Gene Expression and RNA Function Quiz : Biology Unit 3

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Questions and Answers

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

To splice introns from pre-mRNA

To catalyze peptide bond formation between amino acids

To synthesize proteins directly from DNA

To carry genetic information from DNA to the ribosome (correct)

Which of the following describes the elongation phase of transcription?

RNA polymerase moves along the DNA and adds ribonucleotides complementary to the template strand (correct)

RNA synthesis begins with the formation of a hairpin structure

RNA polymerase binds to the promoter region of a gene

RNA polymerase synthesizes RNA in the 3’ to 5’ direction

What occurs during the initiation phase of transcription?

Ribonucleotides are added to the growing RNA strand

The sigma subunit helps RNA polymerase position at the transcription start site (correct)

RNA polymerase forms a hairpin structure

The DNA double helix is unwound

Which type of RNA forms the core structure of ribosomes?

Ribosomal RNA (rRNA) Signup and view all the answers

What is the result of RNA polymerase reaching a terminator sequence during transcription?

Synthesis of the mRNA ends Signup and view all the answers

How does transfer RNA (tRNA) function during translation?

It reads mRNA and brings the correct amino acids to the ribosome Signup and view all the answers

What is the role of small nuclear RNA (snRNA) in eukaryotic cells?

Splices pre-mRNA by removing introns Signup and view all the answers

Which of the following statements about RNA synthesis is true?

Uracil replaces thymine in RNA during synthesis Signup and view all the answers

What is the function of codons in mRNA?

They determine the sequence of amino acids during translation. Signup and view all the answers

How many possible codons exist, and what is their redundancy in relation to amino acids?

64 codons are available, but only 20 amino acids result from them, indicating redundancy. Signup and view all the answers

What is the start codon, and what amino acid does it specify?

AUG, specifying methionine. Signup and view all the answers

What type of molecule can recognize multiple codons due to wobble pairing?

tRNA Signup and view all the answers

Which statement accurately describes the role of the small ribosomal subunit during the initiation of translation in eukaryotes?

It binds directly to the 5’ cap of the mRNA to find the start codon. Signup and view all the answers

During the elongation phase of translation, how does the ribosome move along the mRNA?

In the 5’ to 3’ direction, aligning codons with incoming tRNA. Signup and view all the answers

Which of the following codons are stop codons that signal the termination of translation?

UAA, UAG, UGA Signup and view all the answers

What occurs during the initiation phase of translation in prokaryotes?

The small ribosomal subunit binds to the ribosome-binding sequence. Signup and view all the answers

What happens during prometaphase of mitosis?

The nuclear envelope fully breaks down. Signup and view all the answers

Which checkpoint assesses DNA damage and completion of DNA replication?

G2/M checkpoint Signup and view all the answers

What is one role of the spindle checkpoint during mitosis?

To ensure all chromosomes are aligned at the metaphase plate. Signup and view all the answers

Which phase of mitosis involves sister chromatids being pulled apart Toward opposite poles?

Anaphase Signup and view all the answers

During which phase do chromosomes condense and the mitotic spindle form?

Prophase Signup and view all the answers

What is a critical function of the G1/S checkpoint?

To evaluate the availability of nutrients and growth factors. Signup and view all the answers

Which of the following occurs during telophase?

The nuclear envelope reforms around separated chromosomes. Signup and view all the answers

What is the outcome of cytokinesis?

The cytoplasm is divided between two daughter cells. Signup and view all the answers

What is the primary way gene expression is commonly controlled?

Through transcriptional regulation Signup and view all the answers

Where does transcriptional regulation commonly occur in the DNA?

At the promoter region Signup and view all the answers

What role do activators play in positive control of transcription?

They enhance the binding of RNA polymerase to the promoter. Signup and view all the answers

In prokaryotes, how can multiple genes be controlled simultaneously?

By having a single promoter regulate an operon Signup and view all the answers

What is the function of a repressor in negative control of transcription?

