Lecture 18 - Genetic Variation & Disease #2 Flashcards
What are monogenic traits?
An inherited trait/characteristic that is controlled by a single gene
What patterns do monogenic traits follow?
Usually simple dominant/recessive inheritance patterns
Can environment influence monogenic traits?
Yes (e.g how many freckles you have)
What are polygenic traits?
Inherited trait/characteristic that is controlled by multiple genes.
What patterns do polygenic traits follow?
They do not follow an obvious inheritance pattern
Can environment influence polygenic traits?
Yes
What are continuous traits?
Traits that will be measures as a range (e.g height)
What are dichotomous traits?
Traits that will be measured by either yes or no to having it. (e.g myopia)
After a certain point in ranging of phenotypes it is considered what?
That you have the disease/trait
What both contribute to polygenic traits?
Genes and Environment
What is an example of 100% genetics?
eye colour
What is an example of 100% environment?
Tattoo’s
What is an example of 50% genetics, 50% environment?
Heart disease
Majority of traits are?
Polygenic
How many different genes contribute to eye colour?
16 (two main ones)
Monogenic traits are usually?
Rare (6% of people with any monogenic disease)
Polygenic traits are usually?
Common
(people can be affected by more than one complex disease at once)
What are the two key concepts of polygenic traits?
- Any type of protein can have a genetic variant/change in function.
- Proteins anywhere in a pathway/process can be affected.
What is Phenylketonuria (PKU) an example of?
Loss of an enzyme at the START of a pathway
What does Phenylketonuria (PKU) lead to?
Increased Phenylalanine, decreased concentrations of all other products in pathway.
What is ALDH2 deficiency (asian flush syndrome) an example of?
Loss of an enzyme at the END of a pathway
What does ALDH2 deficiency (asian flush syndrome) lead to?
Increased Acetaldehyde (toxic), Decrease Acetate
What is Human purine metabolism as example of?
Loss of an enzyme (uricase) in the MIDDLE of a pathway
What does Human purine metabolism lead to?
Increased uric acid
What is Hyperuricaemia?
Polygenic condition: “too high” levels of uric acid
What do genetic studies look for?
Inheritance patterns
What do genetic studies of polygenic traits look for?
correlations and/or associations
Pros of genetic studies:
(polygenic)
Polygenic traits are usually common
- can find a lot of people with the condition you’re studying
- can design studies to account for environmental factors
Cons of genetic studies: (polygenic)
Not looking for one gene/variant
- multiple ways to get the same phenotype
Range of phenotypes available
- how you measure traits/conditions can change the result
What does GWAS stand for?
Genome Wide Association Studies
What do GWAS see?
If genetic variants are associated with a phenotype of interest
What do GWAS use?
Many variants spread throughout the genome (>1,000,000 SNPs)
What is cancer caused by?
Uncontrolled growth of cells, forming a tumour
What are the steps of cancer?
- Normal cells
- Increased division
- Uncontrolled growth
- Increasingly uncontrolled growth
- Spread
Genetic variant:
Specific difference in DNA sequence between individuals
Mutation:
Process by which new genetic variants arise
(permanent change in base sequence of DNA)
Somatic:
All the type of body cells
Germline:
Reproductive cells, can be passed to next generation.
What is cancer a result of?
Accumulation of mutations
What can cause mutations?
Errors in DNA replication, Exposure to carcinogenic chemicals or agents (damages DNA)
Risk of cancer increases with?
Age (cells undergo more cell divisions)
What are proto-oncogenes?
Genes that normally help cells grow and divide to make new cells, or to help cells stay alive
What are oncogenes?
Mutated proto-oncogenes, Genes encoding proteins that promote cell growth.
What are tumour suppressor genes?
Genes encoding proteins that prevent uncontrolled cell growth.
Oncogenes are?
Gain of function mutations, (Dominant.)
Tumour suppressor genes are?
Loss of function mutations,
(Recessive.)
What do Proto-Oncogenes and tumour suppressor genes work together to do?
Control normal cell growth.
Mutation to only one oncogene causes?
Accelerated cell growth, increased risk of cancer, tumour suppressor genes still working to prevent uncontrolled cells growth.
Mutation to both tumour suppressor genes causes?
No prevention to uncontrolled cell growth, increased risk of cancer, Proto-Oncogenes working normally (cells growing at ‘regular’ rate)
What does mutation to both Proto-Oncogenes and tumour suppressor genes cause?
Uncontrolled cell growth, increases mutation rate of cancer cells.
What can increase a persons chance of developing cancer?
Inherited genetic variants
