Genes and inheritance exam revision sheet . Be able to describe and identify the structure of a chromosome, from base nucleotides to the entire chromosome. nucleus chromosome cell telomere centromere chromatids- nucleosomes base pairs histones DNA gene . Be able to draw a punnet square cross to determine the pattern of inheritance of a recessive sex-linked gene (i.e., haemophilia, colour-blindness) and know the difference between genotype and phenotype. . Be able to draw a dihybrid cross involving two traits. Be able to describe how modern medicine has affected the prevalence of recessive genetic conditions such as haemophilia. Explain the process of natural selection as demonstrated by antibiotic resistance. HID0000