Honor Biology 1 Exam 4 Study Guide PDF

EXAM 4/FINAL Meiosis Meiosis vs Mitosis CHAPTER 13 ❖ Genotype vs phenotype Genotype: genetic makeup of a cell/organism Genetic sequence Phenotype: visible trait Appearance, behavior, physiology ❖ Polymorph...

EXAM 4/FINAL Meiosis Meiosis vs Mitosis CHAPTER 13 ❖ Genotype vs phenotype Genotype: genetic makeup of a cell/organism Genetic sequence Phenotype: visible trait Appearance, behavior, physiology ❖ Polymorphism Polymorphism: mutation that persists through time and becomes common in the population Single nucleotide polymorphism (SNP) A mutation that changes one nucleotide in a population ❖ Explain how phenotypes can be altered by mutations in genes If there is a mutation in the gene it can cause a downstream affect that can change/affect the subsequent mRNA, amino acids, and polypeptide protein chains which can change the resulting phenotype ❖ Describe the different types of mutations and scale at which they are found Large scale mutations Mutations of large parts of a chromosome or the entire chromosome. Deletion, duplication, inversion, translocation, reciprocal translocation Small scale mutations Mutations within one or a few nucleotides in a chromosome. Point mutations [substitution, frameshift (insertion/deletion)] ❖ Types of point mutations Substitution: one nucleotide is substituted for another Nonsense substitution mutation Nucleotide substitution causes a codon to be changed to a stop codon causing premature termination of a protein Silent (synonymous) substitution mutation Nucleotide change has no effect on the amino acid sequence (coding wobble) Missense (nonsynonymous) substitution mutation Nucleotide change changes the amino acid that is added to the polypeptide chain. Change in amino acid may or may not affect the functionality of the protein.  Frameshift: insertion of 1 or 2 nucleotide base insertions or deletions Insertion 1 or 2 nucleotide base insertions Deletion 1 or 2 nucleotide base deletions ❖ Explain how a frameshift mutation has its consequences Frameshift mutations change the reading frame of the codons on the DNA sequence. The entire gene sequence following the frameshift mutation will be incorrectly read resulting in a different code for amino acids therefore affecting the resulting polypeptide chain and proteins. Mutation could result in a premature stop codon or a nonfunctional protein. The earlier in the sequence the mutation occurs then the more detrimental and severe the consequences will be. ❖ Type of chromosomal rearrangement (recognize based on a diagram)  Duplication Segment of chromosomal DNA is repeated during DNA replication which increases gene dosage for specific genes Consequence: gene dosage imbalance Inversion DNA segment of a chromosome is reversed with respect to gene order Regulatory/Control elements surrounding the inverted region will change Consequence: gene disruption (disrupts genes at break point and changes the regulatory elements of the genes inverted) Deletion Segment of a chromosome is removed which also removes the genes in that portion of the chromosome Consequence: gene loss Translocation DNA segment from one chromosome is swapped to another chromosome (that is nonhomologous) Reciprocal Translocation DNA segment of one chromosome is swapped with the DNA segment from another (that is nonhomologous) ❖ Synonymous vs nonsynonymous point mutations (within substitution point mutations) Nonsynonymous point mutations Missense substitution mutations are nonsynonymous point mutations because they change amino acid that is coded for by the change in the nucleotide in a codon in a larger DNA sequence. Nonsynonymous point mutations affect the amino acid sequence in a protein. Synonymous point mutations Synonymous means having the same or nearly the same meaning Silent substitution mutations are synonymous point mutations because they do not change the amino acid that the codon codes for so the correct amino acid is still added to the polypeptide chain. Synonymous point mutations do not affect the amino acid sequence in a protein and it is as it should be. ❖ How does a substitution differ from frameshifts (insertions or deletions)? Substitution does not change the number of nucleotides in a sequence. A substitution is where one nucleotide in the sequence will