genetics unit 6. what is genetics? genetics : is the science of heredity genetics began with mendel...

GeneticsUnit 6

What is genetics?

Genetics: Is the science of heredity

• Genetics began with Mendel

• Mendel is considered the “Father of Genetics”

• Mendel was a monk who experimented with pea plants to study heredity

What is a trait?

Trait: Is a notable feature or characteristic in an organism

• Physical traits– Examples - Hair color, eye color, & height

• Behavioral traits – Example – Sheepdog has herding instincts

• Medical conditions– Examples – Cancer, Sickle cell, cystic fibrosis

Why did Mendel study peas?• Peas reproduce and grow quickly

• They had easy to observe traits

• Can reproduce using 2 different plants or using 1 plant– True-Breeding: Can produce offspring with only 1 parent

Cross Pollination – 2 parents self-fertilizing/true-breeding

What are alleles?Allele: Alternative form that a single gene may have for

a particular trait. (huh?)

A gene in a particular place on a particular chromosome will express a particular trait….like flower color

Chromosome from MOM

Chromosome from DAD

But what color will the

offspring show?

Purple is an Allele coming from mom

White is an Allele coming from dad

How do alleles determine what traits will show?

Some alleles are dominant and others are recessive

Dominant: A trait that will appear (show) * Represented with a CAPITAL letter

Example: Tall (T), Black (B), Brown (B)

Recessive: A trait that is masked (hidden) if a dominant allele is present, but will show if both alleles are recessive * Represented with a lower case letter Example: short (t), blond (b), blue (b)

Do you have to remember which traits are dominant and which are

recessive?...

NO…

Punnett Square questions will give you clues or will tell you in the

question! You HAVE TO READ!

I do you know a trait will show or not?

Rule #1: If there is a dominant trait present, it will always show that trait.

T TDominant Dominant

Tall is dominant over short

T tDominant Recessive

Shows Tall Shows Tall

Capital “T” bosses the little “t”

I do you know a trait will show or not?

Rule #2: If there is NOT a dominant trait present, then the recessive trait will always show.

t tRecessive Recessive


Shows Short

Clicker Question #1

Who is considered the “Father of Genetics”?

a. Darwin

b. Hooke

c. Mendel

d. Paquin

Clicker Question #2

These plants were used in Mendel’s experiments because they grow & reproduce quickly:

a. Peas

b. Corn

c. Wheat

d. Roses

Clicker Question #3

What is true-breeding?

a. 2 parents reproduce offspring

b. 2 offspring with three parents

c. Self fertilizing plants

d. Cross pollinating plants

Clicker Question #4

If a girl has Tt, she will show:

a. Short

b. Tall

c. Both (a) & (b)

d. None of the above


Before we start Punnett Squares, we have a few more things to learn…

What are some terms that will help with understanding Punnett Squares?

Homozygous: Organism with 2 of the same alleles for a particular trait. Also called “pure”.

Examples – TT tt DD dd

Same sized letters!Same sized letters!Same sized letters!Same sized letters!

Homo means: ________SameThink: Same SIZED letters


Heterozygous: Organism with 2 different alleles for a particular trait. Also called “hybrid”.

Examples – Tt Dd Gg Bb

Different sized letters!Different sized letters!Different sized letters!Different sized letters!

Hetero means: __________DifferentThink: Different SIZED letters


Phenotype: The observable characteristic or outward expression of an allele pair

Characteristics you can see with your eyes!

Think: Phenotype -- PhysicalBlond Hair

Red HairBlack Hair

Brown Hair


PhenotypeCharacteristics you can see with your eyes!

Blue Butterfly

Multi color Butterfly

White Butterfly Orange

Butterfly


Genotype: The organism’s allele pairs

Characteristics you can NOT see with your eyes!

Think: Genotype – Genetic CodeGG

Gggg BB

Bbbb HH

Hhhh

Clicker Question #5

Another term for heterozygous is:

a. Allele

b. Same

c. Hybrid

d. Pure

Clicker Question #6

tt is an example of:

a. homozygous

b. heterozygous

c. hybrid

d. all of the above

Clicker Question #7

tt is an example of:

a. phenotype

b. heterozygous

c. hybrid

d. genotype

Clicker Question #8

If a boy has tt, he will show:

a. tall

b. short

c. both (a) & (b)

d. none of the above


Clicker Question #9

Tall is an example of:

a. phenotype

b. Heterozygous

c. pure

d. genotype

What is Mendel’s Law of Segregation?

Law of Segregation: States that the two alleles for each trait separate during meiosis.

During meiosis, the alleles separate

During fertilization, the alleles unite into a pair again

What’s the difference between monohybrid ?& dihybrid crosses?

Monohybrid Cross: The use of Punnett Square for 1 trait (will have 4 boxes)

Punnett Square: A diagram used to predict the possible outcomes (offspring) of a particular cross or breeding.

http://upload.wikimedia.org/wikipedia/commons/2/22/Punnett_Square.svg

Punnett Square Video


Dihybrid Cross: The use of Punnett Square for 2 traits

(will have 16 boxes)

http://upload.wikimedia.org/wikipedia/commons/6/6c/Dihybrid_cross.png


Law of Independent Assortment: Mendelian law stating that two alleles for each trait separate during meiosis

During Dihybrid crosses: The random assortment of alleles results in four possible gametes…each of which is equally likely to occur

I will show you this when I show dihybrid crosses

Sometimes two traits can be dominant at the same

time

What’s the difference between incomplete dominance and co-dominance?

Incomplete Dominance: Complex inheritance pattern in which the heterozygous phenotype is intermediate between those of the two homozygous parent organisms…huh?

R R

W

W

RW RW

RW RW

Mixes like paint!

http://www.fleurs-du-jour.com/pink-carnation.gif




What’s the difference between incomplete dominance and co-dominance?Co-Dominance: Complex inheritance pattern that

occurs when neither allele is dominant and both alleles are expressed.

B B

W

W

BW BW

BW BW

Clicker Question #10

Each gamete has only one allele for a trait

because of:

a. recessive

b. Law of segregation

c. dominance

d. phenotype


When a white flower & a red flower have pink

offspring, this is because of:

a. Co-dominance


c. Law of Independent assortment

d. Incomplete dominance


In speckled chickens, both alleles are

expressed because of:

a. Co-dominance


c. Law of Independent assortment

d. Incomplete dominance


The cross with one trait is called:

a. Dihybrid

b. Trihybrid

c. Monohybrid

d. All of the above


A dihybrid cross will have how many squares?

a. 4

b. 16

c. 18

d. 20

Lets start Punnett Squares!

genetics unit 6. what is genetics? genetics : is the science of heredity genetics began with mendel...

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