Higher Biology - Unit Three - Control of Growth and Development
What is a gene?
A gene is a segment of DNA that codes for a protein. The structure and function of a cell is controlled by its genes
The ability to switch genes on or off prevents resources being wasted. Give one of these resources
What is lactose composed of?
Glucose and galactose
Lactose is digested to glucose and galactose by the enzyme...?
E-coli only produces β-galactosidase when lactose is present / absent ?
Switching on a gene only when the enzyme is needed is called...?
What does the regulator gene do?
It codes for the repressor molecule
What does the operator gene do?
It controls the structural gene
What does the structural gene do?
It contains DNA which codes for the enzyme
What does a repressor molecule do?
It stops the operator gene switching the structural gene on
What does the inducer do?
The inducer joins with the repressor and stops it inactivating the operator gene
Draw the diagram to show the Jacob - Monod hypothesis of gene action in bacteria
See jotter or P142 in textbook
What is metabolism?
The name given to all the chemical reactions which occur in the body.
PKU is an example of inborn...?
error of metabolism
What is the normal metabolic pathway that phenylalanine undergoes?
A PKU sufferer has a mutation of gene...?
Using a diagram, show what happens as a result of this mutation
Enzyme 1 is not produced
Phenylalanine is not converted to tyrosine
Phenylalanine accumulates in the blood
Some phenylalanine passes through a different metabolic pathway which produces toxins
Excess phenylalanine and toxins disrupt normal development of organs, including brain
Limits mental development if untreated
How are the worst effects of PKU being reduced?
By screening newborn babies and restricting any sufferers diet
In the same metabolic pathway what enzyme are albinos unable to make and therefore what subtance are they unable to make?
Enzyme 3 - melanin
What physical differences do albinos have?
They have light skin, pure white hair, pale blue or pink irises
What must albinos avoid exposure to?
What are expressed genes?
Genes that are switched on in all cells - needed for essential biochemical processes eg enzymes involved in respiration
What are cell specific genes?
Genes that are only switched on in particular types of cells where they code for proteins characteristic of that cell type eg haemoglobin in red blood cells. Other genes not needed by the cell are permanently switched off.
The more specialised the cell the _____ genes switched on