Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple...

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BEYOND MENDELIAN EXTENSIONS The inheritance pattern of many traits cannot be explained by simple Mendelian genetics.

Transcript of Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple...

Page 1: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

BEYOND MENDELIAN EXTENSIONSThe inheritance pattern of many traits cannot be explained by simple Mendelian genetics.

Page 2: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Mendelian Ratios are SimpleThe work done by Gregor Mendel investigated simple, dominant/recessive relationships.

The inheritance of many traits is more complex.

In all cases, the complexity alters the ratios of offspring.

Presenter
Presentation Notes
Many traits are not inherited in simple Mendelian ratios. These traits can involve a lot of different aspects of genetics and physiology, but will always affect the ratios of offspring that are shown.
Page 3: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Incomplete DominanceXWhen the heterozygous condition

expresses a third phenotype, different from either homozygous condition.

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Presentation Notes
Incomplete Dominance/Codominance: The heterozygote has a different phenotype than either homozygote (ex. Snapdragon color, human blood type)
Page 4: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Codominance and Multiple AllelesWhen the heterozygous condition expresses both of the homozygous conditions simultaneously.

Multiple Alleles:When there are more than two alleles for a gene.

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Presentation Notes
Multiple alleles: Traits have more than two alleles (ex. Human ABO blood types)
Page 5: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Non-Mendelian InheritanceMany traits are not inherited according to Mendelian principles.

Mendelian ratios only refer to situations where each gene is inherited independently of each other.

Presenter
Presentation Notes
Certain modes of inheritance are non-mendelian. Many traits are linked to certain chromosomes. Mendelian ratios only refer to situations where each gene is inherited independently of each other. The inheritance of these traits depends on the inheritance of these chromosomes.
Page 6: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Sex LinkageRefers to the inheritance of traits on sex chromosomes. First investigated by the lab of T.H. Morgan in Drosophila

Presenter
Presentation Notes
Much of this work was done by TH Morgan’s lab at Columbia in the early 1900’s.
Page 7: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Sex Linked traits show up in males more frequently due to the presence of one X chromosome

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Presentation Notes
Sex linkage: Traits are on the X chromosome. Males will show the recessive characteristic much more often than females. (Ex. white eyes, color blindness)
Page 8: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

The X chromosome in humans has many genes. The Y chromosome has very few

Page 9: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Sex Limited TraitsTraits that are only expressed in one gender.

Unit 4: Pod 4 Mendelian Genetics

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Presentation Notes
Sex-limited traits: Traits that are only expressed in one sex. (ex. milk production, pattern baldness)
Page 10: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Linked GenesRefers to any genes that are on the same chromosome.

Linked genes will usually be inherited together.

Presenter
Presentation Notes
Linked genes: Genes that are on the same chromosome will be inherited together, except when crossing over results in recombination. Can be identified by their divergence from Mendelian expected ratios of offspring.
Page 11: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Linkage AnalysisCrossing over can separate linked genes. The more distance between two genes on a chromosome, the more frequently crossing over will occur.

Presenter
Presentation Notes
Linkage analysis: Can be used to investigate the distance between linked genes on the same chromosome. The greater the distance between two genes on a chromosome, the more often crossing over will occur between them (the greater the frequency of recombinants).
Page 12: Beyond Mendelian Extensions...The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Mendelian Ratios are Simple. The work done by Gregor Mendel investigated

Non-Nuclear InheritanceChloroplast and Mitochondrial Genomes are inherited entirely from the egg cell.

Presenter
Presentation Notes
Some genes are not inherited through the nuclear genome of a cell. Non-nuclear inheritance refers to the inheritance of genes in the chloroplast and mitochondrial genomes. The chloroplasts and mitochondria of cells are randomly assorted when daughter cells and gametes are being produced, so the traits they carry are not inherited via Mendelian mechanisms. Ex. All mammals inherit their mitochondria from their mother’s egg cell (“matrilineal inheritance”). This can be used to track human ancestry and historical migration.