Mutations and Gene Pools Flashcards
What is a species
A group of individuals that share many characteristics and are able to interbreed under natural conditions to produce fertile offspring
What is a population
A group of organisms of he same species living together in a particular place at a particular time
What is an allele
Alternative forms of a gene
What is a gene pool
The sum of all the alleles in a given population
What is allele frequency
How often each allele of a gene occurs in the gene pool for that population which can change due to mutations or changes in the environments, this will differ between populations
What is genetic drift
A type of activity which causes allele frequencies within Gene pools to change
What is the bottleneck effect
Division of genetic drift
Occurence of characteristics in a populations as a result of chance rather than natural selection which causes allele frequencies to change as there are different genes being passed on
This can cause alleles to be fixed or lost
What can cause the bottleneck effect
Natural Disasters, Can limit populations and eliminate people from the community which causes allele frequencies to change
What is the founder effect
Division of genetic drift
Occurs when a small group purposely moves away from its homeland and establishes a new community, which later expands
The migrants group is usually not genetically representative of the original community, so the next community generally shows features that are not typical of original homeland population
What is an example of the founders effect?
The Dunkers Populations
What is a mutation
Permanent change in a gene or chromosome which occurs by chance
What is a mutant
An organisms resulting from a mutation
What is a mutagen
Increases the rate at which mutations occur
What is a somatic mutation
Occurs in body cells in which only the individual is affected and can only be passed through daughter cells in mitosis
What is a Germline Mutation
Occurs in reproductive cells which results in gametes having altered DNA but the individual who had the mutation is no affected
What is a frameshift mutation
When a base has been added or deleted
What is a gene mutation
Changes in DNA of a single gene
What are the 3 types of gene mutations
Insertion - Implementing a base
Deletion - removing a base
Substitution - Replacing a base
What are the 4 types of effects from mutations
Missense - Changes amino acid and protein
Nonsense - codes to STOP due to changes in base sequence
Silent - Not change in amino acid
Neutral - Change in amino acid but no change in protein produced
Examples of Gene Mutations
Albinism
Cystic Fibrosis
What are chromosomal mutations
Involved mutation of some or all parts of a chromosome
What are the 5 types of Chromosomal mutations
Deletion - the loss of parts of a chromosome
Duplication - Where a section of a chromosome occurs twice
Inversion - when a breakage in chromosome occurs but rejoin wrong way around
Translocation - part of chromosome breaks off and rejoins a different chromosome
Nondisjunction - When a chromosome pair does not seperate so one daughter cell has an extra chromosome and one daughter cell has less
What are examples of chromosomal mutation
Turners syndrome
Down Syndrome
What is migration
Type of evolutionary mechanism also known as gene flow
When immigrants travel to another country. As they travel they can bring alleles that are not already in the population therefore, overtime, the allele frequencies will change
Example of migration changing allele frequencies
Chinese Rh blood group factor
What can cause restrictions to gene flow
- Barriers that inhibit the amount to interbreeding
- Environmental differences
- Which characteristics are favourable for survival
- Members of different religious groups or different language are tended not to interbreed
- Economic status
What is mutations (evolutionary)
Mutation is a permanent shift in a gene or chromosome which causes a different variation of the trait
Mutations introduce new and different alleles into a gene pool so, can change allele frequency
What is natural selection
Process by which species become adapted to its environment as those with favourable characteristics have a survival advantage
What is speciation
The process of forming two seperate species
Steps of speciation
- Variation
- Isolation
- Selection
- Speciation
What is variation step?
A range of variations exist within the population which shares a common gene pool
What is the isolation step?
A barrier has formed, dividing the population into two. Causing no interbreeding to occur between the two populations so each population has their own gene pool
What is the selection step?
Different selection pressures act on each of the two populations over generations. This brings about a change in the gene frequencies of each gene pool. Such changes lead to the evolution of seperate subspecies
What is the speciation step?
