Biological Anthropology - Midterm 2

Population

A group of interbreeding individuals of a same species sharing a common geographical area

Gene pool

Sum of alleles in a population at a particular time which can be passed on to the next generation

Evolution

The change of allele frequencies over time in a population

allele frequency

Number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene

Hardy-Weinberg Principle

principle that states that allele frequencies in a population remain constant unless one or more factors cause those frequencies to change

Hardy-Weinberg equations

P + Q = 1

p2 + 2pq + q2 = 1

What does Hardy-Weinberg equilibrium assume?

Genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors (mutations, random mating, etc.)

Mutation

Ultimate source of genetic variation

Deletion (mutation)

Type of mutation that involves the loss of one or more nucleotides from a segment of DNA

Duplication (mutation)

Type of mutation in which one or more copies of a DNA segment is produced

Insertion (mutation)

Type of mutation that involves the addition of one or more nucleotides into a segment of DNA

paracentric inversion

Happens when 2 breaks in one chromosome arm rejoins together after the broken piece has been inverted

pericentric inversion

Structural chromosomal defect caused by a 180 rotation of the chromatin segment between the breaks which happen from a breaks on both sides of the centromere

Reciprocal translocation

Occurs when part of one chromosome is exchanged with another

Robertsonian translocation

the structure produced when two telocentric chromosomes fuse at their short arms

DNA transition

Interchanges of two-ring purines or one-ring pyrimidines (A for G)

DNA transversion

Interchanges of purine for pyrimidine bases or one-ring for two-ring (A for C)

Synonymous mutation

A change in the DNA sequence that codes for proteins but does NOT change the encoded amino acid

nonsynonymous mutation

Change in the protein sequence that are frequently subjected to natural selection

Frameshift deletion

Type of mutation involving the insertion or deletion of a nucleotide in which the number of deleted pairs is not a multiple of 3

random genetic drift

When a population has a small size, by chance alone, the allele frequencies can fluctuate form generation to generation

Population bottleneck

A large population and then for whatever reason, a dramatic change in the population size

Founder effect

the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population

Tristan da Cunha

Athasma due to founder effect, population bottleneck and random genetic drift

Fitness (Biology)

the differential ability to survive and reproduce; 1 is the maximum passing on of a genotyope to the next generation

Mean population fitness (w-bar)

the sum of the fitness of the genotypes multiplied by the frequency at which they occur

Selection (biology)

proportional reduction in fitness of a genotype with respect to the genotype with the maximum fitness; 1 means none survived and reproduced

Differences in fitness

when differences are large, the effect of selection is strong and allele frequencies will change fast in the population from generation to generation

Over dominant selection

Gene flow/admixture

the movement of alleles between populations

Acclimatization

physiological adjustment of individual organisms to different environmental conditions; reversible process which entails no genetic change

IPD

immediate pigment darkening; happens within 1-2 hours of exposure and fades away after 24 hours

Delayed tanning reaction

happens within 2-3 after exposure and can last several months

Developmental plasticity

an anatomical or physiological change occurring during growth or development as a result of environmental stresses

Adaptation

inheritable genetic changes that develop in populations over long periods of time

Malaria

caused by Plasmodium falciparum; invades red blood cells

According to the WHO 2021 malaria report

~241 million cases of malaria; ~627,000 deaths

How did malaria come to spread across Africa

the arrival of horticulture thousands of years ago changed the ecological conditions making them ideal for the spread of mosquito-causing malaria

DNA Sequence causing malaria

mutation in the beta-chain of the hemoglobin responsible for oxygen transport (HbS); glutamic acid to valine

Sickle cell disease

Abnormal hemoglobin structure

Sickle Cell and Malaria

Balancing Selection; where malaria is very prevalent, natural selection favours those with sickle cell

Lactose persistence

an example of nutritional adaptation

Lactose production in humans

stops in humans around the age of 5

Where is lactose intolerance high in the population?

Africa and Asia

which variants are associated with lactase persistence?

