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UNI / Biology / BIOL 1014 / What is the group of organisms that can breed and produce fertile offs

What is the group of organisms that can breed and produce fertile offs

What is the group of organisms that can breed and produce fertile offs

Description

School: University of Northern Iowa
Department: Biology
Course: Life: Continuity and Change
Professor: Kurt pontasch
Term: Spring 2016
Tags: population, Genetics, demes, genotype, and phenotype
Cost: 25
Name: Population Genetics
Description: How genes are expressed and passed through a population
Uploaded: 04/10/2016
3 Pages 159 Views 2 Unlocks
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Population Genetics


What is the group of organisms that can breed and produce fertile offspring?



∙ 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  


What is the study of why differences in gene frequencies occur in a population?



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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


What is the definition of a gene pool?



 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  If you want to learn more check out How can we determine that jean dubuffet did not use a wash in corps de dame?

o Gene Frequencies have nothing to do with dominant and recessive  genes If you want to learn more check out What is the difference between matrix operation and component operation?

 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  We also discuss several other topics like What does central dogma do?
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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  Don't forget about the age old question of What is stated in bowlby and ainsworth attachment theory?

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

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