Скачать или смотреть Genetic Diversity Calculations | A-Level Biology Exam Revision | AQA, OCR, Edexcel

Our A-Level Biology Experts are here to help you ace A-Level Biology! This week we are revising Genetic Diversity. A-Level Biology can be tough but fortunately, we’ve made this tutorial to help you score the A you need for questions on everything to do with calculating genetic diversity. This Study Mind Tutorial covers various specification points across AQA, OCR, Edexcel A & B, and CIE.

📖 NOTES FOR STUDENTS:

Comparative Genomics

So far we have looked at the grouping of organisms into *taxonomical groups* and the study of **evolutionary relationships**. Both of these involve looking at the diversity between and within species. We touched earlier on how we can use gene sequencing to understand evolutionary relationships (comparative genomics). Comparative genomics enables us to understand the diversity of genes present within a population or community, and how these genes change over time to understand evolution and evolutionary relationships.

1. Observable and Measurable Characteristics

We can deduce similarities between organisms by looking at observable characteristics such as facial features, body shape, and bone structure.

We can also look at *measurable* characteristics such as weight, height, and blood pressure.

2. DNA Sequences

New techniques enable rapid sequencing of whole genomes. Using novel biotechnological breakthroughs such as ‘Next Generation Sequencing, we have been able to *rapidly* sequence the genomes of many organisms - i.e. determine the whole base sequence.
We can compare the DNA of different organisms. By comparing the DNA sequences between species, we can determine how related organisms are. The degree of similarity between the sequences tells us (to an extent) the degree of similarity between the species, and even organisms within the same species.
We compare by aligning DNA. By aligning the DNA of one species to another, we can determine how similar the base DNA sequence is.

3. mRNA Sequences

Exon sequences are similar between organisms. As we just discussed, the underlying base DNA sequences of different genes may be very different, making DNA comparison slightly ineffective. However, most genes have similar exon sequences, so we can compare them instead.
We can analyze axons on mRNA. Because mRNA only has exons, it is useful to compare **alignments of mRNA to see the similarity between organisms.
BUT, there are still limitations in mRNA comparison. Similar to DNA, mRNA sequences between different organisms for the same gene can be quite different due to the degenerate nature of the genetic code.

4. Amino Acid Sequences

There are limitations to DNA comparison. When comparing evolutionary relationships, we compare genes (DNA). However, the sequences of the genes, as we have learned, can be very different.
Amino acid sequences vary less between organisms. Despite the degenerate nature of the genetic code, the amino acid sequences of most proteins across various organisms are very similar.
We can compare the function of proteins in different organisms. When making evolutionary relationships, we want to determine if the function of a protein in one species is conserved in another species. And for the function to be conserved, so must the structure.

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