DNA Review??? gene???

Transcription

1 DNA Review??? gene???

2 Human Chromosomes Humans have 23 pairs of chromosomes; 46 all together Females have 23 matched pairs; males have 22 matched and one unmatched pair

3 Gregor Mendel Born in 1822, Austria Grew up on family farm After completing his studies at a university, he entered a monastery Worked in the garden studying how traits are passed from parents to offspring

4 Genetics Vocabulary (add to SNB) Heredity: the passing of traits from parents to offspring Characteristic: a distinguishing quality or feature of an individual (height, color, etc.) Trait: different forms of the characteristic (tall/short, or white/purple)

5 Self-pollination: when pollen from one plant fertilizes the eggs of the same plant (glossary)

6 Change place!!!!

7 Cross-pollination: when the pollen from one plant fertilizes the eggs of a different plant (glossary)

8 Mendel Begins to Study Heredity Mendel noticed: -sometimes traits disappeared in offspring -sometimes those traits reappeared in the 2 nd generation -similar patterns in both plants and animals Mendel decides to work with garden peas: -grow quickly -usually self-pollinating -come in many varieties (characteristics)

9 Only studies one characteristic at a time Mendel Chooses Plants Trait 1 Trait 2 Chooses characteristics that only have two traits

10 True-Breeding Plants (SNB) When a true-breeding plant self-pollinates, it will always produce offspring with the same trait the parent plant has. Parent (true-breeding for white flowers) self-pollinates All offspring have same trait (white flowers)

11 Characteristic: Flower Color (Trait: purple or white) Mendel creates a true-breeding P (parent) generation

12 He then cross-pollinates a true-breeding purple plant with a true-breeding white plant.

13 The offspring from this cross pollination are called the first generation (F1). What do you think the results were for the first generation when the purple and white parent generations were crossed?

14 Change place!!!!

15 First Generation (F1). Only purple flowers are produced in F1! What happened to the white flower trait?

16 Which flower color is dominant? Which flower color is recessive?

17 Second Generation (F2) Mendel then allowed the first generation (F1) plants to self-pollinate. What do you think the results were for the SELF POLLINATE second generation (F2)?

18 Genetics Vocabulary (SNB) Dominant Trait: a trait that will appear in the offspring, even if only one of the parents contributes it. Recessive Trait: a trait that must be contributed by both parents in order to appear in the offspring. Recessive traits can be carried in an organism s genes without appearing in that organism.

19 Second Generation (F2) The recessive (white flower) trait always reappeared in the F2 generation!

20 705 purple: 224 white Simplifies to a 3 purple: 1 white ratio or 3 dominant: 1 recessive This happened EVERY TIME Mendel had the F1 generation self pollinate

21 Summary 1. True-breeding parent plants are crossed. 2. In the first generation (F1), only the dominant trait is expressed. 3. When the first generation is allowed to self pollinate, the recessive trait reappears in the second generation (F2). 4. The dominant: recessive ratio in F2 is always 3:1.

22 Genetics Vocabulary Gene: a set of instructions donated by parents to offspring Allele: different forms of a gene; each parent donates one allele to the offspring Genotype: the inherited combination of alleles Phenotype: an organism s appearance based on its genotype Genotype: BB Phenotype: purple Genotype: bb Phenotype: white

23 Mendel s Brilliant Idea 3 dominant: 1 recessive There are two sets of instructions (alleles) for each characteristic (genes) Each parent donates one form (allele) of the gene to the offspring An allele can be dominant or recessive

24 Female Alleles: White Phenotype Using Probability to Explain Genetics Cross true-breeding plants; white flowers x purple flowers Complete the Punnett Square (outcome grid) Male Alleles: Purple Phenotype Parent generation genotypes: x

25 Change place!!!!

26 Female Alleles: White Phenotype Using Probability to Explain Genetics Cross true-breeding plants; white flowers x purple flowers Parent generation genotypes: BB x bb Complete the Punnett Square (outcome grid) Male Alleles: Purple Phenotype B B b b

27 Female Alleles: White Phenotype Genetics and Probability Male Alleles: Purple Phenotype B B Parent Generation (P): BB x bb b Bb Bb b Bb Bb First Generation (F1): Genotypes: Phenotypes: purple: white Second Generation (F2):??? Set up a Punnett Square to determine outcomes if F1 were to self-pollinate

28 Female Alleles: White Phenotype Genetics and Probability Male Alleles: Purple Phenotype B B Parent Generation (P): BB x bb b Bb Bb b Bb Bb First Generation (F1): Genotypes: Bb Phenotypes: purple 4 purple: 0 white Second Generation (F2):??? Set up a Punnett Square to determine outcomes if F1 were to self-pollinate

29 Female Alleles: Purple Phenotype Genetics and Probability F1 is allowed to self-pollinate: X Complete the Punnett Square to determine F2 Male Alleles: Purple Phenotype

30 Female Alleles: Purple Phenotype Genetics and Probability F1 is allowed to self-pollinate: Bb x Bb Complete the Punnett Square to determine F2 Male Alleles: Purple Phenotype B b B b

31 Female Alleles: Purple Phenotype Male Alleles: Purple Phenotype B b B BB Bb b Bb bb F2 outcomes: Genotypes: Phenotypes: purple; white purple: white

32 Female Alleles: Purple Phenotype Male Alleles: Purple Phenotype B b B BB Bb b Bb bb F2 outcomes: Genotypes: BB, Bb, bb Phenotypes: ¾ purple; ¼ white 3 purple:1 white