Mendel and the gene idea
Download
1 / 108

Mendel and the Gene Idea - PowerPoint PPT Presentation


  • 193 Views
  • Updated On :

Mendel and the Gene Idea. Inheritance. The passing of traits from parents to offspring. Humans have known about inheritance for thousands of years. Genetics. The scientific study of the inheritance. Genetics is a relatively “new” science (about 150 years). Genetic Theories.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Mendel and the Gene Idea' - fidelina


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Inheritance l.jpg
Inheritance

  • The passing of traits from parents to offspring.

  • Humans have known about inheritance for thousands of years.


Genetics l.jpg
Genetics

  • The scientific study of the inheritance.

  • Genetics is a relatively “new” science (about 150 years).


Genetic theories l.jpg
Genetic Theories

1. Blending Theory -

traits were like paints and mixed evenly from both parents.

2. Incubation Theory -

only one parent controlled the traits of the children.

Ex: Spermists and Ovists


Slide5 l.jpg

3. Particulate Model -

parents pass on traits as discrete units that retain their identities in the offspring.


Gregor mendel l.jpg
Gregor Mendel

  • Father of Modern Genetics.



Reasons for mendel s success l.jpg
Reasons for Mendel's Success by Science until the early 1900’s.

  • Used an experimental approach.

  • Applied mathematics to the study of natural phenomena.

  • Kept good records.


Slide9 l.jpg

Mendel was a pea picker. by Science until the early 1900’s.

He used peas as his study organism.


Why use peas l.jpg
Why Use Peas? by Science until the early 1900’s.

  • Short life span.

  • Bisexual.

  • Many traits known.

  • Cross- and self-pollinating.

  • (You can eat the failures).


Cross pollination l.jpg
Cross-pollination by Science until the early 1900’s.

  • Two parents.

  • Results in hybrid offspring where the offspring may be different than the parents.


Self pollination l.jpg
Self-pollination by Science until the early 1900’s.

  • One flower as both parents.

  • Natural event in peas.

  • Results in pure-bred offspring where the offspring are identical to the parents.


Mendel s work l.jpg
Mendel's Work by Science until the early 1900’s.

  • Used seven characters, each with two expressions or traits.

  • Example:

  • Character - height

    • Traits - tall or short.


Monohybrid or mendelian crosses l.jpg
Monohybrid or Mendelian Crosses by Science until the early 1900’s.

  • Crosses that work with a single character at a time.

    Example - Tall X short


P generation l.jpg
P Generation by Science until the early 1900’s.

  • The Parental generation or the first two individuals used in a cross.

    Example - Tall X short

  • Mendel used reciprocal crosses, where the parents alternated for the trait.


Offspring l.jpg
Offspring by Science until the early 1900’s.

  • F1 - first filial generation.

  • F2 - second filial generation, bred by crossing two F1 plants together or allowing a F1 to self-pollinate.


Another sample cross l.jpg
Another Sample Cross by Science until the early 1900’s.

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 l.jpg
Results - Summary by Science until the early 1900’s.

  • In all crosses, the F1 generation showed only one of the traits regardless of which wasmaleorfemale.

  • The other trait reappeared in the F2 at ~25% (3:1 ratio).


Mendel s hypothesis l.jpg
Mendel's Hypothesis by Science until the early 1900’s.

1. Genes can have alternate versions called alleles.

2. Each offspring inherits two alleles, one from each parent.


Mendel s hypothesis24 l.jpg
Mendel's Hypothesis by Science until the early 1900’s.

3. If the two alleles differ, the dominant allele is expressed. The recessive allele remains hidden unless the dominant allele is absent.

Comment - do not use the terms “strongest” to describe the dominant allele.


Mendel s hypothesis25 l.jpg
Mendel's Hypothesis by Science until the early 1900’s.

4. The two alleles for each trait separate during gamete formation. This now called: Mendel's Law of Segregation


Law of segregation l.jpg
Law of Segregation by Science until the early 1900’s.


Mendel s experiments l.jpg
Mendel’s Experiments by Science until the early 1900’s.

  • Showed that the Particulate Model best fit the results.


Vocabulary l.jpg
Vocabulary by Science until the early 1900’s.

  • Phenotype - the physical appearance of the organism.

  • Genotype - the genetic makeup of the organism, usually shown in a code.

    • T = tall

    • t = short


Helpful vocabulary l.jpg
Helpful Vocabulary by Science until the early 1900’s.

  • Homozygous - When the two alleles are the same (TT/tt).

  • Heterozygous- When the two alleles are different (Tt).


