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B3 Revision:Genetic Diagrams and Inheritance (Key words: (Alleles: (A…
B3 Revision:Genetic Diagrams and Inheritance
Key words:
Genes:
A section of DNA which contains instructions needed to make a specific protein which controls the development of a characteristic
Alleles:
A different version of a gene
Letters are used to represent
Homozygous trait:
If a particular gene has two alleles that are the same
Heterozygous trait:
If a particular gene has two alleles that are different
Dominant:
An allele for a characteristic that is shown by an organism if the allele is present (Cc or CC)
Recessive:
An allele whose characteristic is only shown if there are two copies present
Genotype:
The combination of all the alleles you have
Phenotype:
The characteristics an organism has
Genetic diagrams:
Monohybrid inheritance:
Crossing two parents to look at a characteristic
Parents' characteristics
Parents' alleles
Gametes' alleles
Possible alleles of offspring
Possible characteristics of offspring
Punnet squares
Family Pedigrees
Shows how a characteristic or disorder is inherited in a group of related people
Gregor
Mendel
Austrian monk, studied maths, natural history at university of Vienna
His experiment:
1.Crossed a tall and a dwarf pea plant producing all tall pea plant
2.Bred two of these tall pea plants, producing 3 tall and 1 dwarf pea plant
Explanaition of results:
Height characteristic in pea plants were determined by separately inherited
hereditary units
passed on from each parent
Explained using genetic diagrams, T(hereditary unit for tall) and t(hereditary unit for dwarf)
T is dominant over t
Conclusion:
Characteristics in plants determined by hereditary units
Hereditary units passed to offspring unchanged from both parents (1 unit from each parent)
Hereditary units can be dominant or recessive
Dominant characteristic will be expressed if both dominant and recessive unit is shown
Importance:
Hereditary units are ow genes
Only realised significance of work after death as they didn't have background knowledge to understand his findings