Ch. 10 Flashcards
What distinguishes the 20 types of amino acids in proteins?
R group (side chain)
Polypeptides
one or more long chains of amino acids
Conformation
protein’s 3D shape
Transcription
synthesizes RNA molecule
Translation
uses the info in RNA to make protein by aligning and joining specified amino acids
Central Dogma
(nucleus)replication- DNA - transcription- RNA - (cytoplasm) translation - protein
RNA polymerase
builds an RNA molecule (during transcription)
Messenger RNA (mRNA)
least abundant; carries info for a particular protein
codon
3 mRNA bases in a row = specified amino acid
Ribosomal RNA (rRNA)
most abundant; associates with certain proteins to form ribosomes, forms part of the enzyme that drives translation
Ribozymes: catalyst align ribosome and mRNA
Transfer RNA (tRNA)
transports specific amino acids to the ribosome for protein synthesis (translation); links amino acid to anticodon
clover or L shaped
Steps of Transcription
- Initiation
- Elongation
- Termination
Transcription Initiation
transcription factors and RNA polymerase attracted to a promoter, then RNA polymerase binds start of sequence
Transcription Elongation
enzymes unwind DNA double helix 5’-3’
free RNA nucleotides bond w/ exposed complementary bases and RNA polymerase adds RNA nucleotides
Transcription Termination
terminator sequence in dna indicates end
TBP
general transcription factor that is essential for all transcription of all genes
mRNA Processing (maturation of message)
DNA template strand (3’-5’) - transcription - pre- mRNA - modification - 5’ mRNA cap & 3’ poly A tail - splicing - mature mRNA cap - transport out of nucleus into cytoplasm for translation
mRNA translation
assembles a protein from mRNA sequence, uses codon (group of 3 bases) to turn into amino acid sequence (polypeptide)
Codon
three successive mRNA bases
64 codons
Reading frame
altering DNA sequence by 1 or 2 bases produces a different amino acid sequence due to disruption, causes frame-shift mutation
Translation
needs mRNA, tRNA’s w/ amino acids, ribosomes, energy molecules (ATP, GTP) and protein factors
the closer the end of the gene, the longer the polypeptide
Translation Steps
- Initiation
- Elongation
- Termination
Protein Primary Structure
sequence of amino acids in a polypeptide chain
Protein Secondary Structure
loops, coils, sheets, or other shapes form by h-bonds between neighboring carboxyl and amino groups
Protein Tertiary Structure
3D forms shaped by bonds between R groups, interaction btwn R groups and water
Protein Quaternary Structure
protein complexes formed by bonds btwn separate polypeptides
Protein Folding
fold after the amino acid chain winds away from the ribosome; helped by chaperone proteins or if damaged go to proteasome
This substance contains the genetic information for the production of a protein from a structural gene
mRNA
This is the process of producing an RNA copy of a gene
Transcription
This is the process of synthesizing a specific sequence of amino acids on a ribosome.
Translation
This substance in the nucleus of cell constitutes the cell’s genome
DNA
This is a sequence of amino acids that correspond to the genetic information in a structural gene.
Polypeptide
DNA
contains thymine, double stranded, contains deoxyribose
RNA
contains ribose, single stranded, contains uracil
You are studying the levels of proteins in different tissue types in samples from mice. The levels of some proteins are rather uniform among tissue types. In contrast, you are surprised to find that a protein called class III β-tubulin is present only in brain tissue from the mouse and is undetectable in other tissues.
What is the most likely explanation for this finding?`
The difference is most likely due to the action of transcription factors; All cells in an organism have the same genes. The difference in gene expression between different cells is largely due to the action of transcription factors. Transcription factors respond to signals from outside the cell that control what genes are expressed in what cells and when.
Transcription factors function in the expression of genes by
turning transcription of specific genes on or off.
