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Bio 162 Module 2
Biology
| Question | Answer |
|---|---|
| What is a genotype? | Information stored in DNA |
| What is a gene? | A segment of DNA that contains the instructions for building a specific protein or performing a particular function in an organism's body |
| What does it mean to say that genotype is an indirect target of selection? | The relative frequency of different genes for a certain trait only change to the extent that they can influence the phenotype and the ability of different phenotypes to reproduce |
| T or F: Genotype is a direct target of selection. | False, genotype is an indirect target of selection |
| What is phenotype? | All structures, processes, and behaviors of an organism and the artifacts of behavior that is formed as a result of complex interactions between genetic and environmental information |
| T or F: Phenotype is an indirect target of selection. | False, phenotype is the direct target of selection |
| What is the central dogma? | DNA --> RNA (by transcription) --> protein (by translation) |
| How does genotype contribute to phenotype? | Through the central dogma that makes DNA into a protein that can serve a function or display traits |
| What is a monogenic phenotype? | When one single gene affects a trait |
| What is a polygenic phenotype? | When multiple genes affect a single trait |
| What is a pleiotropic phenotype? | When one gene influences multiple, seemingly unrelated phenotypic traits |
| How are polygenic traits caused? | Caused by the interaction of multiple genetic loci and the environment interacting as a network or integrated pathway |
| T or F: Most complex traits are polygenic. | True |
| What is a character or trait? | Some facet of the phenotype |
| What is a character state (trait)? | A particular version of a character |
| What is continuous variation? provide an example | A trait that can vary in a population with no specific limitations. An example of this is human height |
| What is discrete variation? provide an example | Choices or outcomes of a test -- it either "is" or "is not" -- there are no graduations or "continuity" between the choices. An example is round peas vs wrinkled peas |
| What variable measures the amount of variation in phenotype? | Phenotypic (total) variance Vp or Vt |
| T or F: Phenotypic variation (Vp) across populations is always the result of the interaction between information from the environment and genotype. | True |
| What is the variable for variation in phenotype associated with variation in genotype? | Vg |
| What is the varaible for variation in phenotype associated with variation in environment? | Ve |
| What is the variable for variation in phenotype associated with specific types of gene-environment interactions | Vge |
| What equation determines total phenotypic variation? | Vp = Vg + Ve + Vge |
| What is phenotypic plasticity? | The ability of individuals with a particular genotype to express different phenotypes as a result of environmental differences (ex. learning) |
| Give 2 examples of phenotypic plasticity involving morphological/physiological changes. | 1) Daphnia change morphology dependent on presence of predators 2) Food availability affecting morphology |
| What is the major unifying principle of biology? | Evolution |
| What is evolution? | Changes in the heritable traits of a biological population over generational time |
| T or F: Individual organisms evolve | False, evolution acts on populations |
| How does evolution occur? | Selection is one mechanism |
| What is selection in evolution? | Refers to an advantage the occurs with a particular phenotype (ex. selection for different beak types depending on food availability) |
| What are the key requirements for phenotypic selection(4)? | 1) phenotypic variation 2) heritability 3) superfecundity (overproduction of offspring) 4) differential reproductive success (survival of the fittest) |
| What is natural selection based on? | increased survival, better condtion, more survival offspring, or more resources |
| What is sexual selection based on? | Differences in the ability to obtain mates in sexually reproducing species |
| What is the result of selection forces on a biological population over generational time? | Selection results in over-representation of specific traits/phenotypes in future generations of the population, but only if the selected phenotypes are heritable and variable |
| T or F: If the phenotype can't be inherited by future generations OR if there is no possible variation in phenotype, then it will/can not be subject to selection | True |
