DNA, Genetics, Evolution Flashcards

Question

Meiosis

Answer 1

**Meiosis:** Reduction div of diploid germline cells in reproductive organs into 4 gen. distinct hap nuclei (gametes) 1. 1^st meiotic division separates homo. pairs to halve chrom. # (diploid → haploid) (red. div). 2. 2^nd meiotic division separates sister chromatids 3. **Interphase:** 1. ****DNA replic. during S phase so red. div. → ½ diploid # of chroms in gametes. 2. Thus, when gametes fuse during fertilisation, they form diploid zygote. 3. If not, polyploidy occurs. 4. As meiosis results in gen distinct gametes, random fert. by egg & sperm always generates diff. zygotes 4. **Prophase I:** 1. **Synapsis:** Homo. chromosomes pair up at points (chiasmata) to form bivs (synapsis) 2. **Crossing-over:** DNA exchanged between non-sister chromatids across chiasmata → chromatid alleles recomb. 3. **Chiasmata:** Inc. stability of bivalent, so likely occcur at random pos &/or \>1 in each, so cross-over can occur anywhere. 5. **Metaphase I:** * **Random Orientation:** Orientation of bivs is random. 6. **Anaphase I:** * **Disjunction:** Splitting of homologous chroms to opp. poles. * **Random & ind. orientation** **→ random & ind. assortment →** Gamete combos = 2ⁿ (n = haploid number). * If crossing over also occurs, gamete combos becomes immeasurable

Answer 2

1. Gregor Mendel came up with inheritance laws by performing experiments on pea plants 2. He crossed diff. purebred pea plant varieties. 3. Collected & grew their seeds to determine their traits. 4. Next, he self-fertilised offspring & grew their seeds to similarly determine their traits. 5. Crosses were performed many times to establish reliable data trends. 6. Mendel discovered the following things: 1. When crossing 2 diff. purebred varieties together, results weren't a blend – only 1 feature expressed 2. When Mendel self-fertilised offspring, 2 diff traits expressed in 3:1 ratio. 7. From these findings, Mendel drew the following conclusions: 1. Organisms have discrete factors (genes) that determine its features. 2. Furthermore, organisms possess 2 versions (alleles) of each factor (gene). 3. Each gamete contains only 1 allele (hap). 4. Parents contribute equally to inheritance of offspring due to fert. of randomly selected egg & sperm 8. Certain laws were derived: 1. **Law of Segregation:** When gametes form, alleles separated so that each gamete carries only 1 allele for each gene. 2. **Law of Independent Assortment:** The segregation of alleles for 1 gene occurs independently to that of any other gene\* * \* Not true for linked genes. 3. **Principle of Dominance:** Recessive alleles will be masked by dominant alleles.\* * \* Some genes show co-dom.

Answer 3

1. **Genotype:** Allele combo for specific trait. 2. **Phenotype:** Observable traits of a specific trait. (determined by genotype & env. influences). 3. **Dominant:** Expresses trait that is always present in phenotype when present. 4. **Recessive:** Only expressed in phenotype when in a homozygous state. 5. **Co-dom:** Allele pairs that affect phenotype equally when present in heterozygote.

Answer 4

1. Human RBCs categorised into blood groups based on structure of its antigen. 2. I^A, I^B & i alleles all produce basic antigen on surface of RBCs: 1. I^A & I^B alleles co-dom & each modify antigen to produce different variants. 2. i allele is recessive & doesn't modify the basic antigenic. 3. Incorrect blood transfusions lead to agglutination and lysis of RBCs.

Answer 5

1. **Sex Linkage:** Gene controlling trait located on sex chrom. Most X-linked as ↓ genes exist in Y. 2. **Sex Rules:** 1. Only ♀ carriers as ♂ can't be hetero. (only have 1X). 2. ♂ always inherit X-linked trait from mom (as Y received from dad). 3. ♀ can't inherit X-linked recessive trait from unaffected dad (must receive dom allele). 3. Many genetic diseases identified, but most are rare because: 1. Alleles that ↓ survival + reprod. unlikely to be passed onto offspring. 2. Recessive conditions more common, as faulty allele can be present in carriers without causing disease/harm. 3. Dominant conditions may have late onset, as this doesn't prevent reprod. & the transfer of faulty allele.

