Dihybrid & Sex-linked inheritance

Question 1

Define dihybrid inheritance

Answer 1

• inheritance of 2 pairs of traits

Question 2

Principle of independent assortment

Answer 2

• each pair of alleles segregate independently during gamete formation
• each pair of contrasted characters may be combined with another pair

Question 3

Reason for independent assortment

Answer 3

• behaviour of chromosomes at metaphase 1
• homologous chromosomes line up is random
• orientation of 1 pair does not influence others
• when separate during anaphase 1, assorted independently
• 4 diff types of gametes formed from heterozygous for 2 traits

Question 4

Define sex-linked inheritance

Answer 4

• involves traits found on either 1 of sex chromosomes

Question 5

Why males have higher chance of having a sex-linked condition

Answer 5

• XY chromosome, only have 1 X chromosome
• males always inherit X-linked trait from mother, Y from father
• females have 2 X chromosomes, potential of having at least 1 normal allele that will express phenotype over recessive allele

Question 6

Trends of X-linked recessive conditions

Answer 6

• only females can be carriers (heterozygous)
• females cannot inherit X-linked recessive condition frm normal father
• X-linked condition common in males, conditions cannot be masked by second allele

Question 7

X-linked dominant traits

Answer 7

• common in females