Molecular Biology

Arts 1–4

Foreign Languages 1–4

DNA replication, transcription, translation, and gene expression.

📘 Topic Summary

Molecular biology is the study of the structure, function, and interactions of biological molecules such as DNA, RNA, and proteins. This topic covers the fundamental processes of DNA replication, transcription, translation, and gene expression, which are crucial for understanding how genetic information is passed from one generation to the next.

📖 Glossary

DNA: Deoxyribonucleic acid, a molecule containing the genetic instructions used in the development and function of all living organisms.
RNA: Ribonucleic acid, a single-stranded molecule that plays a crucial role in protein synthesis and gene expression.
Gene Expression: The process by which the information encoded in a gene is converted into a functional product, such as a protein.
Transcription: The process of creating a complementary RNA copy from a DNA template.
Translation: The process of building a protein chain based on the sequence of nucleotides in mRNA.

⭐ Key Points

DNA replication is semi-conservative, meaning that each new DNA molecule contains one old strand and one new strand.
Transcription occurs in three stages: initiation, elongation, and termination.
Translation involves the formation of a peptide bond between amino acids during protein synthesis.
Gene expression can be regulated at multiple levels, including transcriptional regulation and post-translational modification.
Mutations in DNA can occur through various mechanisms, such as point mutations or chromosomal rearrangements.

🔍 Subtopics

DNA Replication

DNA replication is the process by which a cell makes an exact copy of its DNA before cell division. This process occurs in the nucleus and is semi-conservative, meaning that each new DNA molecule contains one old strand and one new strand. The enzyme helicase unwinds the double helix structure of DNA, while another enzyme called primase adds short RNA sequences to the template strands. Then, the enzyme polymerase builds a new DNA strand by adding nucleotides to the primer sequence.

Transcription

Transcription is the process by which genetic information from DNA is copied into RNA. This occurs in the nucleus and is initiated when an enzyme called RNA polymerase binds to a specific region of DNA called the promoter. The enzyme then unwinds the double helix structure, reads the template strand, and adds nucleotides to the growing RNA chain. Transcription can be terminated by various mechanisms, including the formation of a terminator sequence.

Translation

Translation is the process by which the genetic information in mRNA is used to create a protein. This occurs in the cytoplasm and involves the assembly of amino acids into a polypeptide chain. The process begins when a ribosome binds to the mRNA molecule, reads the sequence of nucleotides, and adds the corresponding amino acid to the growing polypeptide chain. Translation can be terminated by various mechanisms, including the formation of a stop codon.

Gene Expression Regulation

Gene expression regulation refers to the control of gene transcription and translation in response to environmental cues or cellular signals. This is achieved through various mechanisms, including transcription factors that bind to specific DNA sequences, RNA-binding proteins that regulate mRNA stability, and post-translational modifications that affect protein function.

Mutations and Genetic Variation

Mutations are changes in the DNA sequence that can occur spontaneously or as a result of environmental factors such as radiation or chemicals. Point mutations involve the substitution of one nucleotide for another, while frameshift mutations result from insertions or deletions of nucleotides. These mutations can lead to genetic variation and may have significant effects on an organism's phenotype.

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