| T or F: Both natural and sexual selection cause differential inheritance of certain genotypes and associated phenotypes | True |
| T or F: Natural selection is a random process. | False, natural selection is NOT a random process...rather it depends on random process to generate new genetic variation |
| What random processes does natural selection depend on in order to generate new genetic (and phenotypic) variation (2)? | Genetic recombination and mutation |
| What are primary sexual characteristics? | Traits that evolve by natural selection and are directly related to reproduction (the production of gametes, with mating, and with nuturing the young) |
| What are secondary sexual traits? | Traits that evolved to increase an individual's reproduction by attracting mates (intersexual sexual selection) and/or increase success in competing for mates (intrasexual sexual selection) |
| What is chromatin? | DNA (and maybe some RNA) combined with proteins |
| What are the 2 types of chromatin? | 1) Heterochromatin 2) Euchromatin |
| What is heterochromatin? | densely packed chromatin |
| What is euchromatin? | diffuse, uncondensed chromatin |
| What are chromosomes? | Structures that are composed of chromatin... they may be an association of one or two DNA double helices with proteins that can be condensed to various degress and portions of it may be extended |
| T or F: heritable change is carried in genetic material. | True |
| What is ploidy? | The number of sets of chromosomes in a cell |
| What is haploid (n)? | One set of instructions (a minimal set of instructions)... there is one copy of each gene required to build the organism |
| What is diploid (2n)? | Two complete (and different) sets of instructions... two copies of each gene needed to build the organism (homologous chromosomes) |
| What is a polyploid? | more than two sets of instructions |
| What is a chromatid? | An unreplicated chromosome |
| What is the centromere? | The area on the chromatid that splits the chromosomal arms and is the point of attachment for sister chromatids |
| What are sister chromatids? | 2 identical copies (chromatids) formed by DNA replication and joined together (gentically identical) |
| What is a homologous pair? | two chromosomes, one from each parent that have the same genes in the same order, but there may be variation between them (not genetically identical) |
| What does sexual reproduction produces? | genetic novelty in the new individuals |
| What is syngamy? | The union of gametes |
| What is meiosis? | The process of cell division that reduced the chromosome number of the daughter cells by half (2n-->n) |
| What is mitosis? | The process of cell division that does not change the ploidy of the daughter cells |
| Which process, mitosis or meoisis, changes the ploidy of the daughter cells? | Meiosis |
| T or F: S and G2 phases of the cell cycle are different prior to mitosis vs that of meiosis 1. | False, S and G2 are the same prior to mitosis and meosis 1 |
| Describe how prophase differes in meiosis 1 vs mitosis. | In meoisis tetrads form and crossing over occurs, but not in mitosis |
| What is crossing over? | the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring |
| Describe how metaphase differes in meiosis 1 vs mitosis. | Tetrads line up in meiosis with indpendnent assortment and spindles attach to each chromosome; in mitosis chromosomes line up and spindles attach to each chromatid |
| What is independent assortment? | The random orientation of homologous chromosome pairs to allow for the production of gametes with many different assortments of homologous chromosomes |
| Describe how anaphase differes in meiosis 1 vs mitosis. | In meiosis, the two homologous chromosomes of each pair separate, ploidy goes from 2n to n; in mitosis the sister chromatids separate and and ploidy remains 2n |
| What is meiosis 2 comparable to? | Like mitosis of a haploid cell |
| T or F: Animals can either use sexual or asexual reproduction, not both | False, many animals can use both |
| What are advantages of asexual reproduction? | Can resproduce easily/readily through budding/fission/parthanogenesis and only need 2n cells for reproduction |
| T or F: Some species of animals only reproduce sexually. | True |
| What are the two distinct multicellular, mature individuals in the sexual life cycle of plants and are they haploid or diploid cells? | 1) gametophyte (haploid, n cells) 2) sporophyte (diploid, 2n cells) |
| What is a gametophyte? | begins from a spore, cells are all identical, and produces male and females gametes by mitosis |
| What is a spore? | a haploid cell that divides mitoically to produce a gametophyte |
