Ch. 9.1-9.2 Transcription Ch. 9.3 Translation Ch. 9.4 Regulation of gene expression Flashcards
(92 cards)
1
Q
What are genes?
A
Information contained in DNA is stored in blocks
2
Q
What do genes code for?
A
mRNA which codes for protein
3
Q
What ddo proteins determine?
A
How cells will function
4
Q
What is central dogma?
A
Path of genetic information
DNA > RNA > protein
5
Q
List DNA, RNA, protein into central dogma
A
DNA > RNA > protein
6
Q
In what situation is it called gene expression?
A
When gene sequences are used by cell to make protein
7
Q
What is transcription?
A
process by which messenger RNA (mRNA) is made from gene within DNA
8
Q
What is translation?
A
process of using mRNA to direct production of protein
9
Q
What are differences between RNA and DNA?
A
Uracil, ribose, single-stranded in RNA
10
Q
What are 3 kinds of RNA that cell uses?
A
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
11
Q
What is mRNA?
A
“message” that was transcribed from gene
12
Q
What is rRNA?
A
RNA that makes up part of ribosome
13
Q
What is tRNA?
A
RNA that transfers amino acids to ribosome during translation
14
Q
What allows prokaryotes to undergo transcription and translation at same time?
A
Prokaryotes not having nucleus
15
Q
What are introns and do prokaryotes have it?
A
Non-translated regions and prokaryotes do not contain introns
16
Q
What are 3 stages in transcription in both prokaryote and eukaryote
A
initiation, elongation, and termination
17
Q
Which protein produces mRNA copy of DNA during transcription
A
RNA polymerase
18
Q
What is binding process in Transcription?
A
It first binds to one strand of DNA at site called promoter and then moves down DNA molecule and assembles complementary copy of RNA
19
Q
When is transcription terminator happening?
A
Transcription ends when RNA polymerase reaches certain nucleotide sequence that causes transcription to stop
20
Q
What is process of transcription?
A
- RNA polymerase finds promoter region of gene
- Protein called sigma factor binds to RNA polymerase to initiate transcription in prokaryotes
- Proteins called transcription factors determine which genes should be transcribed in eukaryotes, such as growth factors initiating transcription of testosterone during puberty in males
- RNA polymerase transcribes in 5 to 3 direction, like DNA polymerase
- Strand of DNA with gene sequence is template strand, opposite strand is coding strand
- When RNA polymerase encounters termination sequence, a hairpin loop forms in mRNA, causing polymerase and mRNA to dissociate from DNA
21
Q
sense strand: 5’ ATGGCCTATGAATCG 3’
antisense strand: 3’ TACCGGATACTTAGC 5’
Find mRNA sequence from strands above
A
5’ AUGGCCUAUGAAUCG 3’ from template strand which is sense strand in this case
22
Q
What introns be in the transcription of RNA processing?
A
They do not code for amino acid sequence and must be removed
23
Q
What are parts of gene that code for mRNA sequences?
A
Exons
24
Q
What does it happen when eukaryotic cell first transcribes gene?
A
it produces primary RNA transcript (also called pre-mRNA) of entire gene
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What would happen to primary transcription?
Primary transcript is then processed in nucleus
26
What does cut out introns and join together exons to form shorter mRNA transcript
Enzyme-RNA complexes
27
What portion of trypical human genes are not translated?
Sequences of introns, which make up 90% of typical human gene, are not translated
28
What is purpose of added 5 cap′ and 3 poly-A tail in the RNA?
tail protects RNA from being degraded
29
How are genes spliced in humans?
In humans, genes may be spliced together in different ways
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What is alternative splicing?
By using different combinations of same exons, different proteins are created
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How many genes of human genome appear as many as 120 000 different mRNA transcripts
25 000 genes
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When does RNA processing occur?
RNA processing occurs in nucleus immediately after transcription
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Where is mRNA splicing occurs?
mRNA splicing occurs in spliceosome
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What is spliceosome?
combination of “pre-mRNA” and small ribonucleoproteins—snRNPs
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Where does translation occur ?
Ribosomes which are protein-making factories on cells
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Where are your ribosomes?
cytoplasm or ER
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What is each ribosome made of?
Each ribosome is complex of proteins and several segments of
ribosomal RNA (rRNA)
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What do ribosomes consist of?
Ribosomes consist of two subunits: small subunit and large
subunit
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What does small subunit of ribosome have?
small subunit has short sequence of its rRNA exposed, which is
complementary to leader sequence that begins all mRNA
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What binds to small subunit?
mRNA
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What does large ribosomal subunit have?
Large ribosomal subunit has three binding sites for transfer RNA (tRNA) located directly adjacent to exposed rRNA sequence on small subunit
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What are the 3 binding sites of large subunit called?
binding sites are called A, P, and E sites
43
What is it that brings amino acids to ribosome to use in making proteins?
tRNA molecules
44
What shuld cell do to correctly read gene?
cell must translate information encoded in DNA into language of proteins
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What should translation follow?
