2.0 Genetic Variation and Human Populations

Question 1

How many nucleotides in the human genome?

Answer 1

3 billion

Question 2

how many genes in the human genome?

Answer 2

20,000 (2% of genome)

Question 3

What percentage of genetic content do humans share?

Answer 3

95%

Question 4

What are the different classifications of variation in human genomes?

Answer 4

1) Single nucleotide polymorphisms (SNPs)<br></br>2) Insertion/deletions (indels)<br></br>3) Larger scale structural variation

Question 5

Define alleles:

Answer 5

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

Question 6

What processes affect genomic evolution?

Answer 6

1) Genetic drift<br></br>2) Natural selection<br></br>3) Germline mutations<br></br>4) Demography

Question 7

Define genetic drift:

Answer 7

Random change in allele frequency from one generation to the next

Question 8

“What is ““fixation”” and ““loss”” with regards to reduction of genetic diversity?”

Answer 8

Fixation = 100% allele frequency<br></br>Loss = 0% allele frequency

Question 9

Is genetic drift more common in smaller or larger populations:

Answer 9

Smaller populations

Question 10

Define founder effect:

Answer 10

<b>Founder effects</b><br></br>- Loss of genetic diversity when new population is set up by small number of individuals

Question 11

Define Genetic bottleneck

Answer 11

<b>Genetic bottleneck</b><br></br>- Sharp reduction in population size due to environmental/human events

Question 12

What genetic diseases are associated with:<br></br>1) Amis/Hutterite/Mennonite communities<br></br>2) Ashkenazi Jews<br></br>3) Finnish people

Answer 12

<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

Question 13

Define selective sweep:

Answer 13

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

Question 14

What gene is involved with the selective sweep for lighter skin in Europeans?

Answer 14

SLC24A5

Question 15

What caused lactase persistence in Europeans?

Answer 15

A single mutation

Question 16

How many new mutations are there in each individual?

Answer 16

~60

Question 17

What is the relationship between paternal age and de novo mutations?

Answer 17

Increase paternal age -> Increase de novo mutations

Question 18

Give examples of mandelian/simple diseases:

Answer 18

1) Cystic fibrosis<br></br>2) Down’s syndrome<br></br>3) Sickle-cell disease<br></br>4) Charcot-Marie-Tooth disease

Question 19

Given examples of diseases that are influenced by both environment and genetics:

Answer 19

1) Alzheimers<br></br>2) CVS disease<br></br>3) Type II DM<br></br>4) Parkinson’s disease

Question 20

What is a GWAS?

Answer 20

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

Question 21

What is linkage disequilibrium?

Answer 21

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