| What is a sporophyte? | Begins with the syngamy of gametes, is a new (unique) 2n individual that grows by mitosis, and they produce spores by meiosis |
| What is the purpose of sex? | Genetic recombination (to produce variation) that diversifies offspring genotypes and allows favorable combinations of genes to spread |
| T or F: Sexual reproduction results in new individuals with genotypes unique from the parents | True |
| T or F: There can be sex without sexes and without reproduction. | True |
| What is sex? | Any process where there is genetic recombination |
| How are sexes defined? | By the type of gamete they contribute to the new individual (ex. female--> relatively few, large gametes... male --> many small gametes, usually motile) |
| What are the disadvantages of sexual reproduction? (4) | 1) Offspring only receive half your genes 2) Issue of finding a mate 3) The genetically incompatible mate problem 4) Some offspring may be less successful than you are |
| What are the advantages of sexual reproduction? (2) | - Hedging your evolutionary bets - The Red Queen Hypothesis |
| What is hedging your evolutionary bets? | even if the environmental changes and your genotype combination aren't favorable any longer, chances are some of your offspring's different genotype combinations will be |
| What is the Red Queen Hypothesis? | Sexual reproduction is a mechanism that allows favroable combinations of genes to spread rapidly to keep up with challenges produced by other rapidly evolving competitors, predators, and parasites |
| What are biotic environmental factors? | (The opposite of abiotic factors) usually the major and fastest changing environmental challenges |
| Through what means does sexual reproduction achieve an increase in genetic variation? (2) | 1) Shuffling events during meiosis (crossing over and random assortment) 2) Joining of gametes (syngamy) with different genetics |
| T or F: Homologous chromosomes have the same loci in the same places. | True |
| T or F: Only one cross over event can occur during prophase of meoisis 1. | False, numerous crossover events may occur |
| T or F: Crossovers between sister chromatids cause no changes. | True, they are already identical |
| Does meiosis produce new gene alleles? | No, it does not produce new gene alleles, rather it produces new genetic combinations--different gene alleles grouped on different chromosome |
| What is a gene? | A discrete portion of DNA responsible for a genotype |
| What is a locus? | The physical location of a gene sequence on the DNA strand |
| What is an allele? | A variant of a gene |
| What is a trait/character? | Some facet of the phenotype |
| What is true breeding? | With respect to certain traits, these always give the same phenotype, due to extensive inbreeding |
| What is homozygous? | The genetic basis for true breeding; a diploid individual that contains two functionally identical alleles of a particular gene |
| What is hybrid? | Individuals resulting from crosses of different true breeding lines (with respect to certain traits) |
| What is heterozygous? | The genetic basis of a hybrid; a diploid individual possessing tow different alleles for a gene |
| What does P, F1, and F2 stand for in Mendel's experiments? | P = Parental generation F1 = first generation F2 = second generation |
| Can an parental trait that was absent in the F1 generation reappear in succeeding generations? | Yes! |
| What is Mendel's 1st Law of Segregation "particulate inheritance"? (3) | -Genes are not fluid; although unseen, they maintained their identity through generations -At the level of the factor, inheritance was not blending -For a given factor, some alleles (dominant) were able to hide the effects of others (recessive) |
| What is complete dominance? | A condition that occurs when one allele of a gene completely masks another |
| How do you write a dominant and recessive phenotypes in terms of letters? | Dominant--> N_ or simply N (for NN and Nn) Recessive--> nn or simply n (for nn) |
| What is partial or incomplete dominance? | Each genotype is associated with a distince phenotype (treat as synonymous to partial/incomplete dominance) |
| What is semi-dominance? | The heterozygote's phenotype is exactly intermediate between the phenotype of each homozygote |
| Will partial/incomplete and semi-dominance show the 3:1 ratio predicted in the Mendelian complete dominance model? | No |
| What is co-dominance? | Both alleles contribute equally to the phenotype; often they are also dominant over other alleles |