Answer 6

1. **PCR:** Artificial DNA replic. technique used to amplify specific DNA seq. 2. Useful when only small amount of DNA available for testing. E.g. crime scene samples of blood, semen, tissue, hair, or from fossils 3. Reaction occurs in **thermal cycler** & uses variations in temp to control replic: 1. **Denaturation:** DNA sample heated (90ºC) to break H-bonds holding strands tog. → separates them into single DNA strands. 2. **Annealing:** Sample cooled (50ºC) to allow primers to anneal to target DNA seq. + re-form double strand apart from seq. with primers (target seq). 3. **Elongation:** Sample heated to opt. temp. for heat-tolerant Taq polymerase (doesn't denature at high temp) to function (75ºC), isolated from thermophilic bacteria. 4. Repeat procedure. For n cycles, PCR produces 2ⁿ copies of DNA sample.

Answer 7

1. **Gel Electrophoresis:** Used to separate charged molecules, like proteins or DNA fragments, according to their size and charge: 2. Fragmented DNA samples placed in gel block & current applied → samples move through gel 3. Small fragments less impeded by gel so move faster than large fragments, so orders by size. **DNA Separation:** 1. DNA fragmented with restriction endonuclease - diff. DNA samples generate diff frag lengths. 2. DNA samples placed into agarose gel &(DNA)¯ due to (PO₄³¯) so moves to anode, but at diff. rates. 3. Frag sizes calculated by comparing against known industry standards. 4. Separated seq. moved to membrane & specific seq. ID'd by adding comp hybridisation probe, which appears in autoradiograph. **Protein Separation:** 1. Proteins may fold into diff shapes/ diff. sizes & have + & – regions, so treated with anionic detergent (SDS) to induce uniform – charge. 2. Protein samples placed into polyacrylamide gel & move to anode at diff. rates dep. on size. 3. Protein sizes calculated by comparing against known industry standards. 4. Separated proteins moved to membrane & target proteins identified by staining with specific monoclonal antibodies.

Answer 8

1. **Bt corn:** GM maize with insecticide-prod. gene (Bt) 2. Bt-toxin kills **corn borers**, which eat crop 3. Monarch butterflies also feed on milkweed with Bt-corn pollen moved by wind. **Experiments:** 1. 1^st Experiment conducted comparing monarch caterpillars DR's & Bt pollen-based diets. 1. Monarchs fed milkweed leaves with Bt pollen (sim. spread via wind). 2. Growth & DR's compared in monarchs fed on non-dusted, non-GM & dusted diets. 3. Caterpillars exposed to Bt pollen ate less, grew more slowly & exhibited higher DR. 2. **But,** Bt pollen on leaves \> found naturally (rain could wash) & Larva restricted in diet (in field, larva could avoid eating pollen dusted leaves). 3. 2^nd experiment conducted comparing monarch butterfly DR's & proximity to Bt corn fields: 1. No sig. ↑ DR when monarch larva placed in or near actual Bt corn field 2. Exposure to Bt pollen poses no sig. risk to monarch butterfly pops.

Answer 9

1. **Clones:** Groups of gen. identical organisms, derived from single original parent cell. **Natural Methods of Cloning:** 1. Bacteria & fungi reproduce asex. to produce genetic clones via binary fission (mainly bacteria) or by producing spores (mainly fungi) 2. **V****egetative propagation:** Small pieces induced to grow indep. due to totipotent meristematic tissue in adult plants differentiating: * Onion/garlic bulbs = modified plant leaves – all bulbs in group are gen. identical * Underground stems (e.g. potato tubers) can form new plants gen. identical to parent plant 3. Some animal species also reproduce asexually: 1. **Binary Fission:** Parent organism divides equally → 2 daughter organisms (e.g. flatworms) 2. **Budding:** Cells split off parent organism, creating smaller daughter organism that eventually separates from parent (Hydra) 3. **Fragmentation:** New organisms grow from separated frag of parent org (e.g. starfish) 4. **Parthenogenesis:** ♀ prod. diploid egg cells instead of haploid (e.g. ♀ aphids) 4. **Human Twins:** 1. **Monozygotic (_ID_) twins** created when _fertilised egg_ splits into _2 identical cells_, each forming an embryo. Gen. identical. 2. **Dizygotic (_non-ID_) twins** created when _unfertilised egg_ splits into _2 cells_ & each _fertilised by diff. sperm_. **Artificial Methods of Cloning** **Embryonic Division:** 1. Embryonic cells retain pluripotency, so differentiate to form all tissues comprising org. 2. Embryonic cells separated artificially in lab, early in developmental cycle. 3. Separated groups of cells implanted into surrogate uterus to develop into clones. 4. Limited by fact that embryo used still formed randomly via sexual reproduction & so specific genetic features of resulting clones unknown. **(SCNT): Artificial method by which cloned embryos prod. using differentiated adult cells.** 1. Genetic features of resulting clone known. 2. **S****omatic cells** taken from adult donor & their cultured (for their diploid nuclei). 3. **E****nucleated egg cell** made by taking unfertilised egg & removing its nucleus. 4. Egg fused with somatic nucleus → diploid egg. 5. Electric current used to stimulate egg to divide & develop into embryo. 6. SCNT cloning split into 2 purposes: 1. **Reproductive cloning:** If embryo is implanted into surrogate uterus, new cloned organism of donor will develop. 2. **Therapeutic cloning:** Embryonic cells induced to differentiate to create specific tissues or organs for transplantation

