Population Genetics BIOL 1014
Popular in Life: Continuity and Change
Popular in Biology
verified elite notetaker
This 3 page Class Notes was uploaded by Crystal Florman on Saturday April 9, 2016. The Class Notes belongs to BIOL 1014 at University of Northern Iowa taught by Dr. Kurt Pontasch in Spring 2016. Since its upload, it has received 106 views. For similar materials see Life: Continuity and Change in Biology at University of Northern Iowa.
Reviews for Population Genetics
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 04/09/16
Population Genetics Introduction o Most organisms don’t exist as isolated individuals instead they form a population o Population- organisms of a given species found within the same geographic region o Species- group of organisms that have the ability to breed and produce fertile offspring- same number and kinds of chromosomes o Population Genetics- the study of why differences in gene frequencies occur in a population Ex: frequency of gene type, skin color, hair color, etc.- varies among human populations- can be more than 2 alleles for a characteristics among a population Gene Pool o Consists of all the genes of all the organisms that are in the population o Each individual’s genotype is a subset of that gene pool o As a result of several factors such as: geographic barriers or resource availability the individuals within the population are found in clusters These clusters breed with each other more often than with individuals outside the cluster o Because of this breeding within clusters- clusters of genes called demes will occur within the local population If there is little exchange of genes between demes the demes will differ phenotypically Subspecies- still the same species- called breeds in domestic animals Gene Frequency o Usually stated mathematically in terms how often a particular gene turns up in the gametes of a particular population o Possible for 2 demes to have the same gene pool but different gene frequencies Ex: all humans constitute one large gene pool, but different ethnic groups have different gene frequencies o Once gene frequencies are established within a deme- the frequencies don’t change much unless there is a reason o Gene Frequencies have nothing to do with dominant and recessive genes Recessive genes are often more frequent then dominant within a given deme o What determines the frequency of genes within demes and population is the value of the gene in helping the organism survive and produce offspring****** Why Demes Exist o Although no to individuals in a deme are exactly alike the members of a deme resemble each other more closely than they do members of other demes- why? More closely related genetically because they breed with each other more often than members of other demes Exposed to the more similar environmental influences- selection pressures o Demes are not clear cut units of population o Demes exist because of Geographic barriers Environmental differenced Ex: temperatures change with altitude and latitude o New demes form when organisms emigrate and form a new population o A population in which there is little genetic variability often displays a high frequency of undesirable characteristics Ex: hemophilia in the royal family in Europe In addition such a small gene pool can result in a lower adaptability to environment changes- may lead to extinction On the other hand- a large gene pool is more likely to contain genes that will help some of the organisms to survive environmental changes How variability is Generated o 4 main mechanisms that introduce variability into a gene pool Mutations All alleles have originated as a result of mutations Mutations that code for bad characteristics result in alleles that are uncommon in the population- less fit- most mutations are bad Mutations that code for good characteristics result in alleles that become more common in the population- changes gene frequency Sexual Reproduction Tends to result in new genotypes but not additions to the gene pool of population o However when a new genotype is produced that is superior to others in the gene pool it will be more successful in producing offspring- change gene frequency Migration When an individual migrates from one deme to another- genes can be added to the new population and subtracted from the old- changes in the gene pool Size of Population The smaller the population the less variability it can contain Determines the effectiveness of the things above ingenerating variety in the gene pool Domesticated Plants and Animals o Humans often work with plants and animals to artificially construct gene combinations that are desirable o Many plants and now animals can be reproduced asexually to form individuals with exactly the same genotype- clones o We can also bring together desired characteristics in plants and animals by selective breeding o Selective breeding is usually accomplished by: Finding wild demes that are homozygous for the desired trait Breed small groups that are homozygous dominant for desired traits o By breeding 2 organisms that are homozygous for different desired traits we can produce offspring with both traits These offspring are heterozygous for those traits- Hybrids Hybrids wont breed true for these desired traits among themselves- must be managed to prevent the formation of unacceptable gene combinations o When we use selective breeding to increase the frequency of desirable traits other genes are lost from the gene pool Today most of our crops are planted as vast fields of similar genotypes- monoculture o Small gene pool within a monoculture can result in: The need for herbicides and insecticides to maintain the proper conditions for plant growth Greater potential for a new disease or a change in environmental conditions to wipe out entire population
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'