Mendel & GeneticsReview Powerpoint

Gregor Mendel, the father of genetics.

Genetics is the study of…

heredity

Define Heredity.

The passing on of traits from one generation to the next.

Where is genetic information stored?

DNA

Specifically, in each individual’s DNA on chromosomes that contain many genes.

What did Mendel study to understand inheritance?

Common garden pea plantsWhy did he choose pea plants?

1--Fast growing with many offspring = quick results

2—Sexually Reproduce and male as well as female reproductive organs in each plant

3—Traits come in a dichotomy—only two forms.Like tall and short or green and yellow

What did Mendel call true breeding?Plants that come from a long line of plants that show the same trait

When he crossed two true-breeding plants with opposite traits, he called this what?

The “P” cross for Parental generation

What two individuals did Mendel cross in the P generation?True-breeding Tall and Short pea plants

Genotypes?

Tall = TTShort = tt

What resulted in the F1 generation?

Pea plants that were…Phenotypes?All TALL

Genotype?All “Tt”

What was Mendel’s next step?He crossed two F1 plants.What results did he get?The F2 generationWhat interesting ratio did he find?

They were 3:1 (dominant to recessive)

What is the Law of Segregation?1--Individuals must have two copies of genetic information for every trait– one from each parent

2—each copy is passed randomly 3—One of these copies (alleles) can mask the expression of the other, ie. Dominant alleles can mask recessive alleles when both are present

What is the Law of Independent Assortment?

Alleles of different genes separate independently of one another during gamete formation

What does that mean?The allele a parent gives for one trait does not affect what he/she gives for another trait so you can have many different combinations of traits given to the egg or sperm

What are alleles?

Different forms of the same gene for a trait

When an individual has two of the same allele, the genotype is called…

HomozygousWhen there are two different alleles, it is…

Heterozygous

What is the difference between genotype and phenotype?

Genotype is the type of genes or alleles

Phenotype isWhat is looks like--The physical appearance of the organism

Monohybrid vs. Dihybrid

Mono hybrid: a cross when there is just one trait involved, ex.

Height: Tt X tt

Di hybrid: Two traits are involved, ex.The horse’s coat and gait are crossedFFGg X Ffgg

Sex-linked Inheritance

Autosomes are chromosomes not on the.. X or y chromosomes

Sex-linked characteristics are always on…The X-chromosome

Give an example of a sex-linked conditionHemophiliaWhy does it occur more in males?Males only inherit 1 X-chromosome so there is a

better chance they would express (whether its dominant or recessive) the condition.

Contrast a Punnett Square and a Pedigree

A Punnett Square is… a grid that predicts the types of possible

offspring from a cross

A Pedigree is..A diagram that shows a family tree and

how traits pass from generation to generation

Pedigree or Punnett Square?

Is this a monohybrid or dihybrid cross?

Modes of Dominance:

1--Complete dominance…One allele is completely dominant over the

recessive and the recessive is masked in a heterozygous individual

2--Incomplete dominance..The dominant does not completely mask the

recessive and the heterozygous phenotype is a blend of the two- an intermediate variation.

There are three possible phenotypes.

More modes of inheritance

3-- Co dominance..More than one genotype is dominant and when two of

these are together, they form another phenotype

4– Multiple alleles..These traits have 3 or more allelesExample of both codominance and multiple alleles..blood types. How many blood types are possible?Four-- They are..A, B, AB, and O

Modes of Inheritance cont.

5-- Polygenic Inheritance: traits that are..

controlled by multiple genes pairs.This makes many variations of color and

trait possibleWhat are characteristics controlled by

multiple pairs of alleles?Human hair and eye color