be switched with another one so that a different nucleotide is present in the sequence and the total number of nucleotides in a sequence remains the same. Insertions and deletions increase or decrease the number of nucleotides in a sequence. ❖ Describe different causes of mutation Mutagen Chemical or condition that produces mutations by breaking DNA or damaging bases in gamete or somatic cells Physical mutagens: UV light, X rays Chemical mutagens: cigarette smoke, chemical agents that affect DNA structure or replication processes in a cell  Germline mutation Mutations that occur in gametes which are then passed on to the next generation Somatic mutation Mutations that occur in body cells so they are not heritable and only affect the individual that was exposed to what caused the mutation in the gene De novo mutation A mutation that occurs in an individual but it is not present in their parent ❖ Describe how polyglutamine expansion is associated with Huntington’s disease Huntington's disease Neurological disorder caused by a mutation in a HTT gene (encodes a large protein) which is highly expressed in the brain Polyglutamine presence in the gene Nonmutant gene: region of 6-35 consecutive glutamine (Q) amino acids Mutant gene: region of 36-250 consecutive glutamine (Q) amino acids Susceptible to Huntington’s disease Atrophy of cerebral tissue and basal ganglia (motor control) Enlarged ventricles Amino acid threshold Huntington’s disease has a threshold of 35 polyglutamine (Q) amino acids (this number is the difference between normal and Huntington’s) Fate (over the threshold of 35 amino acids) The number of polyglutamine (Q) repeats can determine the decade of death for an individual with Huntington’s disease The more polyglutamine (Q) repeats you have the shorter you will live The less polyglutamine (Q) repeats you have the longer you will live (still with Huntington’s disease) ❖ Deletion at the nucleotide level vs. chromosomal level Deletion at the nucleotide level Are small scale point mutations (frameshift) that alter the codon reading frame for what amino acids to add to the polypeptide chain. The earlier in the sequence the deletion mutation occurs, the greater the downstream effects Deletion at the chromosomal level  Are large scale deletion mutations that remove a physical segment of a chromosome is removed along with any genes or regulatory elements contained within the deleted portion of the chromosome ❖ Understand what is meant by copy-number variation Copy-number variation A structural variation in the number of copies of a specific DNA sequence in an individual’s genome Causes: (chromosomal rearrangements) deletions, duplications, or inversion of a DNA segment which results in a different number of copies of a DNA sequence on a chromosome Copy-number variants contribute to evolutionary differences, the larger the changes the more genetic variation ❖ G.W.A.S. GWAS = genome wide association study DNA sequencing based survey of the entire genome for genetic variation (typically SNP), occurs more frequently in people with disease(trait being assessed) than in a control(people without the disease/trait) person Tracks differences in individuals Variations are helpful for studying human evolution ❖ Consequences of DNA repair mechanisms failing The consequences of DNA repair mechanisms failing include mutations in the DNA which can lead to cancer or disease Mutation examples: small scale point mutations (substitutions and frameshifts) and large scale chromosomal mutations (deletions, substitutions, inversions, translocation, and reciprocal translocations) ❖ Define the chromosomal makeup of individuals with down syndrome. Trisomy 21 (aka down syndrome) People with down syndrome have 3 copies of chromosome 21 Mutation can be due to nondisjunction in sperm or egg, risk for having a child with down syndrome increases with age Viable trisomy means that people can live with this disorder Chapter 13 Vocabulary: Genotype Phenotype Polymorphism Mutant Single-nucleotide polymorphism (SNP) Point mutation  Cyclins Cyclin-dependent kinase Substitution Frameshift mutation Deletion Insertion Synonymous mutation Non-synonymous mutation Mutagen Germline mutation Somatic mutation CRISPR-Cas9 editing Huntington’s disease Duplication (chromosomal) Synteny Syntenic