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How did the How did the study of study of Genetics Genetics begin?begin?

Clip

Gregor MendelGregor MendelGenetics is the

branch of biology that deals with heredity. A great deal of what we know about genetics began with the work of a monk named Gregor Gregor MendelMendel, who experimented with sweet pea plants in the 1800s. 22

Mendel’s Work•Mendel studied Mendel studied the patterns of the patterns of inheritance in inheritance in pea plants.pea plants.

•He chose seven He chose seven traits to follow.traits to follow.

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•Mendel needed to make sure he had plants that always gave the same same offspringoffspring--calledcalled true true breeding.breeding.

•He “self-pollinated” plants until he got seeds that always gave the same offspring.

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Some plants can self-pollinate or cross-pollinate with another

plant.

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He took a purple flower plant and crossed it with a white flower plant?

He called these the parent generation (P generation)

What do you think the offspring looked like?ALL PURPLE

X

Pollen

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POLLEN

SAY SAY

WHAT??????

WHAT??????

??

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Mendel concluded:Mendel concluded:2. Something is being passed

from parent to offspring. He called these “Factors”

3. Sometimes you can see “it” and sometimes you can’t see “it”.

4. If you can see it- it is dominant.1. If it’s there and you can’t see

it- it’s recessive.

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5. There are two two versions of these “FACTORS”.

6. To show the two version we use a capital letter for the dominant (S) version of the trait and a lower case for the recessive version (s) of the trait.

ADD TO NOTES: Each Version is called an AlleleAllele.

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Each chromosome has many genes, but the alleles may be

different

Alleles are different versions of the same gene.

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Common Physical Human Traits- Different Alleles

1133Trait Dominant Recessive

Chin cleft Absent (C) Present (c)

Dimples Present (D) Absent (d)

Earlobe shape

Free (F) Attached (f)

Eye shape Almond (A) Round (a)

Eye position Straight (S) Upward slant (s)

Eyebrow position

Connected (Y) Not connected (y)

Eyebrow shape

Bushy (B) Fine (b)

Eyelash length

Long (L) Short (l)

Face shape Round (R) Square (r)

Freckles Present (P) Absent (p)

Hair Curly (H) Straight (h)

Tongue rolling

Can roll (T) Can't roll (t)

Widow's peak

Present (W) Absent (w)

Activity

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We have two copies of all of our chromosomes Why?

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These are called Homologous Chromosomes

BOY OR GIRL?

                                                                                       

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Karyotype

DNA codes for Proteins

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What is a gene?What is a gene?• A segment on the chromosome that A segment on the chromosome that

codes for a protein.codes for a protein.• People have two copies of each People have two copies of each

gene, one copy inherited from the gene, one copy inherited from the mother and the other copy inherited mother and the other copy inherited from the father. from the father.

• There are many versions of each There are many versions of each gene-gene-allelesalleles

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Remember:Genes come in pairs.

**One from your mother

**One from your father.

If the two alleles in the pair are

identical, then the condition called homozygous.

The term “purebred” is

sometimes used.

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•

If the 2 alleles are different, the condition is called heterozygous. The term “hybrid” is sometimes used to refer to heterozygous.

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What the genes/alleles are …RR.…Rr

What the organism looks like…… Red…..White

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Phenotype

Genotype

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How did you end up with the traits and genes that you got?

During meiosis, each egg or sperm only gets one copy of each chromosome.

Meiosis Review

Animation

Law of DominanceLaw of Dominance•States that the

dominant allele will

prevent the recessive allele

from being expressed.

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Mendel’s Laws

•The recessive allele will appear when it is paired with another recessive allele in the offspring.•Remember: Genes Come in Pairs!

S Phase

Goes throug

h Meiosis

Makes a copy

Law of Segregation (separation) states that gene pairs separate when gametes (sex cells) are formed

•Each gamete has only one allele of each gene pair. (haploid)22

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A

b

a

B

A

b

a

B

A

b

a

B

A

b

a

B

A

b

a

B

Mendel’s Laws

gene pairs separate

Law of Law of IndependenIndependen

t t AssortmentAssortment

states that different pairspairs of genes

separateindependentl

y of each other when

gametes are formed.