To bind to the operator and prevent transcription Signup and view all the answers

Which protein serves as an activator in the lac operon?

CAP protein Signup and view all the answers

What happens if the core promoter region is altered?

RNA polymerase cannot bind and transcription halts Signup and view all the answers

Which scenario exemplifies negative control in the lac operon?

Lac repressor binds in the absence of lactose Signup and view all the answers

What is one way that mutations can positively influence a species?

By enhancing genetic variation necessary for evolution Signup and view all the answers

In eukaryotes, how many promoter sequences does each gene typically have?

One promoter per gene Signup and view all the answers

What does genomic imprinting involve?

Selective inactivation of genes based on whether they are inherited from the mother or father. Signup and view all the answers

What is the consequence of mitochondrial DNA being inherited only from the mother?

All offspring of an affected mother will inherit the mitochondrial trait. Signup and view all the answers

In chloroplast DNA inheritance, which pattern is most commonly observed in plants?

Maternal inheritance, receiving chloroplast traits from the mother. Signup and view all the answers

Which statement best describes maternal imprinting?

The maternal copy of the gene is inactivated, allowing the paternal copy to be expressed. Signup and view all the answers

Why do males with mitochondrial traits not pass them on to their children?

Mitochondria are inherited exclusively from the egg cell. Signup and view all the answers

What is the purpose of dosage compensation in genetics?

To balance gene expression on the X chromosome between sexes. Signup and view all the answers

What is one potential variation in chloroplast inheritance among plant species?

Chloroplasts may be inherited solely from the father in some species. Signup and view all the answers

What genetic condition is characterized by an extra Y chromosome in males?

Jacob's Syndrome Signup and view all the answers

Which of the following is NOT an advantage of genetic testing?

Risk of miscarriage during testing Signup and view all the answers

When can amniocentesis typically be performed during pregnancy?

Around the fourth month Signup and view all the answers

What is a key disadvantage of Chorionic Villi Sampling (CVS)?

Higher risk of miscarriage compared to other methods Signup and view all the answers

What ethical consideration may arise from the knowledge of carrying genetic mutations?

Potential emotional and ethical dilemmas Signup and view all the answers

Which method of genetic testing allows for identification of fetal genetic abnormalities?

Amniocentesis Signup and view all the answers

What is one potential risk associated with genetic testing?

Risk of emotional distress and ethical decisions Signup and view all the answers

How can genetic testing be beneficial in the context of personalized medicine?

It helps tailor treatment options for individuals based on genetic makeup Signup and view all the answers

Study Notes

Gene Expression Overview

Transcription is the process of synthesizing RNA from a DNA template strand; RNA polymerase is the enzyme.
Translation is the process of synthesizing proteins from an mRNA template; ribosomes and tRNA are involved.
Transcription occurs in the nucleus of eukaryotic cells and the cytoplasm of prokaryotic cells.
Messenger RNA (mRNA) carries the genetic code from DNA to ribosomes for protein synthesis.
Ribosomal RNA (rRNA) forms the core of ribosomes and catalyzes peptide bond formation during protein synthesis.
Transfer RNA (tRNA) reads mRNA and brings the correct amino acids to the ribosome.
Small nuclear RNA (snRNA) splices pre-mRNA in eukaryotic cells.
MicroRNA (miRNA) regulates gene expression by inhibiting translation or promoting mRNA degradation.

Transcription

Initiation: RNA polymerase binds to a promoter region. Sigma helps position RNA polymerase at the initiation site (+1). RNA polymerase unwinds the DNA double helix and starts synthesizing RNA with a complementary nucleotide.
Elongation: RNA polymerase moves along the template strand, synthesizing RNA in the 5' to 3' direction. It adds ribonucleotides complementary to the DNA template.
Termination: RNA polymerase reaches a terminator sequence. The RNA forms a hairpin structure, causing the RNA polymerase to pause. RNA polymerase dissociates from the DNA template, releasing the mRNA.

