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BIO 1130 Final key terms definition.docx

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University of Ottawa
Jon Houseman

BIO 1130 Final key terms definition 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) -often caused by migrating populations, island populations etc. -ex: Quebecois in the Saguenay region à increased change of muscular dystrophy in this region because of the founder effect Frame Shift Mutation: a mutation that causes the reading frame of the mRNA to be altered, usually by one codon, which can mess up everything -produces a different, non-functional amino acid sequence in the polypeptide -caused by insertions or deletions of nucleotides -the earlier the frame shift, the more mutated the protein Gametic Isolation: prezygotic reproductive isolating mechanism -is the incompability of the sperm of one species and the egg of another species to join together -ex: giant clams/ sponges/organisms that release their egg and sperm into the water column recognize only each other and don’t end up combining with other species Gene Duplication: a segment of one chromosome is broken off and inserted into its homologue (resulting in duplication of the gene on the homologue) -the opposite of the deletion -identical genes can undergo changes and diverge into 2 different genes -occurs during unequal recombination (crossing over) that occurs between misaligned homologous chromosomes during meiosis Gene flow: the transfer of genes from one population to another through the migration of individuals, thus introducing new genes -can solve the problems of the founder effect, bottleneck effect, genetic drift etc -can also result in loss of genetic variety of the gene flow is out of the population instead of into the population -mobility affects the rate of gene flow Gene pool: the sum of all alleles at all gene loci in all individuals in a population -large gene pool = large genetic diversity, small gene pool = small genetic diversity & lower biological fitness/selection -total gene pool is important for calculating the allele frequency (*remember allele frequency is a percentage) Genetic Drift: random fluctuations in allele frequencies as a result of random change in a finite population -usually happens in smaller populations -basically a sampling error – if the population is large, the effect of chance = low -ex: 50/50 heads/tails coin tossing done 25 times vs. 5000 times Genetic Equilibrium: the time at which allele frequencies and genotype frequencies do not change from one generation to another -defined by the Hardy Weinberg Equilibrium equation -only happens if all of these conditions are met: 1) Random Mating, 2) No Natural Selection 3) No Genetic Drift (A very large population) 4) No Mutation 5) No Gene Flow Genotype frequencies: percentage of individuals in a populations that contain a particular genotype (ex: AA, Aa, aa) -Denoted by p^2, q^2, or 2pq -represented as a proportion of the total number of inidividuals Habitat Isolation: species that live in different habitats -a prezygotic isolation mechanism -basically the same thing as an ecological isolation. Haploid: -contain 1 set of chromosomes -may be gametes in diploids (egg and sperm) or an organism that already exists in a haploid state (fungi) -biologically referred to as ―n‖ Hardy-Weinberg Principle: the ―rule of thumb‖ that states when a population of diploid organisms achieves genetic equilibrium *see genetic equilibrium for the conditions under which this is true IMPORTANCE: It is important to know when things are NOT changing in order to determine if things are changing! Heterozygote Advantage: when heterozygotes have a higher relative fitness than homozygotes -due to dominating allele masking the possible harmful effects of the recessive allele -results in heterozygotes surviving more than homozygotes in the case of diseases -also known as balancing selection ex: sickle cell anemia heterozygotes in sub-saharan Africa have higher resistance to malaria Heterozygous: the state of possessing 2 alleles of a gene – can be dominant + recessive ex: Aa -if dominant + recessive, only the dominant trait will show in the phenotype -ex: a pea plant containing alleles for both yellow and green seeds, if green is dominant; they will have green seeds, but since they still contain the allele for the yellow seed it is possible for it to pass it onto the next generation Homozygous: the state of possessing 2 alleles of the same gene – ex: both alleles are recessive, or both alleles are dominant -ie identical allies for a single trait -ex: the green seeded pea plant has alleles that both code for green seeds, the yellow seeded pea plant has alleles that both code for yellow seeds -2 different homozygous individuals can breed to form heterozygotes Hybrid breakdown: -a post zygotic isolation mechanism -hybrids are capable of reproduction, but the offspring have reduced fertility or reduced viability (fitness) -the hybrids eventually die out from the population -this ensures speciation b/c the species in the long run do not mix successfully Hybrid sterility: post zygotic isolation mechanism -the offspring hybrid is sterile -meaning that it cannot produce progeny so the line of hybrids also dies out -ensures speciation ex: mules are sterile (cross between a horse and a donkey) Hybrid viability: whether or not the hybrid organism will be able to come to term -the zygote may form, but may end up being destroyed -if the hybrid is inviable, this ensures speciation because the hybrid will never exist -or the hybrid will survive, but not to a reproductive age -this is because the developmental programs of the parent organisms are incompatible Ex: goats and sheep can fertilize each other but their ova will never come to term Hybrid zone: geographical area where the hybrid offspring of 2 divergent populations are common -can occur if 2 populations undergo allopatric speciation and then regain contact after isolation -generally very narrow zones -some persist for hundreds or thousands of years Hybridization: when 2 species interbreed and produce fertile offspring -can be the interbreeding between 2 homozygous individuals that creates a heterozygote -ex: more hardy and disease resistant crops can be formed from hybridization -leads to speciation Inbreeding: a form of non random mating -genetically related individuals mate with each other -reduces heterozygosity -increases homozygosity -therefore increases the chances of offspring inheriting deleterious traits Male competition: competition between males for dominance over the females - in order to pass on their genes to the next generation -can be in 3 forms: 1) sperm competition 2) male-male combat 3) infanticide 1) sperm competition à promiscuous mating, ex: dragonfly males attaching onto females, dumping out male sperm and replacing with their own 2) male-male combat: elephant seals & dominance over a harem of females 3) infanticide – a new alpha male kills old alpha male offspring to ensure only his genes will be passed on Mechanical isolation: pre-zygotic reproductive isolation mechanism -differences between reproductive organs make it physically impossible for the sperm and egg of different species to join (this also applies to undesired species ex what type of insect will pollinate a certain flower) ex: the comet orchidà has its reproductive organs behind the petals --12 inch long tube so only a month with a 12 inch long tongue will be able to fertilize it Microevolution: small-scale genetic changes within populations -often in response to shifting environmental circumstances or change events -this type of evolution occurs only in ONE species -i.e. the frequency of alleles in a population changes -ONLY genetic changes -due to: genetic drift, gene flow, mutation, natural selection, non-random mating Migration: The predictable seasonal movement of animals from the area where they are born to a distant and initially unfamiliar destination, returning to their birth site later. -TRAVELLING to find new habitat -Trigger: climate, food availability, season of the year -ANNUAL or SEASONAL E.g. – Canadian Geese = SOUTH for Winter Missense mutation: A base-pair substitution mutation in protein-coding gene that results in a different amino acid in the encoded polypeptide than the normal one. - Single nucleotide changed - May result in the wrong codon being placed Morphospecies: - Species, distinguishable from others ONLY by morphology - E.g. – Yellow Throated Warbler vs. Yellow Rumpled Warbler Mutation: A spontaneous or heritable change in DNA -Can be beneficial increasing reproductive fitness (ex. Bacteria and antibiotic resistance) -Can be netural (different amino acid sequence but codes for same a.a’s, no change) -Can be deleterious decreasing reproductive fitness (usually removed by natural selection, ex. Hemophilia) -POINT mutations in a SINGLE nucleotide Silent: ONE nucleotide changes to corresponding pair NO CHANGE E.g. – CG to GC = SAME thing Missence: ONE nucleotide changes Codon codes for a DIFFERENT aa Protein = non-functioning E.g. – CG to TA E.g. – Sickle Cell Anemia Nonsense: PREMATURE stop codon Codon that DOES NOT specify for any amino acid E.g. UGC to UGA Frameshift: INSERTS or DELETES a set of nucleotides NOT divisible by 3, alters ENTIRE gene expression Disturbs reading frame = COMPLETELY different translation than before E.g. – the one big fly had one red eye = the one rbi gfl yha don ere dey -CHROMOSOMAL: CHANGE genetic structure Inversion: Repair is BACWARDS, USUALLY do NOT cause abnormalities, AS LONG as NO missing / extra information Paracentric – DO NOT include centromere, BOTH breaks in ONE arm of chromosome Pericentric – INCLUDE centromere, breaks in EACH arm Translocation: Rearrangment between parts of NON-HOMOLOGOUS chromosomes Change where MAJOR regions are exchanged E.g. – Leukemia genes Gene Duplication ANY duplication of a region of DNA that contains a gene Primary copy = USED Secondary copy = FREE from selective pressure NO deleterious effect Mutates FASTER than a functional single-copy gene b/c 2x! Polyploidy X > 2 sets of paired chromosomes E.g. – Plants, Goldfish Natural selection: The evolutionary process by which alleles that increase the likelihood of survival and the reproductive output of individuals that carry them become more common in subsequent generations. -FAVOURABLE traits = MORE likely to reproduce -ALLOWS organisms to adapt to environment -IF environment changes, organism MUST adapt to it to survive! -Violates Hardy-Weinburg Neutral mutation: -Spontaneous or inheritable mutation - different amino acid sequence but codes for same a.a’s, no change Non-Random Mating: -Preference of mate -Inbreeding, sexual dimorphism or sexual selection (female choice, competition) -results in less allelle variation in population Nonsense: A base-pair substitution mutation in a gene in which the base- pair change results in a change from a sense codon to a nonsense codon in the mRNA. The polypeptide translated from the mRNA is shorter than the normal polypeptide because of the mutation. -Stop codon is placed. Null hypothesis: A statement of what would be seen if the hypothesis being tested were wrong. -explains what happens if the manipulated variable doesn’t have an effect. -Made so it can be proven FALSE by observations (proof) Parapatric speciation: Speciation between populations with adjacent geographic distributions. -Evolution, like allopatric speciation without geographical speciatioin. -SUBSTANTIAL reproductive isolation b/w spatially adjacent populations have LIMITED gene exchange -population on outskirts of zones Phenotype: - Visible trait - Organism MAY possess recessive traits that are MASKED by the visible or dominant trait - Determined by genes Phylogenetic species: A group of organisms bound by unique ancestry - smallest branch at the end of a cladogram - can place fossils bacteria and archaea -branches can be neverending, subspecies, etc. (Are