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Example:

Just because you get the gene for brown hair does not mean you will get the gene for blue eyes.

Mendel’s Laws

Animation

REVIEWREVIEW1. A trait is a characteristic an individual receives

from its parents. 2. Genes carry the instructions responsible for the

expression of traits. 3. A pair of inherited genes controls a trait. 4. One member of the pair comes from each

parent.5. Alternative versions of genes are known as

alleles.

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REVIEWMendel’s Principles of Inheritance

• Inherited traits are transmitted by genes which occur in alternate forms called alleles

1. Principle of Dominance - when 2 forms of the same gene are present the dominant allele is expressed

2. Principle of Segregation - in meiosis two alleles separate so that each gamete receives only one form of the gene

3. Principle of Independent Assortment - each trait is inherited independent of other traits (chance)

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Peas in a pod- Genetics Clip

Example EOCT Question:Example EOCT Question:Earlobe shape is a human trait. Some people have free earlobes while others

have attached earlobes. Two parents with free earlobes have four children. Three

children have free earlobes and one child has attached earlobes. If these parents

have another child, what is the probability that the child will have attached earlobes?

A 25%

B 50%

C 75%

D 100% 3232

Predicting possible

outcomes of a genetic cross.

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Punnett Squares

•Geneticist use punnett squares to determine the probability of a combination of alleles.

•For example: If a heterozygous black rabbit is crossed with a heterozygous black rabbit, what are the chances the offspring will be black?

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B=Black

b= Brown

Genotypes?

Phenotypes?

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Claymation Clip

Example EOCT question:

In humans, a widow’s peak is dominant over a continuous hairline. Mary’s father has a widow’s peak, but Mary and her mother have a continuous hairline. What is the genotype of Mary’s father?

A HHB HhC hh D cannot be determined

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Incomplete dominance

is a cross between

organisms with two

different phenotypes

produces offspring with a

third phenotype that is a

blendingblending of the parental

traits. 3355

Incomplete Dominance

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CodominanceCodominanceWith codominance, a cross between organisms with two

different phenotypes produces offspring with a third phenotype

in which both of the parental traits appear together. DO NOT blend together.

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CodominanceCodominance•Both

phenotypes are expressed at the same time.

•Example: Blood

Types

Genotype Phenotype

IOIO Type O

IAIO Type A

IAIA Type A

IBIO Type B

IBIB Type B

IAIB Type AB

There are 3 alleles for blood type- multiple alleles

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CodominanceR = allele for red flowers

W = allele for white flowers W = allele for white flowers red x white ---> red & white spotted

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Polygenic traitsMany traits are

controlled by more than one

gene. Ex: Skin Color

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Sex Linked TraitsSex Linked TraitsTraits associated with

particular sexes are called sex-linked or X-linked

traits.

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Examples of Sex-linked

Traits: •Red-green

colorblindness•Hemophilia

Linked Genes

• Occurs when particular alleles are inherited jointly.

• They tend to be inherited together, for example, red hair and freckles.

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KaryotypKaryotyp

ee

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1st 22 are Autosomes, the last pair (XY) are sex chromosomes)

Charts that show relationships within a

family

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Pedigree

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• How many boys? __________________• How many Girls? __________________• How many generations? _______________• How many with the disorder? ____________• How many marriages are shown? ____________

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6

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1. How many generations?

2. How many carriers?

3. How many affected males?

4. How many affected females?

5. Autosomal or sex-linked?

Autosomal-Dominant

What can you tell by the pedigree?Dominant or recessive?

Autosomal or sex-linked?

SEX-LINKED

What can you tell by the pedigree?Dominant or recessive?

Autosomal or sex-linked?

SEX-LINKED

What can you tell by the pedigree?Dominant or recessive?

Autosomal or sex-linked?

Autosomal -Dominant

NO carriers when Dominant.

Dominant or recessive?Autosomal or sex-linked?

Autosomal -Recessive

Carriers when recessive.

• Pedigree Practice-Smart board

Genetic

Disorders

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Huntington’s Disease

• Progressive, degenerative disease that causes certain nerve cells in your brain to waste away.