regions Deletion (chromosomal) Translocation Reciprocal Translocation Inversion Divergence CHAPTER 14 Chapter 14 Section 1: Describe the processes that occur during meiotic cell division. ❖ Roles meiosis and fertilization in increasing genetic diversity. Meiosis contributing to genetic diversity Crossing over (recombination) Physical exchange (recombination) of genetic material between nonsister chromatids in a homologous chromosome pair ◆ Takes DNA from 2 parents and combines it into 1 recombinant chromosome ◆ Chiasmata: location where two chromosomes come into contact to perform crossing over Chiasmata helps to hold the homologous chromosomes together at the synaptonemal (zipper like structure) Errors in chiasmata formation or during crossing over can lead to genetic disorders (aneuploidy) Independent assortment  Homologous chromosomes randomly line up during Metaphase 1 independently of each other ◆ Since homologs line up randomly and independently of each other, every cell will look different from each other which increases genetic variation even farther. The number of possible chromosome combination comes from the independent assortment of gamete cells ◆ 2n (where n is the number of chromosomes in a haploid cell) ◆ 223 possible alternative chromosomal arrangements for human chromosomes Fertilization contributing to genetic diversity Any sperm can fuse with any egg. The fusion of 2 gamete cells produces a zygote (70 trillion diploid combinations). Each zygote has a unique genetic identity Huge source of variability for natural selection to pick which will survive and adapt. ❖ Determine the effect of meiosis on chromosome number. Meiosis halves the number of chromosomes in a cell through two consecutive rounds of rounds of meiosis cell division. The cells must only contain half the number of chromosomes so when they perform sexual reproduction they end up with half from each parent to create one complete set of chromosomes. ❖ Describe the transition of ploidy that occurs during fertilization. ❖ Predict the effects on chromosome number in each stage of meiosis. ❖ Events that occur in meiosis I vs mitosis Differences Final products Mitosis: 2 identical diploid(2n) daughter cells (somatic cells) Meiosis one: 2 genetically unique haploid(n) daughter cells Meiosis 1 is the first step of sexual reproduction while mitosis is asexual reproduction Prophase Meiosis 1 ◆ Homologous chromosomes pair up so you have 4 chromatids together (tetrad, bivalent) ◆ Crossing over Anaphase Mitosis: sister chromatids are pulled apart Meiosis 1: homologous chromosomes are pulled apart Similarities Interphase occurs before both meiosis 1 and mitosis ❖ Events that occur in meiosis II vs mitosis Differences  No interphase(no DNA synthesis) occurs before meiosis 2 Final products Mitosis: 2 identical diploid(2n) daughter cells (somatic cells) Meiosis two: 4 genetically unique haploid(n) daughter cells (gametes) Similarities No crossing over (crossing over only occurs during meiosis 1) ❖ Provide an argument supporting the hypothesis that meiosis evolved from mitosis. Meiosis evolved from mitosis based on the similarities in the cellular processes that occur in the various steps of each form of cell division Both share key proteins/enzymes, perform cytokinesis, and cellular mechanisms (chromosome condensation, spindle formation, chromatid segregation) Meiosis likely modified mitosis by adding additional steps to the existing process ❖ Differences in the division of cytoplasm during meiosis to the production of eggs and sperm Sperm and egg gamete cells have different functional needs so there processes for meiotic cytokinesis are slightly different to adapt to their specific needs Oogenesis - egg cell Unequal cytoplasmic division ◆ The mature egg(oocyte) needs to be large in order to store nutrients. So from the complete process of meiosis you get one mature egg (oocyte) and 3 small polar bodies(typically degenerate) Spermatogenesis - sperm cell Equal cytoplasmic division ◆ Sperm do not require large amounts of cytoplasm to deliver genetic material to the egg. The smaller amount of cytoplasm allows for enhanced mobility in order to reach the egg for fertilization Chapter 14 Section 2: ❖ Describe the effect of the failure of chromosomes to pair or separate properly during mitosis