Transcript Genetics - Montville.net

Genetics
Chapter 10.2, 10.3, 11.1, and
11.2
Do Now- True for False if false, correct
the statement.
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1. Certain acquired characteristics, such as
mechanical or mathematical skill may be inherited.
2. Certain thoughts or experiences of a mother
mark or alter the hereditary makeup of an unborn
child.
3. Color blindness is more common in males than in
females.
4. A person may transmit characteristics to offspring
which he/she does not show.
5. Certain inherited traits may be altered by the
stars, planets or moon early in development.
6. The total number of male births exceeds female
births each year.
Objectives
1. SWBAT hypothesize about the birth of
two twin boys.
 2. SWBAT define homozygous,
heterozygous, gene, allele, and cross
pollination
 3. SWBAT discuss Mendel’s life and the
importance of his study of pea plants.

The Problem….
Born October of 2006:
 These two boys are related… They are
twins.
 http://www.msnbc.msn.com/id/15447465
/

Another Example…
How Can this be? Let’s Brainstorm.
Goal of this chapter on Genetics:
1866 Gregor Mendel
“Father of Genetics”
 Austrian Monk that studied pea plants



Pure breeds
Self Fertilization

Statistician who wanted to be a teacher

Discovered how traits were inherited in a
population
How Genetics Began

The passing of traits to the next
generation - inheritance or heredity.

Mendel performed cross-pollination in
pea plants.

Mendel followed various traits in the pea
plants he bred.
7 Traits Mendel Studied
Mendel studied seven different traits.
Seed or pea color
 Flower color
 Seed pod color
 Seed shape or texture
 Seed pod shape
 Stem length
 Flower position

Mendel’s Crosses

P Generation:

F1 Generation:

F2 Generation:
Generations

P Generation
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
F1 Generation

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Parents
Pure –
Hybrid – 2 different types of genes for a trait
F2 Generation

3:1–Yellow : Green
Animation
Definitions

Genetics:


Gene:

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Study of hereditary
Strand of DNA that codes for a protein (Trait)
Allele:

A version of a gene
Phenotype vs. Genotype

Phenotype:

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Physical characteristics (What the individual
looks like)
Ex) Red Petals
Genotype:


Alleles Received (genes you have)
Ex) RR
Homozygous and Heterozygous

Homozygous:

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
Having two of the same alleles for a particular
trait
Ex.
Heterozygous:
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Having two different alleles for a particular
trait
Ex.
Dominant Vs. Recessive

Dominant hides the recessive trait in the
heterozygous genotype.
Think – Pair - Share
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
If Fred Flintstone is heterozygous for black hair.
(B=Black, b=blonde)

What is Fred’s genotype?

What is Fred’s phenotype?
Tweety bird is yy. (Y= yellow feathers, y=brown
feathers)

1. What is his genotype?

2. What is his phenotype?

3. Is he heterozygous or homozygous? Explain.
Objectives
1. SWBAT do a probability lab in which
they flip a coin to determine the outcome
of crosses.
 2. SWBAT will work in partners to create
punnett squares.

Do Now

Provide an example of the following
terms:
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Heterozygous
Homozygous
Genotype
Phenotype
Dominant
Recessive
Allele
Gene
Mendels 3 Laws

1. Law of Segregation


Each allele a person has separates
into different gametes
Ex. Ww – one W goes in one sperm
and the other w goes into another
sperm
w
w W
W
Sperm
Mendels 3 Laws

2. Law of
Independent
Assortment

Gene pairs
(homologous) will
separate randomly
into gametes
Mendels 3 Laws

3. Law of Dominance

Traits exist in two possible forms (dominant
and recessive)

The dominant forms hides the recessive trait
in the heterozygous condition
Monohybrid Cross
R= Can roll your tongue
 r= Can’t roll your tongue


R
Genotype Ratio:
R

Phenotype Ratio:
r
r
Genotypic vs. Phenotypic Ratios

Phenotype Ratio:



Ratio of different physical traits
Ex) Brown eyes ¼ or 25%
Genotype Ratio:


Ratio of the different possible alleles
Ex) Tt = ¼ or 25%
Sample Problems
1) Daffy Duck is heterozygous for black feathers.
Daisy Duck is homozygous for yellow feathers. Set
up a punnett square and determine probabilities of
their potential offspring. (Both genotype and
phenotype ratios!)
2) B = Black
b = yellow
Do Now

Sponge Bob Square pants is heterozygous
for brown eyes. Sandy is also
heterozygous for brown eyes. Create a
punnett square to determine the possible
outcomes of their children.
Do Now

Sleeping Beauty has freckles. Her prince
charming is heterozygous for no freckles.
What are the chances of her children
having freckles? Please show your work.
Setting up Dihybrid Crosses
1.
 2.
 3.
 4.

