, please look to figures. Base substitution. Means one base replaces another. Missense mutation. mRNA forms different codon, so different TRNA is involved. Different amino acid in the formed polypeptide chain. This affect the primary structure of the polypeptide or enzyme. This also may affect the 3D structure of the enzyme and its binding site. Effecting the catalytic activity of the protein kinase enzyme. Please compare the normal mRNA with the mutated one below. Non-sense mutation. A stop codon may be found earlier on the mRNA, so no complementary TRNA base pairing occurs. Rather short polypeptide chains formed where protein synthesis ceased. Question letter C. One rare dominant mutation of the pink one gene codes for a product that inhibits the normal protein kinase. Explain how this mutation causes EOPD in a heterozygot. In a heterozygous individual, only one allele is enough to produce the inhibitor. In presence of the inhibitor other proteins cannot be phosphorylated like protein kinase enzyme. So less aerobic respiration in neuron mitochondria. Which means. Less ATP needed for. Dopamine production or recycling. Sodium potassium pumps. Establishing resting potential. According to Neurone Death. Thank you for watching.