6 mendelian crosses are possible l.jpg
6 Mendelian Crosses are Possible by Science until the early 1900’s.

CrossGenotypePhenotype

TT 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 l.jpg
Test Cross by Science until the early 1900’s.

  • Cross of a suspected heterozygote with a homozygous recessive.

  • Ex: T_ X tt

    If TT - all dominant

    If Tt - 1 Dominant: 1 Recessive


Dihybrid cross l.jpg
Dihybrid Cross by Science until the early 1900’s.

  • Cross with two genetic traits.

  • Need 4 letters to code for the cross.

    • Ex: TtRr

  • Each Gamete - Must get 1 letter for each trait.

    • Ex. TR, Tr, etc.


Number of kinds of gametes l.jpg
Number of Kinds of Gametes by Science until the early 1900’s.

  • Critical to calculating the results of higher level crosses.

  • Look for the number of heterozygous traits.


Equation l.jpg
Equation by Science until the early 1900’s.

The formula 2n can be used, where “n” = the number of heterozygous traits.

Ex: TtRr, n=2

22 or 4 different kinds of gametes are possible.

TR, tR, Tr, tr


Dihybrid cross37 l.jpg
Dihybrid Cross by Science until the early 1900’s.

TtRr X TtRr

Each parent can produce 4 types of gametes.

TR, Tr, tR, tr

Cross is a 4 X 4 with 16 possible offspring.


Results l.jpg
Results by Science until the early 1900’s.

  • 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 l.jpg
Law of Independent Assortment by Science until the early 1900’s.

  • The inheritance of 1st genetic trait is NOT dependent on the inheritance of the 2nd trait.

  • Inheritance of height is independent of the inheritance of flower color.


Comment l.jpg
Comment by Science until the early 1900’s.

  • Ratio of Tall to short is 3:1

  • Ratio of Red to white is 3:1

  • The cross is really a product of the ratio of each trait multiplied together. (3:1) X (3:1)


Probability l.jpg
Probability by Science until the early 1900’s.

  • Genetics is a specific application of the rules of probability.

  • Probability - the chance that an event will occur out of the total number of possible events.


Genetic ratios l.jpg
Genetic Ratios by Science until the early 1900’s.

  • The monohybrid “ratios” are actually the “probabilities” of the results of random fertilization.

    Ex: 3:1

    75% chance of the dominant

    25% chance of the recessive


Rule of multiplication l.jpg
Rule of Multiplication by Science until the early 1900’s.

  • The probability that two alleles will come together at fertilization, is equal to the product of their separate probabilities.


Example ttrr x ttrr l.jpg
Example: TtRr X TtRr by Science until the early 1900’s.

  • The probability of getting a tall offspring is ¾.

  • The probability of getting a red offspring is ¾.

  • The probability of getting a tall red offspring is ¾ x ¾ = 9/16


Comment47 l.jpg
Comment by Science until the early 1900’s.

  • Use the Product Rule to calculate the results of complex crosses rather than work out the Punnett Squares.

  • Ex: TtrrGG X TtRrgg


Solution l.jpg
Solution by Science until the early 1900’s.

“T’s” = Tt X Tt = 3:1

“R’s” = rr X Rr = 1:1

“G’s” = GG x gg = 1:0

Product is:

(3:1) X (1:1) X (1:0 ) = 3:3:1:1


Tips for dihybrid problems l.jpg
Tips for Dihybrid Problems by Science until the early 1900’s.

  • Identify all of the alleles that can be identified from the phenotypes of the parents or kids.

  • Work from the monohybrid ratios to solve for the missing alleles.


Variations on mendel l.jpg
Variations on Mendel by Science until the early 1900’s.

1. Incomplete Dominance

2. Codominance

3. Multiple Alleles

4. Epistasis

5. Polygenic Inheritance


Incomplete dominance l.jpg
Incomplete Dominance by Science until the early 1900’s.

  • When the F1 hybrids show a phenotype somewhere between the phenotypes of the two parents.

    Ex. Red X White snapdragons

    F1 = all pink

    F2 = 1 red: 2 pink: 1 white


Result l.jpg
Result by Science until the early 1900’s.

  • No hidden Recessive.

  • 3 phenotypes and 3 genotypes (Hint! – often a “dose” effect)

    • Red = CR CR

    • Pink = CRCW

    • White = CWCW


Another example l.jpg
Another example by Science until the early 1900’s.


Codominance l.jpg
Codominance by Science until the early 1900’s.

  • Both alleles are expressed equally in the phenotype.

  • Ex. MN blood group

    • MM

    • MN

    • NN


Result56 l.jpg
Result by Science until the early 1900’s.

