Bio 1001 > Gene Expression > Flashcards

Gene Expression Flashcards

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1
Q

What is gene expression?

A

The process of using DNA information to make RNA and protein

Gene expression is essential for the functioning of cells and the manifestation of traits.

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2
Q

What is the central dogma of biology?

A

DNA → RNA → Protein

This concept outlines the flow of genetic information within a biological system.

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3
Q

What process makes RNA from DNA?

A

Transcription

Transcription is the first step in gene expression.

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4
Q

What process makes protein from mRNA?

A

Translation

Translation occurs after transcription and is crucial for protein synthesis.

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5
Q

What did Beadle and Tatum study?

A

Neurospora crassa (bread mold)

Their work contributed to the understanding of gene function.

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6
Q

Why use Neurospora crassa?

A

Haploid, so mutations show immediately

This characteristic makes it easier to study genetic mutations.

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7
Q

What did Beadle and Tatum conclude?

A

One gene codes for one enzyme

This conclusion laid the groundwork for the one gene-one enzyme hypothesis.

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8
Q

What was the revised hypothesis?

A

One gene–one polypeptide

This reflects the understanding that genes can code for proteins that are not enzymes.

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9
Q

Why was ‘one gene–one enzyme’ inaccurate?

A

Some proteins have multiple subunits or code for RNA instead of proteins

This highlights the complexity of gene function.

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10
Q

What is transcription?

A

Copying DNA sequence into RNA

Transcription is a key step in gene expression.

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11
Q

What enzyme transcribes mRNA in eukaryotes?

A

RNA polymerase II

This enzyme is crucial for synthesizing mRNA from DNA.

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12
Q

Where does transcription occur in eukaryotes?

A

In the nucleus

This is where the DNA is located in eukaryotic cells.

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13
Q

Where does translation occur in eukaryotes?

A

In the cytoplasm

This is where ribosomes synthesize proteins.

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14
Q

Are transcription and translation coupled in prokaryotes?

A

Yes

In prokaryotes, both processes can occur simultaneously.

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15
Q

What are the three stages of transcription?

A
  • Initiation
  • Elongation
  • Termination

These stages describe the process of synthesizing RNA from DNA.

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16
Q

What is the promoter?

A

DNA region where RNA polymerase binds

The promoter is essential for initiating transcription.

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17
Q

What is the TATA box?

A

A promoter sequence in eukaryotes

It plays a critical role in the initiation of transcription.

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18
Q

What do transcription factors do?

A

Help RNA polymerase bind to the promoter

These proteins are essential for regulating gene expression.

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19
Q

Which strand is read during transcription?

A

The template strand

This strand serves as the guide for synthesizing RNA.

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20
Q

Which strand matches mRNA sequence?

A

The coding strand

This strand has the same sequence as the mRNA (except for uracil replacing thymine).

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21
Q

In what direction is RNA made?

A

5′ to 3′

This directionality is crucial for RNA synthesis.

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22
Q

In what direction is the template strand read?

A

3′ to 5′

This allows RNA polymerase to synthesize RNA in the 5′ to 3′ direction.

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23
Q

What nucleotide pairs with adenine in RNA?

A

Uracil

This is a key difference between RNA and DNA.

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24
Q

What nucleotide pairs with cytosine in RNA?

A

Guanine

This pairing is consistent with base pairing rules.

