molecular genetics - grace mariniello

What is the Central Dogma of molecular biology?

The Central Dogma states that genetic information flows from DNA to RNA to proteins.

What is mRNA?

mRNA (messenger RNA) uses a template to create a strand of corresponding base pairs, acting as instructions for protein synthesis.

What is tRNA?

tRNA (transfer RNA) brings the corresponding amino acid to the mRNA, which will form the primary structure of the protein.

What is rRNA?

rRNA (ribosomal RNA) is the RNA found inside the core of the ribosome that helps with structure and does not code.

What starts and ends the transcription process?

Transcription begins with a promoter and ends with a terminator, which includes the starting codon and the stop codon.

What role does RNA polymerase play in transcription?

RNA polymerase binds to the promoter site and reads the DNA template to synthesize mRNA.

What happens during the elongation phase of transcription?

The DNA double helix unwinds and mRNA is synthesized from the template strand in a 5’ to 3’ direction.

What is intron splicing?

Intron splicing is the process of removing non-coding regions (introns) from mRNA and adding a 5’ cap and a 3’ poly-A tail.

What is a spliceosome?

A spliceosome is a complex of proteins and RNA that facilitates the splicing of introns from mRNA.

How does mature mRNA exit the nucleus?

Once mature mRNA is created, it exits through a nuclear pore.

What occurs during the initiation phase of translation?

During initiation, the ribosomal unit assembles with mRNA and the first tRNA carrying the corresponding amino acid.

What are the three sites present in the large ribosomal subunit?

The A (aminoacyl), P (peptidyl), and E (exit) sites.

What happens during the elongation phase of translation?

Amino acids brought by tRNA bond to the previous amino acid forming a polypeptide chain.

What is the significance of the stop codon in translation?

The stop codon signals termination, causing the hydrolysis of the bond between tRNA and the ribosomal subunit.

What are point mutations?

Point mutations are base substitutions that affect only one base pair in the DNA sequence.

What is a missense mutation?

A missense mutation alters a single amino acid in a protein sequence due to a change in the corresponding DNA base.

What is a silent mutation?

A silent mutation changes a nitrogen base but does not affect the amino acid sequence.

What is a nonsense mutation?

A nonsense mutation changes a nitrogen base to a stop codon, leading to premature termination of the protein.

What are frameshift mutations?

Frameshift mutations are caused by insertions or deletions of nucleotides that shift the reading frame of the genetic message.

What is the role of the repressor in an operon?

The repressor binds to the operator region of the DNA to inhibit transcription of the gene.

What are repressible operons?

Repressible operons are genes that are typically on but can be turned off in the presence of a certain substance (e.g., trp operons).

What are inducible operons?

Inducible operons are genes that are typically off but can be turned on in the presence of a substrate (e.g., lac operons).

What is the epigenome?

The epigenome consists of the structure of DNA and histones covered in chemical tags that influence gene expression.

What are epigenetic tags?

Epigenetic tags act like long-term memory, helping determine whether a gene is expressed or not.

What signals can influence the epigenome?

Signals such as stress, diet, toxins, and physical activity can affect epigenetic changes.

What does tightly wrapped DNA mean for gene expression?

Tightly wrapped DNA denotes inactive genes, which cannot be read, while relaxed DNA indicates active genes that can be transcribed.

What is epigenetic inheritance?

Epigenetic inheritance refers to how experiences can influence gene expression and be passed down through generations.

What is a regulator gene?

A regulator gene encodes for the repressor molecule that controls transcription in an operon.

What happens to the operator when the repressor is inactive?

When the repressor is inactive, RNA polymerase can bind to the promoter and initiate transcription.

What are the parts of an operon?

An operon consists of a DNA strand, a promoter, an operator, a regulator gene, and the genes being transcribed.

How do environmental factors affect gene expression?

Environmental factors can affect the chemical tags on DNA or histones, altering gene expression without changing the DNA sequence.

What happens during reprogramming of reproductive cells?

During reprogramming, epigenetic tags are reset, but some can bypass this reset and influence gene expression in offspring.

What is genetic mutation?

A genetic mutation is a change in the DNA sequence that can lead to various functional changes in proteins.

What is the function of the operator in an operon?

The operator is where the repressor molecule binds to block transcription.

What is transcription?

Transcription is the process of copying a segment of DNA into RNA.

What is the role of ribosomes in translation?

Ribosomes facilitate the bonding of amino acids to form protein chains during translation.

What can happen if mutations occur in genes?

Mutations in genes can lead to changes in protein structure and function, potentially resulting in diseases.

What is the function of histones?

Histones are proteins that help package and organize DNA into structural units called nucleosomes.

What triggers the operon switch?

The presence or absence of specific metabolites triggers the operon switch for gene expression.

What is a transcription factor?

Transcription factors are proteins that help regulate transcription by binding to nearby DNA.

What does the 5’ cap and 3’ poly-A tail do for mRNA?

The 5’ cap protects mRNA from degradation and assists in ribosome binding, while the 3’ poly-A tail aids in export from the nucleus.

How do silent mutations occur?

Silent mutations occur when a base change does not affect the protein produced due to the redundancy in the genetic code.

Why are frameshift mutations often more harmful than point mutations?

Frameshift mutations disrupt the entire downstream reading frame, leading to significant changes in the resulting protein structure.

What are the functions of the P and A sites in the ribosome?

The P site holds the tRNA carrying the growing polypeptide chain, while the A site holds the tRNA carrying the next amino acid to be added.

What happens when excess tryptophan is produced in trp operons?

Excess tryptophan activates the repressor, which then binds to the operator to halt transcription.

What is a complete set of an organism's DNA called?

A complete set of an organism's DNA is referred to as its genome.

What determines if a gene is 'on' or 'off'?

The presence of epigenetic tags and their chemical modifications determines if a gene is expressed ('on') or silenced ('off').

What occurs during the hydrolysis of the tRNA bond at the stop codon?

Hydrolysis at the stop codon releases the newly synthesized polypeptide and allows the ribosomal subunits to dissociate.