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
KEY VOCABULARY
Recessive:
 inherited
characteristics often
masked
 Represented with lowercase
letter.
Ex: b, x, r
EXAMPLE:
Dominant

Brown Eyes: B
Recessive

Blue Eyes: b
Phenotype:
 physical
traits that appear in an
individual as a result of its
genetic make-up
How
Ex:
to remember…….
Phenotype= Physical
brown eyes, blonde hair
Genotype:
 genetic
Make Up of an
individual
How
to remember….
GENotype= GENEtic
Ex:
 B-
brown eyes
 b- blue eyes
Homozygous
 having
two
identical alleles
 Ex:
Heterozygous
 having
two
different alleles
for a trait
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
GREGOR MENDEL
 Austrian
Monk
 Famous for his work with pea
plants
 WHY?????
They weren’t messy
Rapid results
Many generation
 He is known as the father of
genetics
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
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 (Principle #1).
Most sexually reproductive organisms have two
sets of genes that separate during gamete
formation (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
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
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
 Gives
that involves two traits
16 offsprings
 Example: Pea
color and wrinkles
STEPS FOR A DIHYBRID CROSS
1.
2.
3.
4.
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. similar to FOIL
2. there are four for each parent
3. 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

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
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?
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
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
b
b
B
Bb
Bb
Bb
Bb
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
Phenotype
IAIA
A Blood
IAIO
IBIB
B Blood
IBIO
IAIB
AB Blood
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 their a mistake in the hospital?

HINT: Draw a Punnett Square to help!!!!!!!!!