  • No hidden Recessive.

  • 3 phenotypes and 3 genotypes (but not a “dose” effect)


Multiple alleles l.jpg
Multiple Alleles by Science until the early 1900’s.

  • When there are more than 2 alleles for a trait.

  • Ex. ABO blood group

    • IA - A type antigen

    • IB - B type antigen

    • i - no antigen


Result58 l.jpg
Result by Science until the early 1900’s.

  • Multiple genotypes and phenotypes.

  • Very common event in many traits.


Alleles and blood types l.jpg
Alleles and Blood Types by Science until the early 1900’s.

TypeGenotypes

A IA IA or IAi

B IB IB or IBi

AB IAIB

O ii


Comment62 l.jpg
Comment by Science until the early 1900’s.

  • Rh blood factor is a separate factor from the ABO blood group.

  • Rh+ = dominant

  • Rh- = recessive

  • A+ blood = dihybrid trait


Epistasis l.jpg
Epistasis by Science until the early 1900’s.

  • When 1 gene locus alters the expression of a second locus.

  • Ex:

  • 1st gene: C = color, c = albino

  • 2nd gene: B = Brown, b = black


Gerbils l.jpg
Gerbils by Science until the early 1900’s.


In gerbils l.jpg
In Gerbils by Science until the early 1900’s.

CcBb X CcBb

Brown X Brown

F1 = 9 brown (C_B_)

3 black (C_bb)

4 albino (cc__)


Result66 l.jpg
Result by Science until the early 1900’s.

  • Ratios often altered from the expected.

  • One trait may act as a recessive because it is “hidden” by the second trait.


Epistasis in mice l.jpg
Epistasis in Mice by Science until the early 1900’s.


Problem l.jpg
Problem by Science until the early 1900’s.

  • 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 l.jpg
Bombay Effect by Science until the early 1900’s.

  • Epistatic Gene on ABO group.

  • Alters the expected ABO outcome.

  • H = dominant, normal ABO

  • h = recessive, no A,B, reads as type O blood.


Genotypes l.jpg
Genotypes by Science until the early 1900’s.

  • Wife: type A (IA IA , Hh)

  • Husband: type AB (IAIB, Hh)

  • Child: type O (IA IA , hh)

    Therefore, the child is the offspring of the wife and her husband (and not the boss).


Bombay detection l.jpg
Bombay - Detection by Science until the early 1900’s.

  • When ABO blood type inheritance patterns are altered from expected.


Ap biology l.jpg

AP Biology by Science until the early 1900’s.

Best Looking Bio Teacher EVER.

Who’s Hungry?

It Came From Space!

He Made New Friends.

FEED ME!

This Isn’t a Human at All!

Zachary - IASMH


Homework l.jpg
Homework by Science until the early 1900’s.

  • Readings – Chapters 14, 47

  • Lab – changed to Chi Square and other genetics.

  • Chapter 47 – Wed. 12/1

  • Chapter 14 – Fri. 12/3


New 1 800 l.jpg
New 1-800 by Science until the early 1900’s.

  • You can now reach my office directly 24/7 by calling:

    1-800-316-3163 ext. 31


Polygenic inheritance l.jpg
Polygenic Inheritance by Science until the early 1900’s.

  • Factors that are expressed as continuous variation.

  • Lack clear boundaries between the phenotype classes.

  • Ex: skin color, height


Genetic basis l.jpg
Genetic Basis by Science until the early 1900’s.

  • Several genes govern the inheritance of the trait.

  • Ex: Skin color is likely controlled by at least 4 genes. Each dominant gives a darker skin.


Result78 l.jpg
Result by Science until the early 1900’s.

  • Mendelian ratios fail.

  • Traits tend to "run" in families.

  • Offspring often intermediate between the parental types.

  • Trait shows a “bell-curve” or continuous variation.


Genetic studies in humans l.jpg
Genetic Studies in Humans by Science until the early 1900’s.

  • Often done by Pedigree charts.

  • Why?

    • Can’t do controlled breeding studies in humans.

    • Small number of offspring.

    • Long life span.


Pedigree chart symbols l.jpg
Pedigree Chart Symbols by Science until the early 1900’s.

Male

Female

Person with trait


Sample pedigree l.jpg
Sample Pedigree by Science until the early 1900’s.


Slide82 l.jpg

Recessive Trait by Science until the early 1900’s.

Dominant Trait


Human recessive disorders l.jpg
Human Recessive Disorders by Science until the early 1900’s.

  • Several thousand known:

    • Albinism

    • Sickle Cell Anemia

    • Tay-Sachs Disease

    • Cystic Fibrosis

    • PKU

    • Galactosemia


Sickle cell disease l.jpg
Sickle-cell Disease by Science until the early 1900’s.

