Genetic variation - Biochemistry Flashcards
(58 cards)
What is genetic variation and why does it matter?
Genetic variation refers to differences in DNA among individuals and is crucial for populations to adapt to biotic (e.g. pathogens) and abiotic (e.g. temperature) challenges through natural selection or genetic drift.
How can the same species look very different?
Selective breeding or adaptation can produce diverse phenotypes (e.g. cabbage vs. broccoli) from one species due to variation in gene expression and selective pressures.
What’s the difference between intra- and inter-population variation?
Intra-population variation = diversity within a population;
Inter-population variation = divergence between populations, often increased by barriers to gene flow.
What is genetic drift and how does it occur?
Genetic drift is random change in allele frequencies, especially in small populations or when populations are isolated, leading to fixation or loss of alleles.
What is natural selection?
Natural selection favors traits that increase survival or reproduction. Over time, it can lead to significant adaptations (e.g. aquatic traits in ancestors of whales).
How has human activity influenced genetic variation?
Through selective breeding and artificial mutagenesis, humans have dramatically shaped crop and livestock genomes (e.g. modern watermelon or pasta wheat).
What are common sources of mutations in nature?
Mostly from DNA replication errors, though also from environmental factors like radiation. Mutation rates are higher in dividing cells and male germlines.
What roles do sexual reproduction and recombination play?
They shuffle alleles to produce new genetic combinations, increasing diversity in offspring.
What are synonymous vs. non-synonymous mutations?
Synonymous: No change in amino acid = typically neutral
Non-synonymous: Alters amino acid = may affect protein function
What does it mean for a mutation to be “fixed”?
A mutation is fixed when it is present in all individuals of a species/population — this can occur via drift or selection.
What are synonymous sites in the genome?
Sites where DNA mutations do not affect protein function, maintaining protein coding despite variation.
What is a founder population?
A new, isolated population formed by a small number of individuals from a larger population, often after a bottleneck event.
How does isolation affect evolutionary divergence?
Isolated populations diverge faster due to limited gene flow and stronger genetic drift.
What is a genetic bottleneck?
A sharp reduction in population size that limits genetic diversity and accelerates allele fixation.
Give an example of an artificial bottleneck.
Artificial insemination in cattle, where using a few males across many females reduces genetic diversity.
Why are potatoes an example of low genetic diversity?
Because they are propagated clonally through tubers, bypassing genetic recombination.
What happens to most new mutations in small populations?
They are lost due to drift, but those that do fix do so quickly.
How does fixation differ in large populations?
More mutations are eventually fixed, but the process is slower due to larger gene pools.
What is polyploidy?
Whole genome duplication resulting in more than two sets of chromosomes.
Difference between autopolyploidy and allopolyploidy?
Autopolyploidy = duplication within one species; Allopolyploidy = combining genomes from different species.
Example of extreme polyploidy in plants?
Black mulberry has 44 chromosome sets.
Example of extreme polyploidy in animals?
Ugandan clawed frog (Xenopus) with 12 chromosome sets.
What is paleo-polyploidy?
Ancient whole genome duplications followed by rediploidization over time.
What are homeologous chromosomes?
Chromosomes from different origins that are similar due to ancient polyploidy
