Interpretation of genetic diagrams

Genetic diagrams: These are a type of diagram used to predict an outcome of a particular cross or breeding experiment.

Punnett squares: These are used to predict the genotypes of offspring from a genetic cross.
Pedigree charts: These diagrams show a person’s ancestors and are used to analyse inheritance of traits through generations.

Understanding the types of alleles: An allele can be either dominant or recessive. Dominant alleles will always express their characteristic, even when only one copy is present, and are represented by a capital letter while recessive alleles are shown with a minor letter.
Recognising phenotype and genotype: The phenotype is the visible characteristics that result from the combination of those alleles, e.g., eye colour, height etc. The genotype is the exact alleles an individual has for a particular gene.
Deciphering homozygous and heterozygous genotypes: Homozygous genotypes contain two copies of the same allele (either two dominants or two recessives). Heterozygous genotypes contain one copy of each allele (one dominant and one recessive).
Probability of outcomes: The squares in a Punnett square represent the possible combinations of alleles from the parents. The ratio of dominant to recessive alleles in the squares gives an idea of the probability of having offspring with certain characteristics.
Understanding complete, incomplete, and codominance: In complete dominance, one allele completely masks the effects of another. In incomplete dominance, the phenotype is mixed. Codominance is when both alleles express their traits simultaneously without blending.

Identifying carriers: Carriers are individuals who have one copy of a recessive allele for a particular genetic trait or condition.
Understanding carrier status: In the context of genetic diagrams, carrier status can be identified for recessive disorders by recognising heterozygous genotypes.

Understanding sex-linked traits: Some traits are controlled by genes located on the sex chromosomes. Typically, males have one X chromosome (from their mother) and one Y chromosome (from their father), while females have two X chromosomes.
Identifying sex-linked inheritance patterns: Males are more likely to express a trait controlled by a gene located on the X chromosome because they have only one X chromosome (they are hemizygous). Females, having two X chromosomes, can be carriers without expressing the trait.

Understanding dihybrid crosses: These crosses involve two gene pairs instead of just one. The principles of interpreting dihybrid crosses are the same as for monohybrid crosses, but they may involve extra combinations and ratios.