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Unit 4: Cell Division & Heredity. Part 3 Ch. 14 & Ch. 15 Mendelian Genetics & Chromosomal Basis of Inheritance. I. Genetics As A Science. Genetics = Study of heredity Heredity = How information gets transferred to us from our parents. II. Genetics Vocabulary.

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Unit 4 cell division heredity

Unit 4: Cell Division & Heredity

Part 3

Ch. 14 & Ch. 15

Mendelian Genetics & Chromosomal Basis of Inheritance


I genetics as a science
I. Genetics As A Science

  • Genetics = Study of heredity

    • Heredity = How information gets transferred to us from our parents.


Ii genetics vocabulary
II. Genetics Vocabulary

  • Trait: Characteristic that is different among individuals.

    Eye color, height, skin color


Ii genetics vocabulary1
II. Genetics Vocabulary

  • Cross: When 2 individuals mate.

    2 trees, 2 dogs, etc.


Ii genetics vocabulary2
II. Genetics Vocabulary

  • Hybrid: Result of crossing individuals with different traits.


Iii discovery of genetics
III. Discovery of Genetics

  • Gregor Mendel: Used pea plants to explore heredity.


Iii discovery of genetics1
III. Discovery of Genetics

  • Mendel concluded 2 things

    • “Factors” determine what organisms will be like .

      • Genes – determine traits

        1. Height

        2. Hair color


Iii discovery of genetics2
III. Discovery of Genetics

b. Each “factor” can come in different varieties.

1. Alleles- varieties of genes

a. Hair color gene

1. Brown allele

2. Blonde allele

3. Red allele


Iii discovery of genetics3
III. Discovery of Genetics

  • Mendel concluded 2 things…

    • Some alleles are “stronger” than others


Iii discovery of genetics4
III. Discovery of Genetics

  • Law of Dominance: Some alleles are dominant & others are recessive.

    • Dominant: Will always be seen.

    • Recessive: Only seen if dominant is not there.


Iv mendel s work
IV. Mendel’s Work

  • Crossed a tall plant with a short plant.

    • P Generation = Original pair of plants.

      (Parents)


Iv mendel s work1
IV. Mendel’s Work

B. Results

  • All tall plants

    F1 = First set of offspring.

    (children)


Iv mendel s work2
IV. Mendel’s Work

  • Curious about why none were short.

    1. Crossed 2 plants from the F1. generation.

    Yes, mated 2 siblings!


Iv mendel s work3
IV. Mendel’s Work

D. Results

1. 75% Tall

25% Short

F2 = offspring of the F1 generation.

(grandchildren)


V explaining the outcomes
V. Explaining the Outcomes

  • The allele for “shortness” didn’t disappear.

    B. The allele for “tallness” was dominant.

    How was the recessive allele able to be “recovered”?


V explaining the outcomes1
V. Explaining the Outcomes

  • Segregation: Alleles separate from each other during meiosis.

  • Gametes then combine differently during fertilization.

T t

T t

T

t

T

t

T t

T t

t t

T T


Viii more about alleles
VIII. More About Alleles

A. Allele combinations

1. Have 2 alleles for each gene

Height – Tall or short


Viii more about alleles1
VIII. More About Alleles

B. Each one represented by the first letter of the dominant allele:

  • Dominant = Uppercase

  • Recessive = Lowercase

    a. Height

    T = Tall (Dominant)

    t = Short (Recessive)


Viii more about alleles2
VIII. More About Alleles

a. If 2 of the SAME allele: HOMOZYGOUS

TT = Tall tt = Short

HomozygousHomozygous

DominantRecessive


Viii more about alleles3
VIII. More About Alleles

b. If 2 DIFFERENT alleles: HETEROZYGOUS

Law of dominance: If dominant is present, it will “cover” the recessive.

T t = Tall


Ix looks can be deceiving
IX. Looks Can Be Deceiving!

  • Phenotype: Physical appearance (What’s on the outside)

    White, Red

  • Genotype: Genetic makeup (What’s on the inside)

    RR, Rr, rr


X punnett squares
X. Punnett Squares

  • Diagrams for predicting results of any cross.

    Genotype of parent 1

    Genotypes of

    offspring

    Genotype of

    parent 2


Xi single trait cross
XI. Single Trait Cross

  • A cross for 1 trait.

    1. Hair color ONLY


Xi single trait cross1
XI. Single Trait Cross

Genotype of parent 1

T T

Genotype of

parent 2

t t

T

T

t

t


Xi single trait cross2
XI. Single Trait Cross

Results: All 4 combinations are the same.

