Meiosis and Variarions

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Flashcards by lauratyley, updated more than 1 year ago
lauratyley
Created by lauratyley about 8 years ago
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F215 Flashcards on Meiosis and Variarions, created by lauratyley on 06/01/2013.

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Question Answer
why is it important to keep a common ancestor gene bank; source of alleles; for future (selective) breeding; to counteract, genetic erosion/loss of genetic variation; to counteract, inbreeding/homozygosity; to counteract extinction; for changed conditions; example of changed conditions; e.g. climate/environment/disease/fashion to preserve as yet unidentified, alleles/traits;
why is selective breeding carried out for benefit of humans; to improve, trait(s)/named trait; to produce desirable, phenotype/genotype; to increase number of desirable alleles; to increase homozygosity; AVP;
why does a plant that self poolinates have narrow g.d due to inbreeding & having a limited gene pool
define crossing over reciprocal exchange of portions of, chromatids / DNA; A swapping alleles between (paternal and maternal) homologous chromosomes; A bivalent in prophase I (of meiosis);
WHY IS DNA IN SISTER CHROMATIDS IDENTICAL dna molecule unzips, free dna comp base pairs to reference strand, sugar phosphate back bone form, dna polymerase
predicted phenotype of dominant epistasis 12:3:1
predicted phenotype of recessive epistatsis 12:3:4
what is dominant epsistatis dominant allele on the first allele masks the expression of other genes
What is recessive epistatsis neither a dominant or recessive allele is expressed due the lack of a dominant allele on the previous gene
Contiouse varitiation is effect by how many genes? 2 + and is polygenic
Discountinouse variation is caused by how many gene two or less so is monogenic
What effect does different alleles have on continous variation makes little difference
What effect do different alleles at differnt gene loci have on discontinouse variation has a large effect
define stabilizing selection stabilizing selection is when no environmental change occurs all organisms are under the same selection pressure so no new alleles become advantagouse, each generation keeps getting the same alleles no need for variation
define directional selection when the environment changes/change is selection pressure new alleles become advantageous which previously were not and are passed on to the next generation, changing the gene pool
Ecological isolating mechanisms are when they are in the same area/habitiat but never actually meet e.g. both in pond but one on surface and one on the top
Phylogenetic species concept if can see a difference they must have evolved from common ancestors
Genetic Drift in a population small population with very small election pressures
How does selection pressure occur by chance, one or two populations have breeding success and over time their alleles become more apparent in the population and other allele in a population become less apparent
What do selection pressure cause Changes in the gene pool, a change in the variation/characterisitics in a population
Definition of Codominance Alleles in a hetrozygote are both expressed in the genotype neither is dominant or recessive
An example of co domiance the ABO blood group - red blood cells contain a glycoprotein in their plasma membrane that determines the abo blood group. Two forms of the protein antigen A and antigen B - the gene has 3 allels coding for A/B or no antigen at all
How do you right co dominance with a super script
Define Homozygous homozygous is when two copies of the same allele are at a particular gene locus
How does independent assortment occur during metaphase 2 different combinations of sister chromotids go into each cell
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