Key words

• Gamete- sex cells
• Zygote- fertilised egg cell
• chromosome- DNA molecule tightly coiled and packaged up with proteins
• Gene- short section of DNA
• Allele- different forms of the same gene
• homozygous- both alleles are different
• heterozygous- the alleles are different
• dominant- the allele will always be expressed
• recessive- the allele will only be expressed if both alleles are recessive
• genotype- the alleles in an organism
• phenotype- what the organism looks like
• diploid- a cell that contains two sets of chromosomes ( two sets of 23 in humans - 46 in total)
• Haploid- a cell that contains one set of chromosomes (23 in humans)
• Genome- the DNA of an organism