Download Genetics

DO NOW:
Quietly……..
Take a poll of how many of
you have the following traits:
- brown hair
-blonde hair
-red hair
- black hair
- blue/green eyes
-brown eyes
GENETICS
MAIN IDEA…………
Parent
Traits
Parent
Traits
Offsprings
Traits
ALIEN ACTIVITY

http://www2.edc.org/weblabs/BabyBoom/babyBoo
m.html
WHAT IS GENETICS???

Genetics


is the scientific study of heredity.
Heredity

is what makes each species unique.
KEY VOCABULARY


Dominant:
 inherited characteristic that appear in an
organism
 Represented with capital letter.
 Ex: B, X, R
Recessive:
 inherited characteristics often masked
 Represented with lowercase letter.

Ex: b, x, r
EXAMPLE:
Dominate

Brown Eyes: B
Recessive

Blue Eyes: b

Phenotype:


physical traits that appear in an individual as a result of
its genetic make-up
How to remember…….
Phenotype= Physical

Ex: brown eyes, blonde hair

Genotype:


genetic Make Up of an individual
How to remember….
GENotype= GENEtic

Ex:
B- brown eyes
 b- blue eyes

Homozygous
Heterozygous

having two identical
alleles

having two different
alleles for a trait

Ex: BB or bb

Ex: Bb
PHENOTYPE VS. GENOTYPE
A little girl has blue eyes
Genotype
bb
Phenotype
Blue Eyes
Allele
different forms of a gene for a specific
trait
 2 for each trait

CHROMOSOME FOR FLOWER COLOR
ALLELE
Could code
for a
PURPLE
flower
Could code
for a
WHITE
flower
MAIN IDEA…………
Parent
Traits
Parent
Traits
Offsprings
Traits
HISTORY
FATHER OF GENETICS:
MENDEL
HISTORY
GREGOR MENDEL
Austrian Monk
 Famous for his work with pea plants
 He is known as the father of genetics


WHY did he work with pea plants?
They weren’t messy
 Rapid results
 Many generation

MENDEL
MENDEL’S WORK
 Mendel
used true-breeding plants
 True

Breeding:
When bred with themselves they would produce
identical offsprings.
 He
studied 7 different traits in pea plants.
 Trait:

is a specific characteristic that can vary from
one individual to another.
MORE ON MENDEL’S WORK

Hybrids


are offspring from parents with different traits.
Genes

are the chemical factors that determine a trait.
MENDEL’S EXPERIMENTS: 3 PRINCIPLES
1.
2.
3.
Principle of Dominance
Segregation
Independent Assortment
PRINCIPLE 1:
THE PRINCIPLE OF DOMINANCE



States that some alleles are dominant and others
are recessive.
Dominant alleles are always expressed.
Recessive alleles are only expressed if both
alleles are recessive.
PRINCIPLE 2:
SEGREGATION

The two alleles for a trait separate

HELP……


Segregate  means to separate
Happens during meiosis

form gametes (sex cells)
PRINCIPLE 3:
INDEPENDENT ASSORTMENT


states that genes for different traits separate
independently during the formation of gametes.
EX:
the color of the flower has nothing to do with the
length
 They separate INDEPENDENTLY

LAWS OF INHERITANCE
SUMMARIZE MENDEL’S PRINCIPLES


The inheritance of biological characteristics are determined
by genes.
For two or more forms of a gene, dominance and recessive
forms may exist


Most sexually reproductive organisms have two sets of
genes that separate during gamete formation


(Principle #1).
(Principle #2).
Alleles segregate independently

(Principle #3).
MAIN IDEA…………
Parent
Traits
Parent
Traits
Offsprings
Traits
PROBABILITY AND
PUNNETT SQUARES
PROBABILITY & GENETICS

Probability


is the likelihood that an event will happen.
The principle of probability can be used to predict
the outcomes of genetic crosses.
PUNNETT SQUARES

Diagram used to predict genetic crosses.

