Molecular Biology Flashcards
What is the structure of DNA?
DNA is a double helix composed of nucleotides, each containing:
A phosphate group
A deoxyribose sugar
A nitrogenous base (adenine, thymine, cytosine, guanine)
What are the base-pairing rules in DNA?
Adenine pairs with thymine via 2 hydrogen bonds
Cytosine pairs with guanine via 3 hydrogen bonds
What is the function of DNA?
DNA stores genetic information, directs protein synthesis, and transmits genetic information to offspring during cell division
What is the key enzyme involved in DNA replication?
DNA Polymerase, which synthesises new DNA strands in the 5’ to 3’ direction
What are the steps of DNA replication?
Initiation: Helicase unwinds the DNA, forming a replication fork
Elongation: DNA polymerase adds complementary nucleotides
Termination: Replication ends when the replication forks meet or the process reaches the end of the DNA molecule
What is the function of telomerase?
Telomerase extends the telomeres at the ends of chromosomes to prevent loss of genetic information during replication
What is transcription?
The process of synthesising RNA from a DNA template
What are the key steps in transcription?
Initiation: RNA polymerase binds to the promoter region
Elongation: RNA polymerase synthesizes RNA in the 5’ to 3’ direction
Termination: RNA synthesis ends at the terminator sequence
What are the types of RNA transcribed from DNA?
mRNA: Carries genetic code to ribosomes
tRNA: Transfers amino acids during translation
rRNA: Forms the core of ribosomes
What is translation?
The process of synthesising a protein from mRNA
What are the steps of translation?
Initiation: The ribosome assembles around the mRNA and the first tRNA (carrying methionine)
Elongation: The ribosome moves along the mRNA, and tRNA brings amino acids to form a polypeptide chain
Termination: The process stops when a stop codon is reached
What are the stop codons?
UAA, UAG, UGA
What is the role of the ribosome in translation?
Small subunit: Binds to mRNA
Large subunit: Catalyses peptide bond formation between amino acids
What are the types of mutations in DNA?
Point mutations: Single base change (e.g. substitution)
Frameshift mutations: Insertions or deletions
Nonsense mutations: Lead to premature stop codons
How is DNA damage repaired?
Base excision repair: Removes damaged bases
Nucleotide excision repair: Repairs bulky lesions
Mismatch repair: Fixes replication errors
What is PCR (Polymerase Chain Reaction)?
A method to amplify specific DNA sequences using primers, DNA polymerase, and thermal cycling
What is the role of gel electrophoresis?
Separates DNA fragments based on size using an electric field
What is CRISPR-Cas9?
A gene-editing tool that uses RNA-guided enzymes to target and modify specific DNA sequences
How is molecular biology applied in medicine?
Gene therapy
Development of vaccines
Diagnosing genetic disorders (e.g. using PCR)
What is recombinant DNA technology?
A method to combine DNA from different organisms to produce desired proteins (e.g., insulin)
What is the central dogma of molecular biology?
DNA –> RNA –> Protein
What is reverse transcription, and where does it occur?
The process where RNA is converted back into DNA by reverse transcriptase, as seen in retroviruses like HIV
