Nucleic Acids, DNA, and RNA Flashcards

Flashcards covering key facts, structural details, and differences regarding nucleic acids, DNA, RNA, and protein synthesis components based on the lecture slides.

According to the presentation, how long would it take to speak every letter of human DNA speaking one letter per second, 24 hours a day?

About $100\,\text{years}$

How much digital data storage in CDs is equivalent to the information held in $1\,\text{gram}$ of DNA?

$1\,\text{trillion}$ CDs

What percentage of the DNA sequence is identical between any two humans, and what percentage accounts for individual differences?

$99.9\%$ is identical, and $0.1\%$ causes differences in characteristics such as eye, skin, and hair color and risks for certain diseases.

Who first described the double helix structure of DNA, and when?

Seventy years ago, American biologist James Watson and English physicist Francis Crick first described the structure of deoxyribonucleic acid molecules as a double helix resembling a twisted ladder.

What landmark effort was completed exactly 50 years after Watson and Crick described the DNA double helix structure?

The Human Genome Project, a landmark effort to sequence and map all the genes that compose the human genome.

If all DNA molecules in the human body were unraveled and placed end to end, how far would they stretch?

Over $110\,\text{billion}$ miles, which could stretch to the Sun and back over $600$ times.

What three components make up a nucleotide monomer?

A pentose sugar, a nitrogen-containing base, and a phosphate group.

Which nitrogenous bases belong to the pyrimidine and purine classes?

Pyrimidines are Cytosine (C), Thymine (T), and Uracil (U); Purines are Adenine (A) and Guanine (G).

How do the nitrogen-containing bases differ between DNA and RNA?

DNA contains Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). RNA contains Adenine (A), Guanine (G), Cytosine (C), and Uracil (U).

How does the pentose sugar in DNA structurally differ from the pentose sugar in RNA?

The pentose sugar in DNA is deoxyribose, which has no oxygen atom on carbon $2'$, whereas the sugar in RNA is ribose.

What chemical bond links a nitrogen base to carbon $C1'$ of a sugar in a nucleoside?

A glycosidic bond

How are nucleosides named based on their nitrogen base type?

By changing the nitrogen base ending to -osine for purines and -idine for pyrimidines.

What structural modification turns a nucleoside into a nucleotide?

It forms a phosphate ester with the $C5'\text{--OH}$ group of a pentose sugar (ribose or deoxyribose).

Identify the structure shown in the image, including its nitrogen base and sugar components:

Guanosine 5'-monophosphate (GMP), with nitrogen base guanine and sugar ribose.

What type of bond connects adjacent nucleotides in the primary structure of nucleic acids?

Phosphodiester bonds, where the $3'\text{--OH}$ group of the sugar in one nucleotide forms an ester bond to the phosphate group on the $5'\text{--carbon}$ of the sugar of the next nucleotide.

In what direction is a nucleic acid sequence read?

From the free $5'\text{--end}$ using the letters of the bases to the free $3'\text{--end}$.

How many hydrogen bonds form between A-T and G-C base pairs in a DNA double helix?

Two hydrogen bonds form between Adenine and Thymine (A-T), and three hydrogen bonds form between Guanine and Cytosine (G-C).

What are the diameter, pitch, and rise per residue of the standard double helical structure of DNA?

The diameter is $20\,\text{\AA}$, the pitch (one complete turn) is $34\,\text{\AA}$, and the rise per residue is $3.4\,\text{\AA}$.

What is the complementary base sequence for the matching strand in the DNA section —A—G—T—C—C—A—A—T—C—?

-T-C-A-G-G-T-T-A-G-

How do A-DNA, B-DNA, and Z-DNA compare in helical sense and base pairs per helical turn?

A-DNA is right-handed with $11.6$ base pairs per turn; B-DNA is right-handed with $10$ base pairs per turn; Z-DNA is left-handed with $12$ base pairs (6 dimers) per turn.

Why is DNA resistant to alkali degradation compared to RNA?

DNA resists alkali action due to the absence of an $-\text{OH}$ group at the $2'$ position.

What structural characteristics cap the $5'$ and $3'$ terminal ends of messenger RNA (mRNA)?

The $5'$ terminal end is capped by a 7-methyl guanosine triphosphate cap, and the $3'$ end has a polymer of $20\text{--}250$ adenylate residues.

How do prokaryotic mRNA and eukaryotic mRNA differ in terms of cistronic organization?

Prokaryotic mRNA is polycistronic with multiple translation start sites, whereas eukaryotic mRNA is monocistronic with a single translation start site.

What sequence is present at the unpaired $3'$ end of the tRNA acceptor arm, and how does an amino acid bind to it?

The sequence is Cytosine, Cytosine, Adenine (CCA); the $3'\text{--OH}$ group of Adenine binds with the carboxyl group of an amino acid.

What is the function of the DHU arm in a tRNA molecule?

It serves as the recognition site for the enzyme amino acyl tRNA synthetase that adds the amino acid to the acceptor arm.

Which arm of tRNA contains pseudouridine and functions in binding tRNA to ribosomes?

The $T\Psi C$ arm

What catalytic function can an rRNA component perform in the ribosome during protein synthesis?

Peptidyl transferase activity, functioning as an enzyme (a ribozyme).

What rRNAs and number of proteins compose the 60S and 40S subunits of the 80S mammalian ribosome?

The 60S subunit contains 28S rRNA ($4{,}718\,\text{nt}$), 5.8S rRNA ($160\,\text{nt}$), 5S rRNA ($120\,\text{nt}$), and $49$ proteins. The 40S subunit contains 18S rRNA ($1{,}874\,\text{nt}$) and $33$ proteins.

Which mammalian ribosomal RNA molecule is independently transcribed rather than processed from the single 45S precursor RNA in the nucleolus?

5S rRNA