Heredity - PowerPoint Presentation

Slide1

Heredity

Genetics = the study of

HEREDITY

Heredity = Passing of

Traits

from parents to offspring

Predicted how

TRAITS

are transferred from one generation to the nextSlide2

Father of Genetics

Gregor Mendel, an Austrian monk is known as the FATHER of GENETICS.

Used

QUANTITATIVE approach to science using pea plants between 1856 and 1863.

Counted

the number of each offspring of the garden pea

Analyzed

the data

He was curious when he conducted this simple experiment…Slide3

Testable Question

:

What is the result of crossing (mating) a

tall

pea plant with a

short

pea plant.

Hypothesis

: If a tall pea plant is crossed with a short pea plant, then the resulting offspring will be of medium height.

He

u

sed

a technique called

cross-pollination where he took the pollen from one plant and introduced it to the pistil (where the egg is located) of another plant.

Pistil

Stamen

PollenSlide4

Results:

ALL TALL PLANTS! (much to his surprise)Slide5

Mendel had to investigate further.

How could this be?

Why Did Mendel Choose The Pea Plant?

The pea plants had many

TRAITS

that have ONLY two different variations (different forms).

Example: trait = color

Variations =

purple or white2. Easy to grow3. Had to justify why he was doing the experiments (peas are edible)Slide6

Mendel completed his experiments from 1856 to 1863 and had four major conclusions and a lot of peas.

Mendel’s Findings

Traits are controlled by two factors.

Law of dominance

Law of segregation

Law of independent assortmentSlide7

Traits are Controlled by Two Factors

After many experiments, Mendel speculated that traits were controlled by 2 “factors”, one from each parent. He did not know about genes (remember the structure of DNA was not discovered until almost 100 years after Mendel finished his research).

We

now know that Mendel's inheritance factors are

genes

, or more specifically

alleles

– different variants of the same gene.Slide8

Law of Dominance

Some

alleles

(version of a gene) are

dominant

(represented by a capital letter in the

genotype

) while others are

recessive (represented by a lowercase letter in the genotype); an organism with at least one dominant allele will display the effect (phenotype) of the dominant allele.

TT

(

genotype

)

Tall

(

phenotype)

tt (genotype)Short (phenotype)

T

t (genotype)Tall

(

phenotype

)Slide9

Law of Dominance

Genotypes

are represented by letters that are usually related to the dominant variation of the trait. For example, if the dominant variation for the trait of height is tall, then the genotypes would be represented as Tt or TT. For short height, the genotype could ONLY be

tt

.

Phenotypes

are the physical display of the trait.Slide10

Homozygous/Purebred: Two alleles of a particular gene are the

SAMEAA – must say homozygous dominant or purebred

dominant

OR

aa – must

say homozygous

recessive or

purebred recessive for a recessive variation to be expressed (shown in the phenotype), it MUST be homozygous (aa)Heterozygous/Hybrid

: Two alleles of a particular gene are DIFFERENTExample: AaHow do you describe a genotype?Slide11
Slide12

Let’s Review

Example #1:

If

“

T

”

refers to the

tall allele & “t” refers to the short allele, and the individual is “Tt”, then…What is the genotype of the organism above? What is the phenotype of the organism above?Is the organism above homozygous or heterozygous?Example #2: In flowers, blue is dominant to white. You are observing a white flower. What is the trait?How would I display the dominant allele?How would I display the recessive allele?

What is the genotype of the organism above? What is the phenotype of the organism above?Is the organism above homozygous or heterozygous?