Presentation on theme: "AIM : WHAT IS THE ORIGIN OF HEREDITY? Why it matters? Our understanding of genetics, including what makes us unique, can be traced back to Mendel’s discoveries."— Presentation transcript:
AIM : WHAT IS THE ORIGIN OF HEREDITY? Why it matters? Our understanding of genetics, including what makes us unique, can be traced back to Mendel’s discoveries Do Now : Why do you think our traits are not identical to our parent’s traits?
What is Heredity ? The passing of traits from parents to their offspring Genetics is the scientific study of heredity.
1860s: Gregor Mendel “Father of Genetics” He figured out how traits are passed on before we knew about DNA, or chromosomes or meiosis
Mendelstudied heredity with pea plants Why pea plants? (was it luck?) 1. Small 2. Easy to grow 3. Produces large numbers of offspring 4. Matures quickly 5. Plants can self or cross fertilize 6. Many varieties 7. Each trait has two forms Tall/short purple/white flowers green/yellow seedscolored/white seed coat green/yellow seed podsinflated/narrowed seed pod wrinkled/smooth seed
Vocabulary 1.Self-pollinate- A plant is often able to pollinate itself because it contains both the male and female reproductive structures. This only requires 1 parent. 2.Cross-pollinate – when pollen from the flower of one plant is carried to the flower of another plant. 3. True-breeding- result of self-pollination.All of the offspring will have the same trait as the parent when self-pollinated 4.First-generation- the very first set of offspring from two parents
Characters – physical features that are inherited. Examples : hair color, height, flower color. Trait – one of the possible forms of a character. Example : brown hair color, tall, purple flower.
Mendel’s Experiments led him to 3 Laws of Inheritance The Law of Dominance The Law of Segregation The Law of Independent Assortment
Think-Pair-Share 1.What is the difference between Genetics and Heredity? 2.What is the difference between a character and a trait? 3.What id the difference between cross-pollination and self-pollination?
AIM : How can we predict an outcome of a genetic cross? Do Now : Using your favorite letter represent the homozygous recessive organism.
The Law of Dominance: Each individual has TWO factors for each trait known as alleles Some alleles dominate over others – the dominant allele is expressed in the offspring Freckles Dimples Tongue roller From Mom From Dad No Freckles No dimples Non-roller These are alleles
Alleles are: Represented by a letter of the alphabet Capital = dominant allele A lowercase = recessive allele a Each allele corresponds to a gene on a chromosome - the alleles represent different forms of the gene
Law of Segregation The two alleles for each trait separate and move into different gametes – meiosis Since only one egg or one sperm will contribute to the new offspring, only one allele for a trait is passed on The chance that any allele will be passed on is 50%
Law of Independent Assortment the inheritance of alleles for one trait doesn’t affect the inheritance of alleles for another trait - occurs in meiosis during metaphase 1
Genotype: Genotype is the combination of alleles for a particular trait expressed with letters Examples of Genotypes : Homozygous dominant: TT - two capital letters Heterozygous Tt - one of each letter (big and small) Homozygous recessive tt - two lower case letters
Phenotype: Phenotype is physical expression of the genotype Genotype Phenotype TT tall plant Tt tall plant (dominant allele always is expressed over the recessive allele) tt short plant (recessive trait is expressed only if there is no dominant gene)
If R = red, and r = white What is the genotype of homozygous dominant? RR What is the heterozygous genotype? Rr What is the homozygous recessive genotype? rr
If R=red and r =white What is the phenotype of of RR? Red What is the phenotype of Rr? Red What is the phenotype of rr? White
You can determine phenotypes using a Punnet square. Tt If two parents are crossed (TT X tt), what are the resulting offspring? TT t t parent Genotypes:4 Tt Phenotypes:4 Tall This is the first or parent generation
Now try on your paper a cross of two of the offspring from the parent generation. This is called the first generation or the F1. Tt T T t t TT tt Genotypes:1TT: 2Tt : 1tt Phenotypes:3 Tall: 1 Short.
Vocabulary Heredity Law of Dominance Allele Genotype Phenotype
Review of the Lesson If a character exists in two possible forms, how many different phenotypes can you have ? How many different genotypes can you have? The offspring of self-pollinated plant is called what?