REVIEW:
Homozygous  individuals with identical alleles
 Heterozygous individuals with different alleles
are called
 Phenotype  physical characteristic
 Genotype  genetic makeup

HOW TO USE PUNNETT SQUARES……
1.
2.
3.
4.
5.
6.
Choose a letter to represent the alleles in the
cross.
Write the genotypes of the parents.
Enter the possible gamete at the top and side of
the Punnett square.
Complete the Punnett square by writing the
alleles from the gametes in the appropriate
boxes.
Determine the phenotypes of the offspring.
Using the results of step 4. write down the
genotypic and phenotypic ratios.
EXAMPLE PUNNETT SQUARE
EXAMPLE:
WHAT IS THE PROBABILITY THAT TWO HETEROZYGOUS
PURPLE FLOWERS WILL PRODUCE A WHITE FLOWER?
1.
Choose a letter to represent the alleles in the
cross.
2.
Write the genotypes of the parents.
3.
Enter the possible gamete at the top and side of
the Punnett square.
WHAT IS THE PROBABILITY THAT TWO
HETEROZYGOUS PURPLE FLOWERS WILL
PRODUCE A WHITE FLOWER?
4. Complete the Punnett square by writing the alleles
from the gametes in the appropriate boxes.
5. Determine the phenotypes of the offspring.
6. Using the results of step 4. write down the genotypic
and phenotypic ratios
REVIEW QUIZ ON PROBABLITY AND
PUNNETT SQUARES

http://anthro.palomar.edu/mendel/quizzes/mendq
ui2.htm
DO NOW:
1. Curly hair is dominant to straight hair. If
a heterzygous curly haired woman
marries a man with straight hair, what is
the genotype and phenotype ratio?
2. In dogs, long eyelashes is dominant to
short eyelashes. A short eyelashed dog is
mated with a homozygous long eyelashed
dog. What is the percentage their puppies
will have short eyelashes?
MAIN IDEA…………
Parent
Traits
Parent
Traits
Offsprings
Traits
TEST CROSSES
WHAT IS A TEST CROSS?????

Test that is conducted to determine if the
genotype of an organism
HOMOZYGOUS DOMINANT for a trait
 HETEROZYGOUS for a trait

5 KEY POINTS……
1.
2.
The organism with the dominant trait is always
crossed with an organism that is HOMOZYGOUS
RECESSIVE
If ANY offspring shows the recessive trait than
the unknown genotype is heterozygous.
1.
3.
If ALL offspring have the dominant trait, the
unknown is homozygous dominant.
1.
4.
5.
Recessive trait seen  heterozygous
Dominate trait  homozygous
Large numbers of offspring are needed for reliable
results
Start by making a key and writing down what you
know.
EXAMPLE:

If fire breathing is dominant to not fire breathing
in Gregorous Dragon, how can we determine if
Mendelia is homozygous dominant or
heterozygous?????
SO WHAT DO WE KNOW………….

Let’s say
F= fire breathing
 f= can’t fire breathe.


Set up a two different Punnett squares


Both with a homozygous recessive  ff
Then as the other parent place a:
FF in one Punnett square
 Ff is another


Essentially, your two Punnett squares will have:
Ff crossed with ff
 FF crossed with ff

INTERPRETATION


If all of the Gregorous dragon babies can
firebreathe we can assume that Mendelia is
HOMOZYGOUS DOMINANT
If any of the babies DO NOT fire breathe than
Mendelia is HETEROZYGOUS
DIFFERENT TYPES OF
INHERITANCE
DIHYBRID CROSSES
DIHYBRID CROSSES

Cross that involves two traits
Gives 16 offsprings
 Example:


Pea color and wrinkles
STEPS FOR SOLVE FOR DIHYBRID CROSS
1.
2.
3.
Make a key for the two traits that you are
crossing
Write out the different genotypes of the parents
Figure out the possible gametes
1.
2.
3.
4.
similar to FOIL
there are four for each parent
each gamete must have one allele from each trait
Set up and Solve the Punnett Square
EXAMPLE PROBLEM: A MOTHER IS HETEROZYGOUS
BROWN HAIR AND BLUE EYES.
THE FATHER HAS BLONDE HAIR
AND IS HETEROZYGOUS FOR BROWN EYES. WHAT ARE THE
POSSIBLE GENOTYPES AND PHENOTYPES OF THEIR OFFSPRINGS?

