Unit 3 - Molecular Biology

Proteins

Originally assumed to be the source of hereditary information

Nucleus

Where hereditary information is found

Frederick Griffith

Scientist that concluded that an unknown hereditary material can transfer dead bacteria traits to a living bacteria

1928

Year that Frederick Griffith came to his conclusion

Alfred Hershey and Martha Chase

Scientists who determined that DNA was the hereditary material of the cells using bacteriophages

1952

Year that Hershey/Chase came to their conclusion

Radiolabelling

The exposure of a material to a more radioactive isotope of an element needed to construct something, so that the material can be tracked through a system or organism

Sulfur

Element in proteins radiolabelled by Hershey/Chase

Phosphorus

Element in DNA radiolabelled by Hershey/Chase

1920s - 1950s

Years in which the nitrogenous bases were discovered

Chargaff

Scientist who determined that each of the nitrogenous bases occur in specific ratios

1950

Year Chargaff came to his conclusion

Rosalind Franklin

Scientist determined the helical structure of DNA using x-ray crystallagraphy

1952

Year that Rosalind Franklin made her discovery

Watson and Crick

Scientists that determine the structure of DNA using Franklin's data

1953

Year of Watson and Crick's discovery

Double Helix

Shape of DNA

2 nm

Diameter of DNA

3.4 nm

The length at which DNA makes a complete turn

H-bonds

Force between two nitrogenous bases that holds two strands of DNA together

Antiparallel

Direction that DNA strands run

3' and 5'

Carbons that are used to determine the direction of the DNA strand

5'

Carbon that the phosphate group attaches to

1'

Carbon that the nitrogenous base attaches to

Complementary Base Pairing

The phenomenon in which certain nitrogenous bases will only bind to certain nitrogenous bases (A-T and C-G)

Nucleotide

Monomer of a strand of DNA

Deoxyribose

Sugar in DNA

Ribose

Sugar in RNA

Purines

Adenine, and Guanine. Two ringed

Pyrimidines

Thymine, Cytosine and Uracil. One ringed

Uracil

Replaces thymine in RNA

Nucleoside

Nitrogenous base and sugar. The nitrogenous base is used to name it

Phosphate Group

The acid of the nucleotide

Interphase

The stage of the cell cycle in which DNA replication occurs

Semiconservative

The way DNA is replicated, each double strand is composed of one new strand and one parent (conserved) strand of DNA

Conservative

Model of DNA replication in which the parental DNA strand is completely conserved as new strands are made. Was proven false.

Meselson and Stahl

Scientists who confirmed that DNA replicates using a semiconservative model

Nitrogen

Element in DNA that Meselson and Stahl radiolabelled

DNA Seperation

Step 1 in the process of DNA replication

Replication of DNA Strands

Step 2 in the process of DNA replication

Proofreading and Repair

Step 3 in the process of DNA replication

Replication Origin

Location on the DNA strand where the unravelling of DNA begins

Helicase

Enzyme that unravels DNA

Replication Fork

The point at which the two DNA strands are being seperated

Topoisomerase

Enzyme that prevents DNA from twisting as it gets unravelled

Reannealing

The process of H-bonds reforming right after being split apart due to the close proximity of two nitrogenous bases

Single Stranded Binding Proteins

Proteins that prevent H-bonds from reforming between nitrogenous bases after being broken

Replication Bubble

The formation of a bubble due to the splitting of DNA happening in both directions

DNA Polymerase III

Enzyme that uses nucleotides from the environment to replicate the parent strand of DNA

3' End

The location DNA polymerase III can add nucleotides

Deoxyribonucleoside Triphosphate

The way DNA is attached in order to have enough bonding energy to build the strand (nucleic acids with 3 phosphate groups)

RNA Primase

Enzyme that lays down a short complementary strand of RNA so the DNA Polymerase III can work

RNA Primer

Short, complementary strand of RNA laid down by RNA Primase

Leading Strand

The strand of DNA that goes from 3' to 5' on the parent strand and can be replicated smoothly without interruption

