Mutations and Evolution

• Errors in DNA replication • Errors in Cell Division • Mutagens

• 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

• 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

• 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

• 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

• 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

Barries to gene flow influence the allele frequency Geographical barriers alike deserts, mountains, oceann sociocultural barriers include religion, language and culture

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

Variation Struggle Selection

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

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

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.

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

• 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

• 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

Gene mutation: * a change to a sinlge gene loci, occuring during DNA replications * Changes to nucleotides: * Subsitution: silent (no effect), missence (little), nonsense (proteins wont be made) * Insertion : results in a frame shift * Deletion (framshift) * Albinism

• Changes occur to all or part of a chromosome • can cause severe deformity • Insertion: extra base pairs added • Duplication: section of DNA is replication • Deletion: dna is lost of removed • Translocations: one segment attaches to another chormosome • Inversions: broken segment is reversed and reinserted into a chromosome • Non-disjunction - Chromosome is missing • Down syndrome

• Extremely cold temperatures • Long winters and short summers • Little vegetations • strong winds, icy terrain

• short limbs, long body - higher sa • increased body fat for insulation - serves as an energy reserve and insulation in extreme cold • sturdy and muscular physique - better hunters and gatherers • shorter stature - reduced risk of injuries from falling from icy terrain

Altitude adaptations: Himalayans - developed physiological adaptations to cope with low oxygen levels, incuding increased lung capacity, higher rbc production and alterations on haemoglobin Malaria resistance: Africa - developed sickle cell trait provides resistance to malaria