nucleotide and nucleic acids

What are the three components of a nucleotide?

A pentose sugar, a nitrogenous base, and a phosphate group.

What type of reaction joins nucleotides to form polynucleotides?

Condensation reactions.

What is the name of the bond formed between the phosphate group of one nucleotide and the sugar of another?

A phosphodiester bond.

Which two scientists discovered the DNA double helix structure in 1953?

James Watson and Francis Crick.

What is the structural difference between purines and pyrimidines?

Purines (A and G) are larger with two carbon rings; pyrimidines (T and C) are smaller with one carbon ring.

How many hydrogen bonds form between Adenine and Thymine, and between Cytosine and Guanine?

Adenine and Thymine form 2 hydrogen bonds; Cytosine and Guanine form 3 hydrogen bonds.

What are the three main structural differences between DNA and RNA?

DNA is double-stranded with deoxyribose and uses Thymine; RNA is single-stranded with ribose and uses Uracil.

What is the role of DNA helicase in DNA replication?

It breaks the hydrogen bonds between complementary bases to unwind and separate the DNA strands.

In which direction does DNA polymerase synthesize new DNA strands?

In a 5' to 3' direction.

What did the Meselson and Stahl experiment prove about DNA replication?

It proved that DNA replication is semi-conservative, meaning each new molecule contains one original strand and one newly synthesized strand.

What is a gene?

A short section of DNA that codes for a specific protein.

What are the three characteristics of the genetic code?

It is universal, non-overlapping, and degenerate.

What does it mean that the genetic code is 'degenerate'?

Most amino acids are coded for by more than one triplet (codon).

What is the function of mRNA?

It carries genetic information from the DNA in the nucleus to the ribosome for protein synthesis.

What is the structure and function of tRNA?

It is single-stranded and folded into a clover-leaf shape; it transports specific amino acids to the ribosome during translation.

Where does transcription occur in a cell?

In the nucleus.

What is the role of RNA polymerase during transcription?

It binds to DNA, separates the strands, and catalyzes the formation of phosphodiester bonds between RNA nucleotides.

What occurs during the translation process?

Ribosomes assemble a polypeptide chain by matching tRNA anticodons to mRNA codons and forming peptide bonds between amino acids.

What are the components of an ATP molecule?

An adenine base, a ribose sugar, and three phosphate groups.

What is the equation for the hydrolysis of ATP?

ATP + Water -> ADP + inorganic phosphate (Pi).

Why is ATP considered an ideal energy source for cells?

It releases energy in small, manageable amounts, is easily re-synthesized, and can be broken down in a single step.

What is the purpose of adding detergent in a DNA purification practical?

To break down cell membranes and release the DNA.

Why is ice-cold ethanol used in DNA extraction?

DNA is insoluble in cold ethanol, causing it to precipitate out of the solution.

What is the difference between chromatin and chromosomes?

Chromatin is DNA wound around histones; chromosomes are the highly packed, condensed form of chromatin.

What is the role of the anticodon on a tRNA molecule?

It is a sequence of three bases that is complementary to a specific codon on the mRNA strand.