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Histology/Cell Biology > Gene Expression & Protein Synthesis > Flashcards

Gene Expression & Protein Synthesis Flashcards

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1
Q

What creates differentiation between cells of the same type?

A
  • all cells possess the same info, but different cells express different information
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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

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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

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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
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5
Q

flow of genetic information

A

DNA –> RNA –> protein

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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’
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7
Q

rRNA

A
  • ribosomal RNA

- structural components of ribosomes

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8
Q

tRNA

A
  • transfer RNA

- adaptor molecules in protein synthesis

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9
Q

snRNA and scRNA

A
  • small nuclear RNA and small conditional RNA

- other structural or catalytic units of specialized cellular components

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10
Q

siRNA

A
  • small interfering RNA

- plays a role in regulating gene expression

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11
Q

types of RNA which are the final products of transcription

A
  • rRNA
  • tRNA
  • snRNA
  • scRNA
  • siRNA
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12
Q

mRNA

A
  • messenger RNA

- serves in information transfer for synthesis of proteins

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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
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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)
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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
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16
Q

How is information flow regulated within a cell?/What steps are involved in regulating gene expression?

A
  1. regulating transcription of specific genes into RNA
  2. post-transcriptional modification and degradation
  3. regulating translation of RNA into protein
  4. post-translational modification and degradation
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17
Q

RNA Pol I

A
  • used to transcribe ribosomal RNA (in nucleolus)
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18
Q

RNA Pol III

A
  • used to transcribe tRNA
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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
Q

polyadenylation

A
  • happens immediately after cleavage

- polyA polymerase adds A to 3’ as polyA tail

26
Q

What the functions of the polyA tail?

A
  1. involved in transport of mature mRNA from nucleus
  2. can protect mRNA from degradation
  3. can serve as recognition signal for ribosomes
27
Q

editing of mRNA

A
  • deamination to change coding sequences

i. e. regulation of serotonin receptor subtypes

28
Q

splicing of immature mRNA

A
  • 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
Q

DNA sequences that regulate transcription

A
  1. Promoter
  2. Enhancer
  3. Structural feature of chromatin that modulates binding of transcription factors
  4. Factor specific sequences
30
Q

promoter sequence

A
  • 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
Q

enhancer sequences

A
  • variable sequences frequently at great distances away from transcriptional initiation site
32
Q

factor specific sequences

A
  • within and without promoter region

- make initiation of transcription of specific genes dependent on specific proteins and specific signals

33
Q

positive regulators/affectors

A
  • binding of specific proteins are necessary for RNA pol binding and transcriptional initiation
34
Q

repressors

A
  • binding of specific proteins to DNA prevents binding of RNA pol or prevents initiation of transcription
35
Q

Ability of dif interacting proteins to form proper complexes to regulate transcription requires:

A
  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
Q

What two things affect the proper “forms” of transcription factors?

A
  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
Q

example of feedback loop affecting gene expression

A
  • 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
Q

codons

A
  • 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
Q

Smooth ER

A
  • 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
Q

Rough ER

A
  • have membrane bound polysomes (ribosomes) associated with them
  • site of membrane bound and secreted protein synthesis
41
Q

Describe why ribosomes associate with RER

A
  • 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
Q

translational process for secreted proteins

A
  • signal sequence on polypeptide chain can be removed
43
Q

translational process for integral membrane proteins

A
  • signal sequence on polypeptide chain is retained and embedded in membrane
44
Q

modifications of proteins made within ER

A
  • carbohydrates added to produce N-linked glycoproteins

- lipids and glycolipids can be attached

45
Q

What causes some membrane proteins to “weave” in and out of membrane

A
  • “weaving” results from internal signal sequences and stop and start sequences
46
Q

protein synthesis on free ribosomes and lipid modifications

A
  • 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)

Histology/Cell Biology (12 decks)

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