Biology Quiz on RNA, DNA, and Ribosomes

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Questions and Answers

What is the primary function of small nuclear RNAs (snRNAs)?

They assist in the splicing of pre-mRNA. (correct)

They transport RNA out of the nucleus.

They degrade introns after splicing.

They synthesize new RNA strands.

What is the role of the spliceosome in RNA processing?

To transport RNA into the cytoplasm.

To synthesize new introns.

To add a 5' cap to the RNA.

To join adjacent exons together. (correct)

Which molecules combine to form small nuclear ribonucleoproteins (snRNPs)?

Exons and introns.

snRNAs and various proteins. (correct)

Single-stranded RNA and DNA.

Only proteins.

During the splicing process, what does the specific adenine nucleotide interact with?

The 5’ end of the intron. Signup and view all the answers

What is removed from pre-mRNA to form mature RNA?

Introns. Signup and view all the answers

What is the typical size range of introns?

50 to ≥ 10,000 nucleotides. Signup and view all the answers

What is the consequence of the splicing process?

Joining of adjacent exons. Signup and view all the answers

What happens to the introns after they are spliced out?

They are degraded. Signup and view all the answers

What is the primary difference between constitutive and inducible gene expression?

Constitutive genes are essential for survival, while inducible genes determine tissue specificity. Signup and view all the answers

Which of the following correctly describes the function of transcription factors?

They are proteins that can either activate or repress gene transcription. Signup and view all the answers

What is the role of alternative splicing in gene expression?

It allows a single gene to produce multiple protein isoforms, contributing to tissue specificity. Signup and view all the answers

Which type of RNA is primarily responsible for coding proteins?

mRNA Signup and view all the answers

What sugar is found in RNA?

Ribose Signup and view all the answers

How do extracellular cues affect gene expression?

They trigger signal transduction that drives transcription, affecting protein synthesis. Signup and view all the answers

What is the significance of post-transcriptional regulation in gene expression?

It controls the timing and amount of protein synthesized from mRNA. Signup and view all the answers

What role do ribosomal RNAs (rRNAs) play?

They form the structure of ribosomes and catalyze protein synthesis. Signup and view all the answers

What is the function of promoters in transcription?

They initiate transcription. Signup and view all the answers

Which of the following statements about DNA and RNA is correct?

Uracil is found in RNA but not in DNA. Signup and view all the answers

What is the main role of transfer RNAs (tRNAs)?

To act as adaptors between mRNA and amino acids. Signup and view all the answers

Which type of RNA is involved in the splicing of pre-mRNA?

ncRNA Signup and view all the answers

What does the transcriptional start site (TSS) signify?

The beginning of RNA polymerase activity. Signup and view all the answers

What is the primary function of the basal promoter?

To recruit RNA polymerase II and transcription factors Signup and view all the answers

Which is a common feature of the TATA box?

It is usually located 20-30 base pairs from the transcriptional start site Signup and view all the answers

During which phase does RNA polymerase II synthesize RNA?

Elongation Signup and view all the answers

What happens during the termination phase of transcription?

RNA polymerase II disengages after transcribing the 3' UTR Signup and view all the answers

What is the role of the 5' cap added to mRNA precursors?

To protect mRNA from degradation and promote nuclear export Signup and view all the answers

The process of adding a poly(A) tail is crucial for what purpose?

Regulating mRNA stability and translation Signup and view all the answers

Which statement correctly describes RNA polymerase II?

It incorporates ribonucleotide triphosphates to create mRNA Signup and view all the answers

What is heterogenous nuclear RNA (hnRNA)?

The primary RNA transcript before processing Signup and view all the answers

Which sequence is part of the signal for polyadenylation in eukaryotic mRNA?

AAUAAA Signup and view all the answers

What feature distinguishes the CCAT box from the TATA box?

It is located 50-130 base pairs from the start site and is less common Signup and view all the answers

What is the primary function of microRNA (miRNA)?