or meiosis. Nondisjunction Failure or mistake that occurs in meiosis 1 or 2 that causes the chromosomes to not separate properly The specific effects of nondisjunction depend on whether it occurs during meiosis 1 or 2 Leads to aneuploidy circumstances (genetic consequences in offspring)  ❖ Predict the effects of nondisjunction during meiosis on chromosome number in gametes. Nondisjunction occuring in meiosis 1 Homologous chromosome fail to separate during anaphase 1 so one gamete has an extra chromosome and the other gamete is missing a chromosome Nondisjunction occurring in meiosis 2 Sister chromatids fail to separate during anaphase 2 so one gamete has an extra chromosome, another gamete is missing a chromosome, and two gametes contain the normal number of chromosomes ❖ Describe the effects of missing or extra sex chromosomes Missing or extra sex chromosomes can lead to certain traits or genetic conditions Klinefelter syndrome Mutation: XXY (extra X chromosome) Effect: male sex organs but some female development, mental retardation Turner syndrome Mutation: X0 ◆ Only viable monosomy (condition where only one chromosome in a pair is present) in human Effect: sterile female Normal female (but a different number of barr bodies) Mutation: XXX ◆ 2 barr bodies instead of one (normal females are XX) Effect: no effect Normal male (but tall) Mutation: XYY (extra Y chromosome) Effect: tall but otherwise normal male Chapter 14 Section 3: ❖ Mendel’s experimental conclusions 1. There are 2 alleles for each trait (2 versions of each trait) 2. Hereditary factors do not blend 3. When gametes are formed, factors separate so each gamete only has 1 allele 4. Law of segregation: members of a pair of genes separate/segregate from each other during gamete formation ❖ Describe how the concept of dominance explains why crosses of two true-breeding(homozygous dominant and homozygous recessive) plants displaying contrasting varieties of a single trait produce offspring with only one of the two characteristics. In a cross displaying complete dominance, the dominant alleles will fully cover up the recessive allele so the homozygous dominant and heterozygous genotypes will produce the same phenotype Chapter 14 Section 4: ❖ Explain how the F1 progeny with a heterozygous genotype could produce a 3:1 phenotypic ratio among the F2 offspring. This is an example of complete dominance because the homozygous dominant and heterozygous genotypes will produce the same phenotype among the F2 offspring. ❖ Compare segregation of alleles to the separation of homologous chromosomes during anaphase I of meiosis. ❖ Incomplete dominance A heterozygous genotype will produce a phenotype that is a blending/intermediate of both alleles Example: snapdragon flowers ❖ Codominance Both alleles are expressed in the phenotype for a heterozygous genotype Example: blood with an A and a B allele will have an AB phenotype Chapter 14 Section 5: ❖ Why are alleles for two different traits inherited independently of each other? Mendel’s law of independent assortment (basis of chromosome behavior during meiosis) Definition: alleles for 2 different traits are sorted into gametes independently of each other Only occur when genes are on separate chromosomes (not on the same physical chromosome) ❖ Analyze cases of gene interaction that modify the expected ratios in crosses Epistasis When expression of one gene is modified(masked, inhibited, suppressed) by the expression of another gene Polygenic inheritance Polygenic inheritance is where multiple genes affect one trait The combination of alleles results in a blended phenotype with complex traits Example: skin pigment, hair Pleiotropy  Pleiotropy occurs when one gene at a locus may affect more than one trait (one thing/gene causing multiple effects) Example: sickle cell anemia ◆ Effects hemoglobin, blood cell shape, and traits like fertility and susceptibility to malaria ❖ Know how to determine the possible gamete produced by a parent in a monohybrid or dihybrid cross Determine genotype(s) and phenotype(s) of offspring Understand monohybrid, dihybrid, incomplete dominance, multi-allele, and codominance genetic crosses. Chapter 14 Section 6: ❖ Symbols that are conventionally used in depicting human pedigrees Males are represented as squares  Females are represented