Molecular biology : replication,transcription & translation Flashcards
How is DNA an amphipathic molecule?
Sugar-phosphate backbone hydrophilic and water soluble.
The nitrogenous bases are hydrophobic.
What is the direction/polarity of the parent strand in DNA replication?
3’ to 5’
What is the only direction transcription and replication takes place in?
5’ to 3’
Explain the steps of DNA replication.
- The DNA strand will first separate from each other and forma structure called the replication fork.
- Enzymes will use each strand as a template for the assembly of new nucleotides for the complementary strand.
- Dna polymerase will continously synthesize one of the DNA strand. the other strand will be synthesized in pieces and these pieces will be joined together by DNA ligase.
What type of model does DNA replication follow and why?
DNA replication follows a semiconservative model, because half of the parent DNA helix is conserved into each daughter molecule.
Each new DNA helix has one old strand with one new strand.
What is the difference between 5’ end and 3’ end?
5’ end has a carbon attached to a phosphate group
3’ end has a carbon attached to a hydroxyl group
Differentiate between transcription and translation?
- Transcription is the synthesis of RNA under the direction of DNA.
- Occurs in the nucleus
- Translation is the synthesis of proteins under the direction of RNA.
- Occurs in the cytoplasm
What are the steps of transcription?
- Initiation : The DNA unzips and the RNA nucleotides line up , followed by the RNA polymerase binding to the promotor.
- Elongation : The RNA polymerase keeps adding nucleotides and therby the newly formed RNA strand grows.
- Termination : RNA polymerase will keep adding nucleotides until it reaches a specific sequence of DNA called the terminator.This signals the RNA polymerase to detach from the DNA strand and also detaches the