Biochem 9: The Central Dogma

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Which bond contributes to the stability of the DNA helix?

Ionic interactions
Phosphodiester bond
Hydrophobic interactions
H-bonds (correct)

What is the structural unit for packaging DNA?

Nucleosome (correct)
Histone core
H-bond
Phosphodiester bond

What is the name of the DNA packaging complex composed of DNA and tightly bound proteins?

Heterochromatin
Nucleosome
Euchromatin
Chromatin (correct)

Which form of chromatin is found when the cell is transcriptionally active?

Euchromatin (C) Signup and view all the answers

How many pairs of chromosomes do most human cells have?

23 (B) Signup and view all the answers

What are the maternal and paternal chromosome pair called?

Homologous chromosomes (D) Signup and view all the answers

What is the name for the functional units of heredity?

Genes (A) Signup and view all the answers

What is the name of the non-coding sequence of a gene that is removed during splicing?

Intron (B) Signup and view all the answers

What percentage of the human genome does not encode protein?

98.5% (C) Signup and view all the answers

Which biomolecule is the basis for nucleic acid?

Nucleotide (C) Signup and view all the answers

What are the 3 components of a nucleotide?

Sugar, phosphate, and nitrogenous base (B) Signup and view all the answers

Which of the 4 bases are purines?

Adenine and guanine (D) Signup and view all the answers

Which of the 4 bases are pyrimidines?

Thymine and cytosine (A) Signup and view all the answers

Why does A always pair with T & G always pair with C?

It is determined by hydrogen bonding (B) Signup and view all the answers

Chargaff’s rule states that the number of purines must equal the number of pyrimidines. Why is this necessary to maintain the DNA double helix?

To ensure stability of the DNA molecule (C) Signup and view all the answers

What forces are needed to stabilize the DNA double helix?

Hydrogen bonds between bases (C) Signup and view all the answers

What is the structure of DNA?

Double helix (B) Signup and view all the answers

How many base pairs are there in one complete turn of the DNA double helix?

10 (B) Signup and view all the answers

What is the role of RNA in the central dogma of molecular biology?

Act as an intermediate between DNA and protein synthesis (B) Signup and view all the answers

Which of the following is NOT a chemical difference between RNA and DNA?

Double-stranded helix structure (C) Signup and view all the answers

Which type of RNA serves as a template for protein translation?

mRNA (A) Signup and view all the answers

What is the term for the RNA molecule initially transcribed from DNA?

Pre-mRNA (C) Signup and view all the answers

Which type of non-coding RNA is involved in splicing?

snRNA (D) Signup and view all the answers

Which type of RNA is needed for the basic structure of the ribosome complex?

rRNA (D) Signup and view all the answers

What is the general term for RNA that serves as enzymatic, structural, and regulatory components in the cell?

Non-coding RNA (D) Signup and view all the answers

Which type of RNA forms small nuclear ribonucleoproteins (snRNPs) in the spliceosome?

snRNA (C) Signup and view all the answers

Which of the following RNA molecules is involved in catalyzing the peptide bond between amino acids?

rRNA (D) Signup and view all the answers

What is the term for the process of removing introns from pre-mRNA?

Splicing (C) Signup and view all the answers

Which of the following is NOT a structural difference between RNA and DNA?

Adenine, guanine, and cytosine content (D) Signup and view all the answers

Which type of RNA molecule is responsible for carrying the correct amino acid to the growing polypeptide chain during translation?

tRNA (D) Signup and view all the answers

What is the function of the anticodon region in tRNA?

It pairs with the complementary codon in an mRNA molecule (D) Signup and view all the answers

Which hypothesis explains why there are only 20 amino acids despite 64 possible combinations of nucleotides in a 3 nucleotide codon?

Wobble hypothesis (B) Signup and view all the answers

Which region of the tRNA molecule binds the amino acid that corresponds to the anticodon?

Amino acid binding site (D) Signup and view all the answers

Which type of RNA molecule regulates gene expression by blocking translation of specific mRNAs and promoting their degradation?

miRNA (C) Signup and view all the answers

Which type of RNA molecule reduces gene expression by directly degrading specific mRNA molecules?

siRNA (D) Signup and view all the answers

Which type of RNA molecule can increase or decrease transcription and is involved in X-chromosome inactivation?

lncRNA (D) Signup and view all the answers

Which type of RNA molecule is an adaptor between mRNA and amino acids and is involved in splicing of pre-mRNA?

snRNA (C) Signup and view all the answers

Which type of RNA molecule codes for proteins?

mRNA (C) Signup and view all the answers

Which type of RNA molecule is an important constituent of ribosomes and catalyzes protein synthesis?

rRNA (C) Signup and view all the answers

Which enzyme is responsible for transcription?

RNA polymerase (C) Signup and view all the answers

What is the direction in which RNA polymerase moves during transcription?

5' to 3' (B) Signup and view all the answers

Which region of a gene contains the consensus sequence and specifies the start of transcription?

Promoter region (C) Signup and view all the answers

What is the role of transcription initiation factors in the process of transcription?

They help RNA polymerase recognize the template strand (B) Signup and view all the answers

What are the three main stages of transcription?

Initiation, elongation, termination (C) Signup and view all the answers

Which of the following is NOT a processing step during transcription in eukaryotes?

Polymerization of RNA (B) Signup and view all the answers

Which enzyme is responsible for synthesizing an RNA molecule from a DNA template during transcription?

RNA polymerase (C) Signup and view all the answers

What are the steps of transcription in the correct order?

Initiation, elongation, processing, termination (C) Signup and view all the answers

Which type of RNA molecule carries the correct amino acid to the growing polypeptide chain during translation?

tRNA (C) Signup and view all the answers

What are the steps of translation in the correct order?

