Questions
5How do Mendel's experiments show that traits are inherited independently?
Mendel's dihybrid cross with pea plants (round-yellow x wrinkled-green seeds) showed that the inheritance of seed shape is independent of seed colour, producing a 9:3:3:1 ratio in F2.
How is the sex of the child determined in human beings?
Sex is determined by the sex chromosomes: females have XX, males have XY. The father's sperm (which can carry X or Y) determines the sex — an X-bearing sperm produces a girl (XX), a Y-bearing sperm produces a boy (XY).
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits — blood group A or O — is dominant? Why or why not?
Yes. Blood group O is recessive because the man with blood group A must be heterozygous (Iᴬi) — carrying one dominant A allele and one recessive O allele — for the daughter to have blood group O.
Explain how equal genetic contribution of male and female parents is ensured in the progeny.
Both parents contribute equal genetic material because gametes (sperm and egg) are produced through meiosis, which halves the chromosome number, and fertilisation restores the diploid set with exactly half from each parent.
What are homologous and analogous organs? Give examples.
Homologous organs have the same basic structure and origin but different functions (e.g., forelimbs of humans, birds, and whales). Analogous organs have different structures but similar functions (e.g., wings of birds and insects).