Genetics and Molecular Biology: DNA, Genes, and Protein Synthesis

Chromosome

A structure composed of DNA and proteins that contains genetic information; humans have 23 pairs.

Gene

A segment of DNA that contains the instructions for making a specific protein or set of proteins.

Genome

The complete set of genetic material in an organism, including all of its genes.

Semiconservative replication

The process by which DNA is replicated in cells, where each new DNA molecule consists of one old strand and one new strand.

Transcription

The process of synthesizing RNA from a DNA template, where RNA polymerase plays a key role.

Translation

The process of synthesizing proteins from mRNA, where ribosomes read the mRNA sequence and tRNA brings the corresponding amino acids.

Operon

A cluster of genes under the control of a single promoter, allowing coordinated expression of related genes in prokaryotes.

Mutation

A change in the DNA sequence that can lead to alterations in gene function or expression.

Mutagen

An agent, such as radiation or a chemical, that causes mutations in DNA.

How does DNA serve as genetic information?

DNA contains sequences of nucleotides that encode the instructions for building proteins, which determine the traits of an organism.

What is the basic structure of DNA?

DNA is a double helix composed of two strands of nucleotides, with a backbone of sugar and phosphate and nitrogenous bases (adenine, thymine, cytosine, guanine) paired in the center.

What do 3' and 5' ends of DNA mean?

The 3' end refers to the end of a DNA strand with a free hydroxyl group on the sugar, while the 5' end has a phosphate group; these orientations are crucial for DNA replication and transcription.

Describe DNA replication.

DNA replication involves unwinding the double helix by helicase, followed by the addition of complementary nucleotides by DNA polymerase to form new strands.

What is the role of RNA polymerase?

RNA polymerase is the enzyme that synthesizes RNA from a DNA template during transcription.

What is the role of ribosomes in protein synthesis?

Ribosomes are cellular structures that facilitate the translation of mRNA into proteins by linking amino acids together in the order specified by the mRNA.

What is an inducible operon?

An inducible operon is a type of operon that is normally off but can be turned on in the presence of a specific molecule, allowing gene expression to be regulated.

What are the three types of gene transfer in bacteria?

The three types of gene transfer are conjugation (direct transfer of DNA between bacteria), transformation (uptake of free DNA from the environment), and transduction (transfer of DNA via bacteriophages).

What is a plasmid?

A plasmid is a small, circular piece of DNA found in bacteria that can replicate independently and often carries genes that confer advantageous traits, such as antibiotic resistance.

Complementary DNA Strand

The DNA strand that pairs with a given DNA sequence, following base pairing rules (A with T, C with G).

Process of Protein Synthesis

Protein synthesis involves two main processes: transcription, where DNA is transcribed to mRNA, and translation, where mRNA is translated into a protein at the ribosome.

RNA Polymerase

An enzyme that synthesizes RNA from a DNA template during transcription.

mRNA

Messenger RNA that carries the genetic information from DNA to the ribosome for protein synthesis.

tRNA

Transfer RNA that brings amino acids to the ribosome during translation, matching them to the mRNA codons.

rRNA

Ribosomal RNA that forms the core of the ribosome's structure and catalyzes protein synthesis.

Ribosome

A cellular structure that facilitates the translation of mRNA into proteins.

Codon

A sequence of three nucleotides in mRNA that specifies a particular amino acid.

Eukaryotic vs Prokaryotic Protein Synthesis

In eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm; in prokaryotes, both processes occur in the cytoplasm simultaneously.

Gene Regulation in Bacteria

Gene expression in bacteria is regulated by induction (turning on genes) and repression (turning off genes) through mechanisms involving operons, operators, promoters, and repressor proteins.

Mutation

A change in the DNA sequence that can lead to alterations in gene function, with types including point mutations, insertions, deletions, and frameshifts.

Importance of Mutation in Evolution

Mutations introduce genetic variation, which is essential for evolution and adaptation in populations.

Griffith's Experiment

An experiment demonstrating transformation, where non-virulent bacteria were transformed into virulent forms by exposure to heat-killed virulent bacteria.

Gene Transfer and Antibiotic Resistance

Gene transfer, such as through plasmids, can lead to the spread of antibiotic resistance among bacteria, making infections harder to treat.