heredity: the passing of characteristics from parents to offspring

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Heredity: The passing of characteristics from parents to offspring

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Page 1: Heredity: The passing of characteristics from parents to offspring

Heredity: The passing of characteristics from parents to offspring

Page 2: Heredity: The passing of characteristics from parents to offspring

Genetics:The science of heredity and the

process by which traits are passed from parents to offspring

Page 3: Heredity: The passing of characteristics from parents to offspring

P generation: The 1st two individuals that are crossed (parental generation)

F1 generation : The offspring of the P generation (offspring of the parents)

F2 generation: The offspring of the F1 generation(offspring of the F1 generation)

Page 4: Heredity: The passing of characteristics from parents to offspring
Page 5: Heredity: The passing of characteristics from parents to offspring

Mendel’s Hypotheses

1.) For each inherited character ( red, freckles, etc.), an individual has 2 copies of the gene – 1 from each parent

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2.) There are alternative versions of the gene known as alleles

BrownHair

Blonde Hair

Black Hair

Red Hair

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2.) Two different alleles occur together, one of them may be completely expressed while the other shows no observable appearance

Mother:Brown Hair

Father:Blonde Hair

Child:Brown Hair

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The expressed form a characteristic as: Dominant

R = dominant allele For example R = red hair Rr or RR

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Trait NOT expressed while the dominant form is present is known as the: recessive allele

r = recessive trait = brown hair

Rr

If the allele combination is rr is the recessive trait expressed? _____________ Why or why not?

Page 10: Heredity: The passing of characteristics from parents to offspring

Homozygous

- IF 2 alleles of a certain gene are the same, the individual is said to be: homozygous

(** true regardless of if the two are dominant OR recessive**)

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Heterozygous

• If the alleles of a gene in an individual are different, the individual is: heterozygous

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Genotype: set of alleles an individual has for a characteristic

Example: Rr is the genotype for red hair

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Phenotype: the physical appearance of a characteristic

So … if the genotype is Rr then the phenotype is ____________________.

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Questions:

T = tan colored featherst = white color feathers

Is t the dominant allele or the recessive allele?_________________

An owl has white colored feathers ( tt ) , this physical appearance of having white feathers is known as the owl’s ________________ ?

If an owl’s genotype is Tt, what color feathers will it have? ____________

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Law of Segregation - states that the two alleles for a characteristic

are segregate or SEPARATE when gametes are formed

Page 16: Heredity: The passing of characteristics from parents to offspring

Law of Independent Assortment:

--Alleles of different genes separate independently of one another during gamete formation

-- The inheritance of one characteristic did not influence the inheritance of any other characteristic

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Law of Independent Assortment/Segregation Lab

B – brown hairb – blonde hair F – freckles f– no frecklesC – curly hairc – straight hairG – gap in between front teethg – no gap in between front teeth

Page 18: Heredity: The passing of characteristics from parents to offspring

Punnett Square: --predicts the outcome of a genetic cross

-- the basic 4 chambered Punnett Square can predict the outcome of a monohybrid cross

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Page 20: Heredity: The passing of characteristics from parents to offspring

How could you find the genotype of an

individual if it was not known?

Test Cross- Is performed when an individual shows a dominant

phenotype but we are not sure whether they are heterozygous or homozygous.

- These individuals are crossed with a homozygous recessive individual

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If half of the offspring express the dominant trait and half express the recessive trait, then the unknown individual’s genotype is?

______________________________________

Page 24: Heredity: The passing of characteristics from parents to offspring

IF all of the offspring express the dominant phenotype which genotype is the unknown individual?

_____________________________________

Page 25: Heredity: The passing of characteristics from parents to offspring
Page 26: Heredity: The passing of characteristics from parents to offspring

Section 4: Complex Patterns and Heredity

Polygenic Inheritance: when several genes influence a character

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Incomplete dominance: an individual that displays a phenotype that is intermediate between the two parents

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Codominance:

With codominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together. 

red x white ---> red & white spotted

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Roan Fur in CattleRR = all red hairsWW = all white hairs

RW = red & white hairs together

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Page 31: Heredity: The passing of characteristics from parents to offspring
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Sex-linked gene’s allele is located ONLY on the X or Y chromosome

Carried on the X chromosomeand are recessive

Males: only have one X chromosome (XY)

Male who carries a recessive allele on the X chromosome will express the sex-linked condition

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Female: if she is a carrier

of the recessive allele on

one X chromosome,

she will NOT exhibit

the allele if her

other X chromosome

exhibits the dominant allele

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Page 35: Heredity: The passing of characteristics from parents to offspring

Dihybrid Crosses

- A genetic cross that consists of two different traits instead of one

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Dihybrid Crosses

Instead of Rr x rr R= round, r = wrinkled

You are now including another trait into the cross: Y= yellow, y = green

RRYY x rryy

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Parent 2

Parent 1

RRYY x rryy

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RRYY RRYy RrYy

RrYy

RrYY RrYy

RrYy

Parent 2

Parent 1

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Parent 2

Parent 1

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Pedigree

--- A family history that shows how a trait is inherited over several generations

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Determining Information From a Pedigree

1.) Autosomal or sex-linked?

Autosomal: the gene will appear in both sexes equally

- Autosomes are all the other chromosomes other than the X or Y sex chromosome

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Determining Information From a Pedigree

2. ) Dominant or Recessive

Autosomal Dominant: EVERY individual with the condition will have a parent with that condition

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If the condition is recessive:

-- an individual that expresses the condition can have one, two or neither parent express the condition

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Page 48: Heredity: The passing of characteristics from parents to offspring

Determining Information From a Pedigree

3.) Homozygous or Heterozygous

- if individuals with autosomal traits are homozygous dominant or heterozygous,

- their phenotype will show the dominant allele

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Individual is homozygous recessive,

their phenotype will show the recessive allele

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Two people who are heterozygous carriers of a recessive mutation

Will not show the mutation, but can produce children who are homozygous for the recessive allele

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Characters Influenced by Environment

An individual’s phenotype often depends on the

condition of the environment

Identical twins are used in these types of studies

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Page 53: Heredity: The passing of characteristics from parents to offspring

Human Genetic Disorders

Page 54: Heredity: The passing of characteristics from parents to offspring

Sickle Cell Anemia - Recessive Genetic Disorder

-Cause: Mutated allele that produces a defective form of the protein hemoglobin

1 in 500 African Americans have sickle cell anemia

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Heterozygous Superiority

- Individuals that are heterozygous for sickle cell have what is considered “heterozygous superiority”

-The recessive allele that causes the sickle cell shape protects the individual from malaria * Also do not have sickle cell anemia because they are heterozygous*

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Cystic Fibrosis (CF) - Airways of the lungs become clogged with thick mucus, and the ducts of the liver and pancreas become blocked

- Most common, fatal, hereditary recessive disorders among Caucasians ( 1 in 25 have at least one copy of the defective gene )

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- Caused by a mutated protein that does not allow chloride to be moved into or out of cells

- Then…causes mucus to dehydrate and become thick and sticky in the lungs

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Hemophilia - Recessive genetic disorder that impairs the blood’s ability to clot

- Sex- linked Trait

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Huntington’s Disease (HD)

- Caused by a dominant allele located on an autosome

- Symptoms: Mild forgetfulness and irritability appear in people in their thirties and forties

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- HD causes loss of muscle control, uncontrollable physical spasms, severe mental illness, and eventually death