Question 1

Over time, DNA replaced RNA as the primary carrier of genetic information, and the chemical stability of DNA is believed to be the key reason for this. Which attribute of DNA is the reason behind its chemical stability?

Accepted Answer

The absence of a free hydroxyl group on the 2'-carbon atom of DNA's sugar makes it less reactive and more chemically stable compared to RNA, which has a hydroxyl group at this position.

Question 2

Whereas the nucleotide strand used for transcription is termed the _____, the nontranscribed strand is called the _____.

Accepted Answer

The nucleotide strand used for transcription is called the template strand, while the nontranscribed strand is referred to as the nontemplate strand.

Question 3

The discovery of ribozymes led to the theory that the evolution of life on Earth began with an "RNA world." Describe the chemical properties and functions of RNA that would allow it to be the basis of the first self-replicating systems.

Accepted Answer

RNA, or ribonucleic acid, has several chemical properties and functions that make it a plausible candidate for the basis of the first self-replicating systems in an "RNA world" scenario.

Firstly, RNA is capable of both storing genetic information and catalyzing chemical reactions. This dual functionality is crucial for self-replication, as it allows RNA molecules to not only carry the instructions for their own replication but also to catalyze the chemical reactions necessary for that replication to occur.

Additionally, RNA can form complex three-dimensional structures, allowing it to interact with other molecules and perform specific functions. This structural versatility would have been essential for early self-replicating systems to carry out a wide range of biochemical processes.

Furthermore, RNA is more chemically versatile than DNA, which suggests that it may have been better suited for the diverse roles required in early life forms. For example, RNA can act as a template for protein synthesis, as well as catalyze a variety of biochemical reactions.

Overall, the chemical properties and functions of RNA, including its ability to store genetic information, catalyze reactions, form complex structures, and interact with other molecules, make it a compelling candidate for the basis of the first self-replicating systems in an "RNA world" scenario. Its versatility and adaptability would have allowed for the emergence and evolution of early life on Earth.

Question 4

In eukaryotes, tRNAs are transcribed in:

Accepted Answer

In eukaryotes, tRNAs are transcribed in the nucleus and then transported to the cytoplasm where they function in protein synthesis.

Question 5

In a transcription reaction, two phosphate groups are cleaved from the incoming:

Accepted Answer

In transcription, ribonucleoside triphosphates (NTPs) are used as substrates, and two phosphate groups are cleaved off to provide the energy for the formation of the phosphodiester bond in RNA synthesis.

Question 6

Where are promoters usually located?

Accepted Answer

Promoters are typically located upstream of the start site of transcription, where they serve as binding sites for RNA polymerase and other transcription factors to initiate transcription.

Question 7

Which of the following is a sequence of DNA where transcription is initiated?

Accepted Answer

The promoter is a sequence of DNA where RNA polymerase binds to initiate transcription.

Question 8

Which of the following statements is NOT true?

Accepted Answer

The answer of Which of the following statements is NOT...

Question 9

What types of bonds are created between nucleotides during the process of transcription?

Accepted Answer

The answer of What types of bonds are created between...

Question 10

Which of the following types of RNA gets translated?

Accepted Answer

mRNA is the only type of RNA that gets translated into protein.

Question 11

_____ probably began the evolution of life on Earth.

Accepted Answer

Ribozymes, which are RNA molecules with catalytic properties, are believed to have played a crucial role in the early evolution of life, supporting the RNA world hypothesis where RNA acted as both genetic material and catalyst.

Question 12

Which of the following RNA molecules is required for the process of translation?

Accepted Answer

tRNA (transfer RNA) is responsible for bringing amino acids to the ribosome during the process of translation, facilitating the assembly of proteins.

Question 13

Which of the following molecules is synthesized using nucleotides containing the bases adenine, guanine, cytosine, and uracil?

Accepted Answer

RNA is synthesized using nucleotides that contain adenine, guanine, cytosine, and uracil. DNA contains thymine instead of uracil.

Question 14

In transcription, to which end of the elongating strand are nucleotides always added?

Accepted Answer

Nucleotides are always added to the 3' end of the elongating RNA strand during transcription, regardless of the organism or the type of RNA polymerase.

Question 15

If you were asked to isolate total RNA from two unknown samples and then were required to identify if the RNA was from prokaryotes or eukaryotes, what aspects regarding the classes of RNA present would help you distinguish one from the other?

Accepted Answer

The answer of If you were asked to isolate total...

Question 16

Which of the following statements is TRUE regarding transcription in most organisms?

Accepted Answer

In most organisms, different genes can be transcribed from either strand of the DNA, meaning that one gene might use one strand as the template, while another gene might use the opposite strand.

Question 17

The discovery of ribozymes led to the theory that the evolution of life on Earth began with an "RNA world." What properties of proteins and DNA make them more suitable than RNA as enzymes and the cell's genetic material?

Accepted Answer

The answer of The discovery of ribozymes led to the...

Question 18

In eukaryotes, which RNA polymerase transcribes the genes that encode proteins?

Accepted Answer

RNA polymerase II transcribes the genes that encode proteins in eukaryotes.

Question 19

The discovery of ribozymes led to the theory that the evolution of life on Earth began with an "RNA world." Describe how the current cellular roles of RNA support this theory.

Accepted Answer