Upload
morris-heath
View
227
Download
1
Tags:
Embed Size (px)
Citation preview
Chapter 14 Part I: Mendel and Chapter 14 Part I: Mendel and the Gene Ideathe Gene Idea
• This chapter details Mendel’s discovery of general laws of heredity as well as monohybrid dihybrid genetic crosses.
A. Gregor MendelA. Gregor Mendel
1 Austrian Monk
2 Formulated two laws of inheritance in 1860s.
3 Previously studied math and science at University of Vienna.
B. Blending Concepts of B. Blending Concepts of InheritanceInheritance
1 Theory stated that offspring would possess traits intermediate between those of different parents.
2 Red and White flowers make Pink flowers.
3 Darwin wanted to develop a theory of evolution based on Mendel’s heredity principles.
C. Mendel’s Experimental C. Mendel’s Experimental ProcedureProcedure
1 Mendel did a statistical study
2 Prepared experiments carefullyA . Garden PeaB . 22 true-breeding varietiesC . Simple traits were studied
3 Mendel traced inheritance of individual traits.
4 Principles of probability used for interpretation.
11.2 Monohybrid Inheritance11.2 Monohybrid Inheritance
A . Cross-pollination Monohybrid Crosses1 A hybrid is result of 2 true-breeding parents2 A monohybrid cross is between two true-breeding parents for two distinct
forms of a trait.3 Mendel tracked 2 generations
A . P GenerationB . F1 GenerationC . F2 Generation
B. Mendel’s ResultsB. Mendel’s Results
1 Contrary results to predictions
2 F1 resembled one parent
3 1/4 of F2 resembled one parent; 3/4 resembled other parent like F1 generation.
4 3:1 ratio resultsA . Dominant/recessive shown in F2.B . Factors separated when gametes were formed.C . Random fusion upon fertilization.
B. Mendel’s Results ContinuedB. Mendel’s Results Continued
5 Mendel’s First Law of Inheritance: Law of SegregationA. Each organism contains 2 factors for each
trait; factors segregate in formation of gametes; each gamete contains one factor for each trait.
B . Factors passed from generation to generation
C. As Viewed by Modern C. As Viewed by Modern Genetics Genetics
1 Traits controlled by two alleles, alternate forms of trait found at the same gene locus.
2 Gene locus is a specific location on a gene
3 Homozygous is two identical alleles for a trait.A . Homozygous dominant - 2 dominant allelesB . Homozygous recessive - 2 recessive alleles
4 After cross-pollination, all F1 are heterozygous genotypes.
D. Genotype Vs. PhenotypeD. Genotype Vs. Phenotype1 2 organisms with different allele combinations can
have same outward appearance (TT & Tt)
2 Genotype refers to alleles at fertilization.
3 Phenotype refers to physical appearance.
E. Laws of ProbabilityE. Laws of Probability
1 Probability is the likely outcome a given event will occur from random chance.
2 Multiplicative law of probability = chance of 2 or more independent events occurring together is the product of the probability of the events occurring separately
3 Additive law of probability = probability of an event that occurs in 2 or more independent ways.
F. The Punnet SquareF. The Punnet Square
1 Provides simple method to calculate probable results of genetic cross.
2 Sperm cells lined up vertically; egg cells lined up horizontally.
3 Larger sample sizes give better outcomes for predicted ratios.
4 Humans use phenotypic rations for predictions.
G. One-Trait TestcrossG. One-Trait Testcross1 Mendel performed testcrosses by crossing F1 to
homozygous recessive.2 Results indicated recessive factor in F1.3 Testcross = dominant phenotypic individual crossed with
recessive individual.
11.3 Dihybrid Inheritance11.3 Dihybrid InheritanceA . Dihybrid Crosses1 Dihybrid cross is an experimental
cross between 2 true-breeding parents for 2 different traits.
B . Plants Self-Pollinate1 Mendel observed 4 phenotypes among
F2.2 This gave him Second Law of Heredity:
law of independent assortment.A . Members assort independently of
each other.
C. Dihybrid Genetics ProblemsC. Dihybrid Genetics Problems
1 Laws of probability indicate a 9:3:3:1 phenotypic ratio of F2.A. 9/16 dominant for both traitsB . 3/16 dominant for 1 trait, recessive for otherC . 3/16 dominant/recessive opposite of previousD. 1/16 recessive for both traits
2 9:3:3:1 ratio expected when heterozygous for 2 traits are crossed.