5.biological inheritance

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BIOLOGICAL INHERITANC UNIT 5

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Transcript of 5.biological inheritance

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BIOLOGICAL INHERITANCE

UNIT 5

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Mendel (XIX century) demonstrated that hereditary characteristics are determined by independent factors which are transmitted from generation to generation.

GENETIC INHERITANCE

Chromosomes are the carriers of genetic information. Mendel independent factors are fragments of DNA that determine the characteristic of a specific trait.

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GENE: Unit of DNA that transmit genetic information

ALLELE: Each variant of a gene

GENOTYPE: Set of genes that an individual has

FENOTYPE: Observable traits that an individual has

BASIC CONCEPTS

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HOMOZIGOUS: both alleles are the same

HETEROZIGOUS: both alleles are different

Dominant allele prevent the alternative gene (recessive allele) from appearing

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When both alleles are equally strong are called co-dominant and cause intermediate inheritance

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MENDEL’S LAWS

Mendel discovered the basic principles of heredity by breeding garden peas in carefully planned experiments

Mendel chose a plant whose varieties displayed “pure” traits, which had been selected long before and which remained constant from generation to generation, making them easy to identify.

He used a self-pollinating plant. The petals enclose the stamens and the pistil completely, which means that the plant crosses with itself, so accidental crossing with different plants is avoided, and pure strains can be obtained.

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Traits studied by Mendel

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Principle of uniformity (1st law)

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Principle of segregation (2nd law)

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Principle of independent assortment (3rd law)

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Yellow seed F1 Green seedThe additional experiment which Mendel carried out, to prove that alleles come in pairs and separate at the moment when gametes form, consisted of crossing F1 (yellow seeds) with the pure paternal line of green seeds (recessive homozygote). Let’s take the yellow seed to be Aa.

In this case, 50% green seeds and 50% yellow seeds are obtained.If the yellow seed had been AA, all of the seeds would have been yellow (Aa).

Test cross

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SPECIAL CASES Multiple alleles

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SPECIAL CASES Gene interaction

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SPECIAL CASES Lethal genes

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SPECIAL CASES Quantitative inheritance

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LOCATION OF GENES

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INDEPENDENT GENES

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LINKED GENES

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TYPES OF CHROMOSOMES

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CHROMOSOMES MAPPING

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EXERCISE

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DETERMINING SEX

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A single gene determines sex

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ZZ/ZW

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SEX LINKED INHERITANCE

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GENE MUTATIONS

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CHROMOSOMES MUTATIONS

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NUMERICAL MUTATIONS