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Biol 207 Midterm 2
Lec 5-9, 1
| Term | Definition |
|---|---|
| Genotype | all of an organisms DNA; description of alleles present |
| Phenotype | the physical manifestation of the genotype |
| Discrete trait | one gene and one trait ("yes or no") |
| Haploid | one copy of every chromosome |
| Diploid | two copies of every chromosome (with the exception of sex chromosomes) |
| Homozygote | an organism with identical alleles of the gene of interest |
| Heterozygote | an organism with 2 different alleles of a gene of interest |
| Hemizygous | an organism that, in a natural state, has only one copy of a gene in diploid |
| Gene | a region of DNA that can be selected for |
| Allele | a variant of a gene |
| Locus | a genetic location |
| Haplosufficient | dominant allele |
| Haploinsufficient | recessive allele |
| Homologous chromosomes | share the same gene order but not necessarily the same alleles |
| Non-homologous chromosomes | do not have the same genes and do not pair in meiosis (sort independently in anaphase I) |
| Mono | one trait |
| Hybrid | 2 different parents |
| Monohybrid cross | a cross between 2 individuals identically heterozygous at one gene pair |
| True-breeding | a group of identical individual organisms that always produce offspring of the same phenotype as the parents |
| Monohybrid cross F2 ratio | 3:1 |
| Test cross | when you cross an individual of an unknown genotype with a tester |
| tester | an organism that is homozygous recesive for all alleles and loci being tested |
| Law of segragation | when the alleles separate in meiosis I |
| Dihybrid cross | a cross between 2 individuals identically heterozygous at 2 loci |
| Dihybrid cross F2 ratio | 9:3:3:1 |
| Law of independent assortment | unlinked or distantly linked segregating gene pairs assort independently at meiosis |
| Dihybrid test cross ratio | 1:1:1:1 |
| Y chromosome | gene poor |
| X chromosome | gene rich |
| Reciprocal cross | when you swap the sexes of the parentals to determine if a gene is on an X-chromosome |
| Auxotrophs | organisms that CANNOT grow on minimal media due to mutation (= metabolic mutants) |
| Prototroph | organisms that CAN grow on minimal media (= wild-type) |
| Minimal media (MM) | lab growth medium containing only essential nutrients |
| Complementaion | the production of a WT phenotype when 2 different recessive mutations are combined in a diploid or heterokaryon |
| Crossing over | the physical exchange of DNA between non-sister chromatids of homologs |
| Linkage | over-representation of parental phenotypes in F2 of a test cross (not a 1:1:1:1) |
| For genes to be linked, they are ___ cM or m.u. apart | less than 50 |
| Recombination frequency (RF) | this is proportional to the distance between linked genes |
| Syntenic | genes that are unlinked and appear to assort independently, but still located on the same chromosome (>50 m.u. apart) |
| The percentage of total progeny being recombinant when genes are linked is ____ | 3% |
| Three point testcross | to map 3 loci that are linked |
| Double crossovers | when the numbers on the map don't add up and there is a rare recombinant class |
| Incomplete dominance | a situation in which a heterozygote shows a phenotype intermediate between the corresponding homozygote phenotypes (blend) |
| Incomplete dominance ratio | 1:2:1 genotypic and phenotypic |
| Codominance | a situation in which a heterozygote shows the phenotypic effects of both alleles equally (both) |
| Codominance ratio | 1:2:1 phenotypic |
| Recessive lethal alleles | when one allel is lethal in the homozygous recessive form, often lethal prior to birth |
| Allelic series | when there are multiple allels of the same gene |
| Pleiotropy | when one gene affects multiple phenotypes |
| Genetic interactions | when 2 or more different genes influence the same trait |
| Complementary genes | occurs when 2 or more genes work together to produce a particular trait |
| Complementary genes ratie | 9:7 |
| Redundancy | when 2 copies of the same gene assort independently |
| Redundancy ratio | 15:1 |
| Epi | to sit upon |
| Recessive epistatis | occurs when the effect of an allele of one genes hides the effect of an allele on another gene and expresses its own phenotype instead |
| Recessive epistatis ratio | 9:3:4 |
| Dominant epistatis | when a dominant allele overrides and masks another trait and expresses its own phenotype instead |
| Dominant epistatis ratio | 12:3:1 |
Created by:
leahdemchuk