Nucleic acids, DNA, RNA, replication and transcription

What are the four basic genetic processes?

Replication, transcription, RNA processing, and translation.

What is replication?

DNA synthesis by copying existing DNA.

What is transcription?

RNA synthesis using DNA as a template.

What is RNA processing?

Modification of RNA in the nucleus (splicing

What is translation?

Protein synthesis by decoding RNA.

What are nucleic acids composed of?

A nitrogenous base

Which bases are found in DNA?

Adenine

Which bases are found in RNA?

Adenine

What is the sugar in DNA?

Deoxyribose.

What is the sugar in RNA?

Ribose.

What bonds link nucleotides?

Phosphodiester bonds.

What holds DNA strands together?

Hydrogen bonds between complementary bases (A‑T

What is the directionality of nucleic acids?

Antiparallel 5′ to 3′ strands.

What are major and minor grooves?

Structural features of the DNA helix that allow protein binding.

How many base pairs are in the human genome?

About 3 billion.

How many genes are in the human genome?

About 20

What is chromatin?

DNA packaged with histone proteins.

What is a nucleosome?

DNA wrapped around a histone octamer.

What is the role of histone modifications?

Regulate gene expression by altering chromatin accessibility.

What are telomeres?

Repetitive GC‑rich sequences at chromosome ends that protect DNA.

Why do telomeres shorten?

Due to repeated replication

What is RNA?

A single‑stranded nucleic acid capable of folding into secondary and tertiary structures.

What is mRNA?

Messenger RNA that carries genetic information to the cytoplasm.

What is tRNA?

Transfer RNA that carries amino acids to the ribosome.

What is inosine?

A modified base in tRNA important for wobble pairing.

What is rRNA?

Ribosomal RNA

What are cAMP and cGMP?

Intracellular signalling molecules.

What is ATP?

The main energy currency of the cell.

What is GTP?

A nucleotide used as an energy source in many cellular processes.

What is the key difference between DNA and RNA sugars?

DNA has deoxyribose; RNA has ribose.

What base is unique to RNA?

Uracil.

What base is unique to DNA?

Thymine.

Is DNA single or double stranded?

Usually double stranded.

Is RNA single or double stranded?

Usually single stranded.

What is semi‑conservative replication?

Each daughter DNA molecule contains one original strand and one new strand.

What direction does DNA polymerase read the template?

3′ to 5′.

What direction does DNA polymerase synthesize new DNA?

5′ to 3′.

What is the leading strand?

The continuously synthesized DNA strand.

What is the lagging strand?

The discontinuously synthesized strand made of Okazaki fragments.

What is primase?

The enzyme that synthesizes RNA primers.

What is DNA ligase?

The enzyme that joins Okazaki fragments.

What do helicases do?

Unwind the DNA helix.

What do topoisomerases do?

Relieve supercoiling during replication.

What do single‑stranded binding proteins do?

Stabilize unwound DNA.

Which polymerase replicates mitochondrial DNA?

DNA polymerase γ.

Which polymerases replicate nuclear DNA?

DNA polymerases α

What is proofreading?

Exonuclease activity that removes incorrect nucleotides during replication.

What is the replication fork?

The site where DNA is unwound and replicated.

What are deoxyribonucleotide triphosphates?

The precursors for DNA synthesis.

What is transcription?

Synthesis of RNA from a DNA template.

What is heterochromatin?

Densely packed chromatin that is transcriptionally inactive.

What is euchromatin?

Loosely packed chromatin that is transcriptionally active.

What is hnRNA?

The primary RNA transcript containing introns and exons.

What is mRNA processing?

Splicing

Which polymerase transcribes mRNA?

RNA polymerase II.

Which polymerase transcribes rRNA?

RNA polymerase I.

Which polymerase transcribes tRNA?

RNA polymerase III.

Does RNA polymerase require a primer?

No.

Does RNA polymerase have proofreading activity?

No 3′→5′ exonuclease activity.

What is a promoter?

A DNA sequence where RNA polymerase binds to initiate transcription.

What is the TATA box?

A common promoter sequence.

What are transcription factors?

Proteins that help RNA polymerase bind and initiate transcription.

What is TFII‑D?

A transcription factor containing TBP that binds the TATA box.

What are enhancers?

DNA sequences that increase transcription rates from a distance.

What are exons?

Coding regions of a gene.

What are introns?

Non‑coding regions removed during RNA processing.

What is splicing?

Removal of introns and joining of exons.

What direction is RNA synthesized?

5′ to 3′.

What direction is the DNA template read?

3′ to 5′.

What determines transcription start sites?

Promoter sequences and transcription factor binding.

What is the transcription bubble?

The unwound region of DNA where transcription occurs.

What is the final product of transcription?

A mature mRNA ready for translation.