16 Flashcards
L aw of segregation
When gametes form, alleles are separated so that each gamete carries only one allele for each gene
Law of independent assortment
The segregation of alleles for one gene occurs independently to that of any other gene
Law of dominance
Some alleles are dominant while others are recessive; an organism with at least one dominant allele will display the effect of the dominant allele.
Small differences between genes
Make u unique
Differences in gene is called
Allele
What is an allele
An allele is an alternative form of a gene (one member of a pair) that is located at the same place on a chromosome.
Recombination:
More chances allleles are going to assort independently ??
- meiotic recombination ‘shuffling the pages’ during sperm formation
- swapping info of homologous chromosomes
- results in a mix of DNA
Exception to the law if independent assortment
- when two genes are close together on a chromosome - genetic linkage
Recessive allele is a version of the gene that does not encode …
A functional protein
Heterozygous recessive mutation (Aa)
- one parents stopped working
- the other can mask it
- functional copy covers
- will have 50% less protein
Homozygous recessive mutation (aa)
- pathway can’t work
- functional protein isnt there so you pathway stops and you get an accumulation of the precursors
- down stream proteins are made but because there is noting to work on they don’t do anything inside the cell
E Palme of the recessive non functional protein in the flowers
- if you have one functional will still produce a pink flower
We inherit a ____ combination of alleles form out parents
Unique
The DNA between two people is about ___% equal
99.4
How many places does DNA vary in humans
20 million (0.6% of the total 3.2 billion)
_% of differences (________ differences) might affect how our genes funciuton
5% of these differences (1 million differences) might effect how our genes function
Phenaylalanine breakdown
- accumulation
- two non function genes from parents
Phenylalanine breakdown pathway
- people with non functional enzyme in each step exist- all have different outcomes
What is occurs when protein 5 in not produced for the breakdown of phenylanine ?
Alkaptonuria
What happens when a defect in the enzyme that breaks phelynine down into tyrosine stops working?
Defect in this enzyme leads to accumulation of phenylamine to a condition called phenylketonuria
1 in 10,000 people (5 babies a year)
What is the newborn metabolic screening programme?
- screeens newborn babies for 28 metabolic disorders
How many babies a year have a metabolic disorder or condition
45
What can phenylketonuria - inablitlaty to break down phenylalanine - (PKU) lead to?
- Interlectual disablilty
- seizes
- behavioural problems
- mental disorders
What enzyme breaks down phenylalanine into tyrosine
Phenylalanine hydroxylase
In phenealinine breakdown, where is it worst to stop in the pathway
- can’t breakdown in first step = worst consequences
- can’t break down in last step = black urine = not very bad
What do othe enzyme do if phenalynne can’t be converted to tryrosine
converted into other compounds
- build up of other compounds
- build up of phenylanene and other enzymes
Why is it bad if tyrosine can’t be produced form phenalyalaine
- tyrosine is precursors for other elements such as dopamine, noradrenaline and neruotansitmmers there for a decrease in those and that leads to other consequences
Consequence in production / not production from phenlanine not being broken down
Things at top of diagram are toxic
Phenotype can be affected by…
Your environment
In PKU individuals what can you do to prevent interlectal disability and associated problems
- a low phenylalanine diet
- avoid all high protein foods
- limited natural protien (less then 10g)
Can get around our genetics by..
… changing our environment
Some people have a non-functional enzyme thus they can’t breakdown phenylalanine but they have a normal IQ..how?
- Phenylanina is transported across the blood-brain barrier
- genetic variation means the efficient of this transporter differs between individuals
- Individuals with less efficient transporters have lower levels of Phe in the brain and less damage (higher IQ)
(Lower expression of transporter rather then it not working)
Environment determines
How some genetic differences affect us
Most variation in out gene isnt in the coding region.. where is it?
- in the regions that regulate the sequence, regions where transcription factors bind
Reduction in the expression of the transporter that takes pheneelanine into the brain is a result of..
- reduced expression is not from a knock out of a gene but instead it is influenced by variation in regularity seuqaences and transcription factors
