chapter 14 mendel and the gene idea. inheritance
TRANSCRIPT
Chapter 14 Mendel and the
Gene Idea
Inheritance
Genetics
Genetic Theories
1
Genetic Theories (cont.)
Gregor Mendel
Mendel’s paper published in 1866, but was not recognized by Science until the early 1900’s.
Reasons for Mendel's Success
Mendel was a pea picker.
He used peas as his study organism.
Why Use Peas?
Cross-pollination
Self-pollination
Mendel's Work
Monohybrid or Mendelian Crosses
P Generation
Offspring
Another Sample Cross
P1 Tall X short (TT x tt)
F1 all Tall (Tt)
F2 3 tall to 1 short
(1 TT: 2 Tt: 1 tt)
Results - Summary
Mendel's Hypothesis
Mendel's Hypothesis
Mendel's Hypothesis
4
Law of Segregation
Mendel’s Experiments
Vocabulary
Helpful Vocabulary
6 Mendelian Crosses are Possible
Cross Genotype PhenotypeTT X tt all Tt all Dom
Tt X Tt 1TT:2Tt:1tt 3 Dom: 1 Res
TT X TT all TT all Dom
tt X tt all tt all Res
TT X Tt 1TT:1Tt all Dom
Tt X tt 1Tt:1tt 1 Dom: 1 Res
Test Cross
Dihybrid Cross
Dihybrid Cross
Results
9 Tall, Red flowered 3 Tall, white flowered 3 short, Red flowered 1 short, white flowered
Or: 9:3:3:1
Law of Independent Assortment
Probability
Genetic Ratios
Rule of Multiplication
Example: TtRr X TtRr
Comment
Variations on Mendel
Incomplete Dominance
Result
Another example
Codominance
Result
Multiple Alleles
Result
Alleles and Blood Types
Type Genotypes
A IA IA or IAi B IB IB or IBi AB IAIB
O ii
Comment
Epistasis
Gerbils
In Gerbils
CcBb X CcBb
Brown X Brown
F1 = 9 brown (C_B_)
3 black (C_bb)
4 albino (cc__)
Result
Problem
Wife is type A Husband is type AB Child is type O
Question - Is this possible?
Comment - Wife’s boss is type O
Bombay Effect
Genotypes
Bombay - Detection
Polygenic Inheritance
Genetic Basis
Result
Genetic Studies in Humans
Pedigree Chart Symbols
Male
Female
Person with trait
Sample Pedigree
Dominant Trait Recessive Trait
Human Recessive Disorders
Sickle-cell Disease
Tay-Sachs
Cystic Fibrosis
Recessive Pattern
Human Dominant Disorders
Inheritance Pattern
Genetic Screening
General FormalR = F X M X D
R = riskF = probability that the female
carries the gene.M = probability that the male
carries the gene.D = Disease risk under best
conditions.
Example
Risk Calculation Wife = probability is 1.0 that
she has the allele. Husband = with no family
record, probability is near 0. Disease = this is a recessive
trait, so risk is Aa X Aa = .25 R = 1 X 0 X .25 R = 0
Risk Calculation
Assume husband is a carrier, then the risk is:
R = 1 X 1 X .25
R = .25
There is a .25 chance that any child will be albino.
Common Mistake
Carrier Recognition
Fetal Testing
Amniocentesis
Chorionic Villi Sampling
Newborn Screening
Newborn Screening
Multifactorial Diseases
Ex. Heart Disease
Summary
Know the Mendelian crosses and their patterns.
Be able to work simple genetic problems (practice).
Watch genetic vocabulary. Be able to read pedigree charts.
Summary
Be able to recognize and work with some of the “common” human trait examples.