Answer 10

1. **Stem cutting:** Separated portion of plant stem that can regrow into new indep. clone via vegetative propagation. 2. All stems possess nodes, from which leaf, branch or aerial root may grow. 3. Stem cuttings typically placed in soil with lower nodes covered & upper nodes exposed 4. Stem cutting: Common method employed to rapidly propagate plant species (including sugar cane, grapes & roses) 5. Factors affecting rooting of stem cutting: 1. **Cutting pos:** Cutting stem above/below node & relative proximity of cut to node) 2. **Cutting length:** How many nodes remain on cutting. 3. **Growth medium:** Soil, H₂O, potting mix, compost, or open air 4. Use & conc. of growth **hormones** 5. **Temp:** Most cuttings grow optimally at temps common to spring & summer 6. H₂O **availability:** Groundwater or humidity 7. Soil **pH:** 8. Light **E****xposure:**

Answer 11

1. Thomas Morgan discovered non-Mendelian ratios in fruit flies, which aided in understanding gene linkage. 2. Cross-breeding R-eyed wild types with W-eyed mutants → clear sex bias in phenotypic distr. 3. All ♀ offspring of R-eyed ♂ were R-eyed, 4. All ♂ offspring of W-eyed ♀ were W-eyed. 5. Morgan inferred that eye colour gene dep. on X, as it was found on X-chromosome. 6. Morgan then investigated other traits & found that certain phenotypic combos occurred in much lower freq. than expected. 7. Based on this data, Morgan proposed: 1. Alleles for Link-traits located on same chrom (link-genes), so didn't indep. assort. 2. Linked alleles could be uncoupled via cross-over to create alt pheno, but new phenotypes would occur at lower freq. 3. Morgan also observed that cross-over freq. between linked genes differed depending on distance between 2 genes on chrom (cross-over freq. ∝ distance between genes). Which he used to dev 1^st gene linkage maps, showing relative positions of genes on chrom.

Answer 12

1. Offspring with unlinked genes inherit any potential phenotypic combo equally (due to random assortment). of alleles (due to independent assortment). 2. Offspring with linked genes only express the phenotypic combos present in either parent (unless crossing over occurs) 3. Thus, unlinked recomb. phenotypes occur less freq. than ‘linked’ parental phenotypes. **Chi-squared:** Statistical measure used to determine whether diff. between obs. & exp. freq. distribution is statistically significant. 1. **Idenify Hypotheses:** 1. **H₀:** No sig. diff. between obs. & exp. freqs (i. e. genes are unlinked) 2. **H₁:** Sig. diff. between obs. & exp. freqs (i. e. genes are linked) 2. **Construct freq. table:** 1. ****Draw a dihybrid cross to find exp. ratios. 2. Total x exp. ratio = exp. freq 3. **Apply Chi-Squared:** **(O - E)²÷ E** 4. **Degrees of Freedom: (m - 1)(n - 1) = 3 for dihybrid crosses.** 5. **ID p value:** 1. When df = 3, Chi-squared \> 7.8 to be considered stat. sig. (p \< 0.05). 2. If \> 7.8 → p \< 0.05 → Sig. diff → _genes are linked._ 3. If \< 7.8 → p \> 0.05 → Sig. diff. → _genes are unlinked._

