UNIT 3 DAY 6 - WHAT HELPS YOU ALSO HURTS YOU

Question 1

Pleiotropy

Answer 1

single gene that affects 2 or more seemingly unrelated phenotypic traits

Question 2

antagonistic pleiotropy

Answer 2

gene with multiple effects, 1 beneficial but another harmful

Question 3

pleiotropy example

Answer 3

sickle cell anemia

Question 4

Greenwood 2023

Answer 4

deadly diseases left a mark on our DNA –> natural selection in action –> mortality, acting on heritable variation, results in a change in allele frequencies in a population over time

Question 5

Greenwood 2023 - raising risk of autoimmune diseases

Answer 5

• protective variants that have increased frequency –> antagonistic pleiotropy –> accumulated in a population due to natural selection

Question 6

genomics

Answer 6

study of all of a persons genes (their genome), including interactions of those genes with each other and with persons environment

Question 7

DNA

Answer 7

chemical compound that contains instructions needed to develop and direct the activities of nearly all living organisms, made up into a double helix

Question 8

genome

Answer 8

organisms complete set of DNA

Question 9

DNA sequencing

Answer 9

determining the exact order of bases in a DNA strand, due to base pairs, researchers only need to know 1 of the pair

Question 10

Human Genome project

Answer 10

• produced a very high-quality version of the human genome sequence, generates a resource that could be used in biomed studies
• understand genome functions and discovers genetic basis for health and disease

Question 11

What genomes were examined?

Answer 11

• genomes of 2,879 Europeans (lived between Neolithic period)
• genetic variants that have become common in that time are linked to immunity
• living more densely, increased exposure to infectious diseases (farming and raising animals) –> more exposure to bacteria from farming / animals, diseases can spread quicker
• environmental factors important in spread of diseases

Question 12

senescene

Answer 12

the process of bodily deterioration that occurs at older ages

Question 13

how is senescene affected?

Answer 13

• not a single process of bodily deterioration that occurs at older ages
• senescene isn’t a disease but result of every bodily capacity steadily decreases so that we grow steadily more vulnerable to a myriad of diseases

Question 14

senescene information

Answer 14

• no selection against. genes whos harmful effects only after the oldest age of reproduction
  –> force of selection decreases later in life
• a gene might be well selected for, individuals will benefit from its advantageous, some will experience the disadvantages
  –> argument doesn’t depend on prior existence of senescene

Question 15

Alzheimer’s disease

Answer 15

• genes that predispose to Alzheimer’s disease –> selected for because of earlier benefits –> influenced by genetic factors
• genetic changes –> led to very rapid increases in humans brain size
• genes with early benefits contribute to senescene

Question 16

trade-off

Answer 16

• an evolutionary trade-off, advantageous in early life, contributes to diseases
  –> gene involved with big brains, genes that have byproduct of raising risk of Alzheimer’s

Question 17

enhancers

Answer 17

• pieces of DNA with the ability to boost the activities of certain genes, therefore, levels of resulting proteins
• 93 enhancers expresses within neurons and neuronal stem cells that evolve rapidly in humans
• genes close to these enhancers –> under their control, important for the brain development –> enhancers positively selected for during evolution because of effects of these brain-related genes
• selection diminishes with age because fewer and fewer individuals are around to be selected against –> diminishes rather than disappearing all together
• associations between enhancers and aging-related diseases not definite evidence of cause and effect

Question 18

menopause

Answer 18

• unlikely to be simply a result of senescene because most common species continue to have reproductive cycles …
• women make substantial effort in each child, investment will pay off genetically

Question 19

cell genomics

Answer 19

• genetic adaptations to pathogens and increased risk of inflammatory disorders in past-neolithic europe
  1. ancient genomic studies allow detection of extent of natural selection overtime
  2. genetic adaptation in europe–> occurred at start of bronze age
  3. immunity genes –> strongly affected by + and - selection
  4. resistance to infection increased inflammatory disease risk

Question 20

why will selection only very slowly eliminate a fatal, disease-causing, recessive allele from a population

Answer 20

1. Hardy-weinberg equation tells you that most copies of the disease-causing alleles exist as heterozygotes
2. recessive disease-causing alleles do no harm when heterozygous
3. selection only removes fatal disease-causing recessives when they exist as homozygous and homozygous are less common than heterozygous
4. as fatal disease-causing alleles diminish in frequency as removed by selection, homozygous of diseases-causing alleles because especially rare, thus only rarely removed by selection

Question 21

2 components of williams theory of senescene are

Answer 21

1. force of selection diminishes with age
2. that genes benefit you when young and harm you when old (antagonist pleiotropy) will be favoured by selection

Question 22

how does figure 8-1 illustrate that “senescence is a first-class evolutionary mystery?”

Answer 22

• individuals who don’t senesce who have much greater reproductive success (indicated by grey area)