…….
Assignment no 1

ARRANGED BY; ; ; ZOHAIB HUSSAIN AND SAAD IQBAL
TOPIC ; ; ; ;

EPISTATIC INTERACTIONS

SUBMITTED TO:::...
•Epistatic Gene
Interactions
Epistatic Gene Interactions
• Gene interactions occur when two or more different
genes influence the outcome of a single t...
• examine cases involving 2 loci (genes) that each
have 2 alleles
• Crosses performed can be illustrated in general by
– A...
A Cross Producing a 9:7 ratio
Figure 4.18

9 C_P_ : 3 C_pp :3 ccP_ : 1 ccpp
purple

white
Epistatic Gene Interaction

• Complementary gene
action

Enzyme C and enzyme P
cooperate to make a
product, therefore they...
Epistatic Gene Interaction

• Epistasis describes the situation in which
a gene masks the phenotypic effects of
another ge...
Colorless
precursor

Enzyme C

Colorless
intermediate

Enzyme P

Purple
pigment

genotype cc

Colorless
precursor

Enzyme ...
Epistasis of Involving Sex-linked Genes
• Inheritance of the Cream-Eye allele in
Drosophila
– a rare fly with cream-colore...
– Cream-colored eyes in fruit flies are due to
the effect of a second gene that modifies
the expression of the eosin allel...
Testing the Hypothesis
Data obtained
Cross

Outcome

P cross:
Cream-eyed male X
wild-type female

F1: all red eyes

F1 cross:
F1 brother X F1 sis...
Interpreting the Data
Cross

Outcome

P cross:
Cream-eyed male X
wild-type female

F1: all red eyes

F1 cross:
F1 brother ...
Modeling the Data




Cream phenotype is recessive therefore the
cream allele is recessive allele (either sexlinked or a...
Male gametes
CXw+

CY

caXw+

caY

Female gametes

CXw+

CCXw+Xw+

CCXw+Y

cacaXw+Xw+

CcaXw+Y

CXw-e

CCXw+Xw-e

CCXw-eY
...
A Cross Involving a Two-Gene Interaction Can
Still Produce a 9:3:3:1 ratio
• Inheritance of comb morphology in chicken
– F...
N
Figure 4.17b
The crosses of Bateson and Punnett
• F2 generation consisted of chickens with four
types of combs
– 9 walnut : 3 rose : 3 pea : 1 single
• Bateson and Punnet...
Gene Interaction

• Duplicate gene action

– Enzyme 1 and enzyme 2 are
redundant
– They both make product C,
therefore the...
x

Duplicate Gene
Action Epistasis

TTVV
Triangular

ttvv
Ovate

F1 generation
TtVv
All triangular
F1 (TtVv) x F1 (TtVv)

...
Bombay Phenotype
Bombay Phenotype
Bombay Phenotype
Squash Fruit Color
• Genotypes and
Phenotypes:
• W-/G-

white

• W-/gg

white

• ww/G-

green

• ww/gg

yellow
Dominant Epistasis
• LETS HAVE A LOOK AT DOMINANT
EPISTASIS…
• Squash fruit color is controlled by two genes.
• Gene 1 is ...
Squash Fruit Color
• Which allele is epistatic in squash color?
The dominant W allele is epistasis

• How do you know?
Bec...
Wwgg x wwGg
• FOIL: Wg or wg
• FOIL: wG or wg
• F1 generation genotypes:

• Phenotypes:
....THANK..
……
YOU…..
REFRENCE BOOKS
•CELL BIOLOGY, GENETICS
•EPISTASIS AND
EVOLUTIONARY PROCESS BY
JASON WOLF
•COMBINATORIAL APPROACH
TO EPISTA...
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD
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all types of gene action
complementry
epistatic

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  • Figure: 04-02
    Caption:
    Partial pedigree of woman displaying the Bombay phenotype.
  • Figure: 04-05
    Caption:
    Outcome of mating btw individuals heterozygous at 2 genes determining blood type.
  • Figure: 04-05
    Caption:
    Outcome of mating btw individuals heterozygous at 2 genes determining blood type.
  • Figure: 04-07
    Caption:
    Basis of modified dihybrid F2 phenotypic ratios.
  • Figure: 04-08
    Caption:
    Summer squash exhibiting various fruit-shape phenotypes.
  • Epistatic gene interaction by BIOTECHNOLOGY CIIT ABBOTTABAD

