Mendelian Genetics Flashcards
What three scientists did Mendel learn under at the University of Vienna and what did he learn?
-Particulate theory of inheritance from Doppler
-Plant hybridization from Unger
-Probability theory from Ettinghausen
what were the five key features of Mendel’s experiments?
- controlled crosses: identity of parents were known
- pure breeding strain of pea plants used : to idental homozygous alleles
- dichotomous traits used: two possible phenotypes
- Quantified results: patterns of heredity could be predicted
- reciprocal crosses and test crosses used
Parental Crosses
Experiment:
Mendel crosses two pure-breeding parents(Homozygous Dominant and Recessive).
One was violet one was white
The F1 generation was all purple.
Conclusions:
revealed the principle of dominance
rejected blending inheritance–> inheritance is particulate not blending
Reciprocal Crosses:
Experiment:
switched the sex of the purple and white flowers and the f1 generation was still all purple
(pollen from white flowers fertilized ovule from purple flowers= pollen from purple flowers fertilized ovules from white flowers)
Conclusions:
revealed that trait dominance is not influenced by the sex of the parent
Test Crosses:
Experiment:
Crossing the unknown dominant genotype with a homozygous recessive genotype
Conclusions:
Can determine if the dominant phenotype is coming from a Pure breeding genotype or heterozygous
1:1 phenotypic ration if heterozygous
1:0 phenotypic ration of homozygous
Monohybrid Crosses:
Experiment:
All purple F1 generation were self-crossed
Conclusions:
3:1, Dom: rec phenotypic ratio observed
F1 generation is heterozygous dominant
the reappearance of recessive phenotype reveals that:
alleles segregate during gamete formation ( law of segregation)
two alleles are present in each plant
alles exist in pairs (one comes from sperm the other room egg)
F3 self crosses
Experiment:
Round vs Wrinkled determind by the R and r alleles
Conclusions:
all F1 were heterozygous dominant
F2s ha 3:1 round vs wringkled ration
F3s demonstrates that 1/3 of the round plants were homozygous dominant(RR) and 2/3 were heterozygous dominant (Rr)
Dihybrid Crosses
Experiment:
Crosses dihybrid pure breeds( ggWW- green and round x GGww- yellow and wrinkled) and (GGWW-yellow and round x ggww-green and wrinkled)
Conclusion:
F1S ALL GgWw ( yellow and round)
self cross of F1s–>
9:3:3:1 phenotypic ratio
reveals the law of independent assortment (during gamete formation the segregation of allels of one gene is independent of the segregation of alleles of another gene)
What is the law of segregation?
where does it occur in meiosis
alleles separate During gamete formation in a 1:1 ratio.
Occurs in anaphase I during the separation of homologous pairs
What is the law of independent?assortment?
where does it occur in meiosis?
occurs during metaphase I as the homologous pairs ranadomoly and independently align on metaphase plate
The segregation of alleles for one gene is independent of the segregation of alleles for another gene
Tri-hybrid cross
Conclusion:
all F1 are AaBbCc
each F1 can make 8 gametes
Phenotypic ratio: 27:9:9:9:3:3:3:1
What is the product Rule
if two events are independe, the the joint probability of both events occurring is the product of their individual probabilities
KEYWORD: AND–> multiply probabilities
What is the sum rule
when the outcomes are mutually exclusive the sum of the individual probailities calculates the joint probability
What is conditional probability rule
conditioning on one outcome what is the probability of another outcome.
E.g: Probability that F2 purple flower peas(dominant are heterozygous)
What is the binomial probability rule?
given two possible outcomes performed many times the probability of each combination is (p+q)^n
P= probability of dominant trait for respective cross
q= probability of recessive triat for respective cross
if n=3 and find rate of dom chosen 2 times and recssive chosen 1
(p+q)^3= p^3+3p^2q+3pq^2+q^3
choose factor: 3p^2q–> 3*(probability of dom)^2(probability of recessive) ^1