Step 1 (assume brown hair & brown eyes are
dominant)

Make a key for the traits
Brown Hair (B) vs Blonde Hair ( b)
 Brown Eyes (E) vs Blue eyes (e)


Step 2

Genotypes of the parents
Mother Bbee
 Father  bbEe


Step 3

Figure out the possible gamete
Mother Gamete’s  Be, Be, be, be
 Father’s Gamete’s  bE, be, bE, be

STEP 4  SET UP AND SOLVE PUNNET
SQUARE
Be
bE
be
bE
be
Be
be
BbEe
BbEe
bbEe
Bbee
Bbee
bbee
BbEe
Bbee
BbEe
Bbee
bbEe
bbee
be
bbEe
bbee
bbEe
bbee
COUNT UP THE POSSIBLE GENOTYPES AND
PHENOTYPES THAT YOU HAVE FROM YOUR PUNNETT
SQUARE
Genotypes

BbEe


Bbee


4/16
bbEe


4/16
4/16
Phenotypes

Brown Hair; Brown eyes

Brown Hair; Blue eyes

Blonde Hair; Brown eyes

Blonde Hair; Blue eyes
bbee

4/16
DO NOW:

With the person sitting next to you…go through
the DO NOW. Things to discuss:

How do you begin a dihybrid cross?
What are gametes and how do you solve for
them?
How do you interpret the punnett square?

Try to figure out genotypic ratios if time allows


MAIN IDEA…………
Parent
Traits
Parent
Traits
Offsprings
Traits
SEX LINKED
SEX LINKED

sex is determined by the X and Y
chromosomes.

Females  XX

Males  XY
SEX DETERMINATION

Sons:
get their X chromosome from their mothers only.
 Get Their Y chromosome for their fathers


Daughters:

fathers must pass their X chromosomes
SEX LINKED TRAITS
 Traits
found on the SEX chromosomes
 Genes
that are found on the X chromosome
follow a have a special pattern of
inheritance:

X linked traits are only passed to sons from the
mother
 Males
are much more likely to be affected
than females
 If
trait is recessive,

daughters have a second X chromosome so they can
be heterozygous.

Sons only have one X chromosome

therefore more likely to express the trait
Females can be carriers and pass the trait onto
their son.
 Example:

Baldness
 Colorbindness

COLORBLINDNESS
TRY THIS……

A woman is not colorblind but her husband is.
Construct a punnett square to determine what is
the chance that their children will be colorblind.
What is the percentage of children with
colorblindness?

A woman who is a carrier for hemophilia marries
an unaffected male. What is the % chance that
their children will be affected?
EXIT TICKET:
A
female who is a carrier for baldness
marries a man who is bald.
 What percentage of the females will be
carriers for baldness?
 What percentage of the males will be
bald?
 What percentage of the offspring will
NOT be bald?
 How does this relate to the big idea of
the unit?
DO NOW:

Read the instructions on your DO NOW and work
in the following groups:
Group A- Taylor, Alyza, Jason, Sami, Jessie
 Group B- Hannah, Megan, Jess, Montana, Bryce
 Group C- Ashley, Vanessa, Juliann, Clare, Mark
 Group D- Emma, Rebecca, Kyle, Pierce, Taj

MAIN IDEA…………
Parent
Traits
Parent
Traits
Offsprings
Traits
INCOMPLETE DOMINANCE
INCOMPLETE DOMINANCE
when one trait is not completely dominant
over another
 Results



heterozygous form being blended together
Example:

Pink flower
SOLVING INCOMPLETE DOMINANCE:


Same as performing a regular monohybrid
Punnett square
Only difference

Since both traits are equally dominant- you can use
two DIFFERENT letters to symbolize the trait:

Example: Red (R) and white (W)
heterozygous offspring will be mixture of two trait
 Ex:


red + white = PINK
Example Problem: Black fur color are not completely
dominant to white white fur color.
The mother is a homozgygous for black fur color and the
father is homozygous for white fur color. Perform a punnett
square.
B
W
W
B
BW
BW
BW
BW
CODOMINANCE
CODOMINANCE

Two different alleles are present and both are
expressed
Basically……..
 Both alleles contribute to the phenotype.

Example:
Red cow X White Cow = Roan Cow
 Blood types

BLOOD TYPES:



Red blood cells are coated with different protein
markers.
Person can have either
 A
 B
 A and B
 neither protein.
Blood Types are:




A
B
AB
O
Genotype
Genotype
Phenotype
AA or AO
IAIA
A Blood
IAIO
IBIB
BB or BO
B Blood
IBIO
AB
IAIB
AB Blood
OO
IOIO
O Blood
EXAMPLE PROBLEM #1

Melissa has type AB blood. Joe has type AB
blood as well. If Melissa and Joe have a baby girl,
what are the possible blood types the baby can
have?

HINT: Draw a Punnet Square!!!!!!
EXAMPLE PROBLEM #2

David has blood type AB. Jessica has blood type
O. They have a son that has blood type A? Since
neither David nor Jessica have this blood type,
was there a mistake in the hospital?

HINT: Draw a Punnett Square to help!!!!!!!!!