Question

I've seen many textbook images of alleles on homologous chromosomes with the gene loci identified but how could this be visualised on linear DNA sequences with the bases written out? Is it that you would have one DNA strand with its nucleotides and then another adjacent DNA strand with nucleotides at the same locus but different in sequence? Any visual representations would be helpful

Edit: This picture below shows how alleles can be seen on the chromosomes but it's not clear about where the change in sequence would be on the nucleotide bases. The typical diagrams show the homologous pairs but they don't usually show the change of base sequences on a small scale.

Answer 1

Alleles on homologous chromosomes are visualized as variations in nucleotide sequences at the same genetic loci, with recombination during meiosis shuffling these alleles to create genetic diversity.

Step-by-step explanation:

Visualization of alleles on homologous chromosomes at the DNA sequence level can be imagined as two adjacent, yet distinct, sequences of nucleotides. Despite both alleles being found at the same location - or locus - they may feature different nucleotide sequences that code for the same trait, resulting in genetic variation. For instance, at the gene locus determining blood type, you could have different sequences such as 'sequence A,' 'sequence B,' or 'sequence O,' with the combination of these gene sequences from each parent (AA, BB, OO, or a mix like AB) determining an individual's blood type.During meiosis, homologous chromosomes undergo the process of recombination, where segments of DNA are exchanged between chromosome pairs. This recombination does not alter the order of genes, but instead shuffles the alleles, effectively mixing maternal and paternal traits.

Therefore, on a linear representation of a gene sequence, alleles would be depicted as variations in the nucleotide sequences at the same genetic loci of homologous chromosomes.Homologous chromosomes possess the same genes in the same linear order but the alleles may differ. The alleles can be visualized on linear DNA sequences by representing one DNA strand with its nucleotides and then showing another adjacent DNA strand with nucleotides at the same locus but different in sequence. For example, in the case of blood type alleles, the DNA sequence could be represented as A-T-C-G for one allele and G-C-A-T for another allele.