S7L3.a
(Explain the role of genes and chromosomes in inheriting traits)

Genes and chromosomes are the ways you inherit traits. Chromosomes carry your genes. There are 46 chromosomes in your body, or 23 pairs of chromosomes. Each parent gives you 23 chromosomes, with the egg cell carrying 23 and the sperm cell carrying the other 23. There are two forms of genes, known as alleles. Alleles are basically the different phenotype you get. For example, the gene that determines hair color comes in different alleles, like a red hair color allele, a black hair allele, and so on. Alleles can be dominant or recessive. Dominant traits appear no matter what if they are present. Recessive traits only appear if only recessive alleles are present. For example, the allele for black hair is dominant over the allele for red hair. So, if the allele for black hair is present along with the allele for red hair, black hair will be the phenotype.