Lecture 14 - Lifecycle of a Gene Flashcards
Which organisms generally have the smallest genome sizes?
Prokaryotes.
Which groups show the largest genome sizes?
Birds, mammals, and reptiles.
What are the three main categories of genome composition?
Coding DNA, non-coding DNA, and repeats.
How does genome composition differ between S. cerevisiae and H. sapiens?
S. cerevisiae: Mostly coding DNA (~75%).
H. sapiens: Large amounts of non-coding DNA and repeats, with less coding DNA.
What are the three primary sources of new genes?
Horizontal gene transfer.
Duplication of an existing gene.
De novo creation from non-coding DNA.
What is horizontal gene transfer (HGT)?
The exchange of genetic material between different organisms, not involving parent-offspring inheritance (asexual species).
Name the three mechanisms of horizontal gene transfer in bacteria.
Transformation, conjugation, and transduction.
How does transformation work?
DNA from the environment is incorporated into the bacterial genome.
What is conjugation?
Direct transfer of DNA between bacteria using a sex pilus.
How does transduction occur?
Viruses transfer bacterial DNA to another host during infection.
What are the main types of gene duplication in eukaryotes?
Whole genome duplication, whole chromosome duplication, and DNA segment duplication.
What is polyploidisation?
An increase in the number of chromosome sets within an organism.
How can polyploidisation lead to a new species?
Through allopolyploidy, combining genomes of different species.
What are the possible fates of new genes?
Loss or preservation.
What is pseudogenisation?
The loss of gene function through mutation.
What are the three types of preservation mechanisms?
Compensation, neofunctionalisation, and subfunctionalisation.
What is neofunctionalisation?
A duplicated gene acquires a completely new function.
What is subfunctionalisation?
Gene copies specialise in specific functions or timings, e.g., globin gene family in humans.
Give an example of adaptation through gene duplication in humans.
High-starch diets selected for more copies of the AMY1 gene in some populations.
How do transposable elements (TEs) contribute to genome adaptation?
They can duplicate and spread advantageous traits.
What are transposable elements (TEs)?
Genetic sequences that can move within the genome.
What are the two classes of TEs?
Class 1 (retrotransposons): Copy-and-paste mechanism.
Class 2 (DNA transposons): Cut-and-paste mechanism.
What can cause genome instability?
Replication errors, unequal crossover, retrotransposition, and aneuploidy.
What are telomeres, and why are they important?
Telomeres are repetitive DNA sequences at chromosome ends that protect against deterioration during replication.
How does telomere shortening contribute to disease?
It is linked to ageing, cancer, and various metabolic and psychiatric disorders.
What is the role of transposable elements in fruit flies?
They extend telomeres, protecting DNA from shortening.
What are the three main sources of new genes?
Horizontal gene transfer, duplication, and de novo creation.
What are examples of adaptation via genome evolution?
Antibiotic resistance in bacteria.
Starch digestion in humans.
Electric organs in fish.