Results vary depending on parents!

T

T

T t

T t

t

t

T t

T t


Xi monohybrid cross
XI. Monohybrid Cross

F1 Cross: Cross 2 of the “kids”.

Results: 1:2:1 Genotypic Ratio

3:1 Phenotypic Ratio

T t

TT

T t

T

t

T t

t t


Xi monohybrid cross1
XI. Monohybrid Cross

  • RULE: According to the Mendel’s Laws, A monohybrid cross of F1 will ALWAYS result in 3:1 p ratio and 1:2:1 g ratio.

  • If not… something else is acting.

    - Alternate types of dominance


Xii dominant recessive
XII. Dominant/Recessive??

Simple rules of dominance/recessive don’t always hold true.

1. Incomplete dominance:

Both alleles present = Intermediate


Xii dominant recessive1
XII. Dominant/Recessive??

2. Codominance:

Both alleles present = Both appear

Brown & White

both dominant =

both colors

appear


Xii dominant recessive2
XII. Dominant/Recessive??

3. Multiple alleles:

More than 2 alleles for 1 gene

Blood Groups


Xii dominant recessive3
XII. Dominant/Recessive??

4. Lethal Dominant Traits

Monohybrid cross will yield a 2:1 ratio of dominant to recessive.

H.D. not viable so does not count in the total offspring.

T

t

TT

T t

T

t

T t

t t


Sex chromosomes
Sex Chromosomes

44 Autosomes & 2 Sex chromosomes

a. Male: 46,XY b. Female: 46,XX


Sex chromosomes1
Sex Chromosomes

3. Sperm = X or Y 4. Egg = X only

Female

X

X

XX

XX

50% female

50% male

X

Male

XY

XY

Y


Sex linked genes
Sex-Linked Genes

Found on the sex chromosomes, X or Y.

Y-linked traits = “maleness” mostly

X-linked traits = many traits

- Colorblindness


Sex linked genes1
Sex-Linked Genes

Males = Y X

All X-linked traits will be expressed in males.

Only 1 X chromosome, so either YES or NO!

Females = X X

If trait is dominant, it will be expressed if 1 copy is present.

If trait is recessive, it will be expressed if present on BOTH X chromosomes.


More on x chromosomes
More on X Chromosomes

Barr body: One of the X chromosomes in females “turns off” during early development.

2. Only in females; Males need the X!!

3. No baby ever born without an X


Xiii two trait cross
XIII. Two Trait Cross

  • A cross that looks at 2 traits.

    1. R = right handed r = left handed

    2. D = Dimples d = no dimples


The testcross
The Testcross

  • A person has brown hair, and brown hair is dominant. How can we tell the genotype?

  • Testcross: crossing an unknown genotype with a homozygous recessive.

    • h.r. will always have KNOWN genotype.

      • gg jj kk ee


The testcross1
The Testcross

  • If homozygous dominant:

    • BB x bb = ALL Bb (all brown hair)

  • If heterozygous:

    • Bb x bb = HALF Bb, Half bb (half brown, half blonde)


Xii dihybrid cross
XII. Dihybrid Cross

Genotype of parent 1 = R r D d

Genotype of parent 2 = R r D d

  • Figure out the combinations for each parents’ gametes.