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Determine parent genotypes
Determine alleles to be passed down
Set up punnet square
Determine outcome
Phenotype Ratio
Genotype Ratio
Dihybrid Crosses

Looking at two different traits

Ex. Hair color and eye color

B=brown eyes
b=blue eyes
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R=Brown hair
r=blonde hair
Mother is heterozygous for both traits
Father is heterozygous for eye color and homozygous
dominant for hair color
The problem
Aladdin and Jasmine want to have
children. Jasmine is homozygous
dominant for black hair and black eyes.
Aladdin is homozygous recessive for brown
eyes and brown hair.

B=black hair b=brown hair
E=black eyes e=brown eyes
B=black hair b=brown hair
E=black eyes e=brown eyes

Jasmine’s daughter falls in love with a
man who is also heterozygous for hair and
eye color. Determine possible genotype
and phenotype ratios.
Do Now

BbTt X BBTt
Math Method
For a cross between TtBb and TtBB.
 Do each cross individually and multiply the
results together.

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For TtBb
Do Now
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Mickey Mouse is heterozygous for Round ears
and homozygous for Black eyes. Minnie Mouse
also is homozygous for Floppy ears and
heterozygous for Black eyes. Determine
genotype and phenotype ratios. (B=black,
b=brown, R=round, r= floppy.)
Quiz next class on 10.2

QUIZ ON THURS ON:
Vocabulary words
 Mendel
 Mendel’s experiments
 Monohybrid crosses ONLY

Do Now
Peter and Lois decide to try for a 4th child.
 Determine the possible genotype and
phenotype ratios of the following cross:
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DdEe X ddEe
D= Brown hair
 d=red hair
 E=fluffy hair
 e=thinning hair

Do Now
Two dogs have puppies! The male dog
is homozygous brown fur and
heterozygous floppy ears. The female
dog is heterozygous for brown fur and
has straight ears.
 B=brown fur b=blonde fur
 F=Floppy ears f= straight ears

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What ratio of the dogs would have
brown fur and floppy ears?
10.3 Gene Linkage and Polyploidy
Several genes on a chromosome
 Gene Linkage:


When two genes are close to each other on the
same chromosome
Gene Linkage
 Linked genes on a chromosome results in
an exception to Mendel’s law of
independent assortment
 Linked genes usually do not segregate
independently
Drosophila (Fruit Flies)
First organism with linked genes
 Linked genes typically travel together
during crossing over
 http://www.biologyreference.com/LaMa/Linkage-and-Gene-Mapping.html

Chromosome Map
Crossing over occurs more frequently
between genes that are far apart
 Map of genes on a chromosomes and
frequency of crossing over

Polyploidy
Occurrence of one or more extra sets of all
chromosomes in an organism.
 Ex. A triploid organism (3n) - means that it
has three complete sets of chromosomes.

True or False – Correct false statements
_______ 1. Crossing over occurs more frequently
between genes that are close together on a
chromosome.
_______ 2. Gene linkage was first studied by
using garden peas.
_______ 3. Scientists call a drawing like the one
shown below a chromosome map.
_______ 4. Chromosome map percentages
represent actual chromosome distances.
Matching
11.1 Basic Pattern of Human Inheritance

Recessive Genetic Disorders
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Cystic Fibrosis
Albinism
Tay Sachs Disease
Galactosemia
Cystic Fibrosis

Affects the mucus-producing glands,
digestive enzymes, and sweat glands
 Chloride ions are not absorbed into the
cells of a person with cystic fibrosis but
are excreted in the sweat.
 Without sufficient chloride ions in the cells,
a thick mucus is secreted.
Cystic Fibrosis

Not too long ago CF was always fatal in
childhood, but better treatment methods
developed over the past 20 years have
increased the average lifespan of CF
patients to nearly 30 years
Albinism
 Caused by altered genes, resulting in the
absence of the skin pigment melanin in
hair and eyes
 White hair
 Very pale skin
 Blue Eyes
 Pink pupils
Albinism
Impaired Vision
 It is vital that people with
albinism use sunscreen when
exposed to sunlight to
prevent premature skin
aging or skin cancer
 High risk of skin cancer

Tay-Sachs Disease

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Caused by the absence of
the enzymes (in
lysosomes) responsible
for breaking down fatty
acids called gangliosides
Gangliosides accumulate
in the brain, inflating
brain nerve cells and
causing mental
deterioration
Tay Sachs Disease
Children with Tay-Sachs, a progressive
neurodegenerative disease that attacks
nerve cells, usually die before age 5.
 Children will go deaf, have seizures, and,
ultimately, become unable to swallow or
breathe.

