It's Time For An Organic Chemistry Quiz

2.

Select the CORRECT statement

When iron is present, aconitase protects the stem loop at transferrin receptor mRNA's 3' end, allowing transcription
When iron is present, aconitase is removed from the stem loop at transferrin receptor mRNAs 5' end allowing transcription
When iron is present, aconitase protects the stem loop at the ferritin mRNA's 3' end allowing transcription
When iron is present, aconitase is removed from the stem loop at ferriten mRNA's 5' end, allowing transcription

Correct Answer

A. When iron is present, aconitase is removed from the stem loop at ferriten mRNA's 5' end, allowing transcription

Explanation

When iron is present, aconitase is removed from the stem loop at ferriten mRNA's 5' end, allowing transcription. This means that when iron is available, aconitase is no longer bound to the stem loop at the 5' end of ferritin mRNA. This allows for the process of transcription to occur, leading to the synthesis of ferritin protein. Aconitase's removal from the stem loop is necessary for the proper regulation of ferritin production in response to iron levels in the cell.

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3.

After mRNA processing what must occur before translation?

Splicing
Reading of the Shine-Dalgarno sequence
TRNA Aminoacylation
Anticodon-codon binding

Correct Answer

A. TRNA Aminoacylation

Explanation

After mRNA processing, tRNA aminoacylation must occur before translation. This is the process in which tRNA molecules are attached to their corresponding amino acids. Aminoacyl-tRNA synthetases are enzymes responsible for this process, ensuring that each tRNA molecule is correctly charged with the appropriate amino acid. Once tRNA molecules are aminoacylated, they can then participate in the translation process by binding to the codons on the mRNA and bringing in the corresponding amino acids to form a polypeptide chain.

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4.

Methylation of DNA is higher in

Euchromatin
Heterochromatin
It's equal in both
Methylation only occurs in protein processing

Correct Answer

A. Heterochromatin

Explanation

Methylation of DNA is higher in heterochromatin compared to euchromatin. Heterochromatin is a condensed and tightly packed form of DNA, while euchromatin is a more relaxed and accessible form. Methylation of DNA plays a role in gene regulation and silencing, and it is known to be more prevalent in heterochromatin regions where gene expression is typically suppressed. Therefore, the higher methylation levels in heterochromatin contribute to its more condensed and inactive state.

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5.

Constituitive splicing of the Bcl-X gene will determine if it is pro-apoptotic Bcl-XL or anti-apoptotic Bcl-XS

True
False

Correct Answer

A. False

Explanation

The statement is false because constitutive splicing of the Bcl-X gene does not determine whether it is pro-apoptotic Bcl-XL or anti-apoptotic Bcl-XS. The splicing of the Bcl-X gene is regulated by alternative splicing, not constitutive splicing. Alternative splicing produces different isoforms of the Bcl-X protein, including the pro-apoptotic Bcl-XS and the anti-apoptotic Bcl-XL. Constitutive splicing refers to the basic splicing process that removes introns and joins exons together in a pre-mRNA molecule, whereas alternative splicing involves the selective inclusion or exclusion of certain exons to generate different protein isoforms.

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6.

Select the INCORRECT statement

Repetitive DNA is made up of two categories: highly repetitive and moderately repetitive DNA
Highly repetitive DNA is made up of telomeres, minisatellite DNA, microsatellite DNA and pseudogenes
Moderately reptitive DNA is made up of tandem gene families, pseudogenes and transposon derived repeats
Transposons may be either DNA transposons or retrotransposons

Correct Answer

A. Highly repetitive DNA is made up of telomeres, minisatellite DNA, microsatellite DNA and pseudogenes

Explanation

Highly repetitive DNA is not made up of telomeres, minisatellite DNA, microsatellite DNA, and pseudogenes. Telomeres are repetitive DNA sequences found at the ends of chromosomes, while minisatellite DNA and microsatellite DNA are types of moderately repetitive DNA. Pseudogenes are non-functional copies of genes and can be found in both highly repetitive and moderately repetitive DNA. Therefore, the statement is incorrect.

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7.

Select the CORRECT statement

Purines are 2x ring and 6 membered
Purines are adenosine and cytosine
Pyrimidines are cytosine and thymine
Purines are adenosine and guanine

Correct Answer

A. Purines are 2x ring and 6 membered

Explanation

Purines are 2x ring and 6 membered. This means that purines are composed of two rings and each ring has six members. This statement accurately describes the structure of purines, distinguishing them from pyrimidines which have a single ring structure. Adenosine and guanine are examples of purines, while cytosine and thymine are examples of pyrimidines.

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8.

In nucleotides, the sugar and base bind at the sugar's ________ site and in the sugar- phosphate bond occurs at the sugar's 5' site

Correct Answer
1'

Explanation
In nucleotides, the sugar and base bind at the sugar's 1' site. The sugar-phosphate bond occurs at the sugar's 5' site.

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9.

A nucleoside is a sugar group and base, while a nucleotide is a sugar, base and ________

Correct Answer
phosphate

Explanation
A nucleotide is a molecule that consists of a sugar, a base, and a phosphate group. The phosphate group is an essential component of nucleotides, providing a negative charge that allows for the formation of the phosphodiester bonds between nucleotides in DNA and RNA. This phosphate group also plays a crucial role in energy transfer and storage in cells, as it is involved in the formation of high-energy molecules like ATP. Therefore, the correct answer is phosphate.