• Experience uncontrolled movements, emotional disturbances and mental deterioration.

• No cure. Fatal. ages:30-60

• Dominant Allele

49 1/249 1/2

Colorblindness•Sex-linked trait• Gene for color

vision located on the X chromosomes.

• MalesMales are more likely to have colorblindness because they have only one X chromosome

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What do you see?

The individual with normal color vision will see a 5 revealed in the dot pattern. An individual

with Red/Green (the most common) color blindness will see a 2 revealed in the dots.

What What

do do

you you

see?see?

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TEST

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Down Down SyndromeSyndrome•3 copies of chromosome #21.

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•Sister chromatid DO NOT separate during Meiosis.

• (or homologues fail to separate )

•Nondisjunction•Also called: Trisomy 21

Nondisjunction

• Sister chromatid DO NOT separate during Meiosis.

• Or homologues fail to separate during Meiosis.

Down Syndrome - Trisomy 21

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NondisjunctionNondisjunction

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Down

Syndrome

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• CF is caused by a recessive allele on chromosome #7.

• More than 1,000 different mutations in the CFTR gene have been identified

• Deletion of 3 bases.• Affects the body's

respiratory and digestive systems.

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Cystic Fibrosis

• 1 in 29 Caucasian Americans have the allele.– Asian & African-less likely to have.– More than 10 million Americans carry

the cystic fibrosis gene

• Treatments:– Pancreatic enzyme

replacement therapy to allow proper food digestion

– Bronchodilators (also used by people with asthma) that help keep the airways open

– Inhaled antibiotics to kill the bacteria that cause lung infections

– Chest physical therapy, in which the patient is repeatedly clapped on the back to free up mucous in the chest

Gene therapy ?????? Currently in clinical trials

Cystic Fibrosis

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Hemophilia

Sex-liked Trait

(X chromosome)

more

commonly in

males

Located on the

X chromosome

Missing a

protein

necessary for

blood clotting

Major bleeding

from minor

cuts.

Recessive allele

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Sickle Cell

People who carry the tendency to have sickle cell anemia are less likely to die from malaria.

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Mis-shaped blood cells.

•Most commonly affects African-Americans. •About 1 out of every 500 African-American babies born in the United States has sickle cell anemia.

Sickle Cell

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Interesting fact:Unlike

normal red blood cells, which can

live for 120 days, sickle-shaped

cells live only 10 to 20 days.

Mis-shaped blood cells.

Tay-Sachs• Progressively destroys nerve cells

(neurons) in the brain and spinal cord.• Harmful quantities of a fatty acids

accumulate in the nerve cells of the brain.• Caused by insufficient activity of an

enzyme called beta-hexosaminidase A that catalyzes the biodegradation of acidic fatty materials

• More common in people of Ashkenazi (eastern and central European) Jewish heritage

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Gene Therapy

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Example EOCT question:Example EOCT question:

What is nondisjunction?

A. failure of chromosomes to separate during meiosis

B. failure of the cytoplasm to divide properly

C. the insertion of a gene into a different chromosome

D. the deletion of a gene from a chromosome

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Which of the following shows how information is

transformed to make a protein?

A DNA RNA proteinB gene chromosome proteinC cell respiration ATP proteinD ATP amino acid protein

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Information on mRNA is Information on mRNA is used to make a sequence used to make a sequence

of amino acids into a of amino acids into a protein by which of the protein by which of the

following processes?following processes?A replicationB translationC transcriptionD transference6868

Pea plants have seeds that are either round or wrinkled. In this cross, what will be thephenotypic ratio of the offspring?

A 50% RR and 50% RrB 25% RR, 50% Rr, and 25% rrC 50% round seeds and 50% wrinkled seedsD 100% round seeds

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What is a source of genetic variation?A mutationB adaptationC replicationD transcription

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A homozygous traitB dominant traitC recessive traitD heterozygous trait

In Mendel’s experiments with a single trait, the

trait that disappeared in the first generation

and reappeared in the next generation is called

the

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•What pattern of inheritance is this?

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Human Genome Project

What would one gene say to another?

FIN

Cloning