Galactosemia
Recessive genetic disorder characterized
by the inability of the body to digest
galactose.
 Lactose = Galactose + Glucose
 Symptoms:
 • liver damage or failure
• cataracts
• brain damage
• infection

Galactosemia

Treatment requires the strict exclusion of
lactose/galactose from the diet.
Do Now Period 3
Dominant Genetic Disorders
 Dominant Gene results in disorder:
 Huntington’s Disease
 Achondroplasia
Achondroplasia
 is a genetic condition that
causes small body size and
limbs that are comparatively
short.
 Obesity
 Breathing problems (apnea)
 Recurrent ear infections
(otitis media).
 Other health problems
Matching Do Now Period 8
Huntington’s Disease
 affects the nervous system.
 Huntington's disease is a progressive,
degenerative disease that causes certain
nerve cells in your brain to waste away.
 As a result, you may experience
uncontrolled movements, emotional
disturbances and mental deterioration.
Huntington’s Disease
Diminished memory,
immediate and shortterm (long-term
memory usually
remains intact)
 Disease usually
manifests itself by
age 35

Do Now
Peter and Lois decide to try for a 4th child.
 Determine the possible genotype and
phenotype ratios of the following cross:


DdEe X ddEe
D= Brown hair
 d=red hair
 E=fluffy hair
 e=thinning hair

Do Now

Explain how gene distances are
determined on a chromosome.

What does “3n” mean?
Pedigree
Shows history of a trait in a family
 Allows researchers to analyze traits within
a family

Symbols for Pedigree
Using Pedigrees

Inferring Genotypes


Knowing physical traits can determine what
genes an individual is most likely to have.
Predicting Disorders
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Scientists use pedigree analysis to study:
inheritance patterns
determine phenotypes
genotypes.
Sample Pedigree
Think – Pair - Share
Do Now

Fill in the pedigree for Achondroplasia. Use
the variable A.
Dominant or Recessive Trait?
Dominant or Recessive Trait?
Test Cross
When the genotype of an individual is
unknown, cross the individual with a
homozygous recessive
 The outcome of the cross determine the
genotype of the unknown

11.2 Incomplete Dominance:
Heterozygous phenotype is an
intermediate phenotype between the two
homozygous phenotypes.
 Two alleles are blended
 Ex) Four O’clock Flowers
 Red + White = Pink

Codominance
Neither trait is dominant instead, both
traits are shown (No Blending)
 Ex) Roan Cows
 Red + White = RED AND WHITE

Sickle Cell Disease

Affects red blood cells and ability to
transport oxygen.

Homozygous recessive alleles=

Heterozygous=

Homozygous dominant alleles=
Sickle Cell and Malaria

People who are
heterozygous for sickle
cell, have a higher
resistance to malaria.
Do Now
Fill in the genotypes for the following
pedigree
 B=brown eyes
 b = blue eyes

Do Now

Explain how gene distances are
determined on a chromosome.

What does “3n” mean?
Multiple Alleles

Traits determined by
more than 2 alleles
Ex. Blood Typing
(3 alleles ABO)

A and B are dominant
to O
Universal Donor
Sample Problem

Determine the possible offspring of the
following crosses
1. AB and O
 2. AA and BO
 3. AB and AB

Coat Color of Rabbits
Rabbits have a hierarchy of coat color
 4 alleles (C, cch, ch, and c)
 Dominant C > cch> ch > c
Recessive

C Full color
 cch Chinchilla
 ch Himalayan
 c albino

Complex Inheritance and Human Heredity
Coat Color of Rabbits
Chinchilla
Albino
Full Color
Himalayan
Do Now period 6

cc x Ccch
 Genotype and phenotype ratios
Do Now
A parent with the blood type A and one
with B have a child with type O blood.
What are the parents genotypes?
 Draw out the punnett square.

Do Now
Do the following cross between the these
rabbits.
 Cch x Ccch

What color were the parents?
 What are the genotype and phenotype
ratios of the offspring.

What do you see?
What do you see?
Sex Linked Traits
Traits located on the sex chromosomes
(X or Y)
 X linked: gene is located on the X
chromosomes
 Y linked: gene is located on the Y
chromosome

What are the chances of having a girl?

How would you go about solving it?
Sex-Linked Traits

A man who is color blind marries a woman
that is heterozygous for color blindness.
What is the chance of having a color blind
boy?
Do Now- per. 1

A man that is color blind marries a
woman that is a carrier for the disorder.
What is the chance of having a color blind
girl?
Hemophilia
Sex linked disorder characterized by
delayed blood clotting
 Located on the X Chromosome
 Seen in the Royal Family of England

Hemophilia
Do Now –

A man with hemophilia marries a woman
the is homozygous normal phenotype.
What is the chance of having a boy with
hemophilia?

A girl with hemophilia?
Chapter
11
Complex Inheritance and Human Heredity
Polygenic Traits
 Polygenic traits arise from the interaction
of multiple pairs of genes.
Polygenic Inheritance
P Generation
aabbcc
(very light)

Skin Pigment
AABBCC
(very dark)
F1 Generation
AaBbCc
AaBbCc
F2 Generation
Eggs
Sperm
Figure 9.22
What is the difference between
polygenetic and multiple alleles?
Complex Inheritance and Human Heredity
Environmental Influences
 Environmental factors
 Diet and exercise
 Sunlight and water
 Temperature
Complex Inheritance and Human Heredity
Twin Studies
 Helps scientists separate genetic
contributions from environmental
contributions
 Traits that appear frequently in identical
twins are at least partially controlled by
heredity.
 Traits expressed differently in identical
twins are strongly influenced by
environment.
Let’s try to explain the inheritance of the
babies’ skin color.