Biology Chapters 7-8

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MeiosisIn sezually reproducing organisms, a special two-stage type of cell division in which one diploid (2n) parent cell produces haploid (n) cells (gametes); rusults in halving the chromosome number.Meiosis IThe first cell division of meiosis, in which synapsis and crossing over occur and homologous chromosomes are separated from each other, producing daughter cells with half as many chromosomes (each composed of two sister chromatids) as the parent cellMeiosis IIThe second division of meiosis, in which sister chromatids are separated from each other. Similar to mitosis.SynapsisThe physical pairing of two homologous chromosomes during prophase I of meiosis. Crossing over is observed during synapsis.NondisjunctionWhen the number of chromosomes that go to each cell in a division in meiosis is uneven. Causes disorders such as downe syndrome.Crossing OverDuring Meiosis I when two chromosomes cross and then exchange genes before being divided. This splits up the genes and allows for genetic variation. More common in alleles far apart than in cells close together.RecombinationThe process by which two DNA molecules exchange genetic information, resulting in the production of a new combination of alleles.Reciprocal CrossA cross in which the mother's and the father's phenotypes are the reverse of that examined in a previous cross. Doesn't matter if the mom or dad is giving the gene.PParental Generation (Organism)F1First Generation (Organism)F2Second Generation (Organism)Particulate Inheritance1. Two versions, or alleles of each gene 2. Alleles don't blend together 3. Each gamete contains one allele of each gene 4. Males and females contribute equally to the genotype of their offspring 5. Some alleles are dominant to other allelesPrinciple of SegregationsExplained the 3:1 ratio by reasoning that the allele must segregate and then be passed on. Used letters to represent alleles RR round, Rr round, rr is wrinkledDominantA trait that is encoded in a gene in a way that it will show.RecessiveA trait that is encoded in a gene so that it will only show if there is no dominant trait. Usually caused by a damaged allele.Incomplete DominanceExpress both alleles at the same time. Wavy hair is a smooth allele and a curly allele. Pink Flower.Principle of IndependenceAllele pairs separate independently during the formation of gametes. This means that traits are transmitted to offspring independently of one another.Sex-linked TraitA trait that is either carried on the x or y chromosome, but more typically the x. This is why men are more likely to be colorblind than women, because if they receive a recessive trait on the x chromosome, they will show it for sure because there is no chance that a more dominant gene from the father could overpower it because it will be a y chromosome doesn't carry that genePleiotropyThe ability of a single gene to affect more than one trait.EpistasisA single phenotype depends on more than one gene. Black, brown, and yellow labsWhat are the three purposes of mitosis as discussed in class?Growth, repair, reproductionWhy is it important to have regulation checkpoints in the cell cycle?So that mutations aren't passed on.Sketch the phases of mitosis and be able to identify each phase by the orientation and number of chromosomes.Hay que practicar esoSketch the phases of meiosis and be able to identify each phase by the orientation and number of copies of the chromosomes.Eso tambienWhat is the evolutionary explanation for sexual reproduction?Genetic variation is favorable over no variationHow does meiosis increase genetic variation (two ways)?Chromosomes line up differently (independent assortment), and cross-over.What are the characteristics of good model organism for genetic studies?Simple, easy to observe different characteristics, and traits that are carried on different chromosomes. Start with pure bred organisms so that you can be sure to track the alleles. Easy to rear, abundant offspring, and easy to phenotype.Explain Mendel's model of particulate inheritance.The observation that genes from two parents do not blend together in offspring, but remain separate or particle-like.Demonstrate (sketch and explain) how meiosis and chromosomes can be used to explain the principles of segregation and independent assortment.Sex cells are haploid cells which form together to form the first cell of a new human.Predict probabilities of offspring genotypes from a particular crossUse the putnum squareConstruct genetic maps from recombination rate dataLow percentage means that they are closer together, and they have to be in an order that allows them to be that specific distance.Understand dominant and recessive alleles as well as the concepts of codominance and overdominance?Codominance is like a splotchy cat.Understand how patterns of phenotypes in human pedigrees can be used to infer the mode of inheritance.Two parents have one trait but pass on a different trait, than it means that they each had one dominant allele and one recessive allele, and they each passed the recessive allele. If a woman only a recessive trait and all her sons have it, that means that it is a recessive trait. The most common traits are the dominant ones.Genetic RecombinationGenetic recombination is the process by which two DNA molecules exchange genetic information, resulting in the production of a new combination of alleles.