Mendels crosses Gregor Mendel (1822-1884) data analysis => - - PDF document

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Introduction to Human Genetics Module 1 Mendelian genetics

Dr Ewa Piotrowska Department of Molecular Biology

Mendel’s crosses

Gregor Mendel (1822-1884)

Mendel’s scientific approach to the study of heredity

• well characterized materials
• accurate quantitive records
• data analysis => model

Gregor Mendel (1822-1884)

Mendel’s scientific approach to the study of heredity

• well characterized materials
• accurate quantitive records
• data analysis => model

Gregor Mendel (1822-1884)

P:



F1:



F2: 5,474 1,850

2.96:1

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Mendel’s conclusions

• UNIT FACTORS IN PAIRS
• DOMINANCE / RECESSIVENESS
• SEGREGATION

Gene The fundamental unit of heredity and the basic structural and functional unit of genetics. Allele One of the possible alternative forms

• f a gene, usually distinguished from
• ther alleles by its phenotypic effect.

Phenotype The observable properties

• f an organism.

Genotype The specific genetic constitution of an organism.

Definitions

Dominant trait The trait expressed in the F1 (or heterozygous) condition. Recessive trait The trait unexpressed in the F1 but expresses in some members

• f the F2 generation

P:



F1:



RR rr Rr Rr Homozygous Having identical alleles for

• ne or more genes.

Heterozygous Carrying two different alleles for one or more genes. Segregation The separation of members of a gene pair from each other during gamete formation.

P:



F1:



RR rr Rr Rr

F2:

R r R r RR Rr Rr rr

Punnett square

Studying the inheritance of two characters simultaneously

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Variations on a Theme by Mendel

• incomplete dominance
• codominance
• multiple alleles
• epistasis