they species, families, orders?) Point mutation: - Mutations in a SINGLE nucleotide ->Silent ONE nucleotide changes to corresponding pair NO CHANGE E.g. – CG to GC = SAME thing ->Missence ONE nucleotide changes Codon codes for a DIFFERENT aa Protein = non-functioning E.g. – CG to TA E.g. – Sickle Cell Anemia ->Nonsense PREMATURE stop codon Codon that DOES NOT specify for any amino acid E.g. UGC to UGA ->Frameshift INSERTS or DELETES a set of nucleotides NOT divisible by 3, alters ENTIRE gene expression Disturbs reading frame = COMPLETELY different translation than before E.g. – the one big fly had one red eye = the one rbi gfl yha don ere dey Polyploidy: The condition of having one or more extra copies of the entire haploid complement of chromosomes. A second division never occurs, leaving a higher n value Fairly common Mitotic event without division Population: All individuals of a single species that live together in the same place and time. -interbreeding is more probable within the area & more probable than cross-breeding with individuals from another area -any pair of members within the population can breed together; basically means a species -populations are studied to understand microevolution Population genetics: The branch of science that studies the prevalence and variation in genes among populations of individuals. -the study of allele frequency distribution and change under the evolutionary processes of: genetic drift. Natural selection, mutation, and gene flow -attempts to explain the effects of speciation/adaptation Postzygotic isolation mechanisms: A reproductive isolating mechanism that acts after zygote formation. Hybrid inviability, hybrid sterility and hybrid breakdown-maintains speciation Prezygotic isolation mechanisms: A reproductive isolating mechanism that acts prior to the production of a zygote, or fertilized egg. Ecological/habitat, temporal, behavioural, mechanical and gametic- IMPORTANCE: maintains speciation Recessive allele: An allele that is masked by a dominant allele -can be responsible for carrying states of disease -represented by lower case letters -can be present in heterozygotes, but are masked, but can be expressed in future generations Reinforcement: The enhancement of reproductive isolation that had begun to develop while populations were geographically separated. Hybrif invirability reinforces variation.- -also called the ―Wallace Effect‖ -caused by natural selection -i.e. reinforces speciation Reproductive Isolation: A biological characteristic that prevents the gene pools of two species from mixing. Ring Species: A species with a geographic distribution that forms a ring around an uninhabitable terrain. Gene flow between distant population occurs only through intermediary populations Example: Salamanders of California, rattle snake Still capable of interbreeding on border between zones (transition zone) These become different sub species, each zone is a different sub species, but the all under the same species offsprings produced by two different sub-species are usually not capable of successfully surviving - hybrid Sexual dimorphism: Differences in the size or appearance of males and females. Based on sexual selection Female produces large nutrient rich gametes Males objective is to create lots of sperm Sexual selection: a form of natural selection established by male competition for access to females -also the females’ choice for males -concept introduced by Charles Darwin -a significant element of the theory of natural selection -consists of sexual dimorphism à based on the observation that animals develop structures that are more desirable vs. survival traits -the main driving force is reproductive success Sickle Cell Anemia: RBC with a sickle shape Have defective form of Hb In Africa, malaria does not spread as quickly in sickle-celled individuals, often kills parasites. Silent mutation: A base-pair substitution mutation in a protein-coding gene that does not alter the amino acid specified by the gene. The same codon is placed, despite the changed nucleotide. Same amino acid made A type of point mutation Speciation: Species formation 3 types: Allopatric (isolation) Parapatric (barrier spanning) Sympatric (contiguous/touching populations) Ex. Rape seed oil—toxic seed removed creating the subspecies, Canola Oil. Sperm competition: physical competition between the sperm of two separate males to fertilize the eggs of a lone female. The number of females it inseminates often determines a male’s fitness. Ex. copulatory wheel of dragonflies Stabilizing selection: A type of natural selection in which individuals expressing intermediate phenotypes have the highest relative fitness level. Average/mean stereotype is favoured Ex. Not too long or too short tail length are liked by female birds Subspecies: Taxonomic subdivision of species Local variants of a species Sympatric speciation: Speciation that occurs without the geographic isolation of populations, based on environment Sympatric = Species that occupy the same space at the same time Evolves between distinct subgroups that arise within one population Ex. Hybrid offspring has a lower fitness and generations eventually die off Temporal isolation: A prezygotic reproductive isolating mechanism Species live in the same habitat (and sometimes could interbreed) Breed at different times of day or different times of year Tetrapolid: (4n) offspring, each with four complete chromosome sets. Autopolyploidy occurs through an error in either mitosis or meiosis, so that gametes spontaneously receive the same number of chromosomes as a somatic cell Plant can survive as a tetrapolid Tripolid: Reproduce either by self-pollination or by breeding with other tetraploid individuals. Cannot produce fertile offspring by hybridizing with its diploid parents. Fusion of a diploid gamete with a normal haploid gamete produces a triploid (3n) offspring, which is usually sterile because the
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