Transcription and Translation L21-22

What is the primary role of DNA?

DNA contains the genetic instructions for the development and function of living things, including constructing proteins and RNA molecules.

What are the two types of nucleic acids discussed in the Central Dogma?

DNA and RNA.

What are the nucleotide bases in DNA?

Adenine (A), Thymine (T), Guanine (G), Cytosine (C).

What are the nucleotide bases in RNA?

Adenine (A), Uracil (U), Guanine (G), Cytosine (C).

What is the base pairing rule between DNA and RNA during transcription?

A=U, G=C.

What is the template strand of DNA also called?

Antisense strand, (-) strand, or non-coding strand.

What enzyme is responsible for transcription?

RNA polymerase.

What are the three stages of transcription?

Initiation, Elongation, Termination.

Where does RNA polymerase bind to start transcription?

The promoter site, with the help of transcription factors.

In what direction does RNA polymerase move along the DNA template?

3’ to 5’.

In what direction is the mRNA strand synthesized?

5’ to 3’.

What happens during the elongation stage of transcription?

RNA polymerase unwinds DNA, synthesizes RNA, and the DNA helix reforms behind it.

What signals the end of transcription?

The terminator region of DNA.

What is the product of transcription?

An RNA copy of a single gene.

What is a gene?

A specific region of DNA that contains instructions for making RNA or proteins.

What is the role of the ribosome in translation?

To read mRNA and produce a protein according to its instructions.

What are the two subunits of a ribosome?

Large and small subunits.

What is a codon?

A sequence of three mRNA bases that codes for one amino acid.

How many possible codons are there?

64.

What is the start codon, and what amino acid does it code for?

AUG, which codes for methionine.

What are the three stop codons?

UAA, UAG, UGA.

What happens during the initiation stage of translation?

The ribosome binds to mRNA, and the initiator tRNA brings methionine to the start codon.

Where does the initiator tRNA bind on the ribosome?

The P-site.

What happens during the elongation stage of translation?

tRNAs bring amino acids to the ribosome, peptide bonds form, and the ribosome moves along mRNA.

What is translocation in translation?

The ribosome moves to the next codon, and tRNAs shift positions.

What happens during the termination stage of translation?

A release factor binds to the stop codon, releasing the polypeptide and dissociating the ribosome.

What is the role of tRNA in translation?

To bring amino acids to the ribosome based on mRNA codons.

What is the relationship between codons and amino acids?

Each codon corresponds to a specific amino acid (or stop signal).

What is the primary structure of a protein?

The sequence of amino acids in the polypeptide chain.

Where are proteins made for secretion outside the cell synthesized?

On ribosomes attached to the rough endoplasmic reticulum (RER).

What is a mutation?

A change in the DNA sequence that may affect protein function.

What is an example of a single base mutation disease?

Sickle cell anemia.

What causes sickle cell anemia at the molecular level?

A single base change in the hemoglobin beta chain, replacing glutamate with valine.

How does sickle cell anemia affect red blood cells?

Hemoglobin forms insoluble strands, causing cells to sickle and block blood vessels.

What is the Central Dogma of Biology?

DNA → RNA → Protein.

What is the difference between a nucleoside and a nucleotide?

Nucleoside = sugar + base; nucleotide = sugar + base + phosphate.

Why is DNA packing important?

It organizes and compacts DNA to fit inside the nucleus.

What are the forms of RNA mentioned?

mRNA, tRNA, rRNA (implied by translation slides).

What is the role of transcription factors?

To help RNA polymerase bind to the promoter.

What happens to the DNA strands during transcription initiation?

They unwind to expose the template strand.

How many DNA bases are unwound at a time during elongation?

10 to 20 bases.

What is the non-template strand of DNA called?

Sense strand or coding strand.

What determines the sequence of amino acids in a protein?

The sequence of bases in DNA/mRNA.

What determines a protein’s structure and function?

The sequence of amino acids.

What happens to methionine after translation in many proteins?

It is often removed post-translation.

What is the role of release factors in translation termination?

To hydrolyze the bond between tRNA and the polypeptide, releasing the protein.

How does a ribosome know where to start translation?

It binds to the ribosome binding site on mRNA near the start codon (AUG).

What is the anticodon on tRNA complementary to?

The codon on mRNA.

What is the significance of the genetic code being redundant?

Multiple codons can code for the same amino acid, reducing mutation impact.

How does a mutation in DNA affect protein function?

It may alter the amino acid sequence, changing the protein’s structure and function.