To down regulate gene expression Signup and view all the answers

What are tRNAs primarily responsible for in protein synthesis?

Transferring amino acids to mRNA Signup and view all the answers

What type of RNA is primarily involved in the splicing of pre-mRNA?

small nuclear RNA (snRNA) Signup and view all the answers

What percentage of the human genome is responsible for making proteins?

1% Signup and view all the answers

How do microRNAs block gene expression?

By promoting mRNA degradation or blocking translation Signup and view all the answers

What term is used for non-coding RNAs that regulate gene expression?

microRNAs Signup and view all the answers

What project changed the perception of non-coding DNA and RNA in 2012?

ENCODE: Encyclopaedia of DNA Elements Signup and view all the answers

Which of the following is a function of non-coding RNAs?

Regulating gene expression Signup and view all the answers

What is the primary role of messenger RNA (mRNA) in gene expression?

To provide a template for protein synthesis. Signup and view all the answers

Which step is NOT involved in the process of transcription in eukaryotes?

Splicing Signup and view all the answers

How does alternative splicing contribute to gene regulation?

It creates multiple protein variants from a single gene. Signup and view all the answers

Which of the following describes a characteristic feature of transcription factors?

They facilitate the binding of RNA polymerase to DNA. Signup and view all the answers

What is the role of the 5' cap added to mRNA precursors?

To protect the mRNA from degradation. Signup and view all the answers

Which process refers to the addition of a poly(A) tail to mRNA?

Polyadenylation Signup and view all the answers

What is the effect of chromatin structure on gene regulation?

It influences accessibility to transcription factors. Signup and view all the answers

Which statement correctly describes the relationship between gene expression and protein synthesis?

Gene expression involves both transcription and translation leading to protein synthesis. Signup and view all the answers

What type of RNA is primarily responsible for carrying the genetic code from DNA to the ribosome for protein synthesis?

mRNA Signup and view all the answers

What characteristic distinguishes RNA from DNA?

RNA typically has a single-stranded structure Signup and view all the answers

Which component of RNA plays a critical role in ribosome structure and protein synthesis?

rRNA Signup and view all the answers

In the transcription process, what is the role of the promoter?

To initiate transcription Signup and view all the answers

Which type of RNA serves as an adaptor between mRNA and amino acids during protein synthesis?

tRNA Signup and view all the answers

What is the primary function of small nuclear RNAs (snRNAs)?

Assist in splicing pre-mRNA Signup and view all the answers

Which of the following factors influences the initiation of transcription?

Enhancer element Signup and view all the answers

Which sequence within DNA signals the start of transcription?

Transcriptional Start Site (TSS) Signup and view all the answers

What is the function of the poly(A) tail in mRNA stability?

It protects against degradation. Signup and view all the answers

What determines the stability of mRNA longevity?

3’ UTR sequence. Signup and view all the answers

What is the primary role of Poly(A) Polymerase in mRNA processing?

To add adenine residues to the 3’ end. Signup and view all the answers

What occurs after the endonuclease cleaves the mRNA?

Poly(A) Polymerase initiates nucleotide addition. Signup and view all the answers

Which type of RNA is primarily responsible for coding for proteins?

mRNA Signup and view all the answers

Which protein binds to the poly(A) tail to enhance mRNA stability?

Poly-A binding protein (PABP) Signup and view all the answers

What role do destabilizing sequences in the 3’ UTR play?

They target mRNA for degradation. Signup and view all the answers

How does the length of the poly(A) tail change over the mRNA’s lifetime?

It gradually shortens over time. Signup and view all the answers

What is the primary role of inducible transcription factors?

They enable genes to be turned on only when needed. Signup and view all the answers

How do steroid hormones affect transcription factor activity?

They bind to transcription factors, forming homodimers. Signup and view all the answers

What regulates the rate of transcription of a given gene?

