Lecture 8 Flashcards
discontinuous variation
- a dominance-recessive relationship
- Mendel suggested heredity resulted in this
continuous variation
- offspring were a blend of parental phenotypes
- from Darwin and Wallace
Chromosomal theory of inheritance
- genetic material in living organisms contained in chromosomes
- separation of chromosomes during meiosis served as basis for Mendel’s principles of segregation and independent assortment
Independent assortment
leads to extensive genetic variation
When unit factors in pairs
first meiotic prohphase
When segregation of unit factors during gamete formation
first meiotic anaphase
When independent assortment of segregating unit factors
follows many meiotic events
criteria for classifying 2 chromosomes as homologous pairs
- both are same size and exhibit identical centromere locations
- excludes X and Y chromosomes in mammals - forms pairs or synapse during stages of meiosis
- contain identical linear order of gene loci
- one member of each pair is derived from the maternal parent and one from the paternal parent
independent assortment
- genetic variation is due to nonidentical homologous chromosomes
- chromosome combination produces extensive genetic variation
Product law
- calculates probability of outcomes occurring together
- ex) probabilities of heads or tails of each at the same time
sum law
calculates probability of outcomes independent of each other
- probability of tossing our penny and nickel and obtaining one head and one tail
Chi-square analysis
evaluates influence of chance on genetic data
Chance deviation
- change events subject to random fluctuations
- expected outcome is diminished by larger sample size
2 factors in analyzing or predicting genetic outcomes
1) independent assortment- subject to random fluctuations due to change deviations
2) sample size - average deviation decreases as sample size increases
null hypothesis
- assumes data will fit given ratio
- assumes there is no real difference between measured and predicted values
- apparent difference attributed purely to chance
Chi-square Xˆ2
- goodness of fit of null hypothesis
- analysis used to test how well the data fit the null hypothesis
- analysis of observed vs. expected deviations
degree of freedom of 3:1
n=2 df=1
degree of freedom of 9:3:3:1
n=d df=3
twins on pedigree
-diagonal lines stemming form vertical line connected to the sibship line
identical twins on pedigree
diagonal lines are linked by horizontal line
fraternal twins
lack this connecting line
proband
- the individual whose phenotype first brought attention to the family
- is indicated by an arrow connected to the designation P
