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Other Inheritance Patterns

Unlinked Autosomal Genes Rr Y y

Linked Genes Rr Yy RYry RYRRYYRrYy ryRrYyrryy 3 round, yellow : 1 wrinkled, green

Crossing over can create recombinants

Hypothetical Linked Gene Data  Round, Yellow – 93  Round, Green – 7 (recombinants)  Wrinkled, Yellow – 7 (recombinants)  Wrinkled, Green – 93  Recombination Frequency = recombinant total / total offspring  14/200 = 7%

Gene mapping  Each % pt of recombinants = 1 map unit on the chromosome  R is 7 map units away from Y RY 7 map units

Epistasis  When 2 or more genes control 1 phenotype (gene-gene interactions)  Remember – normal dihybrid cross of 2 heterozygotes give you a 9:3:3:1 phenotypic ratio  If 2 genes show epistasis, this ratio can change

Examples  Kernel Color in wheat  If 1 allele of gene A or gene B is dominant, the wheat is colored  The only individual that is white is aabb  Ratio 15:1

Flower color in sweet pea  Both genes need a dominant (functional) allele to create anthocyanin (color)  Ratio is 9:7

Albinism in mice  B gene – determines if mice pigment color is brown or black  C gene – determines if any pigment is present at all

Pleiotropy  When 1 gene has multiple phenotypic effects  Examples –Vestigial wing gene also causes changes in the balancers, the direction of bristles, and the number of eggs in the ovaries –GAPDH – 1 st known for the metabolism of glucose, also known for the regulation of protein translation, aiding in the transport of RNA to cytoplasm, aiding in DNA repair and DNA replication

Polygenic (quantitative) Traits  When multiple genes aid in the expression of a single trait  Examples – height, coloration (skin color, eye color)  Assumptions –Effects of each gene is additive –No dominance (incomplete dominance) –No linkage

Plant Height in Tobacco Plants  7 classes of height – 0 to 6 (depending on number of dominant alleles the plant has at 3 separate genes (A, B, and C)  AABBCC (6) x aabbcc (0) yields all intermediate (3) heterozygotes AaBbCc  Let’s look at the F1 cross –AaBbCc x AaBbCc

ABCABcAbCaBCAbcabCaBcabc ABCAABBCCAABBCcAABbCCAaBBCCAABbCcAaBbCCAaBBCcAaBbCc ABcAABBCcAABBccAABbCcAaBBCcAABbccAaBbCcAaBBccAaBbcc AbCAABbCCAABbCcAAbbCCAaBbCCAAbbCcAabbCCAaBbCcAabbCc aBCAaBBCCAaBBCcAaBbCCaaBBCCAaBbCcaaBbCCaaBBCcaaBbCc AbcAABbCcAABbccAAbbCcAaBbCcAAbbccAabbCcAaBbccAabbcc abCAaBbCcAaBbCcAabbCCaaBbCCAabbCcaabbCCaaBbCcaabbCc aBcAaBBCcAaBBccAaBbCcaaBBCcAaBbccaaBbCcaaBBccaaBbcc abcAaBbCcAaBbccAabbCcaaBbCcAabbccaabbCcaaBbccaabbcc

Polygenic Inheritance Graph

When Bad Things Happen to Good Chromosomes

Research - Disorders