The number and activity of transcription factors. Signup and view all the answers

What is the function of chromatin modifiers in transcription?

They aid in unwinding DNA for transcription. Signup and view all the answers

What dictates the specificity of transcription factors to their target genes?

The binding sites present in the promoter region. Signup and view all the answers

In which scenario would the beta cells of the pancreas turn on insulin gene expression?

In the fed state when glucose levels are high. Signup and view all the answers

What characteristic of inducible transcription factors allows for a dynamic response to stimuli?

They are only expressed under specific conditions. Signup and view all the answers

How does the presence of multiple binding sites for a transcription factor in a promoter affect gene expression?

It increases the likelihood of transcription activation. Signup and view all the answers

What is the role of microRNA (miRNA) in gene expression?

To promote RNA degradation and block translation Signup and view all the answers

Which type of RNA is primarily involved in regulating gene expression and has a length of approximately 20-25 nucleotides?

MicroRNA (miRNA) Signup and view all the answers

What significant finding was highlighted by the ENCODE project regarding non-coding DNA?

Only 1% of it is involved in protein coding. Signup and view all the answers

What function do small nuclear RNAs (snRNAs) serve in cellular processes?

They are involved in the splicing of pre-mRNA. Signup and view all the answers

Which component of non-coding RNA functions in the regulation of gene expression?

MicroRNA (miRNA) Signup and view all the answers

What is a primary outcome of the actions taken by microRNA on mRNA?

Degradation of mRNA Signup and view all the answers

What percentage of the human genome is primarily involved in the expression of proteins?

1% Signup and view all the answers

Which statement accurately describes the relationship between microRNA and mRNA?

miRNA and mRNA have complementary sequences that allow binding. Signup and view all the answers

What distinguishes constitutive genes from inducible genes in terms of their expression?

Constitutive genes are always expressed regardless of external factors. Signup and view all the answers

How do acquiescence to intracellular signals transform gene expression?

They trigger specific transcription factors in response to environmental stimuli. Signup and view all the answers

Which of the following statements accurately reflects the role of transcription factors in gene regulation?

Transcription factors may function as either constitutive or inducible depending on the gene. Signup and view all the answers

What is the main consequence of differential splicing in cells?

It allows the production of multiple protein variants from a single gene. Signup and view all the answers

What role does alternative splicing play in tissue specificity during development?

It allows for the creation of distinct proteins that function in specific types of tissues. Signup and view all the answers

What is the primary function of the poly(A) tail in mRNA stability?

To stabilize mRNA and protect it from degradation Signup and view all the answers

What happens to the 3' UTR sequences in mRNA?

They determine the stability of mRNA through destabilizing sequences Signup and view all the answers

What key event triggers the addition of a poly(A) tail to mRNA?

Cleavage of the mRNA at the polyadenylation signal Signup and view all the answers

Which RNA type is primarily responsible for carrying genetic information for protein synthesis?

Messenger RNA (mRNA) Signup and view all the answers

Which process ensures the regulation of mRNA stability over its lifecycle?

The binding of PABP to the poly(A) tail Signup and view all the answers

Which of the following accurately describes the role of introns in mRNA?

Introns must be removed to form mature mRNA Signup and view all the answers

What is the approximate length of the poly(A) tail added to the mRNA 3' end?

40-250 adenine residues Signup and view all the answers

How does the poly(A) tail influence the degradation of mRNA?

It protects mRNA from being targeted by exonucleases Signup and view all the answers

What is the primary mechanism by which microRNA (miRNA) regulates gene expression?

It promotes RNA degradation by binding to complementary sequences. Signup and view all the answers

What percentage of the human genome is known to encode for proteins?

1% Signup and view all the answers

In what way did the ENCODE project change the understanding of non-coding DNA?

It revealed that non-coding DNA plays essential roles in gene regulation. Signup and view all the answers

Which of the following best describes the primary role of non-coding RNAs?