| What is mulitple alleles? | a population pehnomenon -- the idea that there are more than two alleles for a particular genetic locus within a population |
| What is an example of both co-dominance and multiple alleles? | Human blood type (Ia, Ib, and i alleles Ia and Ib are dominant over i and result in type AB blood if together with each other) |
| What are di- and multi-locus crosses? | Crosses where 2 or more separate traits (and their asscoiated genes) are simultaneously studied in a cross (only used when individuals that are heterozygous at two or more loci are crossed for those investigated) |
| What is Mendel's 2nd Law of Independent Assortment? | Different genetic loci segregate (separate) independently of each other (ex. the movement of one gene into a given gamete does not affect the movement of other genes) |
| What is the Chromosome Theory of Inheritance? | That chromosomes carry "hereditary factors" and segregate/assort independently according to Mendleian predictions |
| How would you calculate expected ratios of offspring without using a Punnett square? | 1) Determine the probability of a given outcome at each locus 2) Multiply the probabilities of each locus's particular outcome together |
| What are additive traits? | Multiple copies of a gene (instead of there being just two copies of a particular gene, there are often many), thus the loci usually assort independently of each other and there is often a lack of dominance at each of these loci |
| What is the effect of additive traits? | Usually each allele of a given type adds a certain amount of phenotypic effect to some minimal version of the phenotype. Thus, the total number of alleles of a particular type produce additive effects |
| What is epistasis? | In epistasis, the phenotype for one particular trait is determined by the interaction of the alleles of two or more independently assorting genes (ex. dog coat color) |
| What is pleiotropy? | When the alleles at one locus affect many traits (ex. Phenylketonuria) |
| What are the 3 testcross cases to determine how we can use genetic crosses to determine if and how different genes are inherited relative to one another? (3) | 1) Testcross w/ independent assortment (2 loci on 2 chromosomes) 2) Testcross w/ complete linkage of the A & B loci (2 loci on 1 chromosome) 3) Testcross w/ incomp. linkage of the A & B loci (2 loci on 1 chromosome w/ crossing over and incomp linkage |
| What is a testcross? | Crosses the individual in question with an individual that has a recessive phenotype for the trait being studied |
| What is the offspring population result of crossing 2 loci that are independently assorting? | 4 phenotypes in a 1:1:1:1 ratio |
| What is the offspring population result of crossing 2 loci that have complete linkage? | 2 phenotypes in a 1:1 ratio |
| What is the offspring population result of crossing 2 loci that are incompletely linked? | 4 phenotypes, with recombinants (w/ crossing over) in 1:1 ratio that will occur less frequently than non-recombinants (w/o crossing over) that are also in a 1:1 ratio |
| What does crossover/recombination frequency provide a measure of? | a measure of what proportion of the population is made up of recombinant individuals |
| What is the recombination frequency equation? | (Recombinant individuals) / (Total) |
| What is the maximum possible recombination frequency? | 50% |
| T or F: Recombination frequency provides useful information about gene arrangement. | True |
| What do chromosomal abnormalities result in? | Extra or missing genetic loci with often very marked phenotypic effects |
| When can chromosomal abnormalities occur?(4) | - Cells gain extra copies of chromosomes or parts of them - Cells lose entire chromosomes or parts of them -Part of a chromosome breaks off and becomes part of a non-homologous chromosome -Breaks off and reinserts in diff area of homologous chromosome |
| What is aneuploidy? | When there is an abnormal number of chromosomes (too many or too few) in a nucleus that is typically a result of non-disjunction, the failure of homologous chrmomsomes or sister chromotids to separate normally during meiosis) |
| What happens as a result of aneuploidy? | During meiosis, all the cells of the offspring resulting from the aneuploid gamete will all possess that aberration |
| Why are too many or too few chromosomes problematic? | Due to gene dosage, in which our bodies function best within a certain range of gene products and develop under the expectation of certain amounts of gene products...thus, a dosage abnormality can cause negative effects |
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ndimarco31
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