Nucleic Acid Structure, Properties and Function Flashcards
What are the two main types of nucleic acids?
DNA and RNA
DNA stands for Deoxyribonucleic acid, and RNA stands for Ribonucleic acid.
What is the basic structure of a nucleotide?
Nitrogenous base, sugar, phosphate group
A nucleotide consists of a sugar, a nitrogenous base, and a phosphate group.
What sugar is found in DNA?
2-deoxyribose
DNA contains the sugar 2-deoxyribose.
What sugar is found in RNA?
Ribose
RNA contains the sugar ribose.
Name the pyrimidine nitrogenous bases.
Cytosine, Thymine (DNA), Uracil (RNA)
Pyrimidines are characterized by their single-ring structure.
Name the purine nitrogenous bases.
Adenine, Guanine
Purines consist of a two-ring structure.
What forms the backbone of nucleic acids?
Sugar-phosphate backbone
The sugar-phosphate backbone is formed by alternating sugar and phosphate groups.
What type of bond joins nucleotides in a DNA sequence?
Phosphodiester bonds
These bonds link the phosphate group of one nucleotide to the hydroxyl group of another.
What is the primary structure of nucleic acids?
Sequence of nucleotides
The primary structure refers to the linear sequence of nucleotides in a nucleic acid.
What is the secondary structure of DNA?
Double helix
The secondary structure refers to the coiling of the DNA into a double helix.
What is the directionality of nucleic acids indicated by?
5’ and 3’ ends
The 5’ end has a phosphate group, while the 3’ end has a hydroxyl group.
What are the base pairs in DNA?
Adenine-Thymine (A-T), Guanine-Cytosine (G-C)
These pairs are held together by hydrogen bonds, with A-T having 2 bonds and G-C having 3 bonds.
True or False: DNA is single-stranded.
False
DNA is typically double-stranded, forming a double helix.
What is the tertiary structure of eukaryotic DNA?
Chromosomes
Eukaryotic DNA is organized into long, thin chromosomes.
What is the role of ribosomal RNA (rRNA)?
Forms the core of ribosomes and catalyzes peptide bond formation
rRNA is essential for protein synthesis.
What is the function of transfer RNA (tRNA)?
Brings amino acids to the ribosome during protein synthesis
Each tRNA molecule is specific to one amino acid.
What is messenger RNA (mRNA)?
Carries genetic information from DNA to the ribosome
mRNA is a copy of the gene’s information necessary for protein synthesis.
What happens during denaturation of nucleic acids?
Loss of secondary structure and separation of strands
Denaturation can be caused by heat, pH changes, or chemical agents.
What is the average distance between bases in a DNA double helix?
0.34 nm
This distance contributes to the stability of the DNA structure.
What type of RNA was originally called soluble RNA?
Transfer RNA (tRNA)
The function of tRNA was not known when it was first named.
What is the function of peptidyl transferase?
Catalyzes the formation of peptide bonds
Peptidyl transferase is a ribozyme, meaning it is an RNA molecule that acts as an enzyme.
What is a polynucleotide?
A biopolymer consisting of more than 13 monomers
Polynucleotides are important in biochemical experiments such as PCR.
What is hypochromicity in relation to nucleic acids?
Decreased absorption of UV light due to base stacking
Double-stranded nucleic acids exhibit hypochromicity compared to single-stranded forms.
What is the typical size of ribosomal RNA (rRNA) in a cell?
80% of all RNA in a cell
rRNA plays a crucial role in the structure and function of ribosomes.
What are the three main types of RNA?
Ribosomal RNA (rRNA), Transfer RNA (tRNA), Messenger RNA (mRNA)
Each type of RNA has a distinct role in protein synthesis and gene expression.
At what wavelength do DNA and RNA absorb light?
260 nm
What causes the absorbance of DNA and RNA at 260 nm?
The bases
How does base stacking affect absorption at 260 nm?
Base stacking decreases absorption
Which absorbs more light: single-stranded DNA or double-stranded DNA?
Single-stranded DNA
Which absorbs more light: nucleotides or polynucleotides?
Nucleotides
What is the term for the phenomenon where double-stranded DNA and RNA absorb less UV light?
Hypochromicity
What is the term for the phenomenon where single-stranded DNA or RNA absorb more light than double-stranded DNA?
Hyperchromicity
What is the formula to estimate the concentration and purity of DNA/RNA?
A260 / A280
What A260/A280 ratio indicates pure DNA?
1.8
What A260/A280 ratio indicates the presence of RNA?
> 1.8
What A260/A280 ratio indicates the presence of protein?
<1.8
What happens to DNA when it is heated?
Denaturation occurs
What is produced when DNA denatures?
Single-stranded DNA
What is the effect of denaturation on absorbance at 260 nm?
Absorbance increases
What is a hyperchromic shift?
Increase in absorbance at 260 nm due to denaturation
What factors influence the melting temperature of DNA?
Proportion of G+C
Which base pairs more strongly: G-C or A-T?
G-C
What happens to denatured DNA when the temperature is decreased slowly?
Complete renaturation occurs
What happens to denatured DNA with rapid temperature decrease?
Partial re-annealing occurs with mismatches
What is the process of creating new DNA fragments identical to target DNA called?
Renaturation
Fill in the blank: The template for renaturation is ________.
double stranded DNA
