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Genetics. Solving Punnett Squares. Vocabulary. Heredity – parent traits appear in offspring Allele – One version of a gene Gene – DNA code for a protein  a trait. Dominant trait – Trait appears even with only one copy of the gene.

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genetics

Genetics

Solving Punnett Squares

vocabulary
Vocabulary
  • Heredity – parent traits appear in offspring
  • Allele – One version of a gene
  • Gene – DNA code for a protein  a trait
slide3
Dominant trait – Trait appears even with only one copy of the gene.
  • Recessive trait – Trait appears only with two recessive alleles
  • Homozygous – (Purebred) – two of the same alleles (AA or aa)
  • Heterozygous – (Hybrid) – two different alleles (Aa)
slide4
 Genotype – the DNA for a trait

i.e. R or r.

  •  Phenotype – the appearance of a trait determined by a genotype,

i.e. round or wrinkled peas.

cross a hybrid white flower with a homozygous purple flower
Cross a hybrid white flower with a homozygous purple flower

The heterozygote (hybrid) trait must be dominating the recessive trait

Ex. If Hh is hybrid.

Then hybrid means one of each. If the Dominant is expressed then white is dominant because white is the trait that is expressed.

seven steps to solve
Seven Steps to Solve

The heterozygote (hybrid) trait must be dominating the recessive trait

1. Dom = white Rec= purple

2. Dom= H rec=h

3. Ma= Hh Pa= hh

4.

5/6.

7. Genotypes = 50% Hh and 50% hhPhenotypes = 50% White 50% Purple

Pa

H

h

h

h

try this
Try This
  • In a certain plant, tall stems are dominant to short stems. A farmer crosses a short-stemmed flower with a homozygous long-stemmed flower. Complete each of the steps.
slide10

1. Dom = T Rec =t

2. T = Tall t = short

3. Ma: TT Pa: tt

4.

Pa

T

T

t

t

  • Genotypes: 100% T t
  • Phenotypes: 100% Tall
codominance
CoDominance
  • There are many different ways that we type blood. Today, we’ll look at two systems, ABO and the Rh- factor.

ABO Typing:

  • Each red blood cell has proteins on its surface that let the body identify it as belonging to yourself.

Genes “A” and “B” are Co-Dominant genes.

Gene “o” is the recessive gene.

sample problem for blood type mom is hybrid type b blood dad is hybrid type a blood
Sample Problem for Blood Type:Mom is hybrid type B blood, Dad is hybrid type A blood.

5/6.

7. Genotypes = 25% AB, 25% Ao, 25% Bo, 25% ooPhenotypes = 25% AB, 25% A, 25% B, 25% O

1. Dom = A & B Rec= o

2. A or B o

3. Ma= Bo Pa= Ao

4.

B

o

A

o

slide13

Rh Factor - is a protein found in blood Rh + means the protein is present. Rh – means it is not.Example: Dad is heterozygous Rh+ factor and mom is homozygous for Rh- factor blood.

1. Dom = + Rec= -

2. + -

3. Ma= - - Pa= + -

4.

5/6.

7. Genotypes =

50% - - 50% + -Phenotypes = 50% Rh + 50% Rh-

-

-

+

-

what are sex linked traits
What are sex-linked traits?
  • Traits on the Y or X chromosomes

Females are XX

Males are XY

Which sex chromosome is home of the most sex-linked traits?

    • X…much, much larger and if any essential gene were on the Y females would not live.
what are examples of traits that are sex linked
What are examples of traits that are sex-linked?

What are examples of traits that are sex-linked?

1)Color blindness – (red-green)

2) Hemophilia

3) Muscular Dystrophy

4) Male pattern baldness

fill in this table of phenotypes with the correct genotype
Fill in this table of phenotypes with the correct genotype

B = normal b = color blind

H = normal h = hemophilia

M = normal m = muscular dystrophy

How should we write these genotypes to help us remember they are sex-linked?

XmXm or XMY

M = Normal

m = muscular dystrophy

should see
Should See
  • Circle, Square, star,
should see21
Should see
  • Square, circle
should have seen
Should have seen
  • Faint Brown boat, colorblind individuals would have seen nothing.
should see26
Should see
  • Colorblind individuals should see a yellow square.
  • Normal sight should see circle and square.
ishihara test
Ishihara Test
  • http://www.toledo-bend.com/colorblind/Ishihara.html
hemophilia blood doesn t clot
Hemophilia – blood doesn’t clot

Czar Nicholas II of Russia and his family, photographed c. 1916, showing his wife Alexandra (who was a carrier of hemophilia), his four daughters, and (in the foreground) his son Alexis, perhaps the most famous European royal with hemophilia. http://www.humanillnesses.com/original/Gas-Hep/Hemophilia.html

muscular dystrophy
Muscular Dystrophy
  • Muscles form incorrectly, including heart and lungs, slowly deteriorate
  •  death by early 30’s
male pattern baldness
Male Pattern Baldness
  • Some evidence hints at X linked status

