Genetics PPT Part Biology-Mrs. Flannery
In an Abbey Garden Mendel studied garden peas because they were easy to grow, came in many readily distinguishable varieties, had easily visible traits are easily manipulated can self-fertilize.
Gregor Mendel s Peas Mendel had true-breeding pea plants, which were the basis of his experiments. True-breeding plants produce offspring that are identical to themselves, if allowed to selfpollinate.
Mendel wanted to cross-pollinate his pea plants, in order to produce seeds that came from two different parents. He did this by cutting off the male parts of one flower and dusting it with the pollen from another flower.
Figure 9.3-3 Removed stamens from purple flower. Parents (P) Carpel 2 Stamens Transferred pollen from stamens of white flower to carpel of purple flower. 3 Pollinated carpel matured into pod. Offspring (F ) 4 Planted seeds from pod.
In an Abbey Garden A character is a heritable feature that varies among individuals. A trait is a variant of a character. Each of the characters Mendel studied occurred in two distinct traits.
Character Dominant Recessive Dominant Recessive Flower color Flower position Purple White Pod shape Pod color Inflated Green Constricted Yellow Axial Terminal Stem length Seed color Seed shape Yellow Round Green Wrinkled Tall Trait Dwarf
In an Abbey Garden What Mendel did.. created purebred varieties of plants plants that when they self-fertilized only produced off spring similar to that of the parent. then he crossed two different purebred varieties.
Hybrids are the offspring of two different purebred varieties. The parental plants are the P generation. Their hybrid offspring are the F generation. A cross of the F plants forms the F 2 generation. His Results???
Monohybrid Crosses A monohybrid cross is a cross between purebred parent plants that differ in only one character.
Figure 9.5-3 P Generation (purebred parents) Purple flowers White flowers F Generation All plants have purple flowers Fertilization among F plants (F F ) F 2 Generation 3 4 of plants have purple flowers 4 of plants have white flowers
Mendel s Law of Segregation Lets examine his experiments and see how his results led him to develop 4 hypotheses.
Mendel s 4 Hypothesis Mendel developed four hypotheses from the monohybrid cross, listed here using modern terminology (including gene instead of heritable factor ).. The alternative versions of genes are called alleles.
Figure 9.7 Homologous chromosomes Gene loci Dominant allele P a B Genotype: P PP Homozygous for the dominant allele a aa Homozygous for the recessive allele b Bb Recessive allele Heterozygous with one dominant and one recessive allele
Mendel s Hypothesis 2. For each inherited character, an organism inherits two alleles, one from each parent. An organism is homozygous for that gene if both alleles are identical. An organism is heterozygous for that gene if the alleles are different.
Mendel s Hypothesis 3. If two alleles of an inherited pair differ, then one determines the organism s appearance and is called the dominant allele the other has no noticeable effect on the organism s appearance and is called the recessive allele.
Mendel s Hypothesis 4. Gametes (sperm and egg) carry only one allele for each inherited character. The two alleles for a character segregate (separate) from each other during the production of gametes (meiosis I = homologous chromosomes separate) This statement is called the law of segregation.
Monohybrid Crosses Do Mendel s hypotheses account for the 3: ratio he observed in the F 2 generation? A Punnett square highlights the four possible combinations of gametes the four possible offspring in the F 2 generation.
Female gametes Figure 9. F Genotypes Bb female Bb male Formation of eggs Formation of sperm F 2 Genotypes Male gametes 2 B 2 b 2 B B B B 2 4 2 ( ) 4 b 2 b b B b b 4 4
Figure 9.6 P Generation Genetic makeup (alleles) Alleles carried by parents Gametes Purple flowers PP All P White flowers pp All p F Generation (hybrids) Alleles segregate Gametes 2 P Purple flowers All Pp 2 p F 2 Generation (hybrids) Sperm from F plant P p Eggs from F plant P p PP Pp Phenotypic ratio 3 purple : white Pp pp Genotypic ratio PP : 2 Pp : pp
Figure 9.6a P Generation Genetic makeup (alleles) Alleles carried by parents Gametes Purple flowers PP All P White flowers pp All p
Figure 9.6b F Generation (hybrids) Alleles segregate Purple flowers All Pp Gametes 2 P 2 p
Figure 9.6c F 2 Generation (hybrids) Sperm from F plant P p Eggs from F plant P p PP Pp Phenotypic ratio 3 purple : white Pp pp Genotypic ratio PP : 2 Pp : pp
Warm Up Freckles (F) in humans is dominant to no freckles (f). Using the letters F and f, what are the genotypes for. A person who is homozygous dominant. 2. A person who is heterozygous. 3. A person who is homozygous recessive. What are the phenotypes for... Ff 2. ff 3. FF Question: What information goes inside of the Punnett Square? What information goes on the outside?