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3.14 Monohydrid Inheritance and Genetic Diagrams - Coggle Diagram
3.14 Monohydrid Inheritance and Genetic Diagrams
Intro
Family trees show the inheritance of different phenotypes over generations in the same family
Punnett Square
This is done using the alleles the two parents have for a gene and a Punnett square diagram
You should be able to draw and use a Punnett square diagram
A monohybrid (single gene) cross looks at the probability of the offspring of two parents having certain genotypes and phenotypes
Recessive and Dominant Alleles
Lowercase letters
represent recessive characteristics
You can choose any letter but usually either A or B is used for simplicity
Uppercase letters are used to represent dominant characteristics
Notice that combining the alleles shown above results in ¼ chance of having an offspring who is homozygous dominant (BB, or has two dominant alleles), and there is no chance of having a homozygous recessive offspring (as both parents have the allele)
Whether or not the Bb (heterozygous recessive) offspring show symptoms
depends on whether the condition itself is recessive or dominant
Family Pedigrees
We usually use squares to represent males, and circles to represent females in the lineage
Black shapes represent an affected individual, and white shapes represent an unaffected individual
A line through the shape means that the individual is deceased
We can use them to better visualise certain patterns - for example, the way that recessive alleles normally ‘skip a generation’
A line passing directly between two shapes means that the two are partners, and a line overhanging a group of individuals means that they are siblings
Family pedigrees are used to show how a condition (or more specifically, the allele which causes it) are passed down through different generations
