Origin of Genetic Variation Flashcards
Why is variation critical to evolution?
Evolution can only happen with variation in characteristics, natural selection needs variation to be able to select individuals
What are silent/synonymous mutations?
Mutations that don’t change the amino acid encoded
What are non-synonymous mutations?
Mutations that change the amino acid encoded
What are gene mutations?
Alterations of genes or chromosomes
What are point mutations?
Alteration of a single base pair
What are base pair substitutions?
One base replaced by another, either transition or transversion
What are frameshifts?
Alteration in the reading frame which changes a bunch of amino acids downstream of the mutation. Caused by indels
What is intragenic recombination?
Difference in two or more base pairs in a gene, which generates a new sequence within the gene
What is gene conversion?
A damaged DNA strand on one chromosome is repaired based on an undamaged homologous chromosome
What causes unequal crossing over and what is the result?
Imperfect alignment between homologous chromosomes during bivalent formation. Results in an unequal exchange of genetic information and one chromosome with a duplication and the other with a deletion
How does the mutation rate compare to the size of the genome of the organism?
Mutation rates are generally pretty low, but tends to increase as the genome gets larger. The exception are viruses, which have high mutation rates to evade host defences
What are somatic mutations?
Mutations that occur in somatic cells and can’t be passed on to the next generation. They don’t matter for evolution
What are germline mutations?
Mutations in the reproductive cells that can be passed on and do matter for evolution because that change can be acquired by the next generation
What are homeotic mutations?
Mutations that can alter developmental processes and can cause an anatomical structure in the wrong place
Why are mutations limited for what can be changed in an evolutionary sense?
Mutations can only modify whats already there, and can’t alter developmental foundations
What is aneuploidy?
The loss or gain of a whole chromosome or a major part of it
What causes polyploidy?
Failure of the reductional division of meiosis
Which group organisms is polyploidy seen in more often?
Plants
Where did the multiple chromosome sets originate from in autopolyploids?
Within one species
Where did the multiple chromosome sets originate from in allopolyploids?
Two or more species
Why are polyploid organisms advantageous commercially?
They are larger than their diploid counterparts
How can polyploidy occur in animals?
Parthenogenic animals, hybrids, some frogs and toads are polyploid
What is parthenogenesis?
A form of asexual reproduction that allows a female to create offspring without fertilization
What causes chromosome structural alteration?
Breaking and resealing of a chromosome
What is a deletion?
A segment of the chromosome is lost
What is a duplication?
A segment gets replicated and is in the chromosome twice
What is an inversion?
A segment has its orientation reversed
What is a translocation?
A segment gets moved to another chromosome
How common are chromosomal abnormalities in human sexual reproduction?
Surprisingly common. 15% of conceptions abort spontaneously, and 50% of those are due to chromosomal abnormalities
Why are chromosomal abnormalities so common in human sexual reproduction?
Cellular processes are error prone
What caused two closely related species of Muntjac deer to have such different chromosome numbers, with one having 2N = 46 and the other with 2N = 8?
Fusion of chromosomes in the 2N = 8 species. The size of the genome hasn’t really changed but the chromosomes have fused into fewer large chromosomes