Answer 13

1. **Monogenic traits** (controlled by 1 gene loci) exhibit discrete variation, with individuals expressing 1 of several distinct phenos. 2. **Polygenic traits** (controlled by \>2 gene loci) exhibit continuous variation, with individuals expressing pheno existing in a bell-shaped cont. spectrum of potential phenos. * # of loci responsible for particular trait ∝ # of possible phenos. 3. **Maize grain colour:** Controlled by 3 gene loci: 1. Grain colour ranges from W to dark R, dep. on amount of pigment expressed 2. Each gene has 2 alleles, which either code for R or W pigment. 3. Most freq. combos have equal # of both. 4. Conversely, combos of extremes are rare 5. Overall pattern of inheritance shows continuous variation. 4. **Height + Skin Colour** also affected by env: 1. Added effect of env pressures functions to ↑ variation seen for particular trait 2. Human height controlled by mutliple genes, but also affected by diet & health (disease). 3. Skin colour controlled by multiple melanin producing genes, but also affected by sun exposure.

Answer 14

1. **Evolution:** Cumulative change in allele freq. of a pop’s gene pool over successive gens. 2. **Gene pool:** Sum total of alleles for all genes present in a sexually reproducing population 3. Gene pool size ∝ amounts of gen diversity → ↑ chances of biological fitness & survival 4. **Natural Selection:** Freq. of alleles that adapt indivs to env. ↑, + vice-versa to bad alleles. **Process (ICE CAGE)** 1. **I**nherited variation exists within population 2. **C**ompetition ← offspring \> env. capacity. 3. **E**nv pressures → differential reprod. within pop 4. **A**daptations (traits that make indiv. suited to its env & way of life) that benefit survival select for and passed onto offspring. 5. **G**enotype/Allele freq. changes cumulatively within pop gene pool across gens (**E**volution).

Answer 15

1. **Stabilising Selection:** Natural sel. favours intermediate pheno over both ends of the range of variation. 1. Results in removal of extreme phenotypes (phenotypic distribution becomes centrally clustered to reflect homogeneity) 2. Operates when env conditions are stable & competition is low. 3. E.g. Human birth weights (too large = birthing complications ; too small = risk of infant mortality) 2. **Directional Selection:** Natural sel. favours 1 end of the range of variation over another. 1. Operates in response to gradual or sustained changes in env conditions 2. Causes progressive change in pop in that direction. 3. Causes species to change enough over time to be regarded as different species (speciation). 4. E.g. Dev of antibiotic resist in bacteria pop 3. **Disruptive Selection:** Natural sel. favours both ends of the range of variation at cost of intermediate phenos 4. Causes pheno distr to deviate from centre & results in bimodal spread 5. Occurs when fluctuating env conditions (e.g. seasons) favour presence of 2 diff phenos, which are adapted to diff. niches. 6. Extreme types adapted to diff. niches (e. g. seasons). 7. Reproductive barriers become established between extreme types (e.g. plants grow in diff. seasons) 8. E.g. proliferation of black or white moths in regions, but not grey-

Answer 16

1. Population bottlenecks & founder effect will exacerbate genetic diffs between geographically isolated pops. 2. **Pop bottlenecks:** Natural or anthropomorphic event that ↓ pop size by an order of magnitude (~ \>50%). 1. Surviving pop has less genetic variability than before, so subject to higher lvl of genetic drift. 2. As surviving members begin to repop, newly deving gene pool div to original. 3. **Founder effect:** Occurs when small pop breaks away from larger pop to colonise new territory 1. As this pop subset doesn't have same degree of diversity as larger pop, it's subject to more genetic drift 2. Consequently, as this new colony ↑ size, its gene pool diverges from original. 3. Original pop stays largely intact as opposed to pop bottlenecks.

Answer 17

**Fossils:** 1. Fossils show changes over time in organisms; as fossilised orgs are diff. from existing ones; yet share homo structures with existing orgs; 2. Seq. of fossils at various geological eras matches expectations of evo: 1. Bacteria 2. Simple invertebrates 3. Complex vertebrates. 3. They also show intermediate stages in evolution of groups. 4. Thus suggest orgs share common ancestors. 5. Some have not changed much, due to little selection pressure. There are also gaps in fossil record, which make conc. difficult. **Selective Breeding:** Form of artificial selection whereby humans select for desirable traits to be passed onto future gens (rather than env). 1. Modern varieties of wheat & rice prod. higher yields & more pest-resist. than wild ancestors. 2. Dog breeds are numerous and sig. different from wild wolf ancestor. 3. Artificial selection shows changes in domestic species can be achived in relatively short time. 4. Does not prove that evolution of new species has occured. **Homo. structures:** Same ancestor that had this structure, but has become diff. as they perform different functions. Implying common ancestry. 1. The more similar the homo. structures between 2 species are, the more closely related they are likely to be. 2. E.g. pentadactyl limbs in all vertebrae: 1. **Human hands** adapted for tool manipulation. 2. **Wings** adapted for flying 3. **Hooves** adapted for galloping 4. **Fins** adapted for swimming 3. AA seq. of diff. species also show how closely related species are. 4. **Speciation:** 1. Provides evidence for evolution of species & origin of new species by evolution due to continuous range in variation between populations. 2. But doesn’t match either belief that: 1. Species created as distinct types of organism, so should be constant across their geographic range 2. Species are unchanging.

