Cystic Fibrosis

Mutation of _____ gene

What type of mutation? _______

What happens as a result?

How is it inherited?

Cystic Fibrosis

Mutation of CFTR gene (this gene makes proteins that make the surface of the lungs and other tissues moist)

What type of mutation? Deletion mutation

What happens as a result?

•  Protein gets stuck in Endoplasmic Reticulum instead of moving out of the cell
• Lung tissue is drier as a result
• Dry tissue = mucus sticks
• Mucus sticks = clogged airway

How is it inherited?

Must be inherited from both parents

Same chromosome

Same gene

Different DNA sequence on the gene

Chromosome 2          Chromosome 2

Gene A                     Gene A

"blue/pink flower gene" "blue/pink flower gene"

AGACTT                    AGAGCC

Blue flower                Pink flower

You need to know which allele is dominant to tell how the inheritance will be expressed

Monk who figured out that traits are inherited using pea plants

Developed Law of Independent Assortment

Developed Law of Segregation

Homozygous = ________ alleles

Heterozygous = ________ alleles

Homozygous = identical alleles (eg: AA or aa)

"breeds true"

Heterozygous = different alleles (eg: Aa)

Law of Segregation

&

Law of Independent Assortment

Gregor Mendel

Law of Segregation

Allele pairs separate during meiosis

A parent 'AA' separates into 'A' and 'A'

A parent 'Aa" separates into 'A' and 'a'

Law of Independent Assortment

After separating, can rejoin in offspring in any order

This is why offspring can inherit either one of the mother's alleles (she has two to offer) and either one of the father's alleles (he has two to offer)

Law of Segregation, Law of Independent Assortment

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Monohybrid Cross

Checks for a dominance relationship between alleles of one gene

Must start with identically heterozygous parents (Aa, Aa)

      A     a

A   AA    Aa              A=pink flower

                              a=blue flower

a   Aa    aa

Generates 1:2:1 genotype

1 - AA

2 - Aa

1 - aa

Generates 3:1 phenotype

3 - pink flower (AA, Aa, Aa)

1 - blue flower (aa)

Dihybrid Cross

Checks for a dominance relationships between alleles of two genes

Must start with homozygous parents for two different genes (AABB, aabb)

STEP ONE: 

      A     A                 B     B

a   Aa    Aa            b  Bb   Bb

a   Aa    Aa            b  Bb   Bb

Offspring are all AaBb

STEP TWO:

Cross two AaBb individuals together:

Generates AB, Ab, aB, ab

A = Pink flower

a = blue flower

B = tall

b = short

STEP THREE:

       AB        Ab        aB        ab

AB  ABAB    ABAb    aABB    AaBb

Ab  AbAB    AbAb    AaBb    Abab

aB  aBAB    aBAb    aBaB    aBab

ab  abAB    abAb     abaB    abab

Generates a bell curve genotype

1 - AABB

1 - aaBB

2 - AaBb

2 - aaBb

4 - AaBb

2 - Aabb

2 - AABb

1 - AAbb

1 - aabb

Generates 9:3:3:1 phenotype

9 - pink and tall (any combo that has at least one AB)

3 - pink and short (at least one A and two bb)

3 - blue and tall (two aa and at least one B)

1 - blue and short (aabb)