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Midterm

mid-term definitions.doc

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Department
Biology
Course Code
BIO1130
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All

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Allele – one of two or more versions of a gene
-different alleles can result in different observable phenotypic traits
-each trait has 2 alleles
-one allele/chromosome for diploid organisms
-genetic variations in alleles can result in differences, also can be unnoticeable
Allele frequencies: the abundance of one allele relative to others at the same gene locus in
individuals of a population to describe genetic diversity
-can be calculated by dividing the number of alleles for a certain trait/the total number of
individuals in the population
-usually expressed as proportion or a percentage
-denoted as “p” or q”
Allopatric speciation: a reproductive isolating mechanism that results from geographical
separation between two populations
-a prezygotic mechanism
- Populations evolve independently and diverge into different species
-caused by glaciers, continental shifts, etc
Allopolyploidy: having 2 or more complete sets of chromosomes from different parent species
-only plants are capable of this, not animals
-results in a fertile hybrid
-can be created from previously sterile species (ex bread wheat)
Autopolyploidy: having 2 or more complete sets of chromosomes from the same parent species
-again only possible in plants through self fertilization
-arise from a failure in the meiotic process
-often resemble parents, except grow more slowly and flower later
Behavioural Isolation: -a prezygotic isolation process
-2 species do not mate because of differences in courtship behaviour
-also known as ethological isolation
-ex: songs of bullfrogs, fireflies example used in class (sequences of bursts of light vary for
different speices of fireflies within males and females)
Beneficial mutation: a mutation that proves to be beneficial for the individual; ex increases
fitness
-can help withstand diseases
-ex: those who carry 1 allele of the sickle cell anemia disease are more resistant to malaria in
areas of sub-saharan Africa
Biological Species: the concept of a species based on the ability of populations to interbreed and
produce fertile offspring
-basically a reproductively isolated gene pool
-no universal agreement to what it is
-problems with the concept: how do you define a fossil species?
how do you define populations that reproduce asexually? (ex archaea and bacteria)
Bottleneck Effect: Type of genetic drift that occurs when an event, such as drought, or intensive
selection pressure causes a population to significantly dwindle in size
-the survivors reproduce, but there is limited genetic variability
-Note: Bottle-neck different from Founder Effect. In Bottle-neck there is no movement of
population whereas in Founder Effect there is.
ex: elephant seals, tomatoe (taste)
Chromosomal Inversion: a chromosome rearrangement in which a segment of a chromosome is
reversed end to end
-occurs when a single chromosome undergoes breakage with itself
-occurs in the arm of the chromosome, does not involve the centromere
-do not usually cause abnormalities as long as the re-arrangement is balanced with no extra
genetic info
--however increased production of abnormal chromatids result in heterozygous individuals à
lowered fertility due to production of unbalanced gametes
Chromosomal translocation: rearrangement of parts between nonhomologous chromosomes
-ie: a piece of one chromosome breaks off and sticks to another chromosome
-2 types: reciprocal & Robersonian
-Reciprocal: 2 different chromosomes exchange places
-Robertsonian: a whole chromosome attaches to another
-Ex: results in Down Syndrome (Trisomy 21; the 21st chromosome has 3 chromosomes instead
of 2)
Crossing over: recombination in meiosis when chromatids exchange segments
-IMPORTANCE: genetic variability
-occurs during prophase I in a process known as synapsis
-matching regions on matching chromosomes break and then reconnect to the other chromosome
Deleterious mutation: a genetic mutation that proves to be harmful for the organism
-cause errors in protein sequence making a partially functional of completely non-functional
protein
-when the protein plays a critical role in organism functioning, it can be crucial à i.e. a medical
condition can result
-ex: genetic disorders
-are often repaired by the “double checking system of DNA”
Diploid: an organism that contains 2 sets of chromosomes
-grow through cell division (mitosis) and reproduce by meiosis (production of gametes)
-ex: animals
Directional selection: type of selection in which individuals at one extreme of the phenotypic
expression have a higher fitness
-the frequency of the phenotype becomes higher & is eventually fixed
-occurs most often naturally under environmental changes.
-ex: breeding for the most desirable trait; i.e. the smallest possible Chihuahua
Disruptive selection: type of selection in which extreme phenotypes have higher fitness than
intermediate phenotypes
-results in speciation
-driving force behind sympatric speciation
-ex: different species of birds with very long and very small beaks
Dominant allele: an allele that expresses its phenotypic effect even when heterozygous with a
recessive allele
-important for masking recessive phenotypes & preserving recessive alleles in a population
-ex: if the pea plant is dominant for green seeds and recessive for yellow seeds, and the individual
is heterozygous then the green seed phenotype will show
Ecological isolation: a prezygotic isolation mechanism
-species that live in the same geographic region occupy different habitats
-thus making it difficult for them to mate with one another
-ex: a marsh species vs. a woodland species
Ecological species: the species concept where a group of organisms is adapted to a particular set
of resources (niche) in the environment
-the ecological & evolutionary processes that control how resources are divided up produce these
clusters
-good for ecological foodwebs
-PROBLEM: the observations are just as subjective as the morphospecies concept
Female choice: -the females having control over whether reproduction occurs based on their
choices of the males
-due to the fact that females produce the eggs, and want the best possible sperm to fertilize her
eggs
-results in elaborate courtship and extravagant visual appearance on the part of the males in order
to attract females
Fitness: the ability to survive and reproduce à stronger fitness means that you are more likely to
survive and reproduce and vice versa for a weaker fitness
-alleles with higher fitness become more common; produces natural selection
-manifested through the phenotype ; affected by developmental environment as well as by genes
Fixation: the state in which where only one allele remains of a particular gene
-the probability of fixation is higher in small populations due to genetic drift
-in fixation, if one allele is fixed, the other coordinating allele is lost
-otherwise known as the domination of a particular allele
-IMPORTANCE: it’s BAD – we’ve lost genetic variation
Founder Effect: a phenomenon in which a colonizing population has only a fraction of the
genetic variety of the parent population
-a reduced gene pool (loss of genetic variation)

