Lecture 18: Genetic variation & disease 2 Flashcards
What types of genes/proteins contribute to polygenic diseases?
Types of Genes/Proteins:
Regulatory Genes:
Involved in controlling gene expression, such as transcription factors.
Structural Proteins:
Contribute to the physical structure of cells and tissues.
Enzymes:
Catalyze biochemical reactions; variations can disrupt normal metabolic pathways.
Receptor Proteins:
Mediate cell signaling and communication; abnormalities can affect cellular responses.
Transport Proteins:
Move substances across cell membranes; dysfunctions can lead to metabolic imbalances.
Do polygenic diseases follow a basic dominant vs. recessive inheritance pattern?
NO
They involve multiple genes, each contributing a small effect, leading to a range of outcomes rather than a simple dominant or recessive trait.
How can the environment affect a person’s phenotype?
Gene-Environment Interaction:
Environmental factors can influence the expression of genes, altering physical traits and health outcomes. eg…
Nutrition:
Affects height, weight, and overall health.
Sunlight:
Influences skin pigmentation and vitamin D production.
Lifestyle Choices:
Smoking or exercise can impact disease risk and longevity.
Stress and Exposure:
Can trigger or exacerbate conditions like depression or asthma, even with a genetic predisposition.
What is the difference between germline mutations and somatic mutations?
Germline mutations occur in sex cells (sperm/egg) and can be passed on to next generation
Somatic mutations occur in any body cells, can be due to the environment and are not passed on to the next generation
What is cancer?
Definition:
Cancer is a disease characterized by the uncontrolled growth and division of abnormal cells in the body.
Cellular Changes:
Mutations in genes regulating cell growth, division, and death lead to the formation of tumors.
Types:
Can occur in almost any tissue, leading to various types of cancers (e.g., breast, lung, skin).
Spread:
Cancer cells can invade nearby tissues and metastasize, spreading to other parts of the body.
Causes:
A combination of genetic factors and environmental influences (e.g., smoking, radiation, infections).
What two types of genes cause cancer when mutated?
Proto-oncogenes -> Oncogenes
* Mutations that increase the activity of these genes increase cancer risk.
* Gain of function mutations.
* Promote cell growth when it is not required.
* New alleles will have a dominant effect (only need one version of gene mutated to cause cancer).
Tumour Suppressor Genes
* Mutations that decrease/remove activity of these genes increase cancer risk.
* Loss of functions mutations.
* Promote cell growth instead of preventing it.
* New alleles will have a recessive effect (need both versions of a gene mutated to cause cancer).
What is a proto-oncogene?
genes that normally help cells grow and divide to make new cells, or to help cells stay alive
What is the role of Tumour suppressor genes?
Tumour Suppressor Genes
* Genes encoding proteins that prevent uncontrolled cell growth, e.g.
* Proteins that inhibit cell division.
* Proteins that prevent other mutations (i.e. DNA repair enzymes).
What is required for cancer to arise?
Need only one oncogene mutation (as it is dominant and Gain of function) AND! ‘both’ tumour suppressor genes (as it is recessive and loss of function) for cancer to arise (mutations to oncognes and not the other is not enough for cancer to arise and vice versa)…
If have both Causes uncontrolled cell growth, which increases mutation rate of cancer cells
What is ALDH2 Deficiency (“Asian Flush Syndrome”)?
Definition:
A genetic deficiency in the enzyme which is responsible for breaking down acetaldehyde at the end of the alcohol metabolism pathway.
Effect:
Causes a buildup of toxic acetaldehyde, leading to flushing, nausea, and other symptoms after alcohol consumption.
No Effect on Blood Ethanol:
There is no significant increase in blood ethanol levels, but acetaldehyde accumulates, causing adverse reactions.
Describe Human Purine Metabolism and Uric Acid:
Lost Enzyme:
Humans and great apes lack the uricase enzyme, which other mammals use to break down uric acid.
End Product:
Purine metabolism stops at uric acid in humans (middle of the pathway) while in other animals it continues to allantoin.
Higher Uric Acid Levels:
Humans naturally have higher uric acid levels than most animals, and some people have even higher levels due to genetics.
Hyperuricaemia:
When uric acid levels are too high, it can lead to conditions like gout. This is a (polygenic) complex condition influenced by multiple genes.
