Inheritance Pattern Complexity

Transcription

1 Inheritance Pattern Complexity complexity from how genes transmitted Sex linkage Linkage (coming soon!) complexity from how genes function dominance relationships multiple alleles pleiotropy conditional gene expression penetrance & expressivity [Intragenic interactions] Intergenic Gene interactions (epistasis)

2 epistasis 1. Genetics. An interaction between nonallelic genes, especially an interaction in which one gene suppresses the expression of another. American Heritage Dictionary of the English Language 2. Medicine. A film that forms over the surface of a urine specimen. 3. The suppression of a bodily discharge or secretion.

3 Epistasis can be described as either recessive epistasis or dominant epistasis. recessive epistasis example: color in Labrador Retrievers DOMINANT epistasis example: squash fruit color

4 2 genes: Recessive Epistasis: Labrador Retrievers B controls color E controls B B- black bb chocolate only if E- ee golden regardless of B ee is epistatic to any B genotype

5 You have decided to breed your golden retriever (bbee) with the neighbor s chocolate retriever (bbee). What color pups will you and your neighbor have to fight over? A. & D. only B. & E. only C. & bb Ee ee chocolate golden

6 2 genes: Recessive Epistasis: Labrador Retrievers B controls color E controls B B- black bb chocolate only if E- ee golden regardless of B Bb;Ee x Bb;Ee F 2 phenotypic ratio?

7 B controls color E controls B B- black bb chocolate only if E- ee golden regardless of B 9 B_E_ : 3 B_ ee : 3 bbe_ : 1 eebb phenotype? phenotype? phenotype? phenotype? black golden chocolate golden 9 black : 4 (= 3 + 1) golden : 3 chocolate

8 Dominant Epistasis: Squash fruit color 2 genes: ww yy ww Y- green yellow W- Y- white W- yy white W is epistatic to any Y genotype

9 Dominant Epistasis: Squash fruit color 2 genes: ww yy ww Y- green yellow W- Y- white W- yy white Ww;Yy x Ww;Yy F 2 phenotypic ratio?

10 2 genes: Dominant Epistasis: Squash fruit color ww yy ww Y- green yellow W- Y- white W- yy white 9 W_ Y_ : 3 W_ yy : 3 ww Y_ : 1 ww yy 12 (= 9 + 3) white : 3 yellow : 1 green

11 Coat color in mice cc is epistatic to B gene BB black Bb black bb agouti Bb x Bb 3 black : 1 agouti P: CC bb x cc BB (agouti) (white) F 1 : Cc Bb (black) F 2 : 9/16 black C_ B_ 3/16 agouti C_ bb 4/16 white cc (3+1) CC pigmented Cc pigmented cc albino Cc x Cc 3 pigmented : 1 albino

12 Coat color in mice P: CC bb x cc BB (agouti) (white) cc is epistatic to B gene BB black Bb black bb agouti Bb x Bb F 1 : Cc Bb (black) F 2 : 9/16 black C_ B_ 3/16 agouti C_ bb 4/16 white cc (3+1) 3 black C : 1 agouti B precursor pigment 1 pigment 2 (white) (agouti) (black) Cc x Cc CC pigmented Cc pigmented cc albino B C pigment 1 3 pigmented pigment : 1 albino 2 deposited in hair (agouti) (black)

13 (duplicate recessive epistasis) figure complementary gene action C P white precursor purple pigment 9/16 C_ P_ 3/16 C_ pp 3/16 cc P_ 1/16 cc pp

14 (duplicate recessive epistasis) figure complementary gene action cc C P white precursor X purple pigment 9/16 C_ P_ 3/16 C_ pp 3/16 cc P_ 1/16 cc pp

15 (duplicate recessive epistasis) figure complementary gene action C P pp white precursor X purple pigment 9/16 C_ P_ 3/16 C_ pp 3/16 cc P_ 1/16 cc pp

16 A_B_ A_bb aab_ aabb :3:1 10:3:3 9:6:1 9:4:3 15:1 13:3 12:4 10:6 9:7

17 substance O G 4 enzyme 4 substance P G 3 substance M enzyme 3 substance N In this pathway, the conversion of precursor substance M to substance N is catalyzed by enzyme 3, which is encoded by gene, G 3. The conversion of precursor substance O to substance P is catalyzed by enzyme 4, which is encoded by gene, G 4. Substance P negatively regulates the synthesis of substance N by binding enzyme 3, thereby inactivating it.

18 complementary gene action

19 strain 11a w1/w1 w1a/w w1 /w1 strain 22 w2/w2 w2b/w b w1 /w1 strain w3/w3 w3/w33 w2/w2 strain w4/w4 wa4/w3 /w44 a w3 strain 5 5 b w5/w5 w5b/w w3 /w3 6 6 c strain w3 w6/w6 w6c/w /w3 7 7 d strain w3 w7/w7 w7d/w /w3 8 8 a strain w4 w8/w8 w8a/w /w4 9 9 b strain w4 w9/w9 w9b/w /w4 c strain w4 w10/w10 w10c/w4 /w1010

20 Complementation is the phenomenon in which two recessive mutations with similar/identical phenotypes result in a wild-type phenotype when both are heterozygous in the same genotype. Complementation means that the mutations are in different genes. Complementation distinguishes different genes based on functional criteria.

21 2 mutant alleles of 1 gene? OR mutations in 2 different genes???

22 2 mutant alleles of 1 gene? OR mutations in 2 different genes?