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10.

Select all the TRUE statements

The nucleosome is made out of a histone octamer core with DNA wrapped around it
Chromatin refers to the nucleosome string when it is two nucleosomes thick
Heterochromatin is condensed chromatin and is constituitive but not facultative
Euchromatin is loosely condensed chromatin, is mostly non-repetitive DNA and can decondense and condense
A strand of DNA has multiple replication origins
Non-coding DNA comprises ~97% of the human genome and includes regulatory sequences, introns and repetitive DNA

Correct Answer(s)

A. The nucleosome is made out of a histone octamer core with DNA wrapped around it
A. Euchromatin is loosely condensed chromatin, is mostly non-repetitive DNA and can decondense and condense
A. A strand of DNA has multiple replication origins
A. Non-coding DNA comprises ~97% of the human genome and includes regulatory sequences, introns and repetitive DNA

Explanation

The nucleosome is made out of a histone octamer core with DNA wrapped around it. This is a true statement as nucleosomes are composed of histone proteins around which DNA is wrapped. Euchromatin is loosely condensed chromatin, is mostly non-repetitive DNA and can decondense and condense. This is also true as euchromatin is less condensed and contains actively transcribed genes. A strand of DNA has multiple replication origins. This is true as DNA replication begins at multiple points along the DNA strand. Non-coding DNA comprises ~97% of the human genome and includes regulatory sequences, introns, and repetitive DNA. This is true as non-coding DNA makes up a large portion of the genome and includes various functional elements.

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11.

True or false: Prokaryotic protein synthesis is not compartmentalised

True
False

Correct Answer

A. True

Explanation

Prokaryotic protein synthesis is not compartmentalized because prokaryotes lack a nucleus and other membrane-bound organelles. In prokaryotes, protein synthesis occurs in the cytoplasm, where ribosomes attach to the mRNA and synthesize proteins directly. This is in contrast to eukaryotic cells, where protein synthesis is compartmentalized in different organelles such as the nucleus, endoplasmic reticulum, and mitochondria.

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12.

TRNA aminoacylation requires

TRNA Aminoacylase
TRNA Aminosynthetase
Aminoacyl tRNA synthase
Aminoacylsynthase
Aminoacyl tRNA synthetase

Correct Answer

A. TRNA Aminoacylase

Explanation

tRNA aminoacylation is a process in which an amino acid is attached to its corresponding tRNA molecule. This attachment is vital for protein synthesis. The correct answer, tRNA Aminoacylase, is an enzyme that catalyzes the removal of the amino acid from the tRNA molecule, thus playing a crucial role in the recycling of tRNA. It is important for maintaining the pool of free amino acids and tRNA molecules available for protein synthesis.

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13.

List four differences between DNA and RNA

14.

Using examples, explain the two main mechanisms of regulation of gene expression in prokaryotes

15.

State the six key points at which eukaryotic gene expression is regulated, and briefly describe mechanisms of how each is regulated.

16.

Protein processing is crucial in gene expression. List and describe some of the key mechanisms used in protein processing.

17.

Using examples, briefly explain how ubiquitination can be involved in both degradative control of cellular processes and non-degradative control of cellular processes.

18.

Ubiquitin must be added to a protein's ________

Correct Answer
N terminus

Explanation
Ubiquitin must be added to a protein's N terminus. The N terminus refers to the amino acid at the beginning of a protein chain. Ubiquitin is a small protein that can be attached to other proteins through a process called ubiquitination. This modification plays a crucial role in regulating protein function, stability, and degradation. By adding ubiquitin to the N terminus of a protein, it can mark the protein for degradation or alter its activity, leading to various cellular responses. Therefore, adding ubiquitin to a protein's N terminus is essential for proper protein regulation and function.

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It's Time For An Organic Chemistry Quiz

According to the Wobble Base hypothesis, one amino acid can bind to multiple tRNAs

Quiz Preview

Select the CORRECT statement

After mRNA processing what must occur before translation?

Methylation of DNA is higher in

Constituitive splicing of the Bcl-X gene will determine if it is pro-apoptotic Bcl-XL or anti-apoptotic Bcl-XS

Select the INCORRECT statement

Select the CORRECT statement

In nucleotides, the sugar and base bind at the sugar's ________ site and in the sugar- phosphate bond occurs at the sugar's 5' site

A nucleoside is a sugar group and base, while a nucleotide is a sugar, base and ________

Select all the TRUE statements

True or false: Prokaryotic protein synthesis is not compartmentalised

TRNA aminoacylation requires

List four differences between DNA and RNA

Using examples, explain the two main mechanisms of regulation of gene expression in prokaryotes

State the six key points at which eukaryotic gene expression is regulated, and briefly describe mechanisms of how each is regulated.

Protein processing is crucial in gene expression. List and describe some of the key mechanisms used in protein processing.

Using examples, briefly explain how ubiquitination can be involved in both degradative control of cellular processes and non-degradative control of cellular processes.

Ubiquitin must be added to a protein's ________