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Biology 120 > Gene Structure And Expression > Flashcards

Gene Structure And Expression Flashcards

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1
Q

What is the function of genes?

A

Genes influence traits by encoding proteins that perform biochemical, cellular, and organismal functions.

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2
Q

What is the Central Dogma of molecular biology?

A

DNA → RNA → Protein

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3
Q

What is transcription?

A

DNA is transcribed into RNA by RNA polymerase.

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4
Q

What is translation?

A

RNA is translated into protein using ribosomes.

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5
Q

What are non-coding RNAs?

A

Not all genes code for proteins (e.g., rRNA, tRNA); these RNAs have specialized functions.

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6
Q

What components are included in gene structure?

A

Promoters, exons, and introns (in eukaryotes)

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7
Q

What is the orientation of genes?

A

5’ → 3’

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8
Q

What is a key difference in gene structure between prokaryotes and eukaryotes?

A

Prokaryotes lack introns.

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9
Q

What do prokaryotes use for transcription termination?

A

Simpler termination sequences.

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10
Q

What processes are required for RNA processing in eukaryotes?

A

Splicing, capping, polyadenylation.

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11
Q

What do eukaryotes use for RNA polymerase binding?

A

Transcription factors.

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12
Q

What are codons?

A

Triplets of nucleotides that encode amino acids.

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13
Q

What is the start codon?

A

AUG (Methionine).

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14
Q

What are the stop codons?

A

UAA, UAG, UGA.

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15
Q

What is meant by redundancy in the genetic code?

A

Multiple codons encode the same amino acid due to ‘wobble pairing.’

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16
Q

What are the four types of mutations?

A
  • Silent
  • Missense
  • Nonsense
  • Frameshift

Each type of mutation can affect protein function in different ways.

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17
Q

What characterizes a silent mutation?

A

No change in protein.

Silent mutations do not affect the amino acid sequence of the protein.

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18
Q

What is a missense mutation?

A

Amino acid substitution (e.g., sickle cell disease).

Missense mutations can lead to altered protein function.

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19
Q

What happens in a nonsense mutation?

A

Premature stop codon.

Nonsense mutations can result in truncated proteins.

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20
Q

Define frameshift mutation.

A

Alteration of the reading frame.

Frameshift mutations can significantly change the resulting protein.

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21
Q

What are the potential impacts of mutations?

A

Can have evolutionary impacts or cause diseases.

Mutations can influence genetic diversity and disease susceptibility.

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22
Q

What is the first step of transcription in eukaryotes?

A

Initiation: Transcription factors recruit RNA polymerase to the promoter.

This step is crucial for starting the transcription process.

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23
Q

Describe the elongation phase of transcription.

A

RNA polymerase synthesizes RNA in 5’ → 3’.

This phase involves the addition of RNA nucleotides complementary to the DNA template.

24
Q

What occurs during the termination phase of transcription?

A

Cleavage occurs after the 3’ UTR.

This step marks the end of RNA synthesis.

25
Q

What is the purpose of 5’ capping in RNA processing?

A

Stabilizes RNA; recognized by ribosomes.

Capping is essential for mRNA stability and translation initiation.

26
Q

What is the function of the Poly(A) tail in RNA processing?

A

Protects RNA from degradation.

The Poly(A) tail enhances mRNA stability and export from the nucleus.

27
Q

What is the role of splicing in RNA processing?

A

Removes introns; allows alternative splicing to create diverse proteins.

Alternative splicing can lead to the production of multiple protein variants from a single gene.

28
Q

What is the first stage of translation?

A

Initiation: Ribosome assembles on mRNA at start codon

The start codon is typically AUG, which codes for methionine.

29
Q

What occurs during the elongation stage of translation?

A

Amino acids added sequentially, reading the mRNA from 5’ to 3’

This process involves tRNA bringing amino acids to the ribosome.

30
Q

What triggers the termination stage of translation?

A

Stop codon prompts release of the ribosome

Common stop codons include UAA, UAG, and UGA.

31
Q

What is the function of the A site on the ribosome?

A

Accepts new tRNA

The A site is crucial for adding new amino acids during protein synthesis.

32
Q

What is the role of the P site on the ribosome?

A

Forms peptide bonds

This site holds the tRNA carrying the growing polypeptide chain.