To regulate various cellular processes including gene expression. Signup and view all the answers

What is the typical length of microRNA (miRNA) strands?

20-25 nucleotides Signup and view all the answers

What function do small nuclear RNAs (snRNAs) primarily serve in the cellular processes?

Splicing of pre-mRNA Signup and view all the answers

How do non-coding RNAs influence gene expression?

They play roles in the regulation of transcription and RNA translation. Signup and view all the answers

What is the main reason why microRNAs (miRNAs) are considered non-coding?

They do not translate into proteins. Signup and view all the answers

What is the function of inducible transcription factors?

They are only present when specific environmental cues are detected. Signup and view all the answers

How do steroid receptor transcription factors function in gene expression?

They form homodimers to bind to specific DNA sequences. Signup and view all the answers

What is the primary role of transcription factors in regulating transcription rates?

They determine the number of specific binding sites in a promoter. Signup and view all the answers

What mechanism allows beta cells of the pancreas to respond differently based on fasting or fed states?

Activation of different transcription factors depending on nutrient levels. Signup and view all the answers

What is a consequence of the interaction between transcription factors and chromatin modifiers?

It aids in the unwinding of chromatin to promote transcription. Signup and view all the answers

Which statement correctly describes how transcription factors regulate gene expression?

They interact with RNA polymerase II to initiate transcription. Signup and view all the answers

What is the primary function of mRNA in the context of transcription factors activating genes?

To serve as a temporary carrier of genetic information for translation. Signup and view all the answers

Which of the following processes is affected by the binding of transcription factors to response elements?

The transcription rate of specific genes. Signup and view all the answers

What is the role of small nuclear ribonucleoproteins (snRNPs) during RNA processing?

To facilitate the recognition and interaction with specific intron sequences Signup and view all the answers

Which statement accurately describes the process of splicing as related to the spliceosome?

A specific adenine nucleotide initiates the cleavage of the intron. Signup and view all the answers

What happens to the exons during the splicing process?

Exons bond covalently after intron removal. Signup and view all the answers

In which phase of RNA synthesis are introns spliced out?

After the 5' cap is added but before cytoplasmic transport Signup and view all the answers

Which of the following best describes the composition of the spliceosome?

A large complex consisting of snRNA and proteins Signup and view all the answers

What is formed when the 5' end of the intron becomes attached to a specific adenine nucleotide during splicing?

A splicing loop structure Signup and view all the answers

What is the arrangement of introns and exons in pre-mRNA as it undergoes splicing?

Introns are positioned between exons, disrupting coding sequences Signup and view all the answers

What is one of the key features of small nuclear RNAs (snRNAs) in the context of splicing?

They participate in the formation of snRNPs to aid in splicing. Signup and view all the answers

Study Notes

Ribosomes

Ribosomes are particles important for the synthesis of new proteins
Ribosomes are made up of ribosomal RNA (rRNA) and proteins

RNA and DNA

RNA is a single-stranded nucleic acid that is involved in protein synthesis.
DNA is a double-stranded nucleic acid that contains the genetic code.
Both RNA and DNA contain the nitrogenous bases adenine (A), guanine (G), and cytosine (C).
RNA has the nitrogenous base uracil (U) in place of thymine (T) found in DNA.
RNA has a ribose sugar, while DNA has deoxyribose sugar.

Types of RNA

Messenger RNA (mRNA): carries genetic information from DNA to ribosomes.
Ribosomal RNA (rRNA): forms the core of the ribosome and catalyzes protein synthesis.
Transfer RNA (tRNA): carries amino acids to ribosomes for protein synthesis.
Small nuclear RNA (snRNA): involved in splicing pre-mRNA.
Non-coding RNA (ncRNA): regulate gene expression and other cellular processes.

