Gene Expression & Protein Synthesis Flashcards
1
Q
What creates differentiation between cells of the same type?
A
- all cells possess the same info, but different cells express different information
2
Q
genes
A
- units of inheritance of traits
- define organism, the properties of each cell, and how cells will respond to dif environments/extracellular factors
3
Q
Where is genetic information stored? How is it copied?
A
- contained in biochemical structure –> DNA
- serves as it’s own template for reproduction –> replication
4
Q
gene expression
A
- series of biochemical events by which information in DNA made operational
- involves turning on expression of some genes and turning off expression of other genes
- only small fraction of total info in DNA expressed in any cell at any time
5
Q
flow of genetic information
A
DNA –> RNA –> protein
6
Q
transcription
A
- synthesis of RNA molecule from region of DNA that contains information (gene)
- polymerases copy info from DNA 3’ to 5’ to create RNA 5’ to 3’
7
Q
rRNA
A
- ribosomal RNA
- structural components of ribosomes
8
Q
tRNA
A
- transfer RNA
- adaptor molecules in protein synthesis
9
Q
snRNA and scRNA
A
- small nuclear RNA and small conditional RNA
- other structural or catalytic units of specialized cellular components
10
Q
siRNA
A
- small interfering RNA
- plays a role in regulating gene expression
11
Q
types of RNA which are the final products of transcription
A
- rRNA
- tRNA
- snRNA
- scRNA
- siRNA
12
Q
mRNA
A
- messenger RNA
- serves in information transfer for synthesis of proteins
13
Q
translation
A
- process of taking info from RNA transcript to a protein
- read mRNA codon pattern
- ribosomes catalyze polymerization of amino acids into protein –> polypeptide formation
14
Q
proteins
A
- serve as structural units or catalytic units of cell
- differences in expression of specific proteins distinguish one cell from another
- free in cytosol and synthesized on free polysomes (aka ribosomes)
15
Q
What happens to RNA transcript before it can be used in any way?
A
- must be modified before it can serve its function as a structural component or as a messenger for protein synthesis
16
Q
How is information flow regulated within a cell?/What steps are involved in regulating gene expression?
A
- regulating transcription of specific genes into RNA
- post-transcriptional modification and degradation
- regulating translation of RNA into protein
- post-translational modification and degradation
17
Q
RNA Pol I
A
- used to transcribe ribosomal RNA (in nucleolus)
18
Q
RNA Pol III
A
- used to transcribe tRNA
19
Q
RNA Pol II
A
- responsible for transcription of mRNA and several of the small structural RNAs (sn and scRNAs)
20
Q
Where does RNA processing/maturation take place?
A
- all RNA processing/maturation steps occur in nucleus
21
Q
Where does RNA degradation take place?
A
- can occur outside nucleus except in some special cases
22
Q
What do RNA processing events depend on?
A
- processing events are an ordered series of biochemical events that depend on specific nucleotide sequences and interactions with specific protein-protein and protein-RNA complexes
23
Q
5’ cap
A
- addition of GTP to 5’ end and methylation of G while transcription is in progress
- occurs simultaneously with transcription
- uses enzymes associated with Pol II transcription initiation complex
- increases efficiency of mRNA in translation and protects it from degradation in nucleus
24
Q
cleavage of mRNA
A
- depends on specific RNA sequence and cleavage enzyme
- TTATTT –> AAUAAA
25
polyadenylation
- happens immediately after cleavage
| - polyA polymerase adds A to 3' as polyA tail
26
What the functions of the polyA tail?
1. involved in transport of mature mRNA from nucleus
2. can protect mRNA from degradation
3. can serve as recognition signal for ribosomes
27
editing of mRNA
- deamination to change coding sequences
| i. e. regulation of serotonin receptor subtypes
28
splicing of immature mRNA
- exon-intron boundaries are determined by nucleotide sequence
- spliceosome cuts out introns and ligates together the exons to produce mature message
- depending on which exons are left in mature mRNA, same mRNA can encode for dif proteins (protein products from related mRNA's = isoforms)
29
DNA sequences that regulate transcription
1. Promoter
2. Enhancer
3. Structural feature of chromatin that modulates binding of transcription factors
4. Factor specific sequences
30
promoter sequence
- consists of several specific sequences that regulate RNA transcription at level of RNA polymerase binding/activation
- TATA box (-25): where protein initiation factor TF1ID binds and binds RNA pol II
- CAAT box (-80): attenuates polymerase binding/activation by interaction with specific protein factors
31
enhancer sequences
- variable sequences frequently at great distances away from transcriptional initiation site
32
factor specific sequences
- within and without promoter region
| - make initiation of transcription of specific genes dependent on specific proteins and specific signals
33
positive regulators/affectors
- binding of specific proteins are necessary for RNA pol binding and transcriptional initiation
34
repressors
- binding of specific proteins to DNA prevents binding of RNA pol or prevents initiation of transcription
35
Ability of dif interacting proteins to form proper complexes to regulate transcription requires:
1. proper DNA sequences
2. accessibility of these sequences (changes in chromatin structure in region of gene being expressed)
i. e. histone modifications
3. proper "forms" of transcription factor
36
What two things affect the proper "forms" of transcription factors?
1. post-translational modifications (i.e. phosphorylation, acetylation, ubiquitination) that change protein's ability to interact with DNA or other proteins
2. translocation from cytoplasm to nucleus
37
example of feedback loop affecting gene expression
- regulation of p53 by mdm2: stability and transcriptional control
- effects on p53 from HPV (E6, E7)
- inability to raise levels of p53 leading to cancer
38
codons
- consist of triplet combinations of bases G/C/U/A
| - usually display "degeneracy" or "wobble" --> multiple codons differing in third base can code for same amino acid
39
Smooth ER
- involved in lipid synthesis
- highly abundant in steroid secreting cells (i.e. testes and ovaries)
- site of cytochrome P450 and other proteins important in detoxification reactions (prevalent in liver)
40
Rough ER
- have membrane bound polysomes (ribosomes) associated with them
- site of membrane bound and secreted protein synthesis
41
Describe why ribosomes associate with RER
- ribosomes have consensus/signal sequence that binds to signal recognition particle (SRP)
- temporarily stops translation and recognizes specific ER sites (docking proteins)
- protein is injected co-translationally (translocon) through ER in energy dependent manner (ATP) --> vectorial discharge
42
translational process for secreted proteins
- signal sequence on polypeptide chain can be removed
43
translational process for integral membrane proteins
- signal sequence on polypeptide chain is retained and embedded in membrane
44
modifications of proteins made within ER
- carbohydrates added to produce N-linked glycoproteins
| - lipids and glycolipids can be attached
45
What causes some membrane proteins to "weave" in and out of membrane
- "weaving" results from internal signal sequences and stop and start sequences
46
protein synthesis on free ribosomes and lipid modifications
- some proteins undergo attachment of lipids (myristoylation, prenylation, palmitoylation) in cytosol
- often leads to attachment in cytosolic surface of PM
- lipid modifications involved in growth control (i.e. Ras oncogene proteins)