a circles FIlled in circle or square represents an affected individual with the specific disease/trait being analyzed ❖ Interpret data from human pedigrees to determine whether traits follow dominant or recessive patterns of inheritance. Characteristics of dominant inheritance patterns Does not skip generations Characteristics of recessive inheritance patterns Can skip one or more generations ❖ Explain how individuals have only two alleles of each gene, yet there can be many alleles of a particular gene in the population as a whole. An individual will get one allele from each parent (one allele from the egg gamete and one allele from the sperm gamete) to give the individual 2 alleles. Chapter 14 Vocabulary: Heredity Inherited variation Gene Allele Locus (plural is loci) Homologous chromosomes Sexual reproduction Gamete Gametogenesis Barr bodies X inactivation Dosage compensation Gene dosage Meiotic cell division Law of Segregation Law of Independent Assortment Meiosis I Meiosis II Prophase I Bivalent Synaptonemal complex Non-sister chromatid Chiasma (plural, chiasmata) Prometaphase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II  Anaphase II Telophase II Zygote Nondisjunction Recombination Recombinant chromosome Random Fertilization Down syndrome (trisomy 21) Viable trisomy Hybridization Hybrid True breeding P1 generation F1 generation Monohybrid cross Alleles Dominant Recessive Homozygous Heterozygous F2 generation Gametes Law of segregation Law of independent assortment Punnett square Test cross Incomplete dominance Codominance Pleiotropy Polygenic inheritance Epistasis Epigenetics Pedigree Siblings CHAPTER 19 Chapter 19 Section 1: ❖ Discuss the criteria to determine if viruses are alive or not 1. Do they contain genetic material? a. Yes, viruses contain DNA or RNA 2. Do they evolve? a. Yes viruses can evolve 3. Do they have cellular structure?  a. No, viruses are not made of cells. Viruses are a capsid (protein coat) that encloses genetic material 4. Do they have a metabolism of their own? a. No, viruses rely on the host cell for energy and metabolic processes 5. Can they reproduce? a. No, viruses only “reproduce” when they host cell that they have infected reproduces 6. Can they respond to stimuli? a. No, viruses do not respond until they infect a host cell ❖ Range of variation in the structure of a virus Shape: circular, helical, polyhedral, or the most complex is helical and polyhedral Enveloped viruses: some viruses are surrounded by an envelope made using the plasma membrane of the host cell The envelope helps the virus camouflage and survive by using the membrane from the host cell to better blend in ❖ Variation in host range of viruses The diverse ability of different viruses to affect a range of host species Different viruses have different limitations on what can become a host cell If a virus has a narrow host range it has less things it can affect ❖ Describe how self-assembly of viral proteins functions in the production of viral particles Viral proteins are spontaneous in terms of self assemble for production Facilitates the spread of the virus ❖ Describe how viral mutation rates and impact viral evolution Chapter 19 Section 2: Viral reproductive cycles ❖ Lytic vs lysogenic pathways of bacteriophage Lytic Pathway 1. Attachment - to host cell 2. Penetration 3. Synthesis - of viral genome and proteins 4. Spontaneous self assemble 5. Release - lysing of the cell Lysogenic Pathway 1. Attachment - to host cell 2. Penetration (or endocytosis with an enveloped virus) a. Enveloped virus: DNA from the phage will be taken in at the membrane surface and then transported to the nucleus where the DNA will be integrated into the host cell’s genome 3. Viral DNA integration a. Remains dormant/latent  b. Now becomes called a provirus(name for a mammalian cell) or a prophage(name for a bacterial cell) 4. Synthesis - only viral DNA replicates with the host cell’s DNA (transmitted by the cell cycle) ❖ Prophage A prophage is a what you call the virus after the bacteriophage genome has been integrated into the genome of the host cell ❖ Explain the difference between temperate and virulent viruses Temperate virus Goes through the lysogenic cycle but can go through a lytic cycle too if triggered Virus genes remain dormant until integrated into the