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Introduction to Genetics
Transcript of Introduction to Genetics
What is an inheritance?
Who was Gregor Mendel?
How does biological information pass from one generation to another? Chapter Mystery (pg. 307)
Answer the questions at the end of the second paragraph (put in your notebook) The Experiments of Gregor Mendel 1. GENETICS - the scientific study of heredity; the key to understanding what makes each organism unique 2. An Austrian monk Mendel used the pea plants in the monastary garden to research inheritance of traits which would have taken decades if he had used humans or mammals 3. FERTILIZATION - the joining of male and female reproductive cells 4. Mendel's pea plants were self-fertilizing (male and female cells from the same plant)
a. they had only one parent
b. offspring were identical to parent
c.traits of each generation were the same 5. To get offspring with two parents Mendel cross-pollinated
a. Removed the male parts of the flower
b. Dusted pollen from one flower onto the female parts of another flower
c. HYBRID - the offspring of crosses between parents with different traits 6. Generations
a. P - parent
b. F1 - first filial (offspring of the parents)
c. F2 - second filial (offspring of the F1) 7. When Mendel looked at the F1 generation all the plants had the characteristics of only ONE of the parents. 8. Conclusions: An individual's characteristics are determined by factors that are passed from one parental generation to the next. 9.Some Vocab:
a. GENE - factors passed from parent to offspring
b. ALLELES - different forms of a gene 10. PRINCIPLE OF DOMINANCE - some alleles are dominant and some are recessive
a. An organism with at least one dominant allele for a trait will exhibit that trait
b. An organism with a recessive allele will exhibit the recessive form of the trait only if the dominant allele is NOT present 11. Mendel allowed F1 plants to self-pollinate to create the F2 generation and the recessive trait reappeared in 25% of the F2 generation 12. Whatever had hidden the recessive trait in the F1 generation must have been removed in the F2 generation for it to reappear so traits must "segregate" in the formation of gametes or sex cells 13. Every organism has one copy of each gene from each parent when making their own gametes or sex cells these alleles get separated. How they combine with their mates gametes is what results in the characteristics of thier offspring. Day 2:
1. Who was Gregor Mendel?
2. What is the principle of dominance? Applying Mendel's Principles A. Probability and Punnett Squares 1. PROBABILITY - the likelihood that a particular event will occur 2. The probability of one event is not affected by past occurences. 3. Mendel's experiment: 4. In Mendealian genetics with simple dominance in the F2 generation 3/4 will be dom. and 1/4 rec. 5. More Vocab:
HOMOZYGOUS - organisms with two identical alleles for a trait
HETEROZYGOUS - organisms that have different alleles for a trait 6. The larger the number of organisms in the offspring the closer you get to the predicted ratio 7. Vocab Again:
PHENOTYPE - physical traits
GENOTYPE - genetic makeup QUICK LAB BREAK!! 8. PUNNETT SQUARE - use mathematical probability to help predict genotype and phenotype combinations in genetic crosses 1. Dihybrids - does the way one traits is passed from parent to offspring impact the way other traits are passed down? 2. Two steps:
a. He took two plants one homozygous dom. for two traits and one homozygous rec. for two traits and crossed them all the offspring were heterozygous for both traits.
b. He allowed the heterozygous F1 generation to self-pollinated and looked at the F2 generation:
9 - round/yellow (both dom.)
3 - round/green (1 dom. and 1 rec.)
3 - wrinkled/yellow (1 rec. and 1 dom.)
1 - wrinkled/green (both rec.) B. Independent Assortment 3. INDEPENDENT ASSORTMENT - genes for different traits can segregate independently during the formation of gametes Homework: Page 318 (1-2, 4) Day 3: Bellwork
What is independent assortment?
A black hen (BB) mates with a white hen (bb). Complete a punnett square for this cross and determine potential phenotypes and genotypes and thier percentages. Other Patterns of Inheritance A. Beyond Dominant
Recessive Alleles 1. Incomplete Dominance a. Some alleles are neither dominant nor recessive b. INCOMPLETE DOMINANCE - when one allele is not completely dominance over another c. Example: Snapdragons - if you mate a red and white snapdragon you will get all pink snapdragons; but if you mate all pink snapdragons you will get 1 red, 2 pink and 1 white snapdragon 2. Codominance a. CODOMINANCE - the phenotypes produced by both alleles are clearly expressed b. A black chicken and white chicken when mated will result in a chicken with both black and white feathers making it look blue. c. Can be expressed in many different ways. 3. Multiple Alleles 4. Polygenic Traits a. Many genes exist in several different forms (there are more then two colors for eyes) b. MULTIPLE ALLELES - a gene with more then two alleles c. Even if there are multiple alleles for a gene each individual can only have two d. Example - There is only one gene for fur color in rabbits but four alleles a. Most traits are produced by the interaction of several genes b. POLYGENIC TRAITS - traits controlled by two or more genes c. Example - The variety of skin colors in humans are related to polygenic traits B. Genes and the Environment a. Environmental conditions can affect gene expressions and influence gentically determined traits b. External conditions such as temperature, soil pH, water availability, etc. c. Internal conditions such as hormone levels, stress, age, etc. Analyzing Data (pg. 320) MEIOSIS A. Chromosome Number 1. Diploid Cells b. HOMOLOGOUS - a pair of identical chromosomes where one came from the mother and one came from the father a. Diploid cells have two copies of all chromosomes one from each parent c. DIPLOID - a cell that contains homologous chromosomes (or two copies of each chromosome d. Represented as 2N 2. Haploid Cells a. HAPLOID - cells with only one copy of each chromosome b. Represented as N B. Phases of Meiosis a. MEIOSIS - the process in which the # of chromo. per cell is cut in half through the creation of a haploid cell from a diploid cell b. Chromo. are copied just before meiosis starts. c. Prophase I - replicated chromosomes pair up with their homologous chromosome; become visible; nucleus dissolves d. Metaphase I - as pairs homologous chromosomes line up in center e. Anaphase I - spindle fibers pull homologous chromosomes to separate sides of cell. f. Telophase 1 - nuclear envelope forms
g. Cytokinesis 1 - 2 new cell form C. Meiosis II a. Prophase II - chromo. become visible; nucleus disolves
b. Metaphase II - chromo. line up
c. Anaphase II - spindle fibers pull chromatids apart at the centromere
d. Telophase II - nuclear envelope starts to form; chromo. dissolve
e. Cytokinesis II - cells divide; only one copy of each chromo. in each cell Day 4: Bellwork
List as many things as you can that will influence how a trait is expressed in the phenotype. D. Comparing Mitosis and Meiosis a. Mitosis is a form of asexual reproduction 2. Replication and Separation of Genetic Material a. DNA is copied before both processes b. In Mitosis each daughter cell receives a complete set of the parent DNA c. In meiosis homologous chromo. are segregated into different cells. Results in a greater variety of gene combinations 3. Changes in Chromosome Number a. Mitosis: does not change the chromo. number b. Meiosis: cut the chromo. number in half. Analyzing Data (page 327) 4. Number of Cell Divisions a. Mitosis: 1 division; 2 cells b. Meiosis: 2 divisions; 4 cells b. Meiosis is an early step in sexual reproduction 1. Type of Reproduction E. Gene Linkage and Maps 1. Gene Linkage a. Genes on the same chromo. are linked. b. Chromo. separate independently not genes pg. 329 (1, 3, 5)
(1-4, 6, 7-9, 11, 13-17, 19-24) Bellwork:
How is meiosis different from mitosis?
Why is it important that some cells complete meiosis?
Why don't all cells complete meiosis?