bicd 100 - lecture 13

bicd 100 - lecture 13 - LECTURE 13 1 2 3 4 5 6 Lethal...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: LECTURE - 13 1. 2. 3. 4. 5. 6. Lethal Alleles Recessive Epistasis Dominant Epistasis Duplicate Recessive Epistasis Cytoplasmic Inheritance Maternal Effect Recessive Epistasis Labrador retrievers: black, brown, yellow coats. Recessive Epistasis • Alleles B: black b: brown • E: allows deposition of dark pigment • e: prevents deposition of dark pigment Genotype Phenotype B_E_ bbE_ B_ee bbee BBEE (Black) X bbee (Yellow) F1= BbEe (Black) F1 intercross 9:3:3:1 B_E_:bbE_:B_ee:bbee Black:Brown:Yellow:Yellow Hence modified phenotypic ratio is 9:3:4 Alleles B and b are hypostatic and e is epistatic Dominant epistasis Dominant epistasis White, Green and W_Y_ wwyy W_yy 9+3= 12/16 1/16 Modified F2 ratio is 12:1:3 Yellow squash wwY_ 3/16 Dominant epistasis wwY_ Enzyme 2 Y_ plants have enzyme 2 Enzyme 1 Dominant allele W inhibits enzyme 1 or W_yy activity. Only ww plants have active enzyme 1 W_Y_ wwyy yy plants have no enzyme 2 yellow white green wwY_ 3/16 W_Y_ 9/16 W_yy wwyy + 3/16 1/16 = 12/16 Therefore 12 : 3 : 1 White: yellow: green Duplicate Recessive Epistasis a is epistatic to B recessive epistasis because b is epistatic to A aa and bb required for albinos Duplicate Recessive Epistasis aaBB X AAbb albino albino (albino snails) AaBb pigmented snails Intercross A_B_ aaB_, A_bb, aabb 9/16 3/16 3/16 1/16 = 7/16 Hence, modified phenotypic ratio is 9:7 Cytoplasmic Inheritance DNA from the sperm enters the oocyte to form the male pronucleus in the fertilized egg, but all the mitochondria are provided by the oocyte. Cytoplasmic Inheritance 1. Mitochondria: Leber hereditary optic neuropathy (LHON) 2. Chloroplast: Leaf variegation in plants heteroplasmy homoplasmy Mitochondrial mutations usually affect only certain tissues… • that require high amounts of ATP • and require the synthesis of sufficient quantities of functional mitochondrial proteins (coded for by the mtDNA). • eg. Leber’s hereditary optic neuropathy (LHON): degeneration of optic nerve accompanied by increasing blindness. Caused my missense mutation in mtDNA gene coding for a subunit of NADH-CoQ reductase. • Ooplasmic transfer: mitochondria from a healthy woman are injected into the oocyte of woman with mitochondrial disorder. Chloroplast: Leaf variegation in plants Maternal Effect ...
View Full Document

This note was uploaded on 01/25/2011 for the course BICD 100 taught by Professor Nehring during the Spring '08 term at UCSD.

Ask a homework question - tutors are online