Human Genetic Variation

Question 1

What are selection and demographics of human subjects in research?

Answer 1

• contemporary ethic guidelines and research norms emphasise that consent from participants is obtained for collecting, strong and analysing their personal data
• IV in planned comparisons, DV in multivariate analysis, structural equation modelling, path analysis
• demographic information to check for biases in selection of subjects, contextualization of findings/post-hoc comparisons

Question 2

What are the differences in DNA sequences?

Answer 2

• between all individuals
• from all individuals in a community that live in the same area and interbreed
• between communities in different areas that have not interbred for period of time

Question 3

What are the origins of variation of genomes?

Answer 3

• multiple variants occur in different frequencies within and between populations
• DNA changes over time and is recombined during reproduction
• migration and admixture between populations change the distribution of alleles and polymorphisms in a population over time

Question 4

How is human skin colour highly variable an complex trait?

Answer 4

• skin colour isn’t uniformly distributed across the body
• variation is also due to biological sex, changes in environments, disease or pregnancy
• complex tangled relationship between genes determining polygenic inheritance, some genes have several alleles but not always dominant
• 15 genes regulate melanin in melanocytes of skin explain some variations

Question 5

How is race a social construct?

Answer 5

• historically used to establish social hierarchies and slavery
• studies showed that large part of genetic variability is due to differences within populations rather than between populations so no genetic base
• it’s a mechanism of discriminatory social segregation

Question 6

What are mtDNA tests?

Answer 6

• whole-genome sequencing for an individual is expensive
• mitochondrial (mtDNA) sequencing is cost effective
• benefits: high number of copies in cell, inherited from egg parent, no recombination, high mutation rate
• share similar mtDNA with all close relatives, important genetic marker

Question 7

How are homosapiens a migratory species?

Answer 7

• human populations have been spatially connected and interacted
• no physiological reproductive barriers
• mixed diet, cognitive functions and cultural innovations enabled survival
• through continued migration and admixing alleles are spread across populations

Question 8

How does genetic variation relate to health?

Answer 8

• genetic and epigenetic changes in different environments and admixture explains patterns of susceptibility to human pathologies
• health conditions can impact on capacity of individuals to respond to health threats
• aging processes have poorly understood impact on cognition and mental disorders
• drive towards personalised medicine based on genetic profiling

Question 9

How does migration expose humans to new environments and diseases?

Answer 9

• 60% mortality rates amongst Dutch colonists in Surinam from epidemics in yellow and typhoid fever
• infectious diseases killed over 10,000 in 59 indigenous communities of Amazonia in past 200 years but mortality rate and incidence have decayed over time due to genetic adaptation
• HIV transmission from apes to humans in 1920s spreading out of Africa from 1960s

Question 10

What are genome-wide association studies (GWAS)?

Answer 10

• current method of genotyping, decipher and study the whole genome and extract the single nucleotide polymorphisms (SNP) called GWAS
• potential for personalised treatments

Question 11

What are the benefits and limitations of GWAS?

Answer 11

• benefits: relies on smallest possible changes in DNA sequence that are frequent in the population, looks at whole genome of many people, SNPs are good markers due to high number and stable inheritance and can be prioritized during analysis, associations with polygenic traits more likely to be uncovered to understand variation and applications
• limitations: requires fully sequenced genomes of hundreds to thousands of individuals and their relatives, higher chance due to number of loci that more associations will be detected

Question 12

What are the ethical challenges of applications and research?

Answer 12

• chance for bias in sampling
• expanded precision and tools for genetic interference
• which are healthy and which are the norm
• don’t understand who is the carrier and who will be affected and the conditions under which they’re affected, difficult to predict
• how, when and where the most detailed genetic ‘fingerprint’ of an individual is used