Genetic Diagrams

• explain how alleles are passed on to an offspring + what traits will be expressed by offspring (genetic cross)

(Using plant experiment, Since $F_1$ offspring (heterozygous) were tall, it means the dominant phenotype is tall)

Let T be dominant allele for tall plants Let t be recessive allele for dwarf plants

Genetic Diagram	Explanation
	Top 2 big square boxes: - organism that is pure bred for a trait is homozygous for that trait. - Mendel’s tall parent plant is homozygous dominant (TT) and dwarf plant is homozygous recessive (tt) Small t circle box: - reduction cell division (meiosis) separates a pair of alleles by splitting up each pair of homologous chromosomes so that each gamete only receives 1 copy of each allele (either T or t) Last square small box: - $F_1$ generation offspring all have the (Tt) genotype
	Top 2 big square boxes + second small circle boxes: - $F_1$ generation offspring also produce gametes by meiosis. Each gamete contains either T or t allele. Random fertilisation gives rise to the $F_2$ generation offspring. Last square small box: - $F_1$ generation are self fertilised. The ratio of dominant to recessive phenotypes in $F_2$ generation is close to expected ratio 3:1. This is especially so when large number of plants is used in breeding experiment.
Another way of presenting results is to use a punnett Square

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