Xii dihybrid cross1
XII. Dihybrid Cross

Genotype of parent 1 = R rD d

FIRST

R r X D d

R D


Xii dihybrid cross2
XII. Dihybrid Cross

Genotype of parent 1 = R rD d

OUTSIDE

R r X D d

R d


Xii dihybrid cross3
XII. Dihybrid Cross

Genotype of parent 1 = R rD d

INSIDE

R r X D d

rD


Xii dihybrid cross4
XII. Dihybrid Cross

Genotype of parent 1 = R rD d

LAST

R r X D d

rd


Xii dihybrid cross5
XII. Dihybrid Cross

Genotype of parent 1 = R rD d

Gamete combinations =

R D R d rD rd


Xii dihybrid cross6
XII. Dihybrid Cross

Genotype of parent 2 = R rD d

Same genotype, same

gamete combinations =

R D R d rD rd


Xii dihybrid cross7
XII. Dihybrid Cross

2. Make a Punnett square: 16 possibilities


Xii dihybrid cross8
XII. Dihybrid Cross

3. Parents’ possible gametes

R D

R d

r D

r d

R D

R d

r D

r d


Xii dihybrid cross9
XII. Dihybrid Cross

4. Perform Crosses

R D

R d

r D

r d

RRDD

R D

RRDd

RrDD

RrDd

R d

RRDd

RRdd

Rrdd

RrDd

r D

RrDd

rrDD

rrDd

RrDD

r d

Rrdd

rrDd

rrdd

RrDd


Xii dihybrid cross10
XII. Dihybrid Cross

5. Results: 9 = right handed w/dimples

R D

R d

r D

r d

R D

RRDD

RRDd

RrDD

RrDd

R d

RRDd

RRdd

Rrdd

RrDd

r D

RrDd

rrDD

rrDd

RrDD

r d

Rrdd

rrDd

rrdd

RrDd


Xii dihybrid cross11
XII. Dihybrid Cross

5. Results: 3 = Right handed, no dimples

R D

R d

r D

r d

R D

RRDD

RRDd

RrDD

RrDd

R d

RRDd

RRdd

Rrdd

RrDd

r D

RrDd

rrDD

rrDd

RrDD

r d

Rrdd

rrDd

rrdd

RrDd


Xii dihybrid cross12
XII. Dihybrid Cross

5. Results: 3 = Left handed w/dimples

R D

R d

r D

r d

R D

RRDD

RRDd

RrDD

RrDd

R d

RRDd

RRdd

Rrdd

RrDd

r D

RrDd

rrDD

rrDd

RrDD

r d

Rrdd

rrDd

rrdd

RrDd


Xii dihybrid cross13
XII. Dihybrid Cross

5. Results: 1 = Left handed, no dimples

R D

R d

r D

r d

R D

RRDD

RRDd

RrDD

RrDd

R d

RRDd

RRdd

Rrdd

RrDd

r D

RrDd

rrDD

rrDd

RrDD

r d

Rrdd

rrDd

rrdd

RrDd


Xii dihybrid cross14
XII. Dihybrid Cross

5. Results:

The probability of having a child with dimples and being left-handed?

3/16 = r r D D

r r D d

r r d D

Out of 16, 3 should be left handed and have dimples.


Xii dihybrid cross15
XII. Dihybrid Cross

6. Independent Assortment

a. New combo’s were made

b. Traits didn’t affect each other

c. Gene for right hand/left hand independent from gene for dimples… why?


Xii dihybrid cross16
XII. Dihybrid Cross

6. Independent Assortment

d. On different chromosomes!

* Different genes can assort without affecting each other if they are on different chromosomes.


Xii dihybrid cross17
XII. Dihybrid Cross

Phenotypic Ratio is always:

9:3:3:1

If not… something else is going on… Alternate type of dominance, sex linked trait…


Probability
Probability

A. Punnett squares can get too large if we look at more than 2 traits. Using rules of probability are much easier!

1. Rule of multiplication

a. signaled by the word “AND”

- what’s the probability I will have a boy and he will have blue eyes?


Probability1
Probability

1. Rule of multiplication

boy = XY girl = XX blue eyes = gg

GgXX (mom) x GgXY (dad)

Do one trait at a time, then multiply both.

Blue eyes = gg… what’s the prob. Of gg? ¼

Boy = XY… what’s the prob of XY? ½

¼ x ½ = 1/8 prob of boy w/ blue eyes.


Probability2
Probability

2. Rule of addition

a. Signaled by the word “OR”

simplest example: what’s the prob. Of getting a boy OR a girl?

XX x XY

prob. of a girl = ½ prob of a boy = ½

½ + ½ = 1 (100%)

Obviously!


Probability3
Probability

3. Combining the rules

P genotypes: GgTtff x GgTtFf

What’s the prob. Of a green eyed, short, freckled child?

1. Green eyes:

can be GG or Gg

GG = ( ½ x ½) = ¼

Gg = ( ½ x ½ ) + ( ½ x ½ ) = ½

GG( ¼ ) + Gg ( ½ ) = ¾


Probability4
Probability

3. Combining the rules

P genotypes: GgTtff x GgTtFf

What’s the prob. Of a green eyed, short, freckled child?

2. Short:

can only be tt

tt = ( ½ ) x ( ½ ) = ¼


Probability5
Probability

3. Combining the rules

P genotypes: GgTtff x GgTtFf

What’s the prob. Of a green eyed, short, freckled child?

3. Freckled

Can be Ff or FF (but looking at the parents, FF will not be a possibility!)

