Gre Bio Chp 8 Replication And Protein Synthesis

Front 1

Purine Bases

Back 1

Adenine and Guanine. Two fused rings made of nitrogen and carbon. Must always pair with a pyrimidine for uniform helix width

Front 2

Pyrimidine Bases

Back 2

Cytosine and Thymine. Single ring of nitrogen and carbon. Must always pair with a purine for uniform helix width

Front 3

DNA Molecule

Back 3

A double-stranded helix with a sugar phosphate backbone and nitrogenous bases as "rungs of a ladder"

Front 4

5'

Back 4

Sugar carbon number 5, where a nucleotide's own phosphate group attaches. DNA Polymerase build from 5' to 3'

Front 5

3'

Back 5

Sugar carbon number 3, where the phosphate group attaches to the next nucleotide. DNA polymerase builds from 5' to 3'

Front 6

Origin of Replication

Back 6

The site within a bacterial chromosome or plasmid where replication begins. Generally found in a AT-rich region. Many origins of replication open at once in eukaryotes.

Front 7

Replication Forks

Back 7

V-shaped forks formed by separating DNA during replication. They move bidirectionally from the replication origin.

Front 8

DNA Polymerase

Back 8

The enzyme responsible for attaching together new nucleotides as the arrive at the original (parental) strands. Rate of 500 nucleotides/second in bacteria, 50 nucleotides/second in eukaryotes.

Front 9

dNTP

Back 9

Deoxynucleotide triphosphate. Form each nucleotide arrives at the growing strand in. Since only one phosphate is used in binding, two phosphates are lost, known as leaving groups. The reaction is therefore exergonic

Front 10

Leading Strand

Back 10

The strand being copied in the direction of the advancing replication fork

Front 11

Lagging Strand

Back 11

The strand being copied in the direction away from the replication fork's movement. Synthesized discontinuously.

Front 12

Okasaki Fragments

Back 12

Small fragments of DNA the lagging strand is built from due to discontinuous synthesis

Front 13

Primer

Back 13

Required to put the first nucleotides in place nest to the parental DNA template. Actually made of RNA and later replaced by DNA

Front 14

Primase

Back 14

The enzyme responsible for building the primer

Front 15

Helicase

Back 15

Enzyme that unwinds DNA. Unzips the DNA double helix which is stabilized by single strand DNA binding proteins until complimentary DNA falls into place

Front 16

Topoisomerases

Back 16

Enzymes that regulate the supercoiling of DNA into chromosomes. Aid in unwinding for transcription and replication. May have a role in crossing over and recombination. Topoisomerase I causes single strand breaks affecting coiling. Topoisomerase II causes double strand breaks.

Front 17

DNA Ligase

Back 17

Enzyme responsible for ligating (connecting) Okasaki fragments left over

Front 18

Exonulease

Back 18

DNA polymerase working to correct mismatches. Works from 3' to 5'

Front 19

Endonucleases

Back 19

Repair enzymes that cleave out and replace damaged DNA from the middle strands such as thymine dimers

Front 20

Thymine Dimers

Back 20

Adjacent nucleotides that become bonded covalently due to UV energy. Prevent DNA polymerase from copying DNA beyond the dimer.

Front 21

Transcription

Back 21

RNA polymerase transcribes DNA into RNA. Works at a rate of 50-100 bases/second. Has no proofreading function

Front 22

Translation

Back 22

Process by which mRNA codons are translated into a sequence of amino acids at the ribosomes

Front 23

Nuclear Localization Signal (NLS)

Back 23

A sequence on amino acids in proteins destined for the nucleus that allow them pass through the nuclear membrane

Front 24

Signal Sequences

Back 24

Amino acid sequences in proteins that tell the ribosomes to remain bound to the ER membrane until synthesis is over. Cut off within the ER membrane

Front 25

Steps of protein translation

Back 25

Initiation, elongation, and termination

Front 26

tRNA

Back 26

Used at the ribosomes to carry the correct amino acid into place for protein binding. Not a long strand, but T-shaped

Front 27

Aminoacyl-tRNA synthetase

Back 27

Enzyme that loads tRNAs with amino acids, creating aminoacyl-tRNA

Front 28

Initiation

Back 28

mRNA binds to the smaller of two ribosomal subunits, an initiator tRNA carrying the AA methionine binds to the initiator (start) codon AUG. The large ribosomal subunit then binds to the small one, creating a complete ribosome with the methionine-tRNA complex sitting in the P(peptidyl-tRNA)-. mRNA strand is locked into place between the subunits.

Front 29

Elongation

Back 29

Hydrogen bonds form between the mRNA codon in the A (aminoacyl-tRNA) site and its anticodon on the aminoacyl-tRNA. Peptidyl tranferase catalyzes a peptide bond between the AA on the tRNA on the A site and the methionine attached to the tRNA on the P site. A ribsome then carries the uncharged tRNA from the A site to the P site and peptidyl tRNA to the A site. Translocation, where the ribosome advances 3 nucleotides along mRNA and the uncharged tRNA is expelled from the P site and the peptidyl-tRNA moves to the P site leaving the A site open for the next aminoacyl-tRNA ends the cycle.

Front 30

Termination

Back 30

Occurs when one of three mRNA termination codons arrives on the A site. These do not code for an AA, instead a protein called a release factor binds to the termination codon, causing a water molecule to be added to the chain. This causes the polypeptide chain to be released from the tRNA and the ribosome. The ribsome dissociates into two subunits once again

Front 31

Polyribosome

Back 31

The structure of an mRNA being read by many ribosomes at the same time

Front 32

Signal Peptides

Back 32

Sorting signals at the end of a protein chain

Front 33

Signal Patches

Back 33

Sorting signals made from various amino acids that bunch together in the middle of the protein's 3D conformation

Front 34

ER Retention Signal

Back 34

Group of four amino acids added at the carboxyl terminal that restrict a protein to the ER lumen

Front 35

Chaperones

Back 35

Proteins that aid in the folding of new ER proteins

Front 36

Glycosylation

Back 36

Process of adding sugars to proteins. Signals protein is destined for export out of cell or for a membrane within and around the cell

Front 37

N-linked Oligosaccharide

Back 37

The most common sugar group added to a protein in the ER to make a glycoprotein. Added to the NH2 group of an asparagine amino acid

Front 38

GPI anchor

Back 38

Switched with some AA on the carboxyl terminus of a protein in the ER lumen. Allows proteins eventually to be anchored into the exterior of the cell membrane

Front 39

O-linked glycosylation

Back 39

Process in which new sugars are added to the -OH groups of certain serine and threonine side chains in the golgi

Front 40

Clathrin

Back 40

A protein that coats the golgi vesicles containing lysosomal proteins

Front 41

Mutagens

Back 41

External cancer-causing agents

Front 42

Point Mutation

Back 42

When a single nucleotide base is substituted for another

Front 43

Frameshift Mutation

Back 43

A change in the reading frame of an mRNA. Occurs if a base is inserted or deleted

Front 44

Nonsense Mutation

Back 44

Produces a premature termination of the polypeptide chain by changing one of the codons to a stop codon.