LPH (lactase phlorizin hydrolase)

what cells produce the melanin pigment?

melanocytes

how does melanin synthesis work?

within melanocytes, melanin is synthesized in organelles known as melanosomes

What are keratinocytes?

surrounding cells in the epidermis where melanosomes are transferred

what is tyrosinase?

an enzyme that is key to melanin synthesis

What is eumelanin?

brown-black pigment

What is pheomelanin?

red-yellow pigment

how do melanosomes differ in light vs dark skinned people?

light skinned people's melanosomes are small and packed in groups
dark-skinned people' melanosomes are bigger and packed as single entities

hypothesis for the evolution of dark skin near the equator?

selective factor of UV radiation

What is folate?

folate is required for adequate fetus development and reproduction and lack of it can result in fetal death

Vitamin D synthesis

necessary for proper absorption of calcium and is synthesized through action of UV radiation

Evolution of skin color

driven by a balance between protection and the need to facilitate vitamin D synthesis in opposite regions

SLC24A5 gene

member of the potassium-dependent calcium exchanger family; subject to natural selection in European populations;o A premature stop codon that causes golden zebrafish mutation

HERC2 gene

controls expression of the OCA2 gene; responsible for the blue eyes mutation

vasoconstriction

narrowing of blood vessels to reduce blood flow and heat loss

vasodilation

opening of blood vessels to increase blood flow and heat loss

Lewis Hunting Phenomenon

a physiological reaction characterized by alternating cycles of vasoconstriction and vasodilation

4 ways to lose heat

radiation, convection, conduction, evaporation

radiation

heat loss through the form of electromagnetic radiation

convection

heat flow through air molecules

conduction

heat exchange through physical contact with others/things

evaporation

heat loss through conversion of water vapour by which energy is consumed

How much heat is lost by the 4 methods?

radiation = 60%, evaporation = 22%, convection = 15%, conduction = 3%

High altitude

8-12,000 feet above the ground

Very High altitude

12-18,000 feet above the ground

Extremely High altitude

18,000+ feet above the ground

Acute Mountain Sickness

altitude higher than 2,500m have low oxygen concentration which can cause headache, dizziness, pulmonary edema and death

Bergmann's Rule

as body mass increases, the relative surface areas decreases proportionately' increased mass allows for greater heat retention/reduced heat loss

Allen's Rule

Appendages are adapted to the climate because the surface/volume area either promotes or reduces heat loss

How do Tibetans differ from Andeans at high altitude

Tibetans = lower hemoglobin levels, higher ventilation rates
Andeans = arterial oxygen saturation

How many types of albinism?

5

what does HIF stand for?

hypoxia inducing factor

What are the genes EPAS1 and EGLN1 associated with?

hemoglobin concentration

How many classifications did Linneaus come up with?

4; americanus, asiaticus, africanus, europeasus

what are linneaus' classifications based on?

biased "cultural" features made by preconceptions about these groups by eurocentric 18th century ideals

Johann Blumenbach came up with how many human types?

5; mongolian, american, caucasian, malayan, ethiopian

who coined the term "race"?

François Bernier in 1684

biological race can be defined as...

A division of a species that differs from other divisions by the frequency with which certain hereditary traits appear amongst its members

anthropometric traits are...

strongly influenced by the environment and are subject to natural selection

define race

discrete units which are used to explain variation that is mostly continuous in nature

isolation of distance

the further apart 2 populations are, the less gene flow that will happen between them

FST

something that is designed to measure the relative amount of variation explained by genetic differences in populations

FST of 1

variation between the groups, but now within the population

FST of 0

no variation between the groups, but within the population

what is the genetic variation between the population?

10-15%

Percentage of genetic variation within the population

85-95%

molecular anthropology

discipline of physical anthropology focused in the study of the genetic variation in human populations

PCR

polymerase chain reaction

SNPs

single nucleotide base substitutions and they are the most abundant markers in the genome

STRs

short tandem repeats; randomly repeated short nucleotide sequences

Microsatellites

faster rate of mutation than the other markers, highly polymorphic and are useful in forensics

Pseudoautosomal region

where recombination occurs between X and Y chromosome

Y-specific region

a place where there is no recombination

How many protein-coding genes are on the Y chromosome?

78 protein genes coding for 27 proteins

How does the Y-specific region get passed on?

Transmitted only from the paternal line and comprises more than 95% of the modern Y chromosome