Unit 8: DNA Structure & Replication

Helicase

Enzyme that splits the double helix by breaking hydrogen bonds

RNA Primase

Enzyme that makes an RNA primer, serving as the starting point for DNA replication

DNA Polymerase III

Enzyme responsible for building the complementary DNA strand during replication

DNA Ligase

Enzyme that connects the gaps in the DNA strands by linking them together

Nucleotide

Basic unit of DNA, consisting of a phosphate group, a sugar, and a nitrogenous base

Purines

Nitrogenous bases (Guanine and Adenine) with two nitrogenous rings in their structure

Pyrimidines

Nitrogenous bases (Cytosine, Thymine, and Uracil) with one nitrogenous ring in their structure

X-ray Crystallography

Technique used by Rosalind Franklin and Maurice Wilkins to capture images of DNA's structure in the 1950s

Watson and Crick's Model

Proposed the double helix structure of DNA in 1953, incorporating data from X-ray crystallography

Hershey-Chase Experiment

Demonstrated that DNA, not protein, carries genetic information by labeling bacteriophages and observing their replication

SSBs

Single strand binding proteins, holds strands apart during DNA replication

Exonuclease

Removies RNA primers

DNA Ligase

Connects gaps after RNA primer is removed and DNA is put in

Bonded with 3 H-bonds

G/C

Bonded with 2 H-Bonds

C/T/U

DNA Sugar

Deoxyribose sugar

Parts of a nucleotide

Phosphate group, a sugar, and nitrogenous base

Ribosomal (rRNA) RNA

Structural component of ribosomes

Messenger (mRNA) RNA

used in transcription of polypeptides

Transfer (tRNA) RNA

deals with the actual building of polypeptides

Trait

Characteristic that is inherited

DNA

Deoxyribonucleic acid

Heritable

ability of trait to be passed from one generation to the next

Central Dogma

DNA codes RNA which codes for building proteins

Gene

section of DNA that codes a protein

Proteins

Carries out instruction of the cell

Transcription

process of copying a sequencce of DNA into messenge

Translation

mRNA is converted into a polypeptide (a part of a protein)

Polypeptides

Long chains of nucleic acids, pre-cursors to proteins

Nucleus

Where transcription happens

Ribosomes

Where translation happens

Chromosome

One DNA molecule (packaged form)

Genome

Sum of all genetic info in an orgganism

Mutation

change in DNA sequence

Initiation (Transcription)

First stage of transcription, the transcription factors assemble, and RNA polymerase is attached to template strand

Elongation (Transcription)

Second stage of transcription, RNA polymerase travels 3’ —> 5’ on template strand, builds complimentary mRNA strand 5’ —> 3’

Termination (Transcription)

Final stage of transcription, RNA polymerase is released from template strand and stops building mRNA strand

Initiation (Translation)

First stage of translation, mRNA enters the assembled ribosomes

Elongation (Translation)

Second stage of translation.

A site: Aminocyl, tRNA brings new amino acid & anticodon bonds to the codon

P site: peptidyl, new amino acid is joined to polypeptide by dehydration synthesis

E site: tRNA releases amino acid, polypeptide exits the ribosome

Termination (translation)

Final stage of translation, polypeptides leaves ribosome after stop codon. No amino acid is added, polypeptide is added to other completed polypeptide.

Stop Codons

UGA, UAG, UAA

Mutation

Change in genetic code

Missense Mutation

codes for a different amino acid

Nonsense Mutation

Makes a stop codon, ends polypeptide in middle of the chain

Frameshift Mutation

Changes many amino acids

Silent Mutation

Doesn’t change any amino acids