Translation should follow rules set by genetic code
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What are codons?
mRNA is “read” in three-nucleotide units
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What does each codon correspond to?
Each codon corresponds to particular amino acid
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Where does tRNA molecule hold amino acid attachment?
at one end and three-nucleotide sequence at other end
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What is anticodon?
that three-nucleotide sequence at other end
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What is anticodon complementary to?
64 codons of the genetic code
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What does activating enzymes match?
It matches to amino acids with their proper tRNAs
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What would happen once mRNA molecule has bound to small ribosomal subunit
other larger ribosomal subunit binds as well, forming complete ribosome
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What does mRNA do during translation?
mRNA threads through ribosome three nucleotides at time
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Where does tRNA holding amino acid to be added enters?
ribosome at A site
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What should previous tRNA do before new tRNA can be added?
previous tRNA in A site shifts to P site
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What happens at P site after previous tRNA in A site shifts?
peptide bonds form between incoming amino acid and growing chain of amino acids
57
What energy is used instead of ATP?
GTP
58
What does enzyme peptidyl transferase do?
catalyzes peptide bond formation reaction
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Where does now-empty tRNA in P site eventually shifts to?
E site, where it is released
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Until when would translation continues?
until stop codon (UAA, UAG, UGA) is encountered that signals end of the protein
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What would happen if translation encounters stop codon?
ribosome then falls apart and newly made protein is released into cell
62
Multiple ribosomes may transcribe one single mRNA, true or false?
true
63
In bacteria where it has no nulcues, how do they transcript or translate?
transcription and translation can occur almost simultaneously which gives them advantage because they can alter their regulation very quickly based on environmental
changes
64
In eukaryote where it has nuclues, where do proteins folds into after translation?
once translation is finished, proteins fold into secondary and tertiary structures and may be further processed by Golgi bodies
65
What is post-translational modification?
Proteins can be packaged into vesicles that pinch off and move to Golgi bodies for further processing
66
What do proteins combined with lipids or sugar in golgi bodies produce?
lipoproteins (like LDLs made in liver); or
glycoproteins (like our blood type markers A, B, and AB)
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How many possible codons
Since necleotides of condon can be one of 4 nucleotides, there are 64 possible codons (4*4*4)
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5 A T G C T T T C A C G C G A G G G T T A G 3′
′3 T A C G A A A G T G C G C T C C C A A T C 5′ make the mRNA
'5 AUG CUU UCA CGC GAG GGU UAG 3′
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change mRNA nucleotides into amino acid sequence using chart
Met – Leu – Ser – Arg – Glu – Gly – Stop
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Normal DNA
'5 ATGCTTTCA 3′
'3 TACGAAAGT 5′
DNA mutation 1
'5 ATGCTTTCA 3′
'3 TTCGAAAGT 5' write amino acid sequence for both
Mutation: TTC-->AAG-->lysine
Before mutation: AUG-->Meth
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What should every cell must be doing when particular genes are transcribed?
Every must be able to regulate
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How can genes be turned off in prokaryotes?
genes can be turned off by binding of repressor which is protein that binds to DNA and blocks access to promoter
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How can genes be turned on?
Genes can be turned on by activator, protein that makes promoter more accessible to RNA polymerase
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What is operon?
operon is segment of DNA containing cluster of genes that are all transcribed as unit
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What is best known example for operon?
lac operon in bacterium Escherichia coli
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What does lac operon contain?
genes that code for enzymes associated with breaking down sugar lactose
77
What else does lac operon contain?
In addition, operon contains regulatory elements: operator and promoter
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What does presence of lac operon affect and cause?
presence of lactose affects repressor protein and causes it to fall off operator, making it possible for RNA polymerase to transcribe operon
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What will be produced with lac operon?
enzymes will be produced to break down lactose
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What do activator work with to control transcription?
Activators work with repressors to control transcription
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What is activator in lac operon?
Activator is known as CAP
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Why is CAP required for RNA polymerase?
CAP is required for RNA polymerase to function properly at operon
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Where does CAP bind to when glucose and lactose levels are low?
CAP binds to DNA but transcription proceeds only when lactose is present (lac operon on when there is only lactose)
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What do eukaryotes that have complex chromosomes need to condense DNA so it can fit into nucleus
histone proteins
85
What DNA does each cell can only transcribe?
DNA that is accessible by RNA polymerase
86
Chromosome in different regions vs. chromosome in certain region, which one is more condensed?
Chromosome in different regions
87
What kind of regions are not transcribed?
Highly condensed regions are not transcribed
88
What is Methylation?
Addition of methyl groups (-CH3) prevents gene transcription: called gene silencing
89
What is alternative spilcing?
That sometimes only certain exons become part of mature mRNA. Depending on which exons are used, each protein product has different function
90
What does alternative splicing allow for?
allows over 100 000 different protein products to be produced from only 25 000 genes
91
What is mRNA degradation?
Various mRNA transcripts have specified lifespan due to the length of the poly(A) tail
92
What are transcription factors?
regulate gene expression by binding to regulatory sequences of DNA upstream of promoter, allowing RNA polymerase to bind and begin transcription
