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Understanding Genetics: From Nucleotides to Inheritance

Learn about nucleotides, genes, inheritance, and the machinery behind transcription and translation. Explore the structure of DNA and RNA, genetic information, chromosomes, and genetic traits. Understand phenotypes and genotypes through Punnet squares.

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Understanding Genetics: From Nucleotides to Inheritance

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  1. Notes on Biology • What are nucleotides? • The concept of genes? • The concept of inheritance? • Machines: transcription/translation? • What are amino acids?

  2. Nucleotides • All have common structure. • Contain a phosphate, a sugar group, and an organic base: • RNA sugar is Ribose • DNA sugar is Deoxyribose • The sugar difference is key!

  3. The Bases • Most Common: • Adenine, Guanine, Cytosine, Thymine, and Uracil (A,G,C,T,U). • Uracil is found in RNA and replaces the Thymine found in DNA. • Linked Nucleotides are Nucleic Acids.

  4. Nucleic Acids • Two most popular nucleic acids are: • DNA: Deoxy Nucleic Acid • RNA : Ribo Nucleic Acid • DNA is a double helix • RNA is (generally) single stranded

  5. DNA • DNA is the carrier of “genetic information”. • Genetic information is termed the collection of genes. • Genes are inheritable “functional” genomic sequences.

  6. Genes Gene: • Located on chromosomes. • Composed of DNA. • classically defined as a unit of heredity. • seen as encoding a functional product, such as a protein.

  7. Chromosomes http://gslc.genetics.utah.edu/basic/concepts/chromosomes.html

  8. Reading a Gene • A gene is read from 5’ to 3’ • That is the functional information is encoded in one direction only. • The sequence of a gene is sub-classed into specific annotated regions.

  9. Examples A list by no means complete: • Promoters • Exons • Introns • Regulatory • 5’ UTR • 3’ UTR

  10. Diploids • 2 copies of each chromosome that are not identical. Why?

  11. Inheritance • Inheritance of Chromosomes from Parents! • You obtain 1 chromosome from each parent. • Sex chromosomes are different: From mother. You obtain and X from father: X or Y.

  12. Subsequently… • The genes on each chromosome are different. Versions. • Classically, these have been referred to as recessive or dominant. • Discovered from Phenotypic Analyses of offspring.

  13. Phenotypes • Homozygous Dominant: AA • Heterozygous: Aa • Homozygous Recessive: aa • Different genotypes can create the same phenotype. • These are autosomal.

  14. A Punnet Square A a AA Aa A a aA aa

  15. Calculate • p(AA) • p(Aa) • P(aa)

  16. What about Sex (linked)? • If a disease or a genetic trait is sex-linked. • Usually diseases are recessive and therefore if not silenced by a dominant allele they will be expressed • More often the disease is X linked and a carrier mother will cause a diseased son.

  17. A Punnet Square 2 X Y XX XY X X XX XY

  18. Decoding… • Best to read handout…

  19. http://www.ornl.gov/hgmis/graphics/slides/03b_lg.gif The central Dogma cartoon of transcription and translation

  20. “Every Problem is an Information Problem”

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