host genome Virulent virus Worse type Goes through the lytic cycle which causes the cell to lyse Takes over the host cell and destroys it ❖ Pathogenicity vs virulence Pathogenicity Refers to whether the virus causes a specific condition in a host cell Virulence Relates to the severity of the disease ❖ Why antibiotics do not work on viruses? Viruses and bacteria have different structures and methods of surviving that make antibiotic ineffective Chapter 19 Section 3: How some viruses are able to cause human diseases ❖ How the flu virus evades the immune system ❖ HIV as an example of a retrovirus Enveloped retrovirus (ssRNA virus) Retrovirus that causes AIDS 1st drugs to treat it were reverse transcriptase inhibitors (AZT) → “cocktails” ❖ How drugs like AZT inhibit HIV replication AZT = azidothymidine Blocks reverse transcriptase The azido group in AZT blocks the 3’ OH end of the nucleotide which prevents replication because the free 3’ OH end is where the next nucleotide would be added. Bad effect of the drug: AZT blocked replication in viral cells( good effect) but AZT also blocked replication in host cells (bad effect) which would make people sick. ❖ Why antiviral “cocktails” are critical in the fight against AIDS Doctors created antiviral “cocktails” using different amounts/ratios of different drugs (like AZT) to get their good effects, but not using too much  as to also get the bad effects of the drugs (like also preventing replication in healthy host cells) Antiviral “cocktails” have reduced mortality rates by > 80% ❖ STDs Risks Permanent brain or organ damage in babies Preventions Abstain from sex during breakouts Use protection ❖ Explain the limitations of herd immunity Herd immunity: occurs when a certain portion of the population are immune to a disease and can help to stop the spread Requires a base threshold of 60%-85% immunity to be effective (immunity either from recovery or vaccination) ❖ Discuss how SARS-Cov-2 infects cells and replicates 1. Virus enters body 2. Spike proteins on the virus mind to membrane receptors on the cells surface 3. Viral RNA is released into the host cell’s cytoplasm 4. Viral RNA is translated to make viral proteins 5. Viral RNA is replicated using RNA-dependent-RNA-polymerase 6. New viruses are assembled 7. New viruses are released Chapter 19 Vocabulary Virus Host cell Capsid Envelope Lysis Bacteriophage (or phage) Reverse transcriptase Retrovirus dsRNA (double stranded RNA) ssDNA virus (single stranded DNA) ssRNA (single stranded RNA) DNA virus (same as dsDNA) AZT (azidothymidine) Lytic pathway Lysogenic pathway Self-assembly Prophage Provirus  Virulence Endocytosis Pathogenicity Incubation period Herd immunity Vaccine(s) Ebola virus Herpes simplex virus (HSV) Coronavirus Adenovirus SARS CoV-2 COVID-19 Epidemic Pandemic CHAPTER 20 Chapter 20 Section 1: Determine sources of different types of genetic variation on which natural selection acts ❖ Recognize phenotypic variation as the result of differences at the DNA level and the influence of the environment ❖ Describe how genetic variation arises due to mutation, recombination, or both Mutations and recombination both increase the diversity of genetic variation ❖ Differentiate between mutations that will be passed to offspring or not Mutations not passed on Mutations in somatic cells that have been acquired (not inherited from parents Caused by other factors like the environments Mutations passed onto offspring Mutations within the germline ❖ Explain the sources of genetic variation that natural selection can act upon ❖ Gene pool The gene pool is the collection of all genes present within a population of organisms (that breed together) Chapter 20 Section 4: Natural selection leads to adaptation ❖ Define the role of differential reproductive success in the process of natural selection Differential reproductive success The ability of individuals in a population to produce offspring that survive to reproductive age Will be affected by environmental factors  Core mechanism driving natural selection Favors traits that help the organism survive longer (specifically to get to the point in its life where the organism will reproduce) ❖ Explain the limitations on evolution in terms of it being an “editing” process Evolution = editing process, not a creating process Evolution