Presentation on theme: "Chapter 11: Introduction to Genetics"— Presentation transcript:
1 Chapter 11: Introduction to Genetics Biology- Kirby
2 11-1: The Work of Gregor Mendel Genetics- the scientific study of heredity.Gregor Mendel- monk who used peas to understand principles of genetics.Fertilization- process in sexual reproduction in which male and female cells join to form a new cell.
3 11-1: The Work of Gregor Mendel True-breeding- describes self-pollinating organisms identical to themselves.Mendel’s pea plants were true-breeding (example-tall plants produced tall plants).Mendel wanted to establish cross-pollination in his plants instead.Cross-pollination- 2 different plants as parents.
4 11-1: The Work of Gregor Mendel Trait- a specific characteristic that varies from one individual to another.Mendel studied 7 traits in peas:seed shape, seed color, seed coat color, pod shape, pod color, flower position, and plant height.Mendel crossed plants to study these traits in offspring.
5 11-1: The Work of Gregor Mendel The original plants were called the Parental (P) generation.The offspring were called first filial (F1) generation.Hybrid- the offspring of crosses between parents with different traits.All the offspring had traits of one parent:
6 11-1: The Work of Gregor Mendel Mendel’s conclusions:1. biological inheritance is determined by factors that are passed from one generation to the next.Genes- chemical factors that determine traits.Allele- different forms of a gene.
7 11-1: The Work of Gregor Mendel 2. Principle of Dominance- states that some alleles are dominant and others are recessive.Dominant-trait will be expressed.Recessive- trait will not be expressed.
8 11-1: The Work of Gregor Mendel Mendel crossed all the F1 generation to make a F2 generation.Some of the recessive traits appeared in the F2 generation.Segregation- separation of alleles during gamete formation.Gametes- sex cells.Each F1 plant has 2 gametes; one allele for dominant trait and one for recessive trait.
9 11-2: Probability & Punnett Squares Probability- the likelihood that a particular event will occur.The principles of probability can be used to predict the outcomes of genetic crosses.
10 11-2: Probability & Punnett Squares Punnett Square- diagram that shows the gene combinations that might result from a genetic cross.The letters of a punnett square represent alleles; uppercase=dominant, lowercase=recessive.Used to predict and compare genetic variations resulting from a cross.
11 11-2: Probability & Punnett Squares Homozygous- the alleles are the same; true-breeding organism-example: TT or tt.Heterozygous- the alleles are different; hybrid organism- example: Tt.
12 11-2: Probability & Punnett Squares Phenotype- physical characteristic- example: tall.Genotype- genetic makeup- example: TT.Organisms can have the same phenotype, but different genotypes; example: TT and Tt.
13 11-2: Probability & Punnett Squares Punnett Square Examples:
14 11-3: Exploring Mendelian Genetics Mendel wanted to know if segregation of one allele affected another pair of alleles.Example: Seed shape affect seed color?Independent Assortment- independent segregation of genes during gamete formation.
15 11-3: Exploring Mendelian Genetics To test independent assortment, Mendel crossed true-breeding round yellow peas (RRYY) with wrinkled green peas (rryy).F1 Cross:
16 11-3: Exploring Mendelian Genetics F1 genotype: RrYyMendel crossed F1 plants to get F2 plants:The results had a 9:3:3:1 ratio.
17 11-3: Exploring Mendelian Genetics The principle of independent assortment states that genes for different traits can segregate independently during gamete formation.Independent assortment also helps give genetic variations in organisms.
18 11-3: Exploring Mendelian Genetics Some alleles are neither dominant or recessive, and many traits are controlled by multiple alleles and genes.Incomplete dominance- the heterozygous phenotype is in between the 2 homozygous phenotypes.Example- Flowers-Red (RR) & White (WW)=Pink (RW)
19 11-3: Exploring Mendelian Genetics Codominance- both alleles contribute to the phenotype.Example: Chicken feathers-Black (BB) & White (WW)=Speckled (BW)Multiple Alleles- 3 or more alleles of the same gene.Example: Rabbits fur-Page 273- full color, chinchilla, himalayan, and albino coat colors.
20 11-4: MeiosisHomologous- the chromosomes that have a corresponding chromosome from the opposite sex parent.Diploid- a cell that has both sets of homologous chromosomes (2N).Haploid- a cell that has one set of chromosomes (N).
21 11-4: MeiosisMeiosis- process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.Involves 2 divisions:Meiosis I and Meiosis II
22 11-4: Meiosis Interphase I- Chromosomes replicate before meiosis I. Prophase I- each chromosome pairs with its corresponding homologous chromosome to from a tetrad.4 chromatids=tetradMetaphase I- spindle fibers attach to chromosomes.
23 11-4: MeiosisAnaphase I- the fibers pull the homologous chromosomes toward opposite ends of the cell.Telophase I & Cytokinesis- nuclear envelopes form and the cell separates.Crossing over- the homologous chromosomes exchange alleles from their chromatids during meiosis. This produces new combinations of alleles.
24 11-4: MeiosisMeiosis II:Prophase II- meiosis I results in 2 haploid (N) daughter cells, each with half the number of chromosomes as the original.Metaphase II- chromosomes line up in the middle.Anaphase II- The sister chromatids separate and move toward opposite ends of the cell.
25 11-4: MeiosisTelophase II & Cytokinesis- meiosis II results in 4 haploid (4N) daughter cells.Gamete Formation-In males, sperm are the haploid gametes produced in meiosis. (4)In females, an egg is the haploid gamete produced in meiosis. (1)
26 11-4: Meiosis Mitosis vs. Meiosis Mitosis results in the production of 2 genetically identical diploid cells.Meiosis produces 4 genetically different haploid cells.
27 11-5: Linkage & Gene MapsAlthough alleles segregate by independent assortment, some genes are linked together.Gene Map- diagram showing the locations of genes on a chromosome.