GeneticsThe study of genes and the

inheritance of traits

THE STUDENTS WILL:

■ Explain how traits are inherited■ Identify the role of Gregor Mendel

in the History of Genetics■ Use a Punnett Square to predict

the results of crosses.■ Compare and Contrast the

difference between an individual’s genotype and phenotype.

Vocabulary:

■ Heredity Phenotype■ Allele Homozygous■ Genetics Heterozygous■ Hybrid■ Dominant■ Recessive■ Genotype

Inheriting Traits

■ Nose shape, eye color, and any other physical features are some of the traits that are inherited from parents.

An organism is a collection of traits, all inherited from its

parents.

Heredity

■ The passing of traits from the parent to the offspring

• Generally, genes on chromosomes control all the traits that show up in an organism.

Alleles

■ The different forms of a trait that a gene may have are called alleles

- When a pair of chromosomes separates during meiosis, alleles for each trait also separates into different sex cells

Important!

Every sex cell has one allele for each trait….

What is Genetics?

The study of how traits are inherited through the interactions of alleles is the science of Genetics.

Gregor Mendel- Father of

Genetics

-Austrian monk/ teacher-Began experimenting with garden peas in 1856-Made use of Scientific Method-First to use the Mathematics of Probability to explain heredity.-First to trace one trait through several generations.-Died in 1884 (work unnoticed)-His work was rediscovered in 1900

Genetics in Garden

Genetics in a Garden

-Each time Mendel studied a trait, he crossed two plants with different expressions of the trait and found that the new plants all looked like one of the two parents.

Genetics in a Garden

Mendel called these new plants HYBRIDS because they received different Genetic information or different alleles, for a trait from each parent.

Genetics in a Garden

An organism that always produces the same traits generation after generation is called a PUREBRED.

■ HybridAn offspring that

was given different genetic information for a trait from each parent.

■ PurebredAn offspring that

always produces the

same traits generation after

generation.

Mendel’s cross between tall pea plants yielded all tall pea plants

X =

His cross between small pea plants yielded all small pea plants.

X =

Mendels’ cross between tall pea plants and small pea plants yielded all tall pea plants.

X =

Mendel then crossed these second generation tall pea plants and ended up with 1 out 4 being small.

X =

DOMINANT AND RECESSIVE

TRAITS

■ Recessive Traits:Describes a trait thatis covered over, or dominated, byanother form of that trait and seems to disappear.-Weaker Trait

● Dominant Traits: Describes a trait that covers over, or dominates another form of that trait.-Stronger trait

Traits compared by Mendel

Using Probability to Make

Predictions

-A branch of mathematics that helps you predict the chance that something will happen.

■ Mendel also dealt with Probability

■ Worked with a large number of plants to make his predictions accurate.

■ Studied almost 30, 000 pea plants over a period of 8 years.

PUNNETTE

SQUARES

-A handy tool used to predict results in Mendelian genetics.

Punnett

Squares

-Letters represent dominant and recessive alleles

HOW?

-An upper case letter stands for a dominant letter.

- A lower case letter stands for a recessive allele

Alleles

■ B – is considered a dominant allele

■ b – is considered a recessive allele

BB – is dominant

Bb or bB – is dominant

bb - is recessive

GENOTYPE & PHENOTYPE

■ Genotype- genetic makeup of an organism

Ex. BB (Homozygous Dominant)■ Phenotype- the way an

organism looks and behavesEx. Black Fur

Alleles Determine Traits

■ Most cells in your body have 2 alleles for a trait.

■ These alleles are located on chromosomes within the nucleus of cells.

Example:Trait- HeightT - allele would be for Tallt - allele would be for short

Alleles determine Traits

■ Homozygous- an organism with 2 alleles that are the same

Ex. TT ( Tall), BB (Blonde Hair), tt, bb

■ Heterozygous- an organism with 2 different alleles for a trait.

Ex. Tt, Bb