2.0 Genetic Variation and Human Populations Flashcards
How many nucleotides in the human genome?
3 billion
how many genes in the human genome?
20,000 (2% of genome)
What percentage of genetic content do humans share?
95%
What are the different classifications of variation in human genomes?
1) Single nucleotide polymorphisms (SNPs)<br></br>2) Insertion/deletions (indels)<br></br>3) Larger scale structural variation
Define alleles:
Different versions of a genetic locus<br></br><br></br>(most variant alleles are unique to that individual)<br></br><br></br>Pairs of alleles = genotype
What processes affect genomic evolution?
1) Genetic drift<br></br>2) Natural selection<br></br>3) Germline mutations<br></br>4) Demography
Define genetic drift:
Random change in allele frequency from one generation to the next
“What is ““fixation”” and ““loss”” with regards to reduction of genetic diversity?”
Fixation = 100% allele frequency<br></br>Loss = 0% allele frequency
Is genetic drift more common in smaller or larger populations:
Smaller populations
Define founder effect:
<b>Founder effects</b><br></br>- Loss of genetic diversity when new population is set up by small number of individuals
Define Genetic bottleneck
<b>Genetic bottleneck</b><br></br>- Sharp reduction in population size due to environmental/human events
What genetic diseases are associated with:<br></br>1) Amis/Hutterite/Mennonite communities<br></br>2) Ashkenazi Jews<br></br>3) Finnish people
<b>1) Amish/Hutterite/Mennonite communities</b><br></br>- Microcephaly<br></br>- Other genetic diseases<br></br><b>2) Ashkenazi Jews</b><br></br>- Tay-Sachs<br></br><b>3) Finnish people</b><br></br>36 monogenic diseases are higher in Finnish populations
Define selective sweep:
Sign of positive selection<br></br>It is the reduction/elimination in variation due to strong +ve selection<br></br>Result = extended region of genetic homogenisity
What gene is involved with the selective sweep for lighter skin in Europeans?
SLC24A5
What caused lactase persistence in Europeans?
A single mutation
How many new mutations are there in each individual?
~60
What is the relationship between paternal age and de novo mutations?
Increase paternal age -> Increase de novo mutations
Give examples of mandelian/simple diseases:
1) Cystic fibrosis<br></br>2) Down’s syndrome<br></br>3) Sickle-cell disease<br></br>4) Charcot-Marie-Tooth disease
Given examples of diseases that are influenced by both environment and genetics:
1) Alzheimers<br></br>2) CVS disease<br></br>3) Type II DM<br></br>4) Parkinson’s disease
What is a GWAS?
Genome-wide association study<br></br>Examination of many common genetic variants in different individuals to see if any variant is associated with a trait. GWASs typically focus on associations between single-nucleotide polymorphisms (SNPs) and traits like major diseases
What is linkage disequilibrium?
Non-random association of alleles at different loci i.e. the presence of statistical associations between alleles at different loci that are different from what would be expected if alleles were independently, randomly sampled based on their individual allele frequencies
