Lecture 2 Flashcards

Question

Natural selection

Answer 1

- selection acts on individuals, but effects are seen at population level - the alleles of individual who reproduce more (dying less helps at that) increase in frequency over time relative to others and this CHANGE is evolution by natural selection

Answer 2

a random change in allele frequencies from one generation to the next based on "sampling" effect Example: Genetic bottlenecks - population is reduced and then expands again - resulting pop may not have the diversity or frequency of the initial population Founder Effect - small subset of a larger population colonizes a new area but said subset is not representative of the allele frequencies present in parent population

Answer 3

- mating rules or sexual selection - small populations - geography - natural selection - genetic drift - gene flow - mutation allele distribution of contemporary populations

Answer 4

Monogenic diseases are genetic disorders that are caused by mutations in a single gene. These diseases can be inherited in a straightforward manner, following Mendelian inheritance patterns. usually not very common: - maintained by recurrent mutations - deleterious effects tend to be post reproductive - deleterious effects tend to be only expressed in the homozygous and/or provide an advantage in the heterozygous

Answer 5

"balancing selection": favours a balance between alleles - some alleles (or sets of them) confer different advantages and disadvantages (e.g. Cancer) - heterozygote advanatge (e.g. hemoglobin, a mutation linked to sickle cell anemia) - frequency-dependent selection - unstable environments

Answer 6

Sickle cell anaemia: hemoglobin mutation (HgbS) leads to rigid, sickle shape erythrocites Sickle cell anaemia: the HgbS affects circulation in the homozygous making them extremely sensitive to oxygen deprivation, causing kidney failure, chest, back and abdominal pain and short life expectancy The HgbS mutation has not been eliminated by NS - The frequency of this HgbS can reach 40% in some populations This phenomenon was only understood after developing a gene frequency map of the HgbS allele - which allowed scientists to see that the frequency of this allele coincided with the frequency of malaria But HgbS in heterozygotes (HgbA/HgbS) provides resistance against malaria HgbA/HgbS has a normal life expectancy and is resistant to malaria which in some regions of the world kills a large number of people each year

Answer 7

diseases associated with multiple genes (polygenic traits) - common diseases depending on various genes each associated with an increased risk for the disease - in some cases disease results from a specific combination of particular alleles - or specific alleles in particular environments (e.g. obesity)

Answer 8

genes associated with multiple traits (pleiotropic traits) Males: - high testosterone costs: aggression, higher blood pressure, more likely to engage on risk taking behaviours (alcohol, smoke, high risk sports) - high testosterone benefits: drive, libido, muscle development

Answer 9

- genetics demonstrate that humans cannot be divided into biologically distinct subcategories of race - inaccurate to claim genetics as the determinative factor in human strengths or outcomes due to education, environment, wealth, and health - no factual basis for attempts to define communities or regions of people with "good" or "bad" genes

Answer 10

- We have some alleles that will work well in our environment and others that may not work that well - Some alleles may be beneficial when present in a heterozygous state (having two different alleles for a gene). - For example, individuals with one normal hemoglobin allele and one sickle cell allele (HgbA and HgbS) have a survival advantage in malaria-endemic regions, as they are less susceptible to severe malaria while avoiding the full effects of sickle cell disease

Answer 11

The individual "adaptive value" of each gene can only be evaluated in the context of: - how it works with other genes in any given genome - how the whole genome interacts with its environment

Answer 12

the "good genes" argument is often used as part of racist discourses

Answer 13

No, biologically speaking there is not such thing as human races Current "popular/traditional" race attributions do not correspond to geographic patterns of human genetic variation

Answer 14

Those whose ancestors have lived for many generations in a particular geographic region tend to share some phenotypic similarities BUT those shared phenotypic traits not always depend exclusively on genetics and those geographic regions tend to be small - about 85% of genetic variation measured is found within "racialised" groups and only 15% of that variation is found among groups. So the majority of between-group variation is local, not racial

Answer 15

- genetic similarities - similar environmental contexts - lead to similar phenotypic expressions that change gradually in time and space, resulting in clines

Answer 16

A geographical gradient in a particular trait across a species - Traits exhibit a smooth transition from one form to another over distance - Traits that can show clinal variation include physical characteristics (such as skin color, height, or body shape), genetic traits (like allele frequencies), and even behavioral traits. For instance, in humans, skin pigmentation often changes gradually from darker shades near the equator to lighter shades in northern latitudes.

Answer 17

- races assumed as valid biological entities and health differences assumed to be mainly based on genetic differences between races Those assumptions are not always tested - most models highlight supposed biological vulnerabilities for groups that, interestingly, have been colonized/marginalized - while other factors such as the effects of marginalisation and inequities are often overlooked or poorly addressed

Answer 18

Compared black and white patients survival following a cancer diagnosis (n=20,000 patients, 12% were black) 35 clinical trials - all patients received same treatment - SES controlled by zip code - black patients had worse survival rates for breast, ovarian, and prostate cancer Authors concludes that observed differences MIGHT be due to "inherited genetic differences across races", yet no genetic data was collected only information about race Variation in exposures to environmental factors known to affects cancer survival such as: - reproductive history - residential segregation - access to nutrition - discrimination

Answer 19

a ground breaking new study suggests that survival gap for at least some types of cancer may also be rooted in biology. In other words, blacks may inherit certain genetic traits that make cancers especially lethal - despite the study not including genetic data and not including a definition of race

Answer 20

- using of simplistic conceptions of human biology - equating race to genetics - ignoring socioeconomic factors - minimising the role of lived experiences, marginalisation, discrimination and environmental exposures

Answer 21

differences in social environment including access to housing quality, exposures to pathogens, nutrition, appropriate health care, etc. Model adapted from Gravel (2009) which explains this Examples: - low birth weight baby (LBW) risks increased 34% for Californian women with Arabic names during the 6 months following 9/11, a phenomenon not observed in other groups for that period - The increased risk of LBW has been argued to be a consequence of stigma as it is often observed among moms exposed to high racial discrimination - potential intergenerational effects: as LBW can be to developmental problems and poor scholastic and later, work achievements, which in turn affects their parental abilities perpetuating the effects of the original exposures across multiple generations

Answer 22

- There are alleles linked disease-risks. - Individual alleles, however, explain only a small fraction of heritable variation in complex diseases such as heart disease, obesity, cancer or stroke - Complex diseases, depend on multiple alleles and the interactions between those alleles and environmental factors

Answer 23

- "race" is argued to not be a meaningful biological concept - Different alleles associated with negative health outcomes (often simpler rather than complex ones) can be more frequent in some geographical regions than others - Those geographical regions do not necessarily overlap with traditional race categories - Race is argued to be a social construct linked to stigma, marginalisation, bullying and ostracism - To attribute negative health outcomes to some genetic trait specific alleles need to be identified. Then their prevalence in a particular group should be assessed and environmental factors such as stigma and marginalisation evaluated.

Answer 24

We urge societal attention to address profound educational, economic and health inequalities that fuel differences in human experience and well-being. By pursuing all of these activities, humans can celebrate our common heritage as one people, embrace and fully tap our valued diversity, and help achieve optimal life outcomes for all.

Lecture 2 Flashcards

(48 cards)