Higher Biology | Key Area 1.8: Genomic Sequencing

Genomic sequencing

The process by which the sequence of nucleotide bases is determined for individual genes and entire genomes.

What can computer programs be used for in genomic sequencing?

Can be used to identify base sequences by looking for sequences similar to known genes.

What is required to compare genomes of different species?

Computer and statistical analysis (bioinformatics) and sequence data is required to compare genomes.

What does the comparison of genomes reveal?

The comparison of genomes reveal that many genes (much of the genome) are highly conserved across different organisms, ie. species share many of the same genes.

Many genomes have been sequenced, particularly of what?

- Disease-causing organisms, for help with accurate diagnoses.

- Pest species, to identify risks which can lead to specific methods of control being developed over general pesticides, ensuring efficiency.

- Species which are important model organisms for research (eg. fruit flies, zebra fish) which can be used in place of mammals in medical research, reducing cost and ethical concerns.

What can the analysis and information of genomic sequencing be used for?

- Analysis and information of genomic sequencing can be compared with the genes or genomes of other individuals or different species to look for similarities and differences.

- Comparison of genomes from different species as research

- Personal genomics and health

- Phylogenetics

Phylogenetics

The use of sequence data to study evolutionary history and relatedness among groups of organisms.

What can phylogenetics be used to work out?

- Lineage, ie. the exact sequence in which species can be traced back through ancestor populations.

- Sequence divergence (mutations leading to changes in DNA sequence data), used to estimate how and when lineages diverged from common ancestry.

How is the sequence of events in evolution and evolutionary relatedness determined?

The use of sequence data and fossil evidence can determine the main sequence of events in evolution and evolutionary relatedness amongst groups of organisms.

Molecular clock

- DNA sequences can be used as molecular clocks to show when species diverged during evolution (ie. when speciation occurred and one lineage separated into two lines) by measuring the number of mutations that accumulate in a DNA sequence over time using sequence data.

- Assumes a constant mutation rate and is based on the principle that random mutations occur over time.

What does a molecular clock show?

Shows differences in DNA or amino acid sequences. Therefore, differences in sequence DNA between species indicate the time of divergence from a common ancestor, as the number of nucleotide substitutions is proportional to the length of time elapsed since divergence.

When DNA sequences are compared between species, how can their relatedness be determined?

The more similar the sequences (ie. species with more similarity in their genomes), the more closely related the species are, and the more recently they shared a common ancestor.

What is the main sequence of events in the evolution of life?

Cell → last universal ancestor → prokaryote → photosynthetic organism → eukaryote → multicellularity → vertebrate → land plant

3 domains of life

The comparison of DNA sequences has proved evidence on the three domains of life, a classification system all cellular life falls into.

- Archaea

- Bacteria

- Eukaryota

Pharmocogenetics

The use of genome information in the choice of drugs, where an individual’s genome can be analysed to predict the likelihood of developing certain diseases.

Personalised medicine

Where an individual’s personal genome sequence can be used to select the most effective drugs and dosage to treat their disease.