Notes on Biology

1
Notes on Biology

• What are nucleotides?
• The concept of genes?
• The concept of inheritance?
• Machines transcription/translation?
• What are amino acids?

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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.

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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.

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Chromosomes
http//gslc.genetics.utah.edu/basic/concepts/chrom
osomes.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.

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Examples

• A list by no means complete
• Promoters
• Exons
• Introns
• Regulatory
• 5 UTR
• 3 UTR

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Diploids

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

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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.

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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.

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Phenotypes

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

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A Punnet Square
A
a
AA
Aa
A
a
aA
aa
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Calculate

• p(AA)
• p(Aa)
• P(aa)

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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.

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A Punnet Square 2
X
Y
XX
XY
X
X
XX
XY
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Decoding

• Best to read handout

19
http//www.ornl.gov/hgmis/graphics/slides/03b_lg.g
if The central Dogma cartoon of transcription and
translation
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Every Problem is an Information Problem