MENDEL’S POSTULATES & LAWS OF INHERITANCE 3.2 Flashcards
MENDEL’S BREEDING EXPERIMENT:
- cross between true-breeding pea plants (p-generation)
- hybridization of true-breeding plants (f1 generation)
- results all hybrid progeny have violet flowers - self-fertilization of hybrid plants (f2 generation)
- results violet flowers and white flowers
MENDEL’S POSTULATES &
LAWS OF INHERITANCE:
- Principles of Paired factors
- Principles of Dominance
- Law of Segregation or Law of Purity of Gametes (Mendel’s First Law of Inheritance).
- Law of Independent Assortment (Mendel’s Second Law of Inheritance)
- Genetic characters are controlled by unit factors that exist in pairs in individual organisms.
Principles of Paired factors
- For each inherited trait, an individual has two copies of the gene (allele) – one from each parent
Principles of Paired factors
These factors can exist in three possible combinations:
Example trait: Flower color
Purple flower (P) and white flower (p)
- 2 factors for purple flower (PP)
- 2 factors for white flower (pp)
- 1 for each factor (Pp)
- having identical alleles (one from each parent) for a particular trait
Example: AA or aa
Homozygous
- having two different alleles for a particular trait
Example: Aa
Heterozygous
When two different alleles occur together, one of them may be completely expressed, while the other may have no observable effect on the organism’s appearance.
PRINCIPLE OF DOMINANCE
- masks or suppresses the
expression of an alternate allele
Dominant
- the one masked by the
dominant allele; gene that is
expressed only in the homozygous
state
Recessive
During the formation of gamete, each gene separates from each other so that each gamete carries only one allele for each gene.
LAW OF SEGRATION
Mendel’s First Law of Inheritance
Alleles for a trait are then “recombined” at fertilization, producing the genotype for the traits of the offspring.
LAW OF SEGRATION
Mendel’s First Law of Inheritance
Mendel found that for the traits he studied, the inheritance of one trait did not influence the inheritance of any other trait.
LAW OF INDEPENDENT ASSORTMENT
Mendel’s Second Law of Inheritance
The law of independent assortment states that the alleles of different genes separate independently of one another during gamete formation
LAW OF INDEPENDENT ASSORTMENT
Mendel’s Second Law of Inheritance
Mendel’s law of independent assortment states that genes do not influence each other with regard to the sorting of alleles into gametes: every possible combination of alleles for every gene is _________ to occur.
equally likely
The independent assortment of genes can be illustrated by the ______________
dihybrid cross
Dihybrid cross is a cross between ____________________-
two individuals with two observed traits