    1. 1. ……. Assignment no 1 ARRANGED BY; ; ; ZOHAIB HUSSAIN AND SAAD IQBAL TOPIC ; ; ; ; EPISTATIC INTERACTIONS SUBMITTED TO:::;;;;;DR SARFARZ SHAFIQ COURSE TITLE ; ; ; ; ; ;ESSENTIAL OF GENETICS
    2. 2. •Epistatic Gene Interactions
    3. 3. Epistatic Gene Interactions • Gene interactions occur when two or more different genes influence the outcome of a single trait • Most morphological traits (height, weight, color) are affected by multiple genes • Epistasis describes situation between various alleles of two genes • Quantitative loci is a term to describe those loci controlling quantitatively measurable traits • Pleiotropy describes situations where one gene affects multiple traits
    4. 4. • examine cases involving 2 loci (genes) that each have 2 alleles • Crosses performed can be illustrated in general by – AaBb X AaBb – Where A is dominant to a and B is dominant to b • If these two genes govern two different traits – A 9:3:3:1 ratio is predicted among the offspring – simple Mendelian dihybrid inheritance pattern • If these two genes do affect the same trait the 9:3:3:1 ratio may be altered – 9:3:4, or 9:7, or 9:6:1, or 8:6:2 or 12:3:1, or 13:3, or 15:1 – epistatic ratios
    5. 5. A Cross Producing a 9:7 ratio Figure 4.18 9 C_P_ : 3 C_pp :3 ccP_ : 1 ccpp purple white
    6. 6. Epistatic Gene Interaction • Complementary gene action Enzyme C and enzyme P cooperate to make a product, therefore they complement one another
    7. 7. Epistatic Gene Interaction • Epistasis describes the situation in which a gene masks the phenotypic effects of another gene • Epistasis interactions arise because the two genes encode proteins that participate in sequence in a biochemical pathway • If either loci is homozygous for a null mutation, none of that enzyme will be made and the pathway is blocked
    8. 8. Colorless precursor Enzyme C Colorless intermediate Enzyme P Purple pigment genotype cc Colorless precursor Enzyme C Colorless intermediate Enzyme P Purple pigment
    9. 9. Epistasis of Involving Sex-linked Genes • Inheritance of the Cream-Eye allele in Drosophila – a rare fly with cream-colored eyes identified in a true-breeding culture of flies with eosin eyes – possible explanations • 1. Mutation of the eosin allele into a cream allele • 2. Mutation of a 2nd gene that modifies expression of the eosin allele
    10. 10. – Cream-colored eyes in fruit flies are due to the effect of a second gene that modifies the expression of the eosin allele
    11. 11. Testing the Hypothesis
    12. 12. Data obtained Cross Outcome P cross: Cream-eyed male X wild-type female F1: all red eyes F1 cross: F1 brother X F1 sister F2: 104 females with red eyes 47 males with red eyes 44 males with eosin eyes 14 males with cream eyes F2 generation contains males with eosin eyes This indicates that the cream allele is not in the same gene as the eosin allele
    13. 13. Interpreting the Data Cross Outcome P cross: Cream-eyed male X wild-type female F1: all red eyes F1 cross: F1 brother X F1 sister F2: 104 females with red eyes 47 males with red eyes 44 males with eosin eyes 14 males with cream eyes F2 generation contains – 151 + eye: 44 we eye: 14 ca eye a 12 : 3 : 1 ratio
    14. 14. Modeling the Data   Cream phenotype is recessive therefore the cream allele is recessive allele (either sexlinked or autosomal) The mutated allele of the cream gene modifies the we allele, while the wt cream allele does not  C = Normal allele   Does not modify the eosin phenotype ca = Cream allele  Modifies the eosin color to cream, does not effect wt or white allele of white gene.
    15. 15. Male gametes CXw+ CY caXw+ caY Female gametes CXw+ CCXw+Xw+ CCXw+Y cacaXw+Xw+ CcaXw+Y CXw-e CCXw+Xw-e CCXw-eY CcaXw+Xw-e CcaXw-eY caXw+ CcaXw+Xw+ CcaXw+Y cacaXw+Xw+ cacaXw+Y caXw-e CcaXw+Xw-e CcaXw-eY cacaXw+Xw-e cacaXw-eY
    16. 16. A Cross Involving a Two-Gene Interaction Can Still Produce a 9:3:3:1 ratio • Inheritance of comb morphology in chicken – First example of gene interaction – William Bateson and Reginald Punnett in 1906 – Four different comb morphologies
    17. 17. N
    18. 18. Figure 4.17b The crosses of Bateson and Punnett
    19. 19. • F2 generation consisted of chickens with four types of combs – 9 walnut : 3 rose : 3 pea : 1 single • Bateson and Punnett reasoned that comb morphology is determined by two different genes – R (rose comb) is dominant to r – P (pea comb) is dominant to p – R and P are codominant (walnut comb) – rrpp produces single comb
    20. 20. Gene Interaction • Duplicate gene action – Enzyme 1 and enzyme 2 are redundant – They both make product C, therefore they duplicate each other
    21. 21. x Duplicate Gene Action Epistasis TTVV Triangular ttvv Ovate F1 generation TtVv All triangular F1 (TtVv) x F1 (TtVv) 15:1 ratio results TV TV Tv tV tv Tv tV tv TTVV TTVv TtVV TtVv TTVv TTvv TtVv Ttvv TtVV TtVv ttVV ttVv TtVv Ttvv ttVv ttvv (b) The crosses of Shull
    22. 22. Bombay Phenotype
    23. 23. Bombay Phenotype
    24. 24. Bombay Phenotype
    25. 25. Squash Fruit Color • Genotypes and Phenotypes: • W-/G- white • W-/gg white • ww/G- green • ww/gg yellow
    26. 26. Dominant Epistasis • LETS HAVE A LOOK AT DOMINANT EPISTASIS… • Squash fruit color is controlled by two genes. • Gene 1 is represented by a W • Gene 2 is represented by a G
    27. 27. Squash Fruit Color • Which allele is epistatic in squash color? The dominant W allele is epistasis • How do you know? Because every time a dominant W allele shows up in a squash genotype, the squash fruit color is white.
    28. 28. Wwgg x wwGg • FOIL: Wg or wg • FOIL: wG or wg • F1 generation genotypes: • Phenotypes:
    29. 29. ....THANK.. …… YOU…..
    30. 30. REFRENCE BOOKS •CELL BIOLOGY, GENETICS •EPISTASIS AND EVOLUTIONARY PROCESS BY JASON WOLF •COMBINATORIAL APPROACH TO EPISTATIS BY R LOWEN •CELL BIOLOGY AND GENETICS BY S.CHAND

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