Transcription

Transcription is the process of copying DNA into RNA.
RNA polymerase II is the enzyme that catalyzes transcription.
Promoter is a region of DNA upstream of the transcription start site (TSS).
Enhancer elements are recognized by proteins that will aid transcription – transcription factors.
The general transcription factors are required for RNA polymerase II binding.
Transcription factors are proteins that bind to specific DNA sequences and regulate transcription.
The transcription process involves initiation, elongation, and termination.
During initiation, RNA polymerase II binds to DNA and unwinds a 17-18 bp segment of the promoter.
During elongation, RNA polymerase II moves along the template synthesizing RNA until it reaches the terminator region.
During termination, a polyadenylation signal sequence is recognized by RNA polymerase II, causing it to dissociate from the DNA.

Post-transcriptional Processing

Post-transcriptional processing is the modification of RNA molecules after transcription.
5' capping is the addition of a 7-methylguanosine residue to the 5' end of mRNA.
3' polyadenylation is the addition of a poly(A) tail to the 3' end of mRNA.
Splicing is the removal of introns from pre-mRNA.
Spliceosome is a molecular machine that carries out splicing.
Alternative splicing allows for the production of multiple proteins from a single gene.

Gene Regulation

Gene regulation is the control of gene expression.
Constitutive genes are expressed continuously.
Inducible genes are expressed only when needed.
Transcription factors can regulate gene expression by binding to DNA and activating or repressing transcription.
MicroRNA (miRNA) is a small non-coding RNA that regulates gene expression.
miRNA can downregulate gene expression by promoting RNA degradation or blocking translation.
Transcription factors can determine tissue specificity by regulating the expression of genes specific to a particular cell type.

ENCODE

The ENCODE project was completed in 2012 and identified that only 1% of the human genome makes protein.
There are other elements required for gene expression such as introns, promoters and enhancers.

RNA Structure and Function

RNA is similar to DNA but has key differences: a ribose sugar instead of deoxyribose, uracil instead of thymine, and a single-stranded structure.
RNA is essential for copying genetic info from DNA and forming ribosomes for protein synthesis.
mRNA (messenger RNA) carries the genetic code for proteins from DNA to ribosomes & is the "photocopy".
rRNA (ribosomal RNA) forms the structure of ribosomes and creates proteins.
tRNA (transfer RNA) transfers amino acids to ribosomes for protein synthesis.

Transcription and Gene Structure

Transcription is the process of creating RNA from a DNA template.
Gene expression is the process of turning a gene into a protein through transcription & translation.
Genes are segments of DNA encoding for proteins.
Genes have a promoter region, which is a DNA sequence that initiates transcription.
Enhancers are DNA sequences that increase transcription rate.
The Transcription Start Site (TSS) marks the beginning of transcription.

Post-Transcriptional RNA Processing

mRNA processing modifies pre-mRNA into mature mRNA before translation.
Introns are non-coding sequences removed from pre-mRNA.
Exons are coding sequences spliced together in mature mRNA.
Polyadenylation adds a "poly-A" tail to the 3' end of mRNA for stability, protecting it from degradation.
Capping adds a 5' cap to the 5' end of mRNA, protecting it from degradation and aiding in ribosome binding.
Alternative splicing allows multiple proteins to be produced from a single gene by splicing exons differently.

Regulation of Gene Expression

Constitutive gene expression occurs continuously, regardless of external factors.
Inducible gene expression is controlled by transcription factors and is responsive to external stimuli.
Transcription factors are proteins that bind to specific DNA regions to regulate transcription.
Transcription factor activity can regulate the rate of transcription.
Non-coding DNA is DNA that does not code for proteins, but plays a crucial role in gene regulation.
MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by blocking translation or promoting degradation.
miRNA binds to target mRNA sequences, preventing protein synthesis.

Other Key Points

ENCODE project revealed the importance of non-coding DNA in regulating gene expression.
Transcription factors can bind to specific DNA sequences, known as response elements, to regulate gene expression.
Chromatin structure can influence gene expression by making DNA more or less accessible to transcription factors.
mRNA stability is influenced by the 3' UTR (untranslated region), which determines the mRNA’s lifespan.

