If a gene has 2 alleles and you compared the DNA sequence of

If a gene has 2 alleles, and you compared the DNA sequence of the 2 alleles, would they be the same? Mostly the same? Completely different? Explain your answer.

Solution

If a gene has two alleles, these alleles will be different at the nucleotide level. This difference can be in nucleotide sequence. For example \'Aa\' means heterozygous alleles. \'A\' and \'a\' correspond to the same gene but their nucleotide content differ with each other by one or many sequence variants (SNPs, Indels). For example, \'A\' can be 1000 bp gene and \'a\' can be 1200 bp gene with extra 200 bp of some kind of repeat. These differences can occur in both coding and non-coding regions. For example, promoter etc. Also, not all the times different alleles will result into difference at the phenotypic level.