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VICBiologyQuick questions
Unit 2: How does inheritance impact on diversity?
Quick questions on Models of inheritance (dominant, codominant, incomplete dominance, multiple alleles, sex-linked): VCE Biology Unit 2
12short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is autosomal dominant and recessive (classical Mendelian)?Show answer
Dominant allele: produces its phenotype in the heterozygote. Conventionally written with a capital letter (P).
What is codominance?Show answer
In a heterozygote, both alleles are fully expressed. Neither allele masks the other; both phenotypes show side by side.
What is incomplete dominance?Show answer
In a heterozygote, neither allele dominates. The phenotype is intermediate between the two homozygotes, as if the traits had blended.
What is multiple alleles?Show answer
A gene can have more than two alleles in a population, although any one diploid individual still carries only two.
What is sex-linked inheritance?Show answer
A sex-linked gene is one whose locus is on a sex chromosome.
What is sex-linked Punnett square example?Show answer
A carrier mother (X-H X-h) and an unaffected father (X-H Y) for haemophilia:
What is calling everything dominant or recessive?Show answer
Codominance and incomplete dominance do not have a "dominant" allele in the classical sense.
What is confusing codominance with incomplete dominance?Show answer
Codominance: both traits visible together (blood AB). Incomplete dominance: intermediate blend (pink snapdragon).
What is forgetting sex notation in X-linked crosses?Show answer
Always include the X superscript, otherwise you lose track of which sex each genotype refers to.
What is saying "the X-linked gene is on the Y too"?Show answer
Most X-linked genes have no Y counterpart. That is why males are hemizygous and recessive disorders show up so much more often in males.
What is calling colour-blind women "carriers"?Show answer
A homozygous X-c X-c female is affected, not a carrier. Carriers are heterozygous.
What is forgetting multiple alleles exist at the population level?Show answer
Any one person has two alleles per locus, but the population may have many alleles total.