Over a long period of time, the changes in the gene frequencies may be great enough to prevent the production of fertile offspring between the two populations from ever occurring again, this causes two species to exist
What is natural selection
Process by which a species becomes adapted to its environment where those individuals with favourable characteristics have a survival advantage
What is a selective agent
Any factor which causes the death of an organisms with certain characteristics but has no effect on individuals without those characteristics
What is survival of the fittest
Where organisms with favourable traits survive, but organisms with unfavourable traits die before they have time to reproduce
What is a variation
The differences which exist between individuals or populations of a species
What is the struggle for existence
The number of organisms is greater than the resource amount in the environment can support, therefore there is competition between the organisms
What is the Natural Selection Theory
- A mutation occurs in a population
- Lead to variation within species
- More offspring produced than can survive
- Selection pressures for the populations causing a competition for survival
- Individuals with favourable characteristics have a survival advantage ‘survival of the fittest’
- They have better reproductive success
- Favourable characteristics passed on
- The alleles frequency that produce favourable characteristics, increases
Body Shape Natural Selection
- Human genes pool has a wide range of body types
- Short bodies and long-limbed physiques gives them large S.A to V ratio, causing heat loss
- The long-bodies and short limbed physiques allow smaller S.A to V ratio and ability to lose less heat
- Overtime, as the alleles in the gene pool decreased so much that they were completely lost, evolution has taken place
Sickle-cell Anemia Natural Selection
- Those with 2 sickle cells are susceptible to sickle cell disease so they die before reproducing
- Those with 1 of each alleles are susceptible to malaria, therefore having a survival advantage therefore, reproduce
- Those with 2 normal alleles are susceptible to malaria therefore, they can pass these traits on
Tay Sachs Inheritance
Recessive trait
Tay Sachs Causes
Missing enzyme which is essential for lipid metabolism
Tay Sachs Effects
Results in the accumulation of fatty substances in the nervous system in the white matter which causes issues with nervous system transmissions
Tay sachs Symptoms
Children can develop mental and physical disabilities, death can occur by age 4 or 5, build up of fatty substances in the nervous system
Benefits of Tay Sachs
Provides survival advantage for heterozygotes of the trait in environments where Tuberculosis is prevalent
Effects on gene pool of Tay Sachs
Homozygous dominant - susceptible to TB
Homozygous Recessive - susceptible to Tay-Sachs
Heterozygote - has a survival advantage to TB, more likely to survive and pass alleles onto offspring therefore Tay-Sachs alleles freq. is increased and maintained
Sickle Cell Anaemia Inheritance
Recessive trait
Sickle Cell Anaemia Causes
A point mutation of the gene responsible for the beta-globulin proteins in haemoglobin
Effects of sickle cell anaemia
Results in sickle shaped RBC which reduces their oxygen carrying capacity which blocks capillaries
Symptoms of Sickle Cell Anaemia
Fatigue, shortness of breath, anaemia
Impacts of Sickle Cell Anaemia
Fatal before 7 years
Benefits of sickle cell disease
Sickle-cell provides a survival advantage in environments where malaria is prevalent, such as Africa as it provides a resistance to Malaria
Sickle Cell impact on gene pool
Homozygous Dominant - susceptible to Malaria
Homozygous recessive - susceptible to Sickle-cell disease
Heterozygote - have the sickle-cell trait, they have a survival advantage therefore more likely to survive and pass alleles onto offspring, allowing sickle cell alleles frequency to increase and be maintained in the black African populations
Thalassemia Inhertiance
Recessive trait
Causes of Thalassemia
Mutation of the gene responsible for haemoglobin production, severity varies depending on number of genes affected
Alpha Thalassemia Causes
Due to mutation on Chromosome 16, which reduces formation of alpha globin
Beta Thalassemia Causes
Due to mutation on Chromsome 11, which reuces formation of beta globin
Effects of Thalassemia
Abnormal shaped haemoglobin molecules leading to fewer functions RBC with reduced oxygen carrying capacity
Symptoms of Thalassemia
Anaemia, fatigue, heart defects, slower functioning RBC, abnormal haemoglobin shape
Impacts of Thalassemia
Fatal before 30 years if has a heart complication
Benefits of Thalassemia
Thalassemia provides a survival advantage in environments where malaria is prevalent (South East Asia and Mediterranean Sea)
Thalassemia effects on Gene Pool
Homozygous Dominant = susceptible to malaria
Homozygous Recessive = susceptible to Thalassemia, however Alpa is fatal and Beta is less fatal therefore, Beta is more likely to reproduce
Heterozygote = have a survival advantage therefore more likely to survive and pass alleles onto offspring therefore Thalassemia alleles frequency is increased and maintained in South-East Asia and Mediterranean Sea populations
