Use appropriate genetic cross to explain: XX-XY XX-XO methods of sex determination. (12 mrks)

Here are the solutions to question 5: 5. (a) Non-disjunction occurred in sex chromosomes of man. Show the genotype and phenotype of their offspring with Klinefelter's Syndrome. Non-disjunction is the failure of homologous chromosomes or sister chromatids to separate properly during meiosis. If non-disjunction of the X chromosomes occurs in the mother during oogenesis, an egg with two X chromosomes (XX) can be formed. If this XX egg is then fertilized by a normal Y sperm from the father, the resulting offspring will have Klinefelter's Syndrome. Step 1: Consider the gametes from parents where non-disjunction has occurred. Mother (due to non-disjunction): Produces an XX egg. Father (normal): Produces X or Y sperm. Step 2: Fertilization leading to Klinefelter's Syndrome. If the XX egg from the mother is fertilized by a normal Y sperm from the father: Offspring genotype: XXY Offspring phenotype: Male with Klinefelter's Syndrome (characterized by features such as reduced fertility, taller stature, and some feminized physical traits). 5. (b) A carrier of haemophilia marries a normal male. Show the chances of their offspring getting haemophiliac. Haemophilia is an X-linked recessive disorder. Let X^H be the normal allele and X^h be the haemophilia allele. Carrier female genotype: X^H X^h Normal male genotype: X^H Y Step 1: Determine the gametes produced by each parent. Female (X^H X^h): Gametes are X^H and X^h. Male (X^H Y): Gametes are X^H and Y. Step 2: Construct a Punnett square. |c|c|c| & X^H & Y \\ X^H & X^H X^H & X^H Y \\ X^h & X^H X^h & X^h Y \\ Step 3: Determine the genotypes and phenotypes of the offspring. X^H X^H: Normal female X^H Y: Normal male X^H X^h: Carrier female X^h Y: Haemophiliac male Step 4: Calculate the chance of their offspring getting haemophiliac. Only the X^h Y genotype results in a haemophiliac child. The chance of having a haemophiliac child is (1)/(4). The chance of their offspring getting haemophiliac is 25\%. 5. (c) State two factors that are revealed in a blood group test. • The specific ABO blood type (e.g., A, B, AB, or O). • The Rh factor status (positive or negative). That's 2 down. 3 left today — send the next one.