MENDELIAN GENETICS

DEFINITIONS Genetics

-the branch of biology that studies heredity

Heredity -the passing on of traits from

parents to offspring

Traits- is a specific characteristic that varies from

one individual to another which make each of us unique

BACKGROUND Organisms usually

resemble their parents because they inherit certain traits from them.

These characteristics, variants called traits, are determined by genetic information on chromosomes.

GREGOR MENDEL

Gregor Johann Mendel, an Austrian monk, carried out the first important studies on heredity (1800s).

Father of Genetics

HISTORY

Mendel was the first person to succeed in predicting how traits would be transferred from one generation to the next.

Earlier observers looked at many traits at once-- Mendel focused on one at a time

MENDEL’S EXPERIMENT Mendel hand-pollinated

pea plant flowers using a paintbrush

- He knew that the male part of each flower produces pollen, (containing sperm).

- the female part of the flower produces egg cells.

- He traced traits through

the several generations

WHY PEAS(PISUM

SATIVUM)?

WHY PEAS(PISUM SATIVUM)?-can be grown in small area

-produces lots of offspring

-produce pure plants when allowed to self-pollinate with several generations

-can be artificially cross-pollinated

-above all, easy to grow

MENDEL’S EXPERIMENTAL DESIGN

TYPES OF GENETIC CROSSES

Monohybrid cross-cross involving a single trait

e.g. flower color

Dihybrid cross-cross involving two traitse.g. flower color & plant height

TERMINOLOGY Hybrid - The offspring of crosses between

parents with different traits Allele - two forms/copies of gene

Dominant – stronger of two genes expressed in the hybrid (R)

Recessive – gene that shows up less often in a cross (r)

Genotype -gene combination/makeup for a traite.g. RR, Rr, rr

Phenotype - physical feature resulting from a genotypee.g. red, smooth

GENOTYPE & PHENOTYPE

The plants have different genotypes (TT and Tt), but they have the same phenotype (tall).

GENOTYPES Homozygous

- when two alleles are same (2 dominant or 2 recessive) ; puree.g. RR or rr

Heterozygous- when two alleles are different(1 dominant and 1 recessive) ; hybride.g. Rr

-Mendel's first conclusion was that biological inheritance is determined by factors that are passed from one generation to the next.

-Each of the traits Mendel studied was controlled by one gene that occurred in two contrasting forms that produced different characters for each trait.

MENDEL’S LAWS OF INHERITANCE

1. Law of Segregation

2. Law of Independent Assortment

3. Law of Dominance

1. LAW OF SEGREGATION Alternative versions of genes

(alleles) account for variations in inherited characteristics

For each character, an organism inherits 2 alleles, one from each parent

If the two alleles differ, then one, the dominant allele, is fully expressed in the organism’s appearance; the other, the recessive allele, has no noticeable effect on the organism’s appearance

The alleles for each character segregate (separate) during gamete production (meiosis).

ALLELES SEPARATE DURING GAMETE FORMATION

PUNNETT SQUARE Diagram that shows gene combinations that

might result from a genetic cross Punnett squares can be used to predict and compare the

genetic variations that will result from a cross.

PUNNETT SQUARE

In this example,

T = tall t = short

2. LAW OF INDEPENDENT ASSORTMENT

- Law of Segregation involves 1 character. What about 2 (or more) characters?

When two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together.

Two-factor cross Independent assortment helps account for the

many genetic variations observed in plants, animals, and other organisms

2. LAW OF INDEPENDENT ASSORTMENT

Principle:

Factors for different traits assort independently of one anotherGenes are inherited

independently of each other

Segregate randomly in gametes

3. LAW OF DOMINANCE

The principle of dominance states that some alleles are dominant and others are recessive

An organism with a dominant allele for a trait will always exhibit that form of the trait

An organism with the recessive allele for a trait will exhibit that form only when the dominant allele for that trait is not present

3. LAW OF DOMINANCE

If your two alleles are different ( heterozygous), the trait associated with only one of these will be visible (dominant) while the other will be hidden (recessive)

END

-Thank You!

GROUP 2

-Aguilar, Ramil

-Alonzo, Lyulxz Anne

-Barroque, Maria Thalia-Bugayon, Lorie Ann-Carlos, Maricor-Dungca, Anneka-Espinosa, Jan Patrick-Mariano, Angela Grace-Toledo, Abel Edward

-BSMT3-A