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25
What is a **terminator**?
Sequence that ends transcription ## Footnote This signals RNA polymerase to stop synthesizing RNA.
26
What signal ends transcription in **eukaryotes**?
Polyadenylation signal (AAUAAA) ## Footnote This sequence is crucial for the termination of transcription.
27
What is **pre-mRNA**?
The unprocessed RNA transcript in eukaryotes ## Footnote Pre-mRNA undergoes several modifications before becoming mature mRNA.
28
What is added to the **5′ end** of **mRNA**?
A modified guanine cap ## Footnote This cap protects RNA and aids in ribosome binding.
29
What does the **5′ cap** do?
Protects RNA and helps ribosome binding ## Footnote This modification is essential for mRNA stability.
30
What is added to the **3′ end** of **mRNA**?
A poly-A tail ## Footnote This tail increases the stability and lifespan of mRNA.
31
What is the function of the **poly-A tail**?
Increases stability and lifespan of mRNA ## Footnote This modification helps protect mRNA from degradation.
32
What is **splicing**?
Removing introns and joining exons ## Footnote This process is crucial for producing mature mRNA.
33
What are **introns**?
Noncoding sequences removed from pre-mRNA ## Footnote Introns do not code for proteins and are eliminated during splicing.
34
What are **exons**?
Coding sequences that remain in mature mRNA ## Footnote Exons are essential for coding the final protein.
35
What complex removes **introns**?
Spliceosome ## Footnote This complex is made up of snRNPs and other proteins.
36
What is **alternative splicing**?
Producing different proteins from one gene ## Footnote This process allows for greater protein diversity.
37
What is a **codon**?
3-base sequence on mRNA coding for an amino acid ## Footnote Codons are the basic units of the genetic code.
38
What is an **anticodon**?
3-base sequence on tRNA complementary to mRNA codon ## Footnote Anticodons ensure the correct amino acid is added during translation.
39
What is the **start codon**?
AUG ## Footnote This codon signals the beginning of translation.
40
What amino acid does **AUG** code for?
Methionine ## Footnote Methionine is the first amino acid in protein synthesis.
41
What are **stop codons**?
* UAA * UAG * UGA ## Footnote Stop codons signal the termination of translation.
42
What does a **stop codon** signal?
End of translation ## Footnote This indicates that the polypeptide chain is complete.
43
What binds **stop codons**?
Release factors ## Footnote These proteins facilitate the termination of translation.
44
How many total **codons** exist?
64 ## Footnote This includes both codons that code for amino acids and stop codons.
45
How many code for **amino acids**?
61 ## Footnote These codons specify the amino acids used in protein synthesis.
46
Why is the code **degenerate**?
Multiple codons can code for the same amino acid ## Footnote This redundancy helps protect against mutations.
47
What is the **wobble position**?
3rd base of a codon that allows pairing flexibility ## Footnote This flexibility contributes to the degeneracy of the genetic code.
48
What is a **reading frame**?
The correct grouping of codons starting at AUG ## Footnote The reading frame determines how the sequence is interpreted.
49
What is a **frameshift mutation**?
Insertion or deletion that shifts reading frame ## Footnote This type of mutation can drastically alter protein synthesis.
50
What is **tRNA**?
Molecule that brings amino acids to the ribosome ## Footnote tRNA plays a crucial role in translation.
51
What enzyme charges **tRNA** with an amino acid?
Aminoacyl-tRNA synthetase ## Footnote This enzyme ensures that the correct amino acid is attached to the corresponding tRNA.
52
How many **aminoacyl-tRNA synthetases** exist?
20 ## Footnote Each synthetase corresponds to one of the 20 standard amino acids.
53
What ensures **tRNA accuracy**?
Aminoacyl-tRNA synthetase specificity ## Footnote This specificity is critical for maintaining the fidelity of protein synthesis.
54
What is **rRNA**?
Ribosomal RNA that forms part of the ribosome ## Footnote rRNA is essential for the structure and function of ribosomes.
55
What is the **ribosome** made of?
rRNA and proteins ## Footnote The ribosome is the site of protein synthesis.
56
What are the ribosome’s **binding sites**?
* A * P * E ## Footnote These sites play distinct roles during translation.
57
Function of **A site**?
Accepts new tRNA carrying amino acid ## Footnote This site is crucial for adding new amino acids to the growing polypeptide chain.
58
Function of **P site**?
Holds tRNA with growing polypeptide chain ## Footnote This site is where peptide bonds form between amino acids.
59
Function of **E site**?
Releases empty tRNA ## Footnote This site allows tRNA to exit the ribosome after delivering its amino acid.
60
What happens during **initiation** of translation?
Ribosome assembles at start codon with initiator tRNA ## Footnote This step is critical for beginning the translation process.
61
Initiator tRNA in **eukaryotes**?
Met-tRNAᵢ^Met ## Footnote This tRNA carries methionine, the first amino acid in eukaryotic proteins.
62
Initiator tRNA in **prokaryotes**?
fMet-tRNAᶠ^Met ## Footnote This tRNA carries formylmethionine, the first amino acid in prokaryotic proteins.
63
What happens during **elongation**?
New tRNAs enter A site, peptide bonds form, ribosome shifts ## Footnote This process continues until a stop codon is reached.
64
What happens during **translocation**?
Ribosome moves one codon along mRNA ## Footnote This movement is essential for the continuation of translation.
65
What catalyzes **peptide bond formation**?
Peptidyl transferase (rRNA activity) ## Footnote This enzymatic activity is crucial for linking amino acids together.
66
What happens during **termination**?
Stop codon → release factor → chain released ## Footnote This marks the end of the translation process.
67
What is a **polysome**?
Several ribosomes translating one mRNA simultaneously ## Footnote Polysomes increase the efficiency of protein synthesis.
68
What sets the **reading frame**?
The first AUG ## Footnote The reading frame determines how the mRNA sequence is translated into amino acids.
69
Do **stop codons** have matching tRNAs?
No ## Footnote Stop codons signal the end of translation and do not correspond to any tRNA.
70
Why does **mRNA** have a short life in cells?
Allows quick gene regulation ## Footnote The transient nature of mRNA enables cells to respond rapidly to changes.
71
What direction is a **polypeptide** built?
From N-terminus to C-terminus ## Footnote This directionality is important for protein folding and function.
72
What direction is **mRNA** read?
5′ to 3′ ## Footnote This is the standard direction for ribosomes during translation.
73
What determines a **protein’s structure**?
Its amino acid sequence ## Footnote The sequence of amino acids dictates how a protein folds and functions.
74
What does **gene expression** ultimately control?
Traits and cell function ## Footnote Gene expression is fundamental to the development and functioning of all living organisms.
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