is descent with modifications Natural selection (mechanism for change) edits desired traits as changes in genetic variation occur over generations With each generation natural selection is performing edits that will continue to be carried through future generations ❖ Determining survival: over-reproduction and resources Population numbers for a species usually remain stable due to the struggle for existence Limited resources Competition for resources limits survival and helps counter over-production by not providing enough resources for all individuals to survive ❖ Be able to recognize the mode of selection based on phenotypic changes in a population including stabilizing, directional, and disruptive selection Directional selection A shift toward one variation/phenotype Most common when the environment changes or the population migrates to a new place with different environmental conditions Stabilizing selection Favors intermediate phenotypes Disruptive selection Favors individuals on both sides of the extreme phenotypes Causes disruption to the middle of the curve on a graph ❖ Artificial selection Artificial selection: humans modify species over generations to produce desired traits Dog breeds with certain traits Cows that produce more milk Corn with larger kernels Flowers with vibrant colors  ❖ Intrasexual selection vs intersexual selection. How are they manifested through phenotypes? Intrasexual selection Males compete with other males Weapons: antlers in moose Intersexual selection Males develop showy traits to attract females Ornaments: abs, peacock feathers Chapter 20 Section 5: Changes in allele frequency are due to mechanisms of evolution that may not be adaptive ❖ Relate genetic drift to changes in allele frequency ❖ Explain how small populations are more susceptible to changes caused by genetic drift Smaller populations are more susceptible to a deviation from the expected results Genetic drift tends to reduce genetic variation through the loss of an allele Alleles frequencies fluctuate randomly from one generation to the next 2 main causes: bottleneck effect, founder’s effect Loss of adaptability: reduced genetic diversity limits the population to respond to environmental changes Increased extinction risk: Harmful alleles can become fixed in a population that also renders them more susceptible to extinction ❖ Predict how allele frequencies in two populations may change when individuals from either or both populations migrate between them (gene flow) Gene flow: addition or subtraction of individuals within the population A population may lose or gain alleles by gene flow Occurs when fertile individuals move (movement of infertile individuals is irrelevant) Tends to reduce the number of alleles in a population ❖ Describe how changes in alleles of a population arise due to mutation Alleles in a population can change from large or small scale chromosomal mutations. ❖ Bottleneck effect vs Founder effect on allele frequencies Examples of genetic drift Bottleneck effect Cause ◆ An event occurs that drastically reduces the population size Effect on allele frequency  ◆ Some alleles may be underrepresented, overrepresented, or absent from the gene pool after the bottleneck event ◆ Reduced genetic diversity (larger gene pool of original population lost after the bottleneck event) Founder effect Cause ◆ A small portion of a population becomes isolated from the larger population Effect on allele frequency: ◆ Some alleles may become more common or fixed due to the prevalence of the allele in the founding group Higher occurrence of certain inherited diseases or conditions ◆ Reduced genetic diversity (genes do not reflect the greater diversity of the gene pool of the larger population) ❖ Anatomical vs molecular homology Anatomical homology Similarity in anatomical structure between different organisms from a common ancestor Molecular homology Similarity of DNA/RNA/proteins between different organisms from a common ancestor ❖ Describe the difference between convergent evolution and homology of a common characteristic between two different species Convergent evolution: when 2 unrelated species independently evolve similar traits/features from each other despite not sharing a common ancestor (different species converge) Example: sugar glider in Australia