BiologyCode 5090
Inheritance
What this topic asks you to be able to do
- Describe inheritance as genetic information being passed on from each generation to the one after it
- Define an allele as one of the alternative forms that a gene can take
- Understand what dominant, recessive, phenotype, genotype, homozygous and heterozygous mean, and use these terms
- Use genetic diagrams, including Punnett squares, to predict the offspring a monohybrid cross will give and calculate the phenotypic ratio among them, limited to ratios of 1:1 and 3:1
- Account for why observed ratios frequently diverge from expected ratios, particularly when few offspring are produced
- State that a pair of homozygous organisms sharing the same genotype, when mated together, will be pure-breeding
- Account for codominance with reference to how the ABO blood groups are inherited (phenotypes A, B, AB, O, gene alleles IA, IB and Io)
- Describe how sex is determined in humans by the XX and XY chromosomes
- Describe a gene mutation as a change to the base sequence in DNA that happens at random; sickle cell anaemia is one example
- Describe a chromosome mutation as any change to the chromosome number or to the structure of a chromosome; Down's syndrome, with 47 chromosomes instead of 46, is one example
- State that genetic variation within populations arises from mutation, meiosis, random mating and random fertilisation
- Understand that ionising radiation and certain chemicals raise the rate at which mutations take place