117838
Description
Flashcards by lauratyley, updated more than 1 year ago
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Created by lauratyley
almost 11 years ago
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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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