Study unit 6 - DNA to protein

What was the scientific experiment involving mutant strains of Neurospora crassa?

The experiment by Beadle and Tatum involved inducing mutations in Neurospora crassa to examine gene function, leading to the proposal of the one gene - one polypeptide hypothesis.

What does the one gene - one polypeptide hypothesis state?

This hypothesis states that each gene encodes a specific polypeptide (protein), which is essential to understanding gene expression in modern biology.

What is the central dogma of molecular biology?

The central dogma describes the flow of genetic information from DNA to RNA to protein, defining how genes express their information.

What are the three types of RNA important in the central dogma?

1. mRNA (messenger RNA) - carries genetic information from DNA to ribosomes. 2. tRNA (transfer RNA) - brings amino acids to ribosomes during translation. 3. rRNA (ribosomal RNA) - forms the core structure of ribosomes and catalyzes protein synthesis.

List the six types of RNA produced in eukaryotic cells.

1. mRNA (messenger RNA) 2. tRNA (transfer RNA) 3. rRNA (ribosomal RNA) 4. snRNA (small nuclear RNA) 5. snoRNA (small nucleolar RNA) 6. miRNA (microRNA)

How is DNA transcribed into RNA?

DNA is transcribed into RNA through the process where RNA polymerase synthesizes RNA using DNA as a template, involving three main steps: initiation, elongation, and termination.

What components are needed for transcription to occur?

1. DNA template 2. RNA polymerase 3. Ribonucleotides (ATP, GTP, CTP, UTP) 4. Transcription factors and necessary transcriptional machinery.

What is the role of RNA polymerase in transcription?

RNA polymerase synthesizes RNA by unwinding the DNA and catalyzing the addition of ribonucleotides to the growing RNA strand.

What are the three steps in transcription?

1. Initiation - RNA polymerase binds to the DNA promoter. 2. Elongation - RNA polymerase synthesizes RNA by adding nucleotides complementary to the DNA template. 3. Termination - RNA polymerase detaches from the DNA when a termination signal is reached.

What is a mature mRNA in eukaryotes derived from?

A mature mRNA is derived from pre-mRNA through processes including the addition of a 5’ cap, a poly-A tail, and RNA splicing, which removes introns.

What is the 5’ cap?

The 5’ cap is a modified guanine nucleotide added to the front of mRNA to protect it from degradation and assist in ribosome binding.

What is the poly-A tail?

The poly-A tail is a string of adenine nucleotides added to the 3’ end of mRNA, which aids in nuclear export and stability of the mRNA.

What is RNA splicing?

RNA splicing is the process of removing introns from pre-mRNA and joining exons together to form a continuous coding sequence in mature mRNA.

What are the most important characteristics of the genetic code?

1. The genetic code is universal, non-overlapping, and degenerate. 2. It specifies the amino acid sequence corresponding to each codon composed of three nucleotides.

How is protein synthesized from mRNA?

Protein synthesis involves translation, where mRNA is decoded by ribosomes with the help of tRNA to assemble amino acids into polypeptides.

What is the role of aminoacyl-tRNA?

Aminoacyl-tRNA is responsible for charging tRNA with the appropriate amino acid, ensuring correct amino acid incorporation during protein synthesis.

What are loaded tRNAs' role in translation?

Loaded tRNAs transport specific amino acids to the ribosome, matching their anticodons with the codons on mRNA during translation.

How are ribosomes structured and assembled for translation?

Ribosomes consist of two subunits (large and small) made of rRNA and proteins, assembling around the mRNA at the start codon to initiate translation.

What is the ribosome's role in translation?

The ribosome facilitates the decoding of mRNA and the formation of peptide bonds between amino acids as tRNAs cycle through the A (aminoacyl), P (peptidyl), and E (exit) sites.

What is a polysome?

A polysome is a complex of multiple ribosomes translating a single mRNA simultaneously, increasing the rate of protein synthesis.

What is the function of the signal sequence?

The signal sequence directs the nascent protein to the correct cellular location post-synthesis, influencing its fate within the cell.

What is post-translational modification?

Post-translational modification involves chemical alterations to proteins after synthesis, crucial for protein folding, activity, stability, and localization.

What is the difference between germline and somatic mutations?

Germline mutations occur in gametes and can be inherited, while somatic mutations occur in non-germline cells and are not passed to offspring.

What is the difference between loss-of-function and gain-of-function mutations?

Loss-of-function mutations result in reduced or abolished gene function, while gain-of-function mutations confer new or enhanced functions to the gene product.

How do different types of mutations affect protein function?

Mutations can lead to changes in amino acid sequences, potentially altering protein structure and function, which may result in diseases or new traits.

What are the types of chromosomal mutations that can change chromosome structure?

1. Deletions 2. Duplications 3. Inversions 4. Translocations.

What is a mutagen?

A mutagen is an agent, such as radiation or chemicals, that can induce mutations in DNA