Lecture 18 - Genetic Variation & Disease #2 Flashcards
Define polygenic (complex) disease
A polygenic disease is condition influenced by multiple genetic variants, often in combination with environmental factors. These disease don’t follow simple inheritance patterns and involve complex interactions between genes and environment
e.g. cancer, heart disease
How can genetic variants lead to polygenic disease?
Genetic variants in multiple genes can collectively increase susceptibility to polygenic diseases. These variants may affect proteins at different points in biological pathways, disrupting processes like metabolism and etc
How do genes and the environment affect the risk of developing disease?
Both genetic factors and environmental influences can contribute to disease risk. Genes may predispose individuals to certain conditions, while lifestyle factors (diet, exposure to toxin and etc) interact with these genetic predispositions to increase or decrease disease likelihood
How do somatic mutations leads to cancer?
Somatic mutations, which occur in non-reproductive cells, can lead to cancer by disrupting normal cell growth and division. Mutations in oncogenes (which promote cell growth) and tumour suppressor genes (which inhibits goth) can lead to uncontrolled cell division, resulting tumour formation
Difference between monogenic and polygenic trait
Monogenic traits are controlled by a single gene and follow simple inheritance patterns. Polygenic traits, involve multiple genes and often do not follow clear inheritance patterns (e.g. height, heart disease)
What is continuous polygenic trait?
A continuous polygenic trait is one that is measured along a scale, with values distributed across a population, such as height or blood pressure. The trait doesn’t have clear cut categories
What is dichotomous polygenic trait?
A dichotomous polygenic trait is a trait where the outcome is either yes or no. like either having a disease or no
Two key concepts of Polygenic traits
- Any type of protein can have a genetic variant / change in function. e.g. PKU (loss of enzyme at the start of a pathway)
- Proteins anywhere in a pathway/process can be affected
e..g. ALDH2 deficiency (Asian flush syndrome - loss of enzyme at the end of the pathway)
- also, Human Purine metabolism - loss of an enzyme in the middle of a pathway
Genetic studies of Polygenetic Traits
In polygenic studies they look for correlation or associations.
Pros; Polygenics traits are usually common
Cons; Not looking for one gene/variant (multiple ways to get the same phenotype), range of phenotypes possible
What is GWAS
Genome wide association studies - if any genetic variants are associated with a phenotype of interest
What is cancer
It ia special kind of complex trait. Cancer is characterised by uncontrolled cell growth and division due to mutations in genes that regulate cell cycle, growth and apoptosis. These mutations lead to the formation of malignant tumours
Genetic Variant VS Mutation in Cancer
- Genetic variation - a specific difference in DNA sequence between individuals.
- Mutations - the process by which new genetic variants arise (somatic mutation - type of de novo variant)
Somatic VS Germline cells
- Somatic - all different types of body cells
- Germline - reproductive cells involved in passing on genetic information to the next generation
Two Cancer causing genes?
- Proto - oncogenes -> Oncogenes
- Tumour suppressor Genes
What are oncogenes?
Oncogenes are mutated forms of normal genes called proton-oncgenes that, when activated, promoted excessive cell proliferation and contribute to cancer development. Mutations that increase the activity of these genes increase the cancer risk.
