Mutations Flashcards
what is a mutation in general terms?
ultimate source of variation
the change in structure of a gene which results in a variant form which may be transmitted to subsequent generations caused by alteration of base units/genes
why do we need mutations?
without every genetic locus would fix and there would be no evolution so no variation
without all individuals would be genetically identical
what are point mutations?
synonymous - silent - don’t change final product
nonsynonymous - miscense - changes a codon
nonsense - stop
read through
how is sickle cell anaemia caused by mutations?
point mutations - single base substitution in HbB gene
sickle cells occur bc the HbB molecules from the mutated gene stick together - form chains
symptoms of sickle cell anaemia?
breathlessness, fatigue, extreme pain and vulnerability to disease
what is caused by insertion and deletion mutations and how?
cystic fibrosis - deltaF508 mutation
mutation causes abnormal folding and fast degradation
increased water retention in cells and cascade effects on body - including thicker mucous membranes - obstruction of airways and infection
what is a frameshift mutation and ORF?
DNA has 6 possible reading frames
ORF - open reading frame - the part between the start and stop codons that can be translated
what happens when you have indels without the coding sequence?
- RNA polymerase can’t bind if the core promoter is deleted - no transcription
- regulatory sequence deleted so transcription factors can’t bind so uncontrolled transcription
what are chromosomal mutations?
a change in the number or structure of chromosomes
can move genes around - one end to another or one chromosome to another
how does deletion work?
loss of all or part of a chromosome caused by (unrepaired) breaks in the chromosome
e.g intellectual disability - symptoms caused by disruption of neuronal migration - most cases not inherited but occurs during gamete formation
how does duplication work?
provides extra copy of all/part of chromosome - errors in DNA replication/repair
why is duplication good?
major mechanism for generation of new genetic material - evolutionary innovation - redundancy means reduced selection pressures on the second copy
what is polyploidy an example of?
whole genome duplication
its when there is 2 or more sets of homologous chromosomes
what causes polyploidy?
problems in gamete formation
what is polyploidy speciation?
when the polyploid plant is not compatible with the ‘parent’ plant
what is translocation?
when one part of one chromosome breaks off and attaches to another
what disease is caused by translocation?
downs - trisomy 21 - 3 copies of the 23rd chromosome
what is inversion?
when the direction of parts of a chromosome are reversed - found as fixed differences between species or segragating within populations of the same species
recombination reduced
what is inversion key in?
supergene formation
tight clusters of two or more genetic loci - each locus affects a different trait
certain allele for one locus then becomes linked to a certain allele of a second locus
this gives integrated control of complex phenotypes and then segragtes within a species
what is shown in swallowtail butterflies?
batesian mimicry
what did fisher predict with Batesian mimicry?
that imitating would require both strong selection and specific trait combos
what is dsx?
a transcription factor which regulates somatic sexual differentitation across insects
ensures femaleness genes are switched on and male genes off
three forms - two in wings
what was the goal of fishers ‘geometric model of adaptation?
predict whether any random mutation will be adaptive given its effect size
smaller mutations have higher chance of being advantageous
what did motoo kimura think
Fisher - probability that a mutation of a given size will be advantageous
but thought fisher had overlooked
- probability of mutation being fixed
- mutations of small effect are less likely to be fixed
derived the distribution of sizes among mutations ‘used’ in adaption
what did motoo kirmura conclude?
mutations of intermediate phenotypic effect are the most likely to play a role in adaptation
what was the overall conclusion of fishers model?
mutations of large effect are more likely when the current trait is far away from the optimum