Answer 18

1. **Fossil:** Preserved remains or traces of any organism from the past. 1. **Reserved Remains:** Provide direct evidence of ancestral forms. (e.g. bones, teeth, shells, leaves, etc.) 2. **Traces:** Provide indirect evidence of ancestral forms. (e.g. footprints, tooth marks, burrows) 2. **Fossil Record:** Totality of fossils, both discovered & undiscovered. 3. Fossil record provides evidence for evo. by revealing features of ancestor for comparison against living descendants. **Law of Fossil Succession:** Chron. seq. by which traits appear to develop. 1. Fossils dated by determining age of rock layer in which fossil is found (rock layers develop in chronological order so oldest = bottom). 2. Different kinds of organisms found in rocks of particular ages in consistent order, indicating a seq. of dev: 1. Prokaryotes appear in fossil record before eukaryotes 2. Ferns appear in fossil record before angiospermophytes. 3. Invertebrates appear in fossil record before vertebrates 3. Ordered succession of fossils suggests that newer species likely evolved as a result of changes to ancestral species

Answer 19

1. **I**nherited variation exists within pop (mel. + pep.) 2. **C**omp. ← offspring \> env. capacity. 3. **E**nv press (poll due to ind. revo.) → SO₂ kills pale lichen + C dark trees → differential reprod. in pop. 4. **A**daptations (black colour) benefit from camo provided by black trees → pass on to offspring. 5. **G**enotype/Allele freq. (mel. variety) cum. ↑ within pop gene pool across gens (**E**volution).

Answer 20

1. **Antibiotics:** Chemicals produced by microbes that either kill or inhibit growth of bacteria 2. Antibiotics are commonly used as treatment for bacterial infections (but not viral infections). **S. aureus:** 1. S. aureus stim. skin lesions + boils, & pneum. + meningitis; treated with antibiotic (methicillin). 2. Initially, only MSSA strands exist. 3. New MRSA strand developed from mutation of antibiotic gene after extensive methicillin use. 4. It reproduces & passes on gene to clones. 5. MRSA survives & reproduces (passing on gene to clones), whilst MSSA die out (don't reprod.) 6. Gene also transferred to other MSSA in another pop via conjugation (turns into MRSA) 7. Results in cumulative change in allele freq. in S. aureus strands → evolution.

Answer 21

1. **Speciation:** Gradual divergence of 2 related pops into diff. species due to geographical separation, which → adaptations. 2. Degree of divergence depends on extent of geographical separation & amount of time since separation occurred: 1. Pops separated recently & are close show less variation (less divergence). 2. Pops separated long ago & are far show more variation (more divergence). 3. As genetic divergence between related pops ↑, their genetic compat. consequently ↓. 4. When 2 pops diverge to point where no longer interbreed & produce fertile, viable offspring = separate species (speciation). 5. **Endemic Species:** Only found in certain geographical area.

Answer 22

**Allopatric Speciation:** Occurs in diff geographical area. Requires a physical barrier to gene flow. **Sympatric Speciation:** Occurs in same geographical area. Requires behavioural or temporal barriers to gene flow. Both lead to genetically isolated pops; up to the point they can no longer interbreed → new species forms;

Answer 23

1. Evolution via speciation may occur via either: 2. **Phyletic Gradualism:** Speciation generally occurs uniformly, via steady & gradual transformation of whole lineages. 1. Supported by fossil record of species with many intermediate forms connecting ancestral species to modern equivalent. 3. **Punctuated Equilib:** Speciation is a periodic process that occurs abruptly & rapidly after long periods of stability. 1. In this view, speciation is seen as a periodic process (big changes occur suddenly, followed by long periods of no change) 2. Supported by general lack of transitional fossils for most species 3. But absences could also be due to unusual & specific events in fossilisation.

