chapter 4 part 2 Flashcards
example of pleiotropic genes
-sickle cell disease (autosomal recessive) caused by lack of B-globin gene
-many red blood cells of ppl w/ sickle cell take on a sickle shape and cause LOTS of problems & complications
pleitropy
alteration of multiple distinct traits by a mutation in a single gene
-many affects
-sickle cell anemia ( many different complications)
gene interaction
many genes working together to produce one trait or a group of related traits
what both involve genes working together through a multi-step process with intermediate products?
-catabolic & anabolic pathways
anabolic pathways
involve biosynthesis of complex comounds
catabolic pathways
involve degradation of complex compounds
what else involves interaction of multiple genes?
-signal transduction pathways & developmental pathways
what is epistasis?
One gene’s alleles can change or block the expression of another gene’s alleles.
-Genes in a multi-step process work together to create the final product.
-mutation of one gene in a pathway can stop the production of the end product
what does epistasis literally mean
“stand upon”
what can gene interaction lead to?
-altered phenotypic ratios of wild type & mutant progeny
what do different patters of epistatic reactions result from?
different ways gene products interact in pathways
where is epistasis readily dedectied?
among progeny of dihybird crosses involving genes with both dominant & recessive alleles
what does the 9:3:3:1 ratio tell us?
that there is an absence of epistasis- the genes of not interact to change the expression of one another
complementary gene interaction ratio
9:7
complementary gene crossing
-crossed two pure-breeding strains of white flowered sweet peas
-all the F1 were purple flowered
-the F1 x F2 cross yielded an F2:9/16 purple 7/16
when genes work in tandem to produce a single product
-complementary gene interaction
-the example of the white flowered sweet peas recognized that the two genes must interact to produce the overall flower color
duplicate gene action ratio
15:1
genes in a redundant system have a _______ ______ ________
duplicate gene
-they encode the same product, or they encode products that have the same effect in a pathway or compensatory pathways
dominant gene interaction ratio
9:6:1 dihybrid ratio
recessive epistasis ration
9:3:4
recessive epistasis
homozygosity for the recessive alleles at one locus will mask the phenotypic expression of the alleles at a second locus
dominant epistasis ratio
12:3:1
dominant epistasis
-a dominant allele at one locus will mask the phenotypic expression of the alleles at a second locus
dominant suppression ratio
13:3
dominant suppression
a dominant allele at one locus completely suppresses the phenotypic expression of the alleles at a second locus
genetic complementation analysis
prefromed by mating two pure-breeding mutants for similar mutant phenotypes & observing phenotypes in the F1 generations
if phenotypically wild type offspring are obtained
-the mutations in the parents must be in two different genes
-complementation has occured
if phenotypically mutant offspring are obtained
-the mutations in the parents must be in the same gene
-complementation has not occured (failed to complement)
genetic heterogeneity
described conditions when mutations in different genes can produce the same or very similar phenotypes
