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Effect of mutation and gene flow on the gene pool of population (Genetic…
Effect of mutation and gene flow on the gene pool of population
Genetic Technology
Sickle Cell
Blood test; checks for defective haemoglobin
Sample examined under microscope
Can be detected in unborn babies
Amniocentesis; fluid around baby is tested
Tests foetus for gene
Genetic councillors; help decide to continue
Vitro fertilisation
Pre-implantation genetic diagnosis
Enables carriers to test embryos
Chose to impart sickle free embryos
Haemoglobin electrophoresis test
Blood test; measures/identifies different haemoglobin
Indicate abnormal haemoglobin, caused by genetic disorders
Diagnose blood disorders
Sickle cell anaemia
Thalassemia
Polycythemia Vera
Screen genetic conditions
Family history of inherited diseases
Planning parents
Blood is drawn and analysed
Passes an electrical current through sample
Causes haemoglobin to separate into bands
Compared with healthy sample
Gel Elctrophoresis
Separating specific amino acid sequences
Observation of fragment bands on gel
Shows how genes are inherited
Allows offspring to predict genetics
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Genetic councillor
Help make genetic decisions
Advantages
New born screening
Disease discovered early
In-depth knowledge about risks
Allows treatments to be chosen/accessed
Information to help future decisions be made
Increase chance of future success rate
Opportunity to educate others
Allows adoption of tests
Positive/negative gene mutation
Couple's possibility of disorder
Determine the severity
If genes will be passed onto offspring
Allows for;
Optimised study conclusions
Inform genetic counselling
Policy decisions
Negatives
Financial
Emotional
Health
Gene flow
Sickle Cell
1 in 500 African American's have sickle cell
Found in Africa, Southern Europe, Southern India
Malaria areas
Increase protective traits from Malaria
Migrated to other areas
Unhelpful/dangerous for other areas
Not selective advantage for other areas
Map of geographical distribution
Africa; correlated with Malaria
Covergent evolution
Arose dependently throughout Africa/Southeast Asia
Gene migration
Introduction of genetic material
One population to another
Changes composition of gene pool
Introduction of new alleles
Increases variability within population
Migration of human populations
Voluntary/forced
Allele frequencies can be changed
Allows alleles to emerge/spread overtime
Creates a mutation
Genetic variation
Genetic drift
Not healthier/better individuals
Reduced by natural disaster
Bottleneck
Size of population is dramatically reduced
Random
Founder
Loss of genetic variation
New population is started
Random
Isolation
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Natural Selection
Sickle cell
Present in select areas due to Malaria
First example of human adaption
Since natural selection previously
Malaria; strong selective pressure
Evolve adaptive traits to survive
Based on survival of the fittest
Fitness independent
Gene pool
Genetics; sickle cell
1 in 4 - sickle cell homozygous (affected)
2 in 4 - heterozygous (carrier)
Resistance to Malaria
1 in 4 - two normal genes (normal)
Survival value of sickle cell gene
Map of sickle cell/Malaria area
Sum of populations genetic material
Includes all genes/combinations in population
Composition of gene pool can change over time
Evolution; natural selection, mutations, genetic drift
Altered for needs of populations environment
Eg sickle cell + Malaria
Ability to adapt and evolve
Size of gene pool influence
Large gene pool = more diversity + survival
Small gene pool = less diversity + survival
Sharing/spreading mutation
Mutations
Sickle cell
Base change of Adenine to Thymine
Haemoglobin gene
Amino Acid change; Valine to Glutamic
CTC change to CAC
Alterations to DNA sequence
Double helix unravels
RNA connects corresponding bases
Changes in nucleotide sequence
Cell division (Meiosis) allows continuation
Stomatic
All body cells
Can't be passed on
Eg Huntington disease
Germ-line
Gamete cells
Passed onto offspring
Eg Sickle Cell
Types
Missense
Altered codon changes Amino Acid
Incorrect Amino Acid inserted
Nonsense
Condon signals transcription to stop
Protein is truncated/non-fuctional
Silent
Base change doesn't affect Amino Acid
Eg ATT to ATC
Way they occur
Substitution
Insertion
Deletion
Translocation
Occur randomly
Internal/external factors increase likely hood
Point mutation
Single nucleotide variation
Small but significant effect on phenotype
Affect gene expression
Substitution
Disease/Disorder
Sickle Cell
Red blood cells become sickle shaped
Don't take enough oxygen throughout the body
Organ failure
Stick to one another
Become stiff
Pile up, cause blockages/damage organs/tissue
Genetic Disease
Parents must at least carry gene
Germ-line
Autosomal recessive
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Anthony Clifford Allison
Tested blood to find sickle cell blood cells
Used a chemical to remove oxygen
Gathered from all over Kenya
Discovered partial protection
Knew areas of Malaria in Africa
Wondered if sickle cell + Malaria was linked
Discovered link; Malaria + sickle cell
Areas of sickle cell = areas of Malaria
Map of sickle cell/Malaria areas
John Burden Sanders Haldane
Looked into red blood cell disorders
Malaria hypothesis confirmed by A. C. Allison
Missense mutation
Substitution
Trait = heterozygous
Disease = homozygous