Lecture 2 Molecular Biology Evolution Review

What is Genetic Material

DNA, which was first isolated by Friedrich Miescher in 1869

Structure solved in 1950s by Watson & Crick

DNA is a polymer of a series of nucleotides. Each nucleotide differs by the nitrogenous base it contains (A,C,G,T)

What are genomes

All of the organism’s DNA-based genetic instructions

Composed of genes

What are genes

DNA instructions for making proteins

promoter at beginning of gene, followed by open reading frame which contains series of codons which encode amino acids, then end by a stop codon

What is central dogma

DNA (gene) → (transcription) → RNA (RNA polymerase) → (translation) → protein (Ribosomes)

What are the three main different types of RNA

mRNA - messenger RNA

tRNA - transfer RNA

rRNA - ribosomal RNA

What is RNA

Primary structure of RNA is similar to DNA

RNA, like DNA, can be single or double stranded, linear or circular

Unlike DNA, RNA can exhibit different confirmations, which permit the RNAs to carry out specific functions in the cell

Contains uracil (U) instead of thymine (T)

What is gene expression and how does it take place

the process of using DNA information to make mRNA and proteins

RNA polymerases look for promoter sequences to recognize beginning of genes

Prokaryotes use positive and negative regulation for transcription

Eukaryotes are complex, they have promoter sequences and enhancers which can lead to complex expression

What are open reading frames

Long stretches of DNA uninterrupted by stop codons tend to be protein coding

Genes are ORFs and additional regulatory information

Translation of RNA to protein starts at Met, or start codon (AUG)

Continues until a stop codon is reached (UAG, UAA, UGA)

Prokaryote vs Eukaryote genes

Prokaryote genes :

transcription initiation, coding region, and termination signal

Eukaryotes :

transcription initiation, coding region (exons) / introns (not coded), and termination signal

Genome structure

Can be circular, or linear

Eukaryote chromosomes are linear

Prokaryote chromosomes are circular (also plasmids, virus’s, organelles, etc)

Four levels of protein structure

primary (linear amino acid sequence),

secondary (beta sheets and alpha helices, form first when linear sequence is forming),

tertiary (global 3D conformation, and called the native state, final and stable), and

quaternary (can be subunit of larger complex, tertiary forming complex with other units)

What is sequencing

Determining the exact nucleotide sequence of DNA

Makes it possible to determine the exact sequence of a gene or the entire genome of an organism

Many methods :

Maxam-Gilbert Method - chemical degradation

Dideoxy (Sanger) Method - chain termination

Next-generation (high-throughput) - many types

What is Dideoxy (Sanger) Sequencing

Uses DNA sequence as a template, adds a primer and then adds dideoxynucleotides, which are chain terminating. This means that the DNA polyermase is unable to further extend the molecule once the dideoxynucleotides are added to the growing sequence.

You end up with a pool of DNA fragments of different length.

Limited in number of base pairs that can be sequenced in a amount of time

What is Next-gen sequencing

non-Sanger high-throughput DNA sequencing technologies

Many different DNA fragments can be sequenced at the same time, so cost of DNA sequencing has gone down dramatically

Illumina is most common

What is evolution

Changes in inherited characteristics of biological populations over successive generations

Generates diversity of genotype and phenotype

What is point mutation

When one nucleotide mutates into another letter

What is a gene duplication

When an entire gene gets duplicated into another copy in a genome. One of the new copies may diverge into another copy

What is insertion mutation

When nucleotides are added to a gene which they were not previously there

What is deletion mutation

When nucleotides are deleted in a gene which were previously there

What is genetic variation

Mutation drive differences between species

Raw material for evolution to act on

Raw data that we analyze in bioinformatics and much of comp. bio

Where are all these sequences stored

A major source is GenBank / NCBI