(1) x ( ½ ) = ½


Probability6
Probability

3. Combining the rules

P genotypes: GgTtff x GgTtFf

What’s the prob. Of a green eyed, short, freckled child?

1. Green eyes = ¾

2. Short = ¼

3. Freckled = ½

¾ x ¼ x ½ = 3/32


A closer look at meiosis
A Closer Look at Meiosis

Crossing over: Parts of a homologous chromosome cross to the other homologous chromosome.


Recombination
Recombination

  • Case 1: Recombination of genes that are on different chromosomes (Unlinked).

    YyRr (yellow, round) x yyrr (green, wrinkled)

    ¼ YyRr (yellow, round) ¼ yyrr (green, wrinkled

    ¼ Yyrr (yellow, wrinkled) ¼ yyRr(green,round)

    ½ Parental Pheno. ½ Recombinant Pheno.


Recombination1
Recombination

Case 1: Recombination of genes that are on different chromosomes (Unlinked).

50% recombinant offspring is the EXPECTED value for unlinked genes.

It is also the MAXIMUM value


Recombination2
Recombination

Case 2: Recombination of genes that are on the same chromosome (Linked).

Any number less than 50% means the genes must be on the same chromosome.

The LOWER the number = the CLOSER the genes are to each other.


Recombination3
Recombination

  • Equation for calculating recombination Frequencies & distance the genes are from each other.

    Freq. R = # recombinants/ total offspring

    Practice Problem


Human traits diseases
Human Traits & Diseases

1. Pedigree Charts: Diagram used to follow inheritance patterns of genes.


F human disorders
F. Human Disorders

  • Recessive disorders

    • Cystic Fibrosis

      Symptoms: Excess mucus in lungs, digestive problems, prone to infections.

      Most Affected: Northern European ancestry.


F human disorders1
F. Human Disorders

  • Recessive disorders

    • Cystic Fibrosis

      Cause: Deletion of 3 bases = no phenylalanine.

      CFTR protein malfunctions = mucus builds up.

      Treatment: Nebulizer = Thins mucus in lungs.


F human disorders2
F. Human Disorders

  • Recessive disorders

    • Cystic Fibrosis

      Frequency: 1 in 2,500

      Diagnosis: Tested before birth or once symptoms are noticed.


F human disorders3
F. Human Disorders

  • Recessive disorders

    b. Sickle Cell Disease

    Frequency: 1 in 400 African Americans

    Other races affected but primarily African Americans.


F human disorders4
F. Human Disorders

  • Recessive disorders

    b. Sickle Cell Disease

    Causes: Substitution on an incorrect amino acid in hemoglobin protein.

    Symptoms: Blood cells are misshapen and clot irregularly.

    Treatments: Blood transfusions.


F human disorders5
F. Human Disorders

  • Dominant disorders

    a. Achondroplasia

    Symptoms: Dwarfism, shortened limbs

    Most affected: Uncertain; Studies show men being affected more.


F human disorders6
F. Human Disorders

  • Dominant disorders

    a. Achondroplasia

    Cause: FGFR3 gene = abnormal cartilage formation.

    Treatment: Growth hormones


F human disorders7
F. Human Disorders

  • Dominant disorders

    a. Achondroplasia

    Frequency: Not known in USA; International = 1 in 15,000- 40,000.

    Diagnosis: Before birth, after birth.


Sex linked disorders
Sex-Linked Disorders

1. Muscular Dystrophy: Weakening of muscles, loss of coordination. 1/3500 males.

2. Hemophilia: Poor blood clotting, smallest injuries can be fatal.


Chromosome disorders
Chromosome Disorders

  • Nondisjunction: Homologous chromosomes don’t separate during meiosis.

  • Incorrect number of chromosomes.


Chromosome disorders1
Chromosome Disorders

  • Down Syndrome

    a. 3 copies of chromosome 21


Chromosome disorders2
Chromosome Disorders

  • Turner’s Syndrome

    • One X chromosome = 45,X

    • Sterile, females

  • Klinefelter’s Syndrome

    • Extra X chromosome = 47, XXY

    • Sterile, males


G genetic testing
G. Genetic Testing

Testing for alleles

Test parents

Fetal testing

Amniocentesis

CVS

c. Newborn Screening


Influences on genes
Influences on Genes

Polygenic Traits: Traits that are controlled by more than 1 gene.

Eye color

Skin color


Influences on genes1
Influences on Genes

B. The Environment

1. Plant height

2. Human weight


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