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Gene Expression and Inheritance (DNA Structure (History (Frederick…
Gene Expression and Inheritance
DNA Structure
Base Pairing
Purines: Adenine and Guanine (double ring)
Pyrimidine: Thymine and Cytosine (single ring)
Consistent with Chargaff's rule
Held together by two hydrogen bonds
History
Frederick Griffith: There is a transforming material that can cause changes in genotypes and phenotypes
Avery, McCarty, Macleod: DNA is transforming material
Archibald Gerrod: People with inherited inborn errors in metabolism lacked specific proteins/enzymes
Hersey and Chase: confirmed that DNA is genetic material
Fredrich Miescher: ID Chemical composition of cell nucleus: acidic, nitrogen, phosphorus
What we know
Base bare of AGTC Arrangement of DNA polymer
DNA is a polymer of nucleotides consisting of nitrogenous base, deoxyribose, and a phosphate group
Unknown: The three dimensional structure
of DNA
Nucleus
Within nucleus: DNA within chromosomes
Chromosomes and Chromatin located inside the nucleus
Membrane bound, studded with pore complex allowing larger molecules to transport out of the nucleus, synthesis of ribosomes
Genes Code for Proteins
RNA Polymerase
Three RNA polymerases (I, II, III in nuclei)
RNA polymerase II is used for mRNA synthesis in eukaryotic
one RNA Polymerase
Discovery
The study of metabolic defects
Beadke and Tatum discovered link between genes and enzymes
and One gene-one enzyme hypothesis
Archibald Garrod attributed biochemical roles to genes
Triplet code
3 bases = codon = 1 amino acids
Read 5' 3 ' direction, there are redundancy but NO ambiguity (several different codons code for secific amino acid, but any one codon indicates only one amino acid), no overlapping, reading frame encodes proteins, and there are start and stop codons
no. of nucleotides per mRNA = 3x no. amino acids
Trait Expression
DNA replicates itself
DNA is transcript RNA and then translated to proteins
DNA code for proteins, proteins give us phenotypes
Transcription and Translation
RNA
Single strand, base of uracikl instead of thymine, sugar is ribose, no specific 3-D shape
Types
Transfer (tRNA)
Ribosomal (rRNA)
Messenger (mRNA)
RNA polymerase an enzyme that synthesizes RNA from a DNA template.
Translation
In Eukaryotes, translation is occured at the ribosomes
Series of nucleotides are used to translate to proteins.
In Prokaryotes: Transcription and translation occur simultaneously
Transcription
Stage 2 Transcription: Elongation (only in Eukaryotic cells) Prior, modified guanine nucleotide to the 5' end (5' cap) and a adenine nuceotide add to the 3' end (Poly A tail). Adds stability
Stage 3 Transcription: Termination RNA splicing is also occurring in which introns are cut out, exon are spliced together are kept in for the mature mRNA (this is because not all are coding sequences)
Stage 1 Transcription: Initiation binding of RNA polymerase to a location near the start of a reading frame.