33
Q

What happens at the E site on the ribosome?

A

Releases empty tRNA

The E site is where tRNA exits the ribosome after transferring its amino acid.

34
Q

What are polysomes?

A

Multiple ribosomes translating a single mRNA

This allows for efficient and rapid protein synthesis.

35
Q

What are post-translational modifications?

A

Folding (chaperones), phosphorylation, glycosylation, lipidation

These modifications can affect protein activity and stability.

36
Q

What is the main purpose of protein sorting?

A

Directs proteins to specific cellular locations

This process is essential for maintaining cellular organization and function.

37
Q

What are sorting signals in proteins?

A

Specific sequences or structural features that act as ‘postal codes’ for protein targeting

Sorting signals guide proteins to their correct destinations within the cell.

38
Q

What are signal peptides?

A

Short amino acid sequences at the N-terminus that direct proteins to the endoplasmic reticulum (ER)

Signal peptides are essential for the initial targeting of proteins during synthesis.

39
Q

Define Nuclear Localization Signals (NLS).

A

Short sequences that direct proteins to the nucleus

NLS are critical for the transport of proteins into the nucleus.

40
Q

What are transit peptides?

A

Target proteins to organelles like mitochondria or chloroplasts

Transit peptides facilitate the import of proteins into specific organelles.

41
Q

Where are proteins destined for secretion or membrane synthesized?

A

In the rough endoplasmic reticulum (ER)

The rough ER is studded with ribosomes, which synthesize these proteins.

42
Q

How are other proteins synthesized?

A

In the cytosol and sorted post-translationally

This means that these proteins are synthesized first and then directed to their destinations.

43
Q

What is the role of a signal recognition particle (SRP)?

A

Binds the signal peptide on a nascent polypeptide and guides the ribosome to the SRP receptor on the ER membrane

SRP plays a crucial role in initiating protein translocation into the ER.

44
Q

What occurs during translation into the ER?

A

The growing polypeptide chain is fed into the ER lumen

This process allows for proper folding and modification of the protein.

45
Q

What happens to the signal peptide inside the ER?

A

It is removed by signal peptidase

This step is essential for the maturation of the protein.

46
Q

What modifications occur inside the ER?

A

Folding and initial modifications such as glycosylation

These modifications are important for protein functionality and stability.

47
Q

What is the role of the Golgi apparatus in protein sorting?

A

Proteins are further modified and sorted for final destinations like the plasma membrane or lysosomes

The Golgi apparatus is a key site for protein processing and distribution.

48
Q

What directs proteins to specific organelles?

A

Transit peptides

Transit peptides are short sequences that signal the destination of proteins within the cell.

49
Q

What role do chaperones play in protein sorting?

A

Assist in translocation across organelle membranes

Chaperones help proteins fold properly and assist in their transport into organelles.

50
Q

What is the function of nuclear localization signals?

A

Allow proteins to pass through nuclear pores

Nuclear localization signals are specific sequences that facilitate the import of proteins into the nucleus.

51
Q

Is full unfolding of the protein required for passage through nuclear pores?

A

No

Proteins can pass through nuclear pores without fully unfolding.

52
Q

What tag is used to send proteins to lysosomes?

A

Mannose-6-phosphate

This tag is added in the Golgi apparatus and directs proteins to lysosomes for degradation.

53
Q

What is phosphorylation in the context of protein sorting?

A

Activates or deactivates sorting signals

Phosphorylation involves adding a phosphate group, which can change a protein’s activity or its interactions.

54
Q

What role does glycosylation play in protein sorting?

A

Helps in sorting within the ER and Golgi

Glycosylation is the addition of sugar molecules to proteins, which aids in their proper localization.

55
Q

What is lipidation’s function in protein sorting?

A

Anchors proteins to membranes

Lipidation involves the addition of lipid groups to proteins, facilitating their attachment to cell membranes.

56
Q

Why is protein sorting important for cells?

A

Maintains cellular compartmentalization

Proper sorting ensures that enzymes and proteins are located where they can function effectively.

57
Q

What can errors in protein sorting lead to?

A

Diseases such as cystic fibrosis or lysosomal storage disorders

Mis-sorted proteins can disrupt cellular functions and lead to various health conditions.

Biology 120 (24 decks)

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