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BIO 1008 Exam Pt3 Latest Update
Forms of human variation - ANSWER physical and metabolic traits - phenotypes. genome variation - genotypes. linguistic variation, cultural variation, geographic variation
variation with a simple genetic basis (aka mendelian traits) - ANSWER one or few genes affect phenotype, variation for common traits, forms of inheritence differs, expression of one gene can be affected by genotype of another, genes can be on autosomes or X chromosomes
examples of simple genetic variation - ANSWER cystic fibrosis, red-green colour blindness, ABO blood types, eye colour
genetic basis of eye colour variation - ANSWER OCA2 gene associated with melanin pigmentation in iris. red eyes (OCA2 gene missing), brown eyes (homo or hetero for dom brown allele BB or Bb), blue (homo for recessive bb), at least three diff recessive alleles for blue eye colour.
OCA2 and HERC2 - ANSWER OCA2 depends on genotype at adjacent gene HERC2 - which regulates expression of OCA2. Recessive allele at HERC2 leads to blue eyes. if missing either then blue eyes.
eyes example of epistaisis - ANSWER where outcome of genotype at one gene depends on genotype at second gene
codominance ABO blood types - ANSWER High frequency of A, B and O alleles might be due to interactions with bacteria and viruses favouring each type when rare. antigens are the expressed phenotypes.
colour blindness - ANSWER humans have trichromatic vision - 3 types of cone cells sensitive to different wavelengths of light, each express different opsin genes which encode photopigments, short/medium/long. medium and long are on X chromosome (X linked inheritance)
red-green colour blindness - ANSWER caused by mutations due to recombination causing depletion or duplication of genes or chimeric genes, absence of L or M cones or abnormal pigments therefore colourblind
Continuous variation - ANSWER eg height, change gradually
polygenic inheritance - ANSWER occurs when multiple genes determine the phenotype of a trait, doesnt follow patterns of mendelian inheritance
polygenetic inheritance height - ANSWER outcomes of crosses between heteroxygotes at 1, 2 and 6 genes with codominant alleles contributing to height, 80% variation in
human height due to genetic variation
P = G + E - ANSWER variation in phenotype = variation in genotype + variation in evironment
Heritability - ANSWER the ability of a trait to be passed down from one generation to the next, (h^2) = G/P
human genome - ANSWER 23 chromosome pairs (2n = 46) in hyper condensed inactive state during cell division, 22 autosome pair, 1 sex pair. in expanded state in the genetically active "interphase" nucleus ~2m long
human sex chromsomes - ANSWER females XX, males XY. X genetically active, many functional genes. Y mostly genetically active major role in determining gene
chromsomes - ANSWER DNA double helix coiled around histone proteins. telomeres (caps), centrome (attachment point to seperate in division), not uniform
chromsomes areas - ANSWER gene-rich areas in euchromatin (lightly packed, light areas in G-banded), gene poor areas, condensed, in heterochromatin (dark areas in G banding)
history of human genome - ANSWER human karyotype showed 2n, methods of cloning and sequencing, international huan genome prohect, functional analysis, genomes project, human pangenome (function of DNA)
what makes human genome - ANSWER 3 billion nucleotides in haploid genome, 20, protein coding genes only 1.5% of genome. 'exome' contains exons and intervening introns. and other regulatory sequences, many inactive copies of coding genes, retroviruses, repetitive sequences, transposable elements
single nucleotide polymorphisms (SNPs) - ANSWER humans can differ by change in a single nulceotide position, arrise through errors in DNA replication in femal or male germline, males contribute most mutations given more cell divisions (males have more cell divisions)
short tandem repeats (microsatellites aka STRs) - ANSWER mutations due to errors in DNA replciation or recombination, rate of mutation can be higher than SNPs. expansions of short (trinucleotide) repeats within coding regions can cause disease = huntingtons (CAG repeated >35 times), repeating sequence of base pairs
copy number variants (CNVs) - ANSWER +/- 1 kb segment of the genome repeated, a genetic trait with a number of copies of a particular gene. gene duplications are important in evolution of multi-gene families, 10% of genome is CNVs
chromosome level changes - ANSWER changes gene expression, gene distribution & duplication/deletion, recombination pattern, complications in meiosis. some cancers show extensive chromsome changes
skin colour variation - ANSWER mutations at multiple genes underpin variation and evolution of reduced pigmentation in europeans vs east asians. MC1R alleles (from neanderthals) for light colour. increase in frequency of alleles at 3 associated genes with pale skin colour. UV near equator, breaks follic acid so want darker skin with melanin. when in less UV want lighter skin to get UV
pathogens cause of selectio - ANSWER contribute to human variation. can wipe out many peopl
immune system variation - ANSWER longer term evolution of immune system genes. high diversity and allele shared across huge evolutionary distances eg ABO antigens. particular immune systems allowing to survive are selected for
pathogen-driven selection evidence - ANSWER ancienet viral epidemic involving coronavirus interacting henes more than 20,000 yrs ago. strong genetic adaptation occured in human east asian populations, at multiple genes that interact with coronaviruses, including SARS
G6PD deficiency alleles - ANSWER G6PD an enzyme with key role in energy metabolism and protects RBC from oxidative damage. several alleles at X-linked G6PD gene cause reduced activity and can lead to jaundice and anemia. G6PD deficiency most common enxyme deficiency in humans, occurs in many people. alleles favoured by selection in areas with malaria as gives resistance
sickle cell anemia - ANSWER a genetic disorder that causes abnormal hemoglobin, resulting in some red blood cells assuming an abnormal sickle shape. a common genetic disease promoted by malaria resistance. HbA = normal beta hemoglobin. HbS = sickle beta hemoglobin (reduced O2 affinity), HbS/HbS = severe anemia
cystic fibrosis - ANSWER autosomal recessive allele (codon deletion in CTFR gene) causing cystic fibrosis. most common autosomal disease. movement away from hunter lifestyle --> domestification of cattle --> increased exposure to TB --> increased CF allele frequency
genetic risk - ANSWER probability that an individual will be affected by a genetic
(heritable) disorder. (1) Recessive mendelian genetic disease. (2) Complex traits P= G+E
diagnosing genetic disease - ANSWER molecular diagnostics - specific genetic markers (eg CF), genome sequencing
personalised genome sequencing industry - ANSWER can detect types of genetic variants. issues include ownership of own genome data, security of genome data
non invasive prenatal testing - ANSWER blood sample from mother also has fetal DNA, test for chromosome mutations based on copy number differeces of DNA fragments, if risk detected, follow up with invasice sampling and definitive diagnostics. down syndrome, edwards, patau syndrome
predicting genetic testing - ANSWER some breast cancers associated with dominant mutations at one or other of two BRCA genes involved in DNA repair. With BRCA gene have greater risk of breast and ovarian cancer
ethical issues with genetic testing - access - ANSWER restricting access to genome information. making lots of revenue with patents, then overturned.
predictive tests for complex traits - ANSWER screened 50 SNPs associated with coronary heart disease in 8k individuals with known environmental risks and disease outcomes. risk of heart attack 91% greater in highest genetic risk group
personalised medicine - pharmacogenetics - ANSWER genetic differences contribute to variation in efficacy and safety of drugs. outcomes for prescriptions affected by genotype. individuals with G6PD deficiency alleles experience several haemolysis and anemia if treated with anti-malaria drug primaquine
inequality in access to genomic information - ANSWER predictive testing for disease or drug sensitivity requires a genetically matched reference population, best developed for europeans as comparing to european genome vs african aus indigenous populations less of, genetically divergent populations are under-served