Eukaryotic vs. Prokaryotic Transcription

Eukaryotes have multiple types of RNA polymerase, while prokaryotes have only one.
Eukaryotic promoters are more complex than prokaryotic promoters, requiring transcription factors.
RNA polymerase can bind directly to promoter sequences in prokaryotes with the help of a sigma factor.
Eukaryotes modify their primary transcripts (pre-mRNA) before translation, including 5' capping and 3' polyadenylation, and intron removal.
Eukaryotic transcripts require processing (splicing) to remove introns before exporting it to the cytoplasm.

RNA Processing in Eukaryotes

Primary transcripts (pre-mRNA) undergo extensive processing.
Addition of a 5' cap protects mRNA from degradation and aids in ribosome binding.
Addition of a 3' poly(A) tail also protects the transcript from degradation.
Removal of non-coding sequences (introns) is accomplished by splicing.
Alternative splicing allows a single gene to produce multiple mRNA variants.

Translation

Initiation: Small ribosomal subunit binds to the ribosome-binding sequence (RBS) and the first initiator tRNA. The large subunit joins, forming the initiation complex.
Elongation: New tRNA molecules (carrying amino acids) enter the A-site. A peptide bond forms between the amino acids. The ribosome moves along the mRNA, shifting the tRNA from the A-site to the P-site, and the tRNA in the P-site to the E-site before exiting.
Termination: The ribosome encounters a stop codon. A release factor protein binds to the stop codon at the A-site. The polypeptide chain is released, and the ribosome disassembles.

Gene Expression, Phenotype & Mutations

Mutations are changes in the DNA sequence.
Point mutations (substitutions): A silent mutation has no effect. A missense mutation causes a different amino acid. A nonsense mutation introduces a premature stop codon.
Frameshift mutations (insertions/deletions): Cause a change in the reading frame of the gene.
Chromosomal mutations involve larger segments of the chromosome.
Genetic modifications alter gene expression without altering the DNA sequence itself.

Cell Reproduction (Mitosis & Meiosis)

Mitosis produces two genetically identical diploid daughter cells for growth, repair and asexual reproduction.
Meiosis produces four genetically diverse haploid daughter cells for sexual reproduction.

Cell Cycle

Interphase: G1 (growth), S (synthesis), G2 (growth).
M phase: Mitosis and cytokinesis.

Cell Cycle Checkpoints

G1/S checkpoint: Checks for sufficient nutrients and growth factors, and whether the cell has grown large enough.
G2/M checkpoint: Ensures DNA replication is complete and checks for DNA damage.
Spindle checkpoint: Ensures all chromosomes are properly aligned at the metaphase plate and attached to spindle fibers.

Non-Mendelian Inheritance

Multiple alleles, codominance, incomplete dominance, polygenic inheritance, pleiotropy, sex-linked traits, X-inactivation, genomic imprinting, and mitochondrial inheritance are examples of non-Mendelian inheritance patterns, in which patterns of inheritance do not follow simple dominant-recessive relationships based on traits like blood type (ABO, Rh), eye color.
Traits influenced by both genetics and the environment (phenotypes).

Genetic Disorders

Mutations can lead to genetic disorders.
Nondisjunction during meiosis leads to aneuploidy (abnormal chromosome number).
Examples include Down syndrome (trisomy 21), Turner syndrome (XO), and Klinefelter syndrome (XXY).

Genetic Testing

Early diagnosis and risk assessment for genetic diseases.
Amniocentesis and chorionic villus sampling (CVS) enable in-utero genetic testing.

Genetic Recombination and Linkage Analysis

Crossing over during meiosis leads to genetic recombination.
Linked genes are located close together on chromosomes and tend to be inherited together.

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Description

Test your knowledge on the roles of different types of RNA in gene expression and translation. This quiz covers key concepts such as mRNA function, transcription phases, and the significance of codons. Perfect for students studying molecular biology or genetics.