Answer 24

1. Charles Darwin’s Theory of Natural Selection used evidence from observing finches in Daphne Major island (in Galapagos). 2. **Adaptive Radiation:** Growing discrepancy of structures from same ancestral line as they perform diff. functions in diff. species due to diff. env. pressures. 3. "Darwin’s finches" are a bird species endemic to Daphne Major island in Galapagos. 4. Darwin’s finches show adapt. rad. & show beak size & shape (inherited var/adaptation) dep. on size of seeds available (env. press): 1. **Drought in 1977:** ↓ small seeds / ↑ large seeds → adv to have larger beak → ↑ in large beak finches / ↓ in small beak sizes. 2. **Floods in 1983:** ↑ small seeds / ↓ large seeds → adv. to have small beak → ↓ in large beak finches / ↑ in small beak sizes.

Answer 25

1. Cladograms have shown that Morphology-based class. doesn’t always correspond with evolutionary origins of group of species. 2. **3 Outcomes of reclassification:** 1. Likely closer to truly natural class. (if new classifications based on cladistics); so predictive value = higher. 2. Unnoticed similarities between groups & diff. between species previously assumed to be similar revealed. 3. Time-consuming & potentially disruptive for biologists. 3. **Reclassification of figwort family:** 1. Until recently, figworts were one of largest family of angiosperms, but problematic as many of figwort plants too diff in structure to function as a meaningful grouping. 2. Taxonomists compared chloroplast gene base seq in figworts & other sim genera & reclassified fam into diff clades. 3. Now

Answer 26

1. **Binomial System:** Formal system by which all living species are classified (taxonomy) 2. Periodically assessed + updated at series across international congresses. 3. Good because: 1. International system; 2. Names agreed at congresses. 3. All scientists use the same names for species, which prevents miscomm due to language diff. 4. First name is the genus name and shows which other species are closely related, so traits can be predicted for new species

Answer 27

1. Drunk Katy Perry Comes Over For Great Sex. 2. Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species 3. All living orgs classified into 3 domains 1. **Eukarya:** Eukaryotes that contain memb-bound nucleus. 2. **Eubacteria:** Prokaryotes lacking nucleus & consist of common pathogenic forms (e.g. E. coli, S. aureus, etc.) 3. **Archaea:** Prokaryotes lacking nucleus consist of extremophiles (e.g. methanogens, thermophiles, etc.) 4. **Genus:** A group of species that share certain characteristics.

Answer 28

1. **Artificial Classification:** Grouping species together solely based on physical characteristics. 2. **Natural Classification:** Grouping species together based on 3. **Artificial Disadv** is that structures may appear different in similar orgs and sim in diff orgs: 1. **Div-Evo**: Growing discrepancy of structures from same ancestral line as they perform different functions in diff species. 2. **Conv-Evo:** Growing assimilation of structures with different ancestral line as they perform same/sim functions in diff species. 4. **Dichotomous Keys:** Consist of pairs of choices; whereby each choice in pair leads to another pair of choices or gives the identification. 1. Requires a good specimen for reliable ID. 2. Key should only use clear/reliable traits.

Answer 29

1. **Cladograms:** Tree-like diagrams; used to show evolutionary history. 2. **Clade:** Group of organisms consisting of all descendants from a common ancestral org. 3. Clade members share inherited characteristics; due to their shared evolutionary history. 4. Nodes represent represent common ancestors as well as when speciation occurred, thus represents sequence in which groups diverged 5. Clades based on AA seq differences between organisms; # of diffs ∝ how close orgs are. 6. Cladograms have led to re-classification of some groups (e.g. figworts). 7. Cladistics allow predictions to be made; and estimations of how long ago groups diverged, due to "molecular clock": 8. Mutation rates generally constant, so used as a "molecular clock" to predict when speciation occurred (indicated by branch length). 9. Molecular clock limited by: 1. Diff genes/proteins change at diff rates 2. Over long time, earlier changes may be reversed by later changes → confounding accuracy of predictions. 3. Rate of change for particular gene may differ between different groups of orgs

Answer 30

1. **Speciation:** Formation of new species; 2. **Polyploidy:** Form of sympatric speciation due to chrom pairs failing to separate during meiosis; or cell failing to divide in cytokinesis 3. Leads to individuals with multiples of normal chrom number; 4. Polyploid indivs can interbreed with one another, but not with diploid indivs as it would lead to infertile hybrids → reproductive barrier. 5. Common in plants (e.g. Allium genus);

DNA, Genetics, Evolution Flashcards

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