Pedigree Charts and Punnett Squares
Pedigree Charts
A pedigree chart is a diagram used to identify inheritance patterns in a family. The Pedigree Chart starts with two parents at the top and moves down with the following generations. Usually, the squares represent males and circles represent females. The charts usually completely shade the individuals which have the trait or disease that is being studied. Sometimes the symbol will be half colored, to show that the individual doesn't have the trait but carries an allele for it.
https://www.expii.com/t/pedigree-definition-charts-10776
Pedigree Charts
Pedigree charts allow tracking of alleles through multiple generations of a family
Pedigree Charts
Pedigree Charts can be used to identify the genetic disorders and predict likelihood of offspring inheriting these traits
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Have a look at the worksheet and see if you can answer the questions following the rules outlined in the videos above and using the symbols chart to help.
Monohybrid Inheritance
- Complete Dominance - the dominant allele masks the presence of the recessive allele
- Incomplete Dominance - both alleles contribute to the expression of heterozygote phenotype which appears as a blend or intermediate
- Sex-Linked - Alleles which are carried on the Sex Chromosomes
- Lethal Alleles - occur when a mutation results in an allele that produces a non-functional version of an essential protein
Complete Dominance
Characterised by a Dominant Allele and a Recessive Allele
Incomplete Dominance
The heterozygous phenotype is a blend or intermediate of the two alleles
Sex-Linked Alleles
Genes which are located on the Sex Chromosomes
Lethal Genes
An individual that inherits a lethal combination of lethal genes will die before birth or shortly afterwards.
Monohybrid Crosses
- used to predict the inheritance patterns for a single characteristic controlled by one gene
We use Punnett Squares to work out possible genotypes and phenotypes of offspring.
The Breeding Cross is set up between two individuals. In the example shown to the left
P = Parents
The cross is written YY x yy. This identifies the two alleles each parent has.
F1 = First generation offspring. All genotypes and phenotypes must be identifed .
Genotype = Yy Phenotype = 100% Yellow
F2 = Second generation offspring. All genotypes and phenotypes must be identifed
Genotypes = YY: Yy : yy 1:2:1 Phenotypes Yellow : Green 3 :1