Polyadenylation

3' poly(A) tail is added to 1' transcript after the polyadenylation signal sequence (AAUAAA) is recognised.
Endonuclease cleaves mRNA after polyadenylation signal is recognised.
Poly(A) Polymerase adds ~ 40-250 adenine residues to the cleaved 3’ end.

Post-Transcriptional Regulation

mRNA processing is essential for the mature mRNA molecule to be translated.
mRNA processing involves:
- mRNA stability
- Differential mRNA splicing

mRNA Stability

3’ UTR sequence determines the stability of mRNA.
The 5’ CAP protects against degradation by exonucleases.
Exonucleases will degrade mRNA from the poly A tail.
The poly A tail confers mRNA stability.
Poly-A binding protein (PABP) binds to the poly A tail and stabilises mRNA.
PABP binds approximately 30 residues.
The poly A tail gradually shortens over the lifetime of mRNA.
Once the poly A tail is less than 30bp, PABP no longer binds and the mRNA is degraded.

Splicing of mRNA precursors

Introns are non-coding sequences that are removed from pre-mRNA.
Exons are coding sequences that remain in mature mRNA.
Introns are removed from mRNA during synthesis after the cap is added, but before the transcript is transported into the cytoplasm.
Introns vary in size from 50 to 10,000 nucleotides.

The Spliceosome

Splicing is carried out by a molecular machine called the spliceosome.
The spliceosome is a complex structure made from RNA and protein.
Small nuclear RNAs (snRNA) combine with proteins to form snRNPs (small nuclear ribonucleoproteins).
snRNPs facilitate splicing by recognising and interacting with specific sequences at each end of the intron.

Differential Splicing

Differential splicing allows for the production of multiple proteins from a single gene.
Different cell types can express different isoforms of the same protein.
The example of calcitonin processing illustrates this:
- Calcitonin is produced in the thyroid and acts as a hormone.
- cGRP (Calcitonin gene-related peptide) is produced in the brain and acts as a neurotransmitter.

Inducible Gene Expression

Inducible gene expression allows cells to respond to environmental cues.
Inducible transcription factors are only turned on when necessary.
Inducible transcription factors determine tissue specificity.

Tissue Specificity

Stem cells differentiate into different cell types through the expression of specific transcription factors.

Constitutive Gene Expression

Constitutive genes are always expressed and are required for essential life processes.
Examples include genes involved in metabolism, DNA repair, transcription and translation.

Inducible Gene Expression

Inducible genes are only expressed when required.
Inducible gene expression:
- Is controlled by transcription factors.
- Allows cells to respond to external cues such as hormones, cytokines, and cell-cell interactions.

Transcription Factors

Transcription factors regulate the rate of transcription by:
- Binding to specific DNA sequences (response elements).
- Interacting with RNA polymerase II to promote transcription.
- Bringing in chromatin modifiers to aid unwinding.
- Bringing in coactivators.

Regulation of Gene Expression by MicroRNA (miRNA)

miRNA are small, non-coding RNA molecules (20-25 nucleotides) that regulate gene expression.
miRNA are transcribed from DNA but don't encode proteins.
miRNA are partially complementary to mRNA.
miRNA bind to specific mRNA sequences and downregulate gene expression.

Mechanisms of miRNA Activity

miRNA can block gene expression in two ways:
- Promotion of RNA degradation: miRNA binds to complementary sequences in the 3’UTR of mRNA and induces degradation.
- Blocking of translation: miRNA binds to mRNA and blocks translation.

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Description

Test your knowledge on the roles and structures of RNA, DNA, and ribosomes in protein synthesis. This quiz covers the differences between RNA and DNA as well as the various types of RNA involved in genetic processes. Dive into the fascinating world of molecular biology and see how well you understand these essential biomolecules.