Mechanisms of Hereditary Flashcards
what are monohybrid crosses?
parents differ in only one trait (phenotype)
what are the 5 properties of peas that made it very useful for studying genetics?
- binary traits (2 possible phenotypes)
- short generation time
- easy to grow
- produces lots of offspring
- self-fertilise
what are true breeding parents?
crosses that results in all offspring having the same phenotype as parents
how did mendel know that parents contribute equally to offspring?
reciprocal crosses gave identical results
what is the principle of segregation?
two alleles for each trait segregate during gamete formation and then unite randomly at fertilisation
when do we use the product rule of probability?
gamete formation
when do we use the sum rule of probability?
after gametes fuse
what does it mean if the p value is greater than 0.05?
the null hypothesis cannot be rejected, thus there is no significant difference in expected vs observed values
what does it mean if the p value is less than 0.05?
the null hypothesis is rejected, and there is a significant difference between the predicted and observed ratios
what are the 5 non mendelian types of inheritance?
- domanince is incomplete
- lethality
- phenotype determined by multiple genes and interaction between them
- sex-linkage
- linkage
what is complete dominance
when you only see the dominant phenotype in 1st generation
what is co dominance?
when the offspring show two traits (e.g. blood types)
what is incomplete dominance?
when a new phenotype occurs that doesnt look like either of the parents
what is lethality (non mendelian inheritance)
an allele or specific genotype leads to death or non-viablity of organism
what are complementation tests?
way to determine whether 2 mutants (with the same phenotype) are defective in the same gene or in different genes
what does it mean if you cross two mutants together and see a mutant phenotype in the F1 generation?
mutants are defective in the same gene
what does it mean if you cross two mutants together and see a wild type phenotype in the F1 generation?
mutants are defective in different genes
what is a complementation group?
a group of mutations that are all defective in the same gene, the groups dont complement one another
what do complementation groups tell you about the number of genes the mutants are defective in
nr of comp groups = nr of different genes mutants are defective in
what is recessive epistasis?
homozygosity for a recessive allele at one locus masks genotype at a second locus (e.g. recessive allele determines whether pigment is deposited or not)
what is dominant epistasis?
having a dominant allele mask the phenotype coded by the second allele
what is the expected phenotypic ratio of recessive epistasis?
9:3:4
A-B- : aaB- : A-bb + aabb
what is the expected phenotypic ratio of dominant epistasis?
12:3:1
A-B- + aaB- : A-bb : aabb
what is penetrance?
% of individuals with phenotype
