VL 2 Genomes and the origin of genetic variation Flashcards
What is the only primary process that increases genetic diversity?
Mutation is the only de-novo process increasing genetic diversity.
What are the two domains of life according to recent discoveries, and where do eukaryotes fit in?
Archaea and Bacteria; Eukaryotes are nested within Archaea.
- Archaea that bridge the gap between prokaryotes and eukaryotes were found at the Black smoker (energy without sunlight, chemoautotroph bacteria create organic matter here)
- Difference to eukaryotes: prokaryotes are not capabe of endocytosis -> found Archea are able to do that + Archaea also have Histones
- Eukarya ae deeply nested within the Asgard archaea
List some key innovations of eukaryotes.
Nucleus, mitochondria, cell organelles, cilia, linear chromosomes,
histones (before the others, even found in early archea)
What are the size ranges of bacterial, archaeal, and eukaryotic genomes?
Bacterial: 0.15 – 14 Mb,
Archaeal: 0.5 – 5.7 Mb,
Eukaryotic: 2.3 – 150,000 Mb
Where is DNA found in human cells and how many protein-coding genes are there and what percentages of the human genome is that?
DNA is found in the nucleus and mitochondria; there are approximately 21,000 protein-coding genes and 46,000 genes in total
-> Only 1-2% is protein-coding; the rest includes introns, control elements, and repetitive DNA.
-> the rest of the non protein coding regions codes for functional RNA (non-coding RNA -> gene regulation)
What is the function of telomeres?
Telomeres protect the ends of linear chromosomes from deterioration (Zerfall) and prevent them from fusing with neighboring chromosomes.
- In somatic cells the telomers are kept on a certain length, to limit the number of cell divisions, serving as a mechanism for detecting and preventing uncontrolled cell growth.
- Telomerase (has RNA-template) is an enzyme that extends the telomeres of chromosomes, allowing cancer cells to divide indefinitely and maintain their immortality by preventing telomere shortening.
What causes silent mutations?
Silent mutations are changes in the DNA sequence that do not alter the amino acid sequence of the protein produced. Synonymous mutations.
Cause: These mutations are caused by the degenerate nature of the genetic code, where multiple codons can encode the same amino acid.
Small mutations and their effect
Pointmutations:
1. Synonymous mutation: no effect
2. Non- synonymous mutations: Missense (different AS) or Nonsense (Stop codon)
Single bp Insertions/Deletions (Indels)
A point mutation involving the addition or loss of a single nucleotide: Frameshift
What are some causes of genetic variation besides mutation?
- Recombination (Crossing over),
- replication slippage,
- unequal recombination and translocation -> produce gene families
- gene duplication -> also produces gene families
- lateral gene transfer
Processes like recombination, gene duplication, exon-shuffling, lateral gene transfer, etc. re-arrange genetic diversity
– i.e. they may increase diversity within a population or species, but not globally.
What is lateral gene transfer and in which organisms is it known to occur?
The transfer of genes between organisms in a manner other than traditional reproduction, known to occur in bacteria and some animals.
-> much more common in animals than assumed until a few years ago.
What is the difference between homologs, orthologs, and paralogs?
Homologs are genes sharing an evolutionary origin;
* Orthologs are homologous genes separated by a speciation event (Gleiches Gen in Maus und Chicken)
* while paralogs are homologous genes separated by a gene duplication event (𝜶- Globin und β-Globin in Maus)
What is the evolutionary significance of gene duplication?
Gene duplication can lead to new gene functions and contribute to evolutionary innovation, such as the globin gene family.
What is the most extreme form of genetic variation?
Whole Genome duplication
WGD
