genetics why do you look like you do?. what you should learn from this presentation you should know...
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GeneticsGenetics
Why Do You Look Like You Do?
What You Should Learn From What You Should Learn From This PresentationThis Presentation
You should know the definition of each of the bold, underlined words
You should know the general theme of the presentation
We will go over the presentation as a group, be prepared to discuss it
GeneticsGenetics
Defined as the study of heredity.
History of GeneticsHistory of Genetics
10,000 years ago, farmers in Egypt bred wheat
4,000 years ago, Asian horse breeders kept records of animal traits
Humans have been controlling the traits of crops and livestock since before the beginning of history
Gregor MendelGregor Mendel
1822-1884 Lived in Austria (now part of Czechoslovakia) Was an Augustinian monk Conducted breeding experiments in the monastery
garden from 1856-1864 Published in 1866 (just after Darwin was
published) No one cared until 35 years later (about 1900)
Gregor MendelGregor Mendel
Experiment consisted of keeping amazingly accurate records of the garden pea
He chose the pea plant because he could get pure strains that had been produced over years by gardeners– The strains had many different varieties with
contrasting traits
He planted and kept records of over 30,000 plants
Gregor Mendel’s ResultsGregor Mendel’s Results
TraitFirst Generation
(F1)Second
Generation (F2)Ratio
Yellow vs. Green Peas
All yellow6022 Yellow2001 Green
?
Round vs. Wrinkled Peas
All round5474 Round
1850 Wrinkled?
Inflated vs. Constricted Pods
All Inflated882 Inflated
299 Constricted?
Long vs. Short Stems All Long787 Long Stems277 Short Stems
?
Colored vs. White Flowers
All Colored705 Colored224 White
?
Axial vs. Terminal Flowers
All Axial651 Axial
207 Terminal?
Green vs. Yellow Pods
All Green428 Green
224 Yellow?
Gregor Mendel’s ResultsGregor Mendel’s Results
Did you see a trend?What is the final F2 ratio for each of the
traits?
Gregor Mendel’s ResultsGregor Mendel’s Results
If you didn’t, go back and take a look againNotice that the trait in the F1 generation is
always the larger number in the F2 generation
Gregor Mendel’s ResultsGregor Mendel’s Results
If you figured out the F2 ratio, you should have noticed something else
Almost all of them are close to 3:1
Gregor Mendel’s ResultsGregor Mendel’s Results
TraitFirst Generation
(F1)Second
Generation (F2)Ratio
Yellow vs. Green Peas
All yellow6022 Yellow2001 Green
3.01:1
Round vs. Wrinkled Peas
All round5474 Round
1850 Wrinkled2.96:1
Inflated vs. Constricted Pods
All Inflated882 Inflated
299 Constricted2.95:1
Long vs. Short Stems All Long787 Long Stems277 Short Stems
2.84:1
Colored vs. White Flowers
All Colored705 Colored224 White
3.15:1
Axial vs. Terminal Flowers
All Axial651 Axial
207 Terminal3.14:1
Green vs. Yellow Pods
All Green428 Green
224 Yellow2.82:1
Gregor Mendel’s ResultsGregor Mendel’s Results
Why did all of the F2 generations have a three to one ratio when the F1 generation were all one trait?
Because the pure parents each gave a gene or “factor” to each of the F1 offspring and one of those genes were dominant over the recessive gene
Gregor Mendel’s ResultsGregor Mendel’s Results
Yet, some of those F1 generations passed on the the genes to their F2 generations
Gregor Mendel’s ResultsGregor Mendel’s Results
The F2 generation must have had some of the traits from the P1 generation, but we were unable to see the recessive traits.– They were masked or covered by the dominant
trait.
Mendel’s First PrincipleMendel’s First Principle
Principle of Dominance and Recessivness– Each trait is controlled by a pair of factors
(chromosomes)– The dominant factor masks or hides the
recessive factor
Genotype vs. PhenotypeGenotype vs. Phenotype
Genotype describes the genetic make-up of the organism– The actual genes
Phenotype describes the physical make-up of the organism– What traits does the organism show
Mendel’s Second PrincipleMendel’s Second Principle
The Principle of Segregation– Heredity factors are determined by distinct
factors– For each trait, an individual carries two factors
for each trait– The two factors of each trait segregate and end
up in separate gametes
Mendel’s Second PrincipleMendel’s Second Principle
Today, those factors are called genes– Part of the DNA
Each gene codes for one trait– Those are called alleles
Mendel’s Second PrincipleMendel’s Second Principle
If you did the cross below, what is the probabilty of each genotype?
Monohybrid CrossMonohybrid Cross
Tt x Tt T t
T TT Tt
t Tt tt
Monohybrid Punnett SquaresMonohybrid Punnett Squares
Now you try some:– Tt x tt– Tt x TT– TT x tt