  • Most common inherited disease among African-Americans.

  • Single amino acid substitution results in malformed hemoglobin.

  • Reduced O2 carrying capacity.

  • Codominant inheritance.


Tay sachs l.jpg
Tay-Sachs by Science until the early 1900’s.

  • Eastern European Jews.

  • Brain cells unable to metabolize type of lipid, accumulation of causes brain damage.

  • Death in infancy or early childhood.


Cystic fibrosis l.jpg
Cystic Fibrosis by Science until the early 1900’s.

  • Most common lethal genetic disease in the U.S.

  • Most frequent in Caucasian populations (1/20 a carrier).

  • Produces defective chloride channels inmembranes.


Recessive pattern l.jpg
Recessive Pattern by Science until the early 1900’s.

  • Usually rare.

  • Skips generations.

  • Occurrence increases with consaguineous matings.

  • Often an enzyme defect.

  • Affects males and females equally.


Human dominant disorders l.jpg
Human Dominant Disorders by Science until the early 1900’s.

  • Less common then recessives.

  • Affects males and females equally.

  • Ex:

    • Huntington’s disease

    • Achondroplasia

    • Familial Hypercholesterolemia


Inheritance pattern l.jpg
Inheritance Pattern by Science until the early 1900’s.

  • Each affected individual had one affected parent.

  • Doesn’t skip generations.

  • Homozygous cases show worse phenotype symptoms.

  • May have post-maturity onset of symptoms.


Genetic screening l.jpg
Genetic Screening by Science until the early 1900’s.

  • Risk assessment for an individual inheriting a trait.

  • Uses probability to calculate the risk.


General formal l.jpg
General Formal by Science until the early 1900’s.

R = F X M X D

R = risk

F = probability that the female carries the gene.

M = probability that the male carries the gene.

D = Disease risk under best conditions.


Example l.jpg
Example by Science until the early 1900’s.

  • Wife has an albino parent.

  • Husband has no albinism in his pedigree.

  • Risk for an albino child?


Risk calculation l.jpg
Risk Calculation by Science until the early 1900’s.

  • 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 calculation95 l.jpg
Risk Calculation by Science until the early 1900’s.

  • Assume husband is a carrier, then the risk is:

    R = 1 X 1 X .25

    R = .25

    There is a .25 chance that every child will be albino.


Common mistake l.jpg
Common Mistake by Science until the early 1900’s.

  • If risk is .25, then as long as we don’t have 4 kids, we won’t get any with the trait.

  • Risk is .25 for each child. It is not dependent on what happens to other children.


Carrier recognition l.jpg
Carrier Recognition by Science until the early 1900’s.

  • Fetal Testing

    • Amniocentesis

    • Chorionic villi sampling

  • Newborn Screening


Fetal testing l.jpg
Fetal Testing by Science until the early 1900’s.

  • Biochemical Tests

  • Chromosome Analysis


Amniocentesis l.jpg
Amniocentesis by Science until the early 1900’s.

  • Administered between 11 - 14 weeks.

  • Extract amnionic fluid = cells and fluid.

  • Biochemical tests and karyotype.

  • Requires culture time for cells.


Chorionic villi sampling l.jpg
Chorionic Villi Sampling by Science until the early 1900’s.

  • Administered between 8 - 10 weeks.

  • Extract tissue from chorion (placenta).

  • Slightly greater risk but no culture time required.


Newborn screening l.jpg
Newborn Screening by Science until the early 1900’s.

  • Blood tests for recessive conditions that can have the phenotypes treated to avoid damage. Genotypes are NOT changed.

  • Ex. PKU


Newborn screening104 l.jpg
Newborn Screening by Science until the early 1900’s.

  • Required by law in all states.

  • Tests 1- 6 conditions.

  • Required of “home” births too.


Multifactorial diseases l.jpg
Multifactorial Diseases by Science until the early 1900’s.

  • Where Genetic and Environment Factors interact to cause the Disease.


Ex heart disease l.jpg
Ex. Heart Disease by Science until the early 1900’s.

  • Genetic

  • Diet

  • Exercise

  • Bacterial Infection


Summary l.jpg
Summary by Science until the early 1900’s.

  • Know the Mendelian crosses and their patterns.

  • Be able to work simple genetic problems (practice).

  • Watch genetic vocabulary.

  • Be able to read pedigree charts.


Summary108 l.jpg
Summary by Science until the early 1900’s.

  • Be able to recognize and work with some of the “common” human trait examples.


ad