and flying squirrel in North America. Evolved separately from each other but now today the species look like they could be related (converged) Vocabulary: ❖ Evolution Natural ❖ Selection ❖ Population ❖ Allele frequency ❖ Gene pool ❖ Adaptation (examples) ❖ Mimicry ❖ Homology (anatomical and molecular) ❖ Vestigial features ❖ Stabilizing selection  ❖ Directional selection ❖ Disruptive selection ❖ Selective pressure ❖ Artificial selection (examples) ❖ Acquired antibiotic resistance ❖ Fitness ❖ Sexual dimorphism ❖ Sexual selection (intrasexual vs. intersexual) ❖ Genetic drift ❖ Bottleneck effect ❖ Founder effect ❖ Migration ❖ Gene flow ❖ Common ancestry ❖ Functional complementation ❖ Phylogenetic tree (know how to interpret) ❖ Convergent evolution CHAPTER 21 Chapter 21 Section 1: ❖ Species concepts 1. Biological (Reproductive) a. Ability to interbreed and produce both viable and fertile offspring 2. Morphospecies a. Shape, appearance 3. Paleontological a. Fossil records 4. Ecological a. Environmental, geographic 5. Phylogenetic a. Molecular, DNA ❖ Limitations of the biological species concept The biological (reproductive) species concept can’t be applied to organisms that reproduce asexual and it is not relevant when studying fossils. ❖ Relate the importance of reproductive isolation to studies of speciation Reproductive isolation is a source of diversity Barriers that impede 2 species from producing viable and fertile offspring (single or multiple barriers can exist) pre/post-zygotic barriers Chapter 21 Section 2:  ❖ Pre-zygotic vs post-zygotic barriers Pre-zygotic barriers: impedes fertilization Post-zygotic barriers: impedes development of a viable and fertile offspring ❖ Be able to identify pre-zygotic vs. post-zygotic isolation examples Pre-zygotic barriers Temporal isolation: two species breed at different times of the year Two skunk species that breed during different months of the year Habitat isolation: two species living in different habitat environments Land and water snakes Mechanical isolation: mating physically prevented due to morphological differences Snails with spirals in different directions Gamete isolation: gametes are not compatible Sea urchins with not optimal pH Behavioral isolation: specificity of courtship rituals Blue footed boobie mating dance Post-zygotic barriers Hybrid inviability: gametes can combine but the embryo doesn’t fully develop due to insufficient genetic information Lizard, tiger/leopard Hybrid sterility: offspring can be produced but offspring is sterile (due to the potential difference in number of chromosomes between parents) Chapter 21 Section 3: ❖ Relate the role of geographic separation to speciation Whether or not geographic isolation occurs determines the type of speciation Allopatric - geographic separation Sympatric - no geographic separation ❖ Peripatric speciation vs vicariance Allopatric speciation Speciation b y geographic isolation Perpatric speciation (gene flow) Dispersal of a portion of the population into a distant location Vicariance (genetic drift) A physical geological barrier arises which separates one population into two isolated populations (speciation occurs due to geological separation) ◆ Shrimp on either side of the Panama canal ❖ Sympatric speciation Sympatric speciation occurs with geographically overlapping groups 2 mechanisms for it to occur  1. Chromosomal changes - mutations 2. Nonrandom mating - females exhibit a reproductive preference for select males ❖ Describe the major factors affecting genetic divergence between two separated populations Differences in actions of natural selection (based on the environment of the respective population) Genetic drift Vocabulary: ❖ Speciation ❖ Species ❖ Biological species concept (BSC) ❖ Morphospecies concept ❖ Hybrid offspring ❖ Ecological species concept ❖ Paleontological species concept ❖ Phylogenetic species concept ❖ Reproductive isolation ❖ Pre-zygotic isolation ❖ Post-zygotic isolation ❖ Habitat (Geographic) isolation ❖ Ecological isolation ❖ Temporal isolation ❖ Behavioral isolation ❖ Gametic isolation ❖ Mechanical isolation ❖ Genetic incompatibility ❖ Hybrid Inviability ❖ Hybrid Sterility ❖ Allopatric speciation ❖ Sympatric speciation ❖ Vicariance ❖ Peripatric speciation ❖ Dispersal ❖ Non-random mating ❖ Punctuated Equilibrium