human bio prac genetic drift crap

5 ways variation occurs through

mutations, random fertilization, random assortment, chiasmata, non dysjunction

species

group of living organisms capable of interbreeding, exchanging genes and producing fertile offspring

allele

different form of the same gene for a specific trait

gene pool

a total set of genes, including all the different alleles present in the population

population

a group of the same species living in the same environment at the same time

mutation

random, permanent change to an organisms DNA

mutagen

an agent that increases rate of mutations in dna

natural selection

the belief that their needs to be variation in the population, and organisms better adapted to their environment tend to survive and pass on the more advantageous traits to their offspring (not random). the organisms with less desirable traits are less likely to survive so wont live to pass on non advantageous traits

random genetic drift

sewell wright effect. the random variation in gene frequency. populations of organisms are constantly changing and adapting to their environment. drastic changes in environmental conditions can sometimes cause drastic changes to the gene pool of the population

example of random genetic drift

a man steps on a group of beetles, randomly killing most of the green ones but leaving most of the brown ones alive, resulting in fewer green beetles being produced in the popuation

mitochondrial eve

all humans in the world today are descendants of one woman who lived 20,000 years ago somewhere in eastern africa.

the human lineage can be traced on the maternal side by studying mutations in mitochondrial DNA

thousands of women probably existed, but through chance, all the other womens daughters sooner or later didnt have daughters breaking their lineages of mitochondrial dna

the founder effecr (type of genetic drift)

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

example of the founder effect

northwest venezuala has an extraordinarily high frequency of Huntingtons disease. during the 1990s, approx 150 people in the area had this condition with a high risk of passing it on to offspring.

the emergence of this disease can be traced to maria concepcion soto, who moved into the area in the 19th century. she had 10 children who remained in the area and were therefore the ‘founders’ of what is now a population of about 20,000 people with a high risk of having this disease.

bottleneck effect (type of genetic drift)

bottleneck effect happens when some catastrophe, like an earthquake or tsunami kills off most of a population at random and leaves only a handful of survivors

example of bottleneck effect

in 1775, a typhoon struck pingelap. only about 20 islanders survived the storm and the famine that followed. from this population and the geographical and cultural isolation, achromatopsia (colour blindness) increased in the pingelap population. today up to 5% have it and 30% are carriers.

migration

migration can affect the gene flow. immigrants bring alleles that are not currently in the population and so the frequency of these alleles will change

gene flow

the number and type of alleles in a gene pool

migration example with rhesus

chinese pop: rh+

european pop: rh-

trading lead to europeans introducing rh- to the chinese population

migration blood groups example

higher proportion of B allele in Asia compared to western europe, aus, nz and the americas

barriers to gene flow

barriers may prevent populations from interbreeding, resulting in different characteristics due to environmental pressures. over time, populations may differ so much that speciation may occur, resulting in the formation of a new and distinct species

geographical gene flow barriers

oceans, river, seas, lakes, moutains, deserts, ice

sociocultural gene flow barriers

economic status, educational background, social positions

genetic diseases

can change the frequency of alleles in a gene pool. alleles resulting in fatal diseases should be eliminated from a population, although some persist in certain populations

sickle cell anemia

recessive diseases, where RBC’s are cresent shaped reducing o2 carrying capacity and they stick together and block vlood vessels. black africans are most affected especially in areas where malaria is present. the benefits of being a carrier is that you have resistance to malaria