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Embed code for: 14.1 - pedigrees
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More 14.1 - Pedigrees
What is a pedigree?
It’s a visual chart that depicts a family history or the transmission of a specific trait. (it’s like a family tree, but focuses on a specific trait)
Can be used by geneticists/counselors to predict genetic predisposition of new family members
How many generations in this pedigree?
Components of a pedigree
Squares indicate male
Circles indicate female
Affected indicated by shading
Unaffected indicated by blank
Horizontal line indicates marriage/union
Vertical line with brackets indicates children
Sometimes a pedigree will have a half shaded symbol to indicate a heterozygote/hybrid, also known as a carrier.
Analyzing a pedigree
Always remember that the pedigree shows TRAITS (PHENOTYPES), not genotypes. If the question is asking for genotypes, you have to figure it out.
Always remember that a shaded figure does NOT denote dominant/recessive, but only the presence/absence of a trait.
Examples – In pedigree to the right, trait is for blue eyes, a recessive trait:
What is mom’s genotype?
What is dad’s genotype?
What is mom’s genotype? bb
What is dad’s genotype? Bb
Allele for white forelock (F) is dominant. Write in the genotypes for each individual
1) start with what you know for sure: since trait is dominant, then all the unshaded shapes must be….
Allele for white forelock is dominant. Write in the genotypes for each individual
2) How do you know if it’s FF or Ff?
2) How do you know if it’s FF or Ff? It’s only possible to have ff kids if EACH parent can give an f allele. If just ONE parent is FF, then ALL the kids will be affect if pedigree shows a dominant pattern
3) Whatever you can’t determine for sure, only provide what information you can guarantee. (F- means you know the genotype has one dominant allele, but the other allele could be either dominant or recessive)
Finish the Pedigree packet and the half-sheet practice problems. There will be a quiz next class (A day: 4/13, B day: 4/17) over pedigrees. It is open-note, so keep today’s materials.
Finish make-up work:
Anything from Chapter 11.
Haploid vs Diploid review
Types of Cells
# of complete sets of chromosomes
Haploid #/Diploid #