9: From Gene to Protein Flashcards Preview

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Flashcards in 9: From Gene to Protein Deck (58):
1

Genotype definition :

an organisms hereditary information

2

Phenotype definition :

actual observable or physiological traits

3

Our _____and its interaction with the
__________determines our _______

genotype
environment
phenotype

4

Gene expression definition :

the process of going from DNA to a functional product

5

The Central Dogma

DNA- RNA -PROTEIN

6

DNA is:

the heritable material that is used
to store and transmit information from
generation to generation

7

RNA acts as a :

messenger to allow the
information stored in the DNA to be used to
make proteins

8

Proteins carry out:

cellular functions

9

Three main steps of Gene expression:

Transcription of RNA from DNA
Processing of the pre-mRNA transcript
Translation of the mRNA transcript to a protein

10

Gene expression is tightly regulated with :

Multiple control points

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Multiple control points

Transcription factors need to
correctly assemble and DNA needs to be accessible.
(Most control here)
Capping, extent of polyadenylation,
alternate splicing, producing a stable mRNA able to be translated
specific proteins assist
in the export of mRNA
Regulatory proteins can block
translation, variable mRNA life-spans

12

Why is control of gene
expression important?

To achieve the right thing at the
right time in the right place

13

Housekeeping proteins are actively transcribed from DNA continuously

Protein and mRNA are present in large quantities (e.g. Tubulin)
• Typically have long half life in cells

14

Other proteins are produced in response to stimuli as required

Cell signaling (e.g. ligand binding a cell surface receptor, or activating an
intracellular receptor)
• Signal transduced and may enter nucleus to activate transcription
• results in the production of a short-lived protein to carry out the required
function

15

3 main steps of Transcription

Initiation, elongation, termination

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Transcription – initiation
Assembly of multiple _______ required before _______can commence

proteins
transcription

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Transcription – initiation
1. A eukaryotic promoter
2. Several transcription factors bind to DNA
3. Transcription

TATA box typically ~25nt
upstream
Assembly of several TFs
including the TATA box
binding protein (TBP)
RNA Pol II can now bind
along with more TFs to
form the transcription
initiation complex
transcription commences

18

Capping definition:

: a modified
guanine nucleotide is
added to the 5’ end

19

Tailing definition:

50-250 adenine nucleotides
are added to the 3’ end

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Exons:

coding regions (inc UTRs)

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Introns:

non-coding regions intervening exons

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UTR:

untranslated regions at 5’ and 3’ ends

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Splicing:

introns are removed from
the transcript

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10-20 ______exposed at a time when unwound during elongation & termination

nucleotides

25

during elongation & termination Complementary RNA nucleotides
added to ___ end of growing transcript

3'
(3’OH binds with 5’ phosphate)

26

_________: after transcription of the
polyadenylation signal (AAUAAA) nuclear
enzymes release the pre-mRNA and RNA
polymerase then dissociates from the DNA

Termination

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Where does splicing occur?

At the spliceosome ( a large complex of proteins and small RNAs), within the nucleus

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_____are removed from the transcript
and rejoined to form mature mRNA

Introns

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short (2bp) _____ and _____ sequences near the ends of the introns determine splicing

donor
acceptor

mutations in these splice
sites can affect generation of gene
products

30

Alternative splicing allows for ?

multiple gene products from the same gene

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Ribosome has binding sites for?

mRNA and tRNA

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mRNA binding site on which subunit?

small

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A site:

holds “next-in-line” tRNA

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P site:

holds tRNA carrying the
growing polypeptide
(EPA)

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E site:

tRNAs exit from here

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Translation - elongation
Codon recognition:

base pairs with complementary anticodon
GTP invested to increase accuracy/ efficiency

37

Translation - elongation
Peptide bond formation:

A large subunit rRNA catalyses peptide
bond formation
Removes it from tRNA in P site

38

Translation - elongation
Translocation:

moves tRNA from A to P site
tRNA in P site moves to E and is released
Energy required (GTP)

39

Empty tRNAs are ‘______’ in the ______using aminoacyl-tRNA synthetase

reloaded
cytoplasm

40

RNA processing order is:

capping tailing then splicing.

41

Primary structure is Determined by the ___ _____. Held by strong polypeptide bonds.
Starts to form secondary structures
as soon as leaves the ______

DNA sequence
ribosome

42

Common (there are 100s) post-translational modifications include:

• Phosphorylation (addition of a phosphate group)
• Methylation (addition of a methyl group)
• Acetylation (addition of an acetyl group)
• Biotinylation (addition of biotin)
• Carboxylation (addition of a carboxylic acid group)
• Carbohydrate addition (particularly for membrane bound proteins, eg. glycoproteins)
• Cleavage
• Ubiquitination

43

Post-translational modifications, Translation is now complete but the protein may not yet be functional. Occur where?

Some occur within the Golgi, others in the cytosol

44

Post-translational modifications provides another level of regulation by:

Can confer activity – eg via phosphorylation or enzyme cleavage
or ability to interact with other molecules – eg. biotinylation, methylation of histones
or direct to particular locations – eg ubiquitination for proteasome degradation

45

__possible codons, __of which code for amino acids, but there are only
~40 ___because tRNAs can base pair to more than one codon

64
61
tRNAs

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Codons are translated into amino acids
tRNA molecules within the _____with
specific ca_____rry corresponding
amino acids

cytosol
anticodons

47

Transfer RNA (tRNAs) are the physical link between...

the mRNA and the amino acid sequence of proteins

48

Initiator AUG is called?

Met
methionine

49

Hydrogen bonds form between initiator anticodon and

mRNA

50

mRNA stop codon in the _
site is bound by a _____ _____

A site
release
factor

51

UAG, UAA and UGA are what?

stop codons

52

In _______, the Bond between p-site ____
and the final amino acid is
hydrolysed(split) , releasing
polypeptide

termination
tRNA

53

After polypeptide released in termination, Ribosome subunits split but ribosome components can
be ______

recycled.
Hydrolysis of two GTP
molecules required

54

What kind of bonds in: Secondary Structure?
Tertiary?
Quaternary?

weak hydrogen
bonds
3D shape stabilized by side chain
interactions+ stronger
disulphide bonds
Multiple proteins
associate to form a
functional protein

55

what direct ribosomes to RER?

Signal peptides

56

SRP: (____ _____ _______ binds to _________ and receptor protein.
SRP detaches and polypeptide synthesis resumes.

signal recognition
particle
Signal peptides

57

Altered DNA sequence
can have major effects on resulting protein function either ____ ____ or _____

germ line – can effect many cells, and be catastrophic
- local – during cell division, not whole body – local effects (mitosis/cancer lecture)

58

silent mutation and Missense mutation and Nonsense mutation results in ?

1-different code, but redundancy means still codes for same protein
2. different code means wrong protein, potential effects
3.protein and now codes for a stop. major effect, functional regions absent