Gregor Mendel
- "Father" of modern genetics
- First developed rules now used to predict inheritance
- Chose to study the pea; easily manipulated in breeding experiments
Mendel's
Discovery
- Assumed that each form of trait was controlled by a hereditary
factor
- Dominant traits (R) mask presence of recessive (r) alleles
- –Phenotype - apparent traits in individuals
- –Genotype - the genetic complement to phenotype
Mendel's First Law - Law of
segregation
- Alleles are randomly donated from parents to offspring
- Key points of theory
- All traits determined by two factors
- Factors (alleles) segregate during the formation
of gametes
- Two factors - joined together in offspring
Mendel's Second
Law - Law of Independent Assortment
- Factors (alleles) can sometimes act independent
Why aren't
members of same species identical?
- Almost every organism is the result of thousands of genes working
together
- There may be many different alleles for a trait in a population
- A combination of traits gives an organism a competitive advantage
- Mutations are another source of variety
Does Mendel's Law
Always Apply?
- Lethality - If particular combination of alleles is deadly to new
embryo The embryo dies & phenotype is not represented in next
generation at all
- One gene can influence two or more traits
- Dominant lethal allele kills its recipient
- Two or more genes can influence a single trait
- Human height is controlled by many traits - termed
"Polygenic"
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