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Description
Alleleone of two or more versions of a genedifferent alleles can result in different observable phenotypic traitseach trait has 2 allelesone allelechromosome for diploid organismsgenetic variations in alleles can result in differences also can be unnoticeable Allele frequencies the abundance of one allele relative to others at the same gene locus in individuals of a population to describe genetic diversitycan be calculated by dividing the number of alleles for a certain traitthe total number of individuals in the populationusually expressed as proportion or a percentagedenoted as p or q Allopatric speciation a reproductive isolating mechanism that results from geographical separation between two populationsa prezygotic mechanism Populations evolve independently and diverge into different speciescaused by glaciers continental shifts etc Allopolyploidy having 2 or more complete sets of chromosomes from different parent speciesonly plants are capable of this not animalsresults in a fertile hybridcan be created from previously sterile species ex bread wheat Autopolyploidy having 2 or more complete sets of chromosomes from the same parent speciesagain only possible in plants through self fertilizationarise from a failure in the meiotic processoften resemble parents except grow more slowly and flower later Behavioural Isolation a prezygotic isolation process2 species do not mate because of differences in courtship behaviouralso known as ethological isolationex songs of bullfrogs fireflies example used in class sequences of bursts of light vary for different speices of fireflies within males and females Beneficial mutation a mutation that proves to be beneficial for the individual ex increases fitnesscan help withstand diseasesex those who carry 1 allele of the sickle cell anemia disease are more resistant to malaria in areas of subsaharan Africa Biological Species the concept of a species based on the ability of populations to interbreed and produce fertile offspringbasically a reproductively isolated gene poolno universal agreement to what it isproblems with the concept how do you define a fossil specieshow do you define populations that reproduce asexually ex archaea and bacteria Bottleneck Effect Type of genetic drift that occurs when an event such as drought or intensive selection pressure causes a population to significantly dwindle in sizethe survivors reproduce but there is limited genetic variabilityNote Bottleneck different from Founder Effect In Bottleneck there is no movement of population whereas in Founder Effect there isex elephant seals tomatoe taste Chromosomal Inversion a chromosome rearrangement in which a segment of a chromosome is reversed end to endoccurs when a single chromosome undergoes breakage with itselfoccurs in the arm of the chromosome does not involve the centromeredo not usually cause abnormalities as long as the rearrangement is balanced with no extra genetic infohowever increased production of abnormal chromatids result in heterozygous individualslowered fertility due to production of unbalanced gametesChromosomal translocation rearrangement of parts between nonhomologous chromosomesie a piece of one chromosome breaks off and sticks to another chromosome2 types reciprocalRobersonianReciprocal 2 different chromosomes exchange placesRobertsonian a whole chromosome attaches to anotherEx results in Down Syndrome Trisomy 21 the 21st chromosome has 3 chromosomes instead of 2Crossing over recombination in meiosis when chromatids exchange segmentsIMPORTANCE genetic variabilityoccurs during prophase I in a process known as synapsismatching regions on matching chromosomes break and then reconnect to the other chromosome Deleterious mutation a genetic mutation that proves to be harmful for the organismcause errors in protein sequence making a partially functional of completely nonfunctional proteinwhen the protein plays a critical role in organism functioning it can be crucialie a medical condition can resultex genetic disordersare often repaired by the double checking system of DNADiploid an organism that contains 2 sets of chromosomesgrow through cell division mitosis and reproduce by meiosis production of gametesex animalsDirectional selection type of selection in which individuals at one extreme of the phenotypic expression have a higher fitnessthe frequency of the phenotype becomes higheris eventually fixedoccurs most often naturally under environmental changesex breeding for the most desirable trait ie the smallest possible ChihuahuaDisruptive selection type of selection in which extreme phenotypes have higher fitness than
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