Download Ch. 10 Mendel`s Genetics

Ch. 10.1 Mendel’s Discoveries
Objectives:
1.
2.
Compare and contrast the blending hypothesis and the
particulate hypothesis of inheritance.
Describe the methods Mendel used in his plant-breeding
experiments.
Vocab:
Trait
Genetics
Cross-fertilization
Gregor Mendel
• Austrian monk
• “Father of
Modern Genetics”
(Study of
heredity)
• Breed pea
varieties.
Pre-Mendel
Blending Hypothesis: Offspring have a blend
of parent traits.
Ex: Red x White flower --> Pink flowers -->
Pink in next generation too.
Problem: Red and white flowers appear
again in future generations; traits are not
really blended.
Background Vocab.
True-breeds: pure gene lines – offspring
match parent
Self-pollination: pollen from flower
fertilizes the same plant
Cross-fertilization: pollen will fertilize
a different plant
Hybrid: Cross between organisms with
different traits (blonde hair & brown
hair)
Trait: Physical characteristics
Mendel’s Pea Traits
Cross-Pollinating
Mendel’s Crosses
TRAIT 1: Seed Shape
P Cross: Round v. Wrinkled
F1 Phenotype: Round
*P = parents
*F1 = “filial” = “son”= off-spring
Mendel’s Crosses
TRAIT 2: Seed Color
P Cross: Green v. Yellow
F1 Phenotype: Yellow
Mendel’s Crosses
TRAIT 3: Flower Color
P Cross: Purple v. White
F1 Phenotype: Purple
Mendel’s Crosses
TRAIT 4: Pod Shape
P Cross: Inflated v. Pinched
F1 Phenotype: Inflated
Mendel’s Crosses
TRAIT 5: Pod Color
P Cross: Green v. Yellow
F1 Phenotype: Green
Mendel’s Crosses
TRAIT 6: Flower Position
P Cross: Axial v. Terminal
F1 Phenotype: Axial
Mendel’s Crosses
TRAIT 7: Plant
Height
P Cross: Tall v. Short
F1 Phenotype: Tall
Mendel’s Conclusions
Biological inheritance is determined by
chemical factors passed from one generation
to the next (Particulate hypothesis)
– Geneticists now refer to these factors as genes
– Genes can come in more than one form, each form is
an allele
ex. B or b (The “B” gene w/ 2 alleles)
Ch. 10.2 Mendel’s Genetics
Objectives:
1.
2.
3.
4.
Explain Mendel’s principle of segregation.
Describe how probability applies to genetics.
Contrast genotype and phenotype.
Explain Mendel’s principle of independent assortment.
Vocab:
Hybrid
Monohybrid cross
Allele
Homozygous
Heterozygous dominant
Recessive
Punnett square
Phenotype
Genotype
Testcross
Dihybrid cross
http://www2.edc.org/weblabs/WebLabDirectory1.html
More Genetics Vocab
• Homozygous: two identical alleles
(AA or aa)
• Heterozygous: two different alleles
(Aa)
• Phenotype: Physical appearance
• Genotype: Genetic make-up
– Homozygous dominant (AA)
– Homozygous recessive (aa)
– Heterozygous (Aa)
Mendel’s Principles
1. There are alternative forms of genes
(alleles)
2. There are 2 alleles for each trait (BB,Bb, bb)
* we now know there can be more.
3. Some alleles are dominant; some
recessive. Dominance: a recessive allele
will be masked by a dominant allele
4. Principle of SEGREGATION: Alleles for
each trait segregate (separate) during
gamete formation (Anaphase I of meiosis)
Monohybrid Crosses = Parents differ in
only 1 trait
Results:
F1: all purple
F1 purples self- fertilize
to see if white trait was
lost.
F2: 75% purple;
25% white
White trait NOT
lost!
Diagram that shows all possible
outcomes of a genetic cross
Phenotype & Genotype Ratios
Phenotype Ratio
3 Purple: 1 White
Genotype Ratio
1 PP: 2 Pp: 1pp
-Reveals unknown genotype thru. Ratios
- Unknown (Dominant phenotype) x homozygous recessive
Mendel’s DIHYBRID CROSSES
Independent Assortment: Alleles for
different traits do not influence each
other’s segregation.
Dihybrid Cross
Traits are inherited
separately.
F2: 9:3:3:1 Ratio