Mutations and Evolution Flashcards
Gene and chromosomal mutations can result from
- Errors in DNA replication
- Errors in Cell Division
- Mutagens
Describe errors in DNA replication
- During DNA Replication errors can occur resulting in wrong DNA being made this is caused by
1. Substituition - wrong base pairs lining up
2. Deletions - bases can be deleted
3. Insertion - duplicated or extra DNA can be added
4. Frameshifts - Incomplete DNA code - DNA is unreadable - these erros can be passed onto new cells (gline or somatic)
- Cancer, cystic fibrosis, sickle cell anaemia
Describe Errors in Cell division
- Occur during Meiosis
- Majority of which occuring during the first stage of Meiosis especially when:
- Homologous chromosomes lineup
- crossing over
- during these, sections can be put in the wrong order, or added to the wrong chromosomes
- whole chromosomes can also be added or deleted
- the gametes produced have either faulty chromosomes or an incorrect number of chromosomes
- Down syndrome, Turners Syndromem
Describe Mutagens
- Mutagens are agents that are known to increase the likelyhood of mutations - known mutagens are mustard gas, radiation
- Mutages cause mutations as they:
- Resemble proteins and become incorporated into DNA
- Triggfer DNA replication errors
- Cause DNA to break
- Block DNA replication or damage structure
- Cells affected by mutagens will replicate with damaged DNA
- Can cause somatic, germline, gene & chromosomal mutations
Describe the changes in allele frequency caused by mutations
- Mutations refers to a change that occurs in our DNA sequence that leads to a new characterisitc.
- Mutations can occur in somatic and germline forms, arising from erros in DNA replication, errors in Cell division and Mutagens.
- Two types: Gene and Chromosomal
- Mutations can create new more favourable adaptations which can be passed on to the next generations
Describe the changes in allele frequency caused by random genetic drift
- RGD is randon and non selective, occurs due to chance
- the effect is stronger on smaller populations
- rare allele has a greater change of becoming more frequent in small populations.
- Bottleneck: drastic reduction in population, surviving individuals breed, thus, alleles are passed on
- Founder effect: Small group migrates establishing new community, the new founding community has different characterisitics that are not typical of the original populations
Describe changes in allele frequency caused bt gne flow betweening adjoining groups
Barries to gene flow influence the allele frequency
Geographical barriers alike deserts, mountains, oceann
sociocultural barriers include religion, language and culture
Genetic diseases in particular populations illustrates the effects of different factors on the dynamics of gene pools. (Tay Sachs)
Tay-Sachs
* Carrier are resistant to tuberculosis
* population: Ashkenazi Jew
* Cause: Missing enzyme essential for fat metabolism
* Symptons: build up of fatty substances, mental and physical disabilities.
* inheritance: recessive trait/passed from two carrier parrents
* Effect on Gene Pool:
* Carrier couples choose not to reproduce
* heterozygous individuals are resisitant to tuberculosis
Natural selection occurs when factors in the environment confer a selective advantage on specific phenotypes to enhance survival and reproduction. What are these factors in the environment
Variation
Struggle
Selection
describe inherited variation
Inherited variation refers to the genetic differences passed down from one generation to the next. large gene pool with a variety of genes creates variation. Variation must be present in individuals
describe struggle for existence
There is an overproduction of offspring with limited resources. There is an evident selection pressure with a competition for the limited resourses, creating the struggle to survive
describe isolation and differential selection
Differential selection: Individuals that have a particular phenotype that is suited for the environment survived and passes on favoured genes to offspring. Over time desirable phenotypes will be more prevalent and can lead to speciation.
Explain how those mechanisms produce significant changes to gene pools to an extent that speciation occurs
Speciation occurs when a combination of variation, isolation, struggle and selection are present.
Variation - wide variety of genes
Isolation - barriers to gene flow
Struggle - Overproduction of offspring with limited resources
Selection : individuals with suitable genes survive, passing it onto next generation.
Speciation: A new species forms when they are no longer able to reproduce with others
vGenetic diseases in particular populations illustrates the effects of different factors on the dynamics of gene pools. (SICKLE CELL)
- Population : african/italian/indian
- Cause: muation of gene responsible for RBC
- Symptoms: RBC have sickle-shape, reduces SA of RBC
- Inheritance: recessive trait
- Effect on gene pool
- individuals homozygous for condition usually die early
- heterozygous have sickle cell trait
Genetic diseases in particular populations illustrates the effects of different factors on the dynamics of gene pools. (Thalassemia)
- Population: Mediteranian sea/greek/italian
- Cause: mutation of gene responsible for RBC. Haemoglobin production
- Symptoms: Defects in formation of haemoglobin. Fewer functioning RBC
- Inheritance: Recessive trait
- Effects on gene pool:
- more mutations in RBC formation increases severity of disease
- individuals affected with mild thalassemia only have 1-2 mutations
- more mutations = higher mortality rate
- resitant to malaria
