2.3.7 Genes and Environment Flashcards
What is discontinuous variation?
- Falls into discrete categories
- Affected by only genes
- EG blood type
What is continuous variation?
- Large range of values
- Affected by genes and environment
- EG height
What is polygenetic inheritance?
When a number of genes are involved in the inheritance
What 3 things have led to a taller population?
- Taller men are shown to have more children
- Better nutrition
- The end of child labour has led to more energy for growth
What is the pigment that causes dark skin called, and where is it made?
Melanin, made in melanocytes
What stimulates melanocytes to make melanin?
Melanocyte-stimulating hormone (MSH)
What causes the skin to darken?
Melanosomes, containing melanin, collect around the nucleus of cells to protect it from UV. More UV light stimulates the amount of MSH
What is MAOA?
Monoamine oxidase A
- Enzymes that catalyse the breakdown of neurotransmitters involved in behavior
What causes a tumour?
When the rate of cell multiplication is faster than cell death
What 3 things causes damage to the DNA, causing cancers?
- UV light
- Carcinogens
- DNA is copied incorrectly in gamete fomation
What are oncogenes?
They stimulate the transition between stages of the cell cycle
What happens when there is a mutation in the oncogenes?
Mutations can cause the cell cycle to be continuously active, which causes excessive cell division, which will lead to a tumour
What are tumour suppressor genes?
They produce proteins that stop the cell cycle when there is a mutation in the DNA being synthesised
What happens when there is a mutation in the tumour suppressor gene?
Mutations mean the cell cycle won’t stop, meaning the faulty DNA will still be synthesised
What is an example of a tumour suppressor gene?
P53 protein