Androgens (male sex hormones) play a key role in balding--castrated men don't go bald--and the AR gene helps them do their work. The researchers found the balding men were much more likely to have a particular version of the AR gene than the non-balding men, which they took to mean they'd found a genetic variant that triggers baldness.

http://www.straightdope.com/columns/050819.html

sample problems
Sample Problems:
  • Genotypes and Phenotypes

XHXh

XhY

XBXB

XMY

XMXm

Woman carrier of hemophilia

Man with hemophilia

Normal Vision Girl

Normal boy

Woman carrier of muscular dystophy

slide32
Color Vision Phenotypes

XBXb

XbY

XBXB

XBY

Woman carrier of color blindness

Man with color blindness

Normal Vision Girl

Normal boy

sex linked traits cross a normal male with a female whocarrier for hemophilia
Sex Linked traits: Cross a normal male with a female whocarrier for hemophilia.

5/6.

7. Genotypes =

1/4 XH Xh 1/4 Xh Xh

1/4 XhY 1/4 XHY

Phenotypes = 50% girls with hemophilia 50% carrier for hemophilia girls, 50% boys have hemophilia 50% boys normal

1. Dom = healthy Rec= hemophilia

2. XH Xh

3. Ma= XHXh Pa=XHY

4.

XH

Xh

XH

Y

incomplete dominance
Incomplete Dominance
  • Sometimes, depending on the way the different proteins from each allele interact genes don’t completely dominate the alternate allele
  • Mendel studying 4 o’clocks (flowers) gave up genetic research because of this fact.
seven steps to solve cross an incompletely dominant white flower with a red flower
Seven Steps to SolveCross an incompletely dominant White flower with a red flower.

1. Dom = Red and White Inc. = Pink

2. R or W or RW

3. Ma=WW Pa=RR

4.

  • 5/6.
  • Genotypes = 100% RWPhenotypes =
  • 100% Pink

W

W

R

R

pedigrees
Pedigrees
  • Looking at ancestor’s traits to predict the genotypes of individuals in a family
add p 1 f 1 and f 2 and genotypes
Add P1, F1, and F2 and genotypes
  • Decide if disorder is dominant or recessive
  • Assign disease letters
  • Fill in only remaining letters you can guarantee
  • Be brave…use ? If you don’t know
dihybrid problems
Dihybrid Problems
  • Definition – Genetics Problems with two traits tracked at the same time

Try This:

  • Given B = brown hair, b = blond hair AND T = Tall while t = short.
  • BbTt = ____________phenotype
  • Bbtt = ____________ phenotype
  • bbTT = ____________ phenotype
  • bbtt = ____________ phenotype
dihybrids continued
Dihybrids continued
  • When drawing your sperm and egg for the 7 steps in this type of problem each:
  • Sperm contains ____ genes?
  • Egg contains ____ genes?
  • Predict the sperm or eggs possible for a critter of BbTt.

Arrow Rule

B b T t = BT & Bt

Then B b T t = bT & bt

slide42
What sex cells could be obtained from the genotypes below?
  • Bbtt: ___________, ___________, ___________, ___________
  • bbtt: ___________, ___________, ___________, ___________
  • BBTT: ___________, ___________, ___________, ___________
  • BbTt: ___________, ___________, ___________, ___________
  • Hint: repeated sperm or eggs can be crossed out.

Bt Bt bt bt

bt bt bt bt

BT BT BT BT

BT Bt bT bt

slide43
Dihybrid:Cross a totally heterozygous brown eyed tall girl with a heterozygous brown eyed homozygous tall guy.
  • Dom =Brown & Tall

Rec= blue & Short

2. B & T b & t

3. Pa= BbTT ma=BbTt

4.

5/6.

BT

BT

Bt

bT

bt

bT

slide44
Genotypes:

1/8 BBTT 2/8 BbTT 1/8 BBTt

2/8 BbTt 1/8 bbTt 1/8 bbTT

Phenotypes:

6/8 Brown eyed and tall

2/8 blue eyes and Tall

multiple genes
Multiple Genes
  • Much like dihybrids, but more capital letter alleles contribute to more of the specific trait
    • Ex. RRSS would be very dark red (4 caps) RRSs is dark red (any 3 caps) RrSs would be medium red (any 2 caps) Rrss would be light red (only 1 cap) rrss would be albino (no caps)
slide46
1. Dom = dark rec = light

2. R or S r or s

3. Ma: RrSs Dad: RrSS

RS

rS

RS

Rs

rS

rs

slide47

Geno:

1/8 RRSS

2/8 RrSS

1/8 RRSs

2/8 RrSs

1/8 rrSS

1/8 rrSs

Pheno:

1/8 Very dark red

3/8 dark red

3/8 medium

1/8 light red