6.1.3. Manipulating Genomes

DNA sequencing

Identifying the base sequence of a DNA fragment.

Sequencing methods change over time

Used to be a manual process, however now it has become automated. Entire genomes can now be read.

Benefits of genome-wide comparisons

Comparing between species allows us to determine evolutionary relationships. Comparing between individuals of the same species allows us to tailor medical treatment to the individual.

DNA sequencing in synthetic biology

Knowing the sequence of a gene allows us to predict the sequence of amino acids that will make up the polypeptide it produces. This in turn allows for development of synthetic biology.

DNA profiling

Identifying the unique areas of a person's DNA, in order to create a profile that is individual to them.

Uses of DNA profiling

Forensics= DNA obtained during crime investigations can be compared to that of victims or suspects. Medicine= to screen for a particular base sequence in order to identify heritable diseases.

Amplifying DNA fragments for sequencing

Using the polymerase chain reaction (PCR). Makes millions of copies of a fragment, which are then cut at different lengths in order to be sequenced.

Reaction mixture in the first stage of PCR

Contains the DNA fragment to be amplified, primers that are complementary to the start of the fragment, free nucleotides to match up to exposed bases, and DNA polymerase to create the new DNA.

Process of amplifying DNA fragments using PCR

1. Heated to break apart the DNA strands. 2. Cooled to allow primers to bind. 3. Heated again to activate DNA polymerase and allow free nucleotides to join. 4. New DNA acts as template for next cycle.

Gel electrophoresis in DNA profiling

Used to separate DNA fragments based on size, allowing for comparison and analysis.

Gel electrophoresis

A technique used to separate DNA fragments of varying lengths by applying an electric current, causing shorter fragments to travel further, creating a unique pattern of bands for each individual.

Genetic engineering

The process of inserting a DNA fragment from one organism into the DNA of another organism, sometimes across different species, using a vector and a host cell.

Isolating a DNA fragment

The process where restriction enzymes cut DNA at specific sequences, allowing for the extraction of a certain gene of interest.

Inserting a DNA fragment into a vector

Using a plasmid as the vector, which is cut with the same restriction enzymes as the DNA, so that the ends are complementary, and then DNA ligase joins the fragment and plasmid together.

Inserting a vector into a host cell

Mixing host cells (bacteria) with vectors in an ice-cold solution and then shocking them to increase the permeability of the cell membrane (electroporation), encouraging the cells to take up the vectors.

Ethical issues around genetic engineering

Concerns include the introduction of insect resistance to crops, the use of genetically engineered animals to produce pharmaceuticals (pharming), and the production of genetically engineered pathogens for research, alongside the challenge of GE seeds being hard to acquire for poorer farmers.

Gene therapy

The process of replacing a faulty allele, such as one that codes for a genetic disease, with a normal allele, which can be somatic or germ line.

Somatic gene therapy

A type of gene therapy where the allele is introduced to target cells only, providing a short-term solution that needs to be repeated.

Germ line gene therapy

A type of gene therapy where the allele is introduced to embryonic cells, making it present in all resultant cells, providing a permanent solution that will be passed to offspring.