Genetics

Genetics

• Study of heredity and the variation of inherited characteristics

• Heredity- the biological process where parents pass on certain genes to their offspring

History

• Gregor Mendel

• Known as the “father of modern genetics”

• As an Austrian monk and botanist, he was able to come up with the basic principles about heredity

• Majority of his research was done on pea plants

Without Mendel, Charles Darwin’s idea of Natural Selection could not be explained

• 1. All organisms produce more offspring than can survive.

• 2. Some organisms in a species survive and reproduce better than others.

• 3. Organisms in a species show wide variation.

• 4. Variations are inherited and passed on to the next generation.

The Principles of Genetics

•Variation is random and created by:

1)Mutations

2)Crossing over in meiosis

3)Independent Assortment*

4)Random mating

What Makes a Trait?

Traits are genetically determined characteristics; a gene

Alleles will make up the alternative forms of that gene.

Ex. Hair Color- trait/gene

Blonde, Black, Brown, Red- alleles

Trait/genes: Alleles

• List 5 different traits or genes and 3 Alleles for each

1._______________:_______________2._______________:_______________3._______________:_______________4._______________:_______________5._______________:_______________

Characteristics of Traits

Genotype

• The genetic make up

• Usually represented by a letter or letters

• Ex. A or Aa

Phenotype

• The observable trait/gene

• The physical characteristic

• Ex. Brown hair, Green eyes

Characteristics of Traits

Dominant

• The trait or allele that will mask(or dominate) over the other.

• Shows up more often

• Represented by a capital letter

• Ex. A

Recessive

• The trait or allele that is being masked(or covered).

• Shows up less often

• Represented by a lower case letter

• Ex. a

Characteristics of Traits

Homozygous

• Both genotype alleles are the same

• Ex. AA or aa, BB or bb

Heterozygous

• Both genotype alleles are different

• Ex. Aa or Bb

practice

• What would be an example of :

Homozygous Dominant (use the letter “H”)?

_ HH___

• Heterozygous Dominant?

___Hh__ ___

• Homozygous Recessive?

__hh______

Practice

• Round eyes are dominant to oval eyes. List the genotypes-Round

__RR_____

-Round

__Rr_____

-Oval

__rr_______

Practice

• Small ears are dominant to big ears. List the phenotypes.

-AA

___Small Ears_____

-Aa

___Small Ears_____

-aa

___Big Ears_______

Mendel’s 3 Laws

• 1st Law – Law of Dominance

One allele from the pair will be expressed while the other is unexpressed.

- The allele that is expressed is considered dominant. The unexpressed allele is recessive.

- Example: Black hair is dominant to Blonde hair

• 2nd Law – Law of Segregation

States that during meiosis two alleles will separate from each trait.

• Recall Meiosis – you create gametes. Law of Segregation ensures that each gamete will have one allele from the allele pair.

F-O-I-L

• F- First

• O- Outer

• I-Inner

• L-Last

• F-AB

• O-Ab

• I-aB

• L-ab

AaBb

A a B b

“INSIDE-OUTSIDE”

PRACTICE

• AABb

• aaBb

• Aabb

• How many different allele combinations were created?

Punnett Squares

• A punnett square is a visual aid that is used to view traits.

• Gives you a probability for possible outcomes when traits are crossed

• Monohybrids are used to view the outcomes in offspring examining only one trait

Genotype and Phenotype Ratio

Genotype Ratio:

#Homozygous Dominant(BB) :

#Heterozygous(Bb) : #Homozygous Recessive(bb)Ex. 0:2:2

Phenotype Ratio:

#Dominant Trait : #Recessive Trait

Ex. 2:2

Looks at the possibilities of

two

Different traits.

• Peas• Two Traits:• Shape (Round or Wrinkled)

• Color (Yellow or Green)

-RrYy x RrYy

FOIL-

R r Y y

RrYy x RrYy