Genetics: Day 5. Pedigree Charts. Pedigree charts are diagrams constructed to show biological relationships and in genetics are used to show how a trait passes from one generation to another Pedigree Key:. Pedigree Analysis.
Genetics: Day 5
Determine the pattern of inheritance for the chart? Is it sex-linked dominant, sex-linked recessive, autosomal dominant, or autosomal recessive?
Let’s work this one out together on the board.
Mrs. Parrott wants to predict whether her kids with Mr. Parrott will have straight hair, wavy hair or curly hair and dimples or no dimples. Below are their alleles.
Mrs.- wavy hair (Hh) and no dimples (dd)
Mr. - straight hair (hh) and dimples (DD)
Genotypic ratio: 1:1 (HhDd:hhDd)
Phenotypic Ratio 1:1 (wavy hair with dimples: straight hair with dimples)
Therefore, all offspring with have a 50% chance to have either wavy hair or straight hair and 100% of offspring will have dimples
Complete the cross.
Determine the resulting phenotypic ratio for the F1 offspring.
Phenotypic ratio – 9:3:3:1
9 black/short, 3 black/long, 3 brown/short, and 1 brown/long
Common Example of Linked Genes
G = grey body
g = black body
L = long wings
l = short wings
G Lg l
G L g l
G Lg l
g l g l
5. Notice the two offspring in bold are in combinations unlike their parents (grey/short wings and black/long wings) therefore they must have formed through crossing over and we call them recombinants
*This is why interpreting the human genome is especially difficult since many genes can effect the same trait