Lagging Strand

The strand of DNA that goes from 5' to 3' on the parent strand that needs to be replicated in sections

Okazaki Fragments

The sections of replicated DNA created along the lagging strand

DNA Polymerase I

Enzyme that removes the RNA primer

DNA Ligase

Enzyme that attaches the Okazaki Fragments together once the primer has been removed

DNA Polymerase II

Replaces incorrect nucleotides during proofreading

Telomeres

The extra, non-coding section of DNA that can be lost to DNA replication without harm to the cell

Beadle and Tatum

Scientists that showed that one gene was responsible for making one protein (later revised to one gene, one polypeptide)

Central Dogma

The process by which genetic instructions in DNA are converted into a functional product

Transcription

The copying of DNA into mRNA

mRNA

An RNA copy of DNA (transcript portion of DNA) that travels to the cytosol to be translated

tRNA

Used to 'read' mRNA and provides the correct a.a. to produce a polypeptide

rRNA

Along with certain proteins, it makes ribosomes which coordinate translation

Codons

Set of 3 nucleotides that codes for an amino acid

AUG

Start codon that codes for amino acid methionine

RNA Polymerase

Enzyme used to copy DNA into a strand of RNA

Initiation (Transcription)

Stage 1 of transcription where RNA Polymerase binds to a promoter

Promoters

Region of DNA that signals the start of a gene, usually full of A and T

Elongation (Transcription)

Stage 2 of transcription where RNA Primase copies the parent strand and elongation occurs on the 3' end of the growing strand

Template

The DNA being copied

Termination (Transcription)

Stage 3 of transcription where the terminator sequence signals the end of a gene and thus the end of RNA synthesis

Precursor mRNA

mRNA before modifications

Primary Transcript

Another name for Precursor mRNA

5' Cap

7 Gunanines that are added to the 5' end

Poly A Tail

Hundreds of Adenines that are added to the 3' end of the pre-mRNAI

Introns

Non-protein coding portions of a gene

Exons

Protein-coding portions of a gene

Spliceosomes

Protein that catalyses the removal of introns in pre-mRNA

snRNPs

Small nuclear ribonucleoproteins in spliceosomes that bind to pre-mRNA and remove the introns

Splicing

The action of removing introns

Transcript

Pre-mRNA that has been modified and can be translated into a polypeptide

Anticodon

Site on tRNA that attaches to the codon of the transcript

Aminoacyl-tRNA

tRNA - a.a complex

Aminoacyl tRNA Synthetase

Enzyme that attaches the a.a. to tRNA

Initiation (Translation)

Stage 1 of translation where the small ribosomal subunit binds to met-tRNA and moves along the mRNA until it reaches the start codon, where a large ribosomal subunit will also bind

Start Codon

Codon that signals the start of a gene, usually AUG

A Site

First binding site for aminoacyl tRNA to bind to

P Site

Second binding site where the amino acid forms a peptide bond with the amino acid on the aminoacyl tRNA in the A Site and is removed from the tRNA

E Site

The binding site where the tRNA goes after it has lost its amino acid. It will be sent back out into the cytosol

Elongation (Translation)

Stage 2 of translation, where amino acids form peptide bonds and the a.a. in the P site detaches from tRNA. This grows a polypeptide

Termination (Translation)

Stage 3 in translation where the polypeptide continues to grow until it reaches a stop codon and the ribosome falls apart

Protein Release Factor

Binds to the A-site at a stop codon to signal the end of a polypeptide chain

Prokaryotic Genes

Circular and found in the cytoplasm of the cell with one replication origin. Transcription and translation happen faster because no post-transcriptional modifications are needed

Eukaryotic Genes

Linear and found in the nucleus of the cell with multiple origins of replication. Transcription and translation takes longer because there is more material and post-transcriptional modifications need to be made

Polysomes

When multiple ribosomes are attached to and transcribing the same mRNA strand

Gene Regulation

The control of gene expression depending on the cell's needs

Housekeeping Genes

Genes that are always "on" because they are necessary for the survival of the cell