Control of Gene Expression

Stem cells are unspecialised cells that indefinitely divide by mitosis and can differentiate into many cell types.

Totipotent, pluripotent and multipotent stem cells.

Transcription factors

The heritable modification of DNA and histones to control gene expression. There is no change to the base sequence of DNA.

The DNA-histone complex.

mRNA splicing (in eukaryotic cells).

The addition of a chemical group, like a phosphate group.

Protein kinases.

Whole-genome shotgun (WGS) sequencing.

Addition of a CH3 group to cytosine bases prevents transcription factors from binding. Therefore gene transcription is inhibited.

To determine whether two variables correlate

• They have a larger and darker nucleus compared to other cells. 

• They may have more than one nucleus.

• They have an irregular shape.

• They don't produce all proteins needed to function correctly

• They have different antigens on their surface compared to normal cells.

• They don't respond to the body's regulating processes.

• They divide by mitosis more frequently than normal cells.

When a piece of tumour cell breaks off and spreads to another part of the body.

Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.

• Diet - There is strong evidence that suggests that a good diet rich in fruit, veg and fibre reduces the risk of getting cancer.
• Obesity - Linked to diet, being overweight also increases the risk of cancer. 
• Exercise - People who are more physically active are at a lower risk than those who do little or no exercise.
• Sunlight - The more ultraviolet light someone is exposed to, the more at risk they are.
• Smoking - Both smokers and those who breathe in tobacco passively are at increased risk of cancer.

A correlation is the statistical measure of the relationship between two variables. It is best demonstrated in variables with a linear relationship between each other.

Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.

A mass of cells that doesn’t invade neighbouring tissue or metastasise

• Malignant cells develop, divide and invade normal tissues.

• Some of the cells detach and spread through the blood and lymph vessels.

• The malignant cells can squeeze through the capillary wall.

• They then divide, producing a secondary tumour in a different location to the original tumour.

Cohort studies are very time consuming and expensive in comparison to case studies. This is because it takes people a long time to develop diseases.

Tumours that spread through the body and cause cancer.

Uncontrolled cell division

1. Picked up by various regulatory functions in the cell cycle
2. Early cell death (apoptosis)
3. Being destroyed by the bodies immune system

Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.

Both benign and malignant tumours can grow large however benign tumours grow slowly, and have more localised effects whereas malignant tumours grow rapidly and have systemic effects. Benign tumours can usually be removed by surgery alone whereas malignant tumours often require radiotherapy or chemotherapy as well. They are also more likely to be life-threatening than benign tumours and have a high rate of recurrence. Benign tumours are often surrounded by a capsule and don't metastasise whereas malignant tumours don't have a capsule and do metastasise.

To determine whether too variables correlate. 

A group of people who have the disease to be studied are compared with a group of individuals who do not have the disease.

To stop an illness before it starts and takes a holistic approach by focusing on the many factors that play a role in health. This includes maintaining a healthy lifestyle.

The complete set of genetic material in an organism.

The complete set of proteins an organism/cell can make at given conditions.

HPG is the human genome project and involved sequencing the whole human genome.

Identifying the DNA base sequence of an organism genome. It allows determining the amino acid sequence of the polypeptides encoded by that DNA.

Automated DNA sequencing methods require large quantities of DNA. PCR allows amplifying the DNA samples taken from the organism.

Dideoxyribonucleotide is a special type of nucleotide that differs from normal deoxyribonucleotides in that it contains an additional hydrogen instead of a hydroxyl group on carbon number.

Dideoxyribonucleotide acts as an inhibitor of chain elongation and once incorporated, terminates further nucleotide addition to the DNA strands.

The 4 different dideoxyribonucleotides (A, G, T, and C) are tagged with different fluorescent labels giving each a distinct colour. Since dideoxyribonucleotides will be incorporated into the growing DNA strands randomly, the result would be new DNA fragments of various lengths and sizes that have the same point of origin (all starting from the primer) but end with a fluorescently labelled dideoxyribonucleotides. The colour of the terminal dideoxyribonucleotide help identifies the nature of the terminal DNA base.

The obtained fragments from the previous step on then run on gel electrophoresis which separates the strands according to their length. Due to the random nature of the last step, there will be strands present that are 1 nucleotide in size, 2 nucleotides in size, 3 nucleotides in size …… n nucleotide in size and they all end with a fluorescently labelled DdNTP. Therefore, the pattern of colour created by the fluorescent tags would tell us the DNA sequence.

The proteome of simple organisms gives us an insight into the biochemistry of the reactions that occur within them. Some of these organisms are used for manufacturing biofuels. Furthermore, organisms with the ability to withstand extreme and toxic conditions can be used for removing pollutants from the environment.

Prokaryotic DNA is much smaller than eukaryotic DNA. Prokaryotic DNA is not associated with histone proteins. There are no non-coding DNA sequences within the genome of prokaryotes. Eukaryotic DNA however contains vast portions of non-coding sequences.

In 2003

The Human Genome Project (HGP) was an international scientific research project aimed at defining the base pairs sequences within the human DNA, as well as identifying and mapping all of the human genome's genes with respect to their position as well as their function.

They could cause disease, either by inhibiting or activating a gene.

Different proteins are made and these proteins modify the cell.

RNA molecules inhibit gene expression, by destroying mRNA so that it cannot be translated.

Not all the genes in a cell are expressed.

DNA is created by combining two or more DNA molecules from different origins.