Initiation, elongation, termination (D) Signup and view all the answers

Which molecule is responsible for catalyzing the peptide bond between amino acids during translation?

rRNA (A) Signup and view all the answers

How are proteins targeted to a cellular location during translation?

By signal sequences (D) Signup and view all the answers

What is the function of the Shine-Dalgarno sequence?

Needed in binding initiation of small ribosomal subunit (D) Signup and view all the answers

Which of the following is NOT a role of elongation factors in translation?

Binding to the stop codon (D) Signup and view all the answers

What happens during termination in translation?

All of the above (D) Signup and view all the answers

What is the first amino acid added to any polypeptide?

Methionine (C) Signup and view all the answers

Which of the following describes the correct order of translation initiation in eukaryotes?

Small ribosomal subunit binds to the 5’ cap and scans the mRNA until it reaches AUG, then Met-tRNAi binds to the P site (B) Signup and view all the answers

During transcription, which of the following proteins bind the TATA box within the promoter region?

TFII D (C) Signup and view all the answers

Which of the following are CORRECT regarding RNA processing?

Splicing is catalyzed by snRNA and proteins complexed into snRNPs (D) Signup and view all the answers

What might happen if a nucleotide was accidentally inserted into the middle of a gene?

The gene would produce a completely different protein (B) Signup and view all the answers

Which of the following is TRUE about the mRNA transcript produced in prokaryotes?

It can begin translation right away (C) Signup and view all the answers

What is the role of the 5’ cap in mRNA processing?

It is involved in translation (C) Signup and view all the answers

What is the role of the Poly A tail in mRNA processing?

It protects the 3’ end of the mRNA from degradation (B) Signup and view all the answers

Which of the following is true about protein synthesis in prokaryotes?

The small ribosomal subunit binds to the Shine Dalgarno sequence (C) Signup and view all the answers

Which of the following is true about protein synthesis in eukaryotes?

The small ribosomal subunit binds to the 5' cap and scans the mRNA until it reaches the start codon (D) Signup and view all the answers

What happens after a protein is fully translated?

All of the above (D) Signup and view all the answers

What is the role of polysomes in protein synthesis?

To speed up the rate of protein synthesis (C) Signup and view all the answers

Which of the following is a clinical application of understanding protein synthesis?

All of the above (D) Signup and view all the answers

What is the purpose of the Shine Dalgarno sequence in prokaryotic protein synthesis?

To bind the small ribosomal subunit to the mRNA (C) Signup and view all the answers

Which of the following is NOT a way a cell can regulate the amount of a particular protein available to a cell?

Location of the protein (C) Signup and view all the answers

Which of the following is true about histone acetylation?

It is carried out by histone acetyltransferases (HAT) (D) Signup and view all the answers

What is the function of histone methylation?

It promotes transcriptional activation (B) Signup and view all the answers

Which of the following is NOT a way mRNA stability can be regulated?

Histone modification can stabilize mRNA (B) Signup and view all the answers

What is the relationship between the stability of mRNA and protein synthesis?

The longer an mRNA lasts in the cytosol, the more protein will be made (C) Signup and view all the answers

What is the role of chromatin remodeling complexes in transcription regulation?

They reposition nucleosomes on DNA (D) Signup and view all the answers

What is the role of histone modifications in transcription regulation?

They increase transcription (D) Signup and view all the answers

Which of the following is true about DNA methylation?

It typically results in transcriptional silencing (A) Signup and view all the answers

What is the function of non-coding forms of RNA, such as miRNA or siRNA?

They promote mRNA destruction (B) Signup and view all the answers

Which of the following is true about histones?

They are highly dynamic structures regulated by nuclear proteins (A) Signup and view all the answers

Which of the following is false about targeting proteins to the rough ER for translation?

Translation of proteins destined for the rough ER occurs in the mitochondria. (A) Signup and view all the answers

What happens when a protein containing a stop transfer sequence comes into contact with the translocator during translation?

Translation is paused and the translocator discharges the polypeptide into the cytosol. (B) Signup and view all the answers

Which of the following is true about the amino acids in the stop transfer sequence?

They are nonpolar. (C) Signup and view all the answers

Which region of the tRNA molecule binds the amino acid that corresponds to the anticodon?

Acceptor stem (B) Signup and view all the answers

What is the function of the signal recognition particle (SRP) in protein targeting to the rough ER?

To direct the ribosome to the rough ER (A) Signup and view all the answers

Which of the following is true about the targeting of proteins to the nucleus, mitochondria, or peroxisomes during translation?

Proteins are translated on free ribosomes in the cytosol. (A) Signup and view all the answers

What is the role of the stop transfer sequence in protein targeting during translation?

To pause translation (C) Signup and view all the answers

Which of the following is true about the targeting of proteins to lysosomes, ER, cell membrane, or secretion during translation?

A signal peptide sequence is translated, which binds a signal recognition particle (SRP). (B) Signup and view all the answers

Match the events of translation to the steps they occurs in:

Initiation = AUG (methionine) marks the start of the codon and the small ribosomal units bind with a 5' end of mRNA Elongation = tRNA binding, Peptide bond formation, Large subunit translocation, Small subunit translocation Termination = Stop codons UAA, UAG, UGA marks the end of a peptide, peptidyl transferase catalyzes the reaction with water releasing the COOH group Translation = The mRNA has been brought out of the nucleus and into the cytosol where protein synthesis can occur Signup and view all the answers

DNA Helix Stability

Hydrogen bonds stabilize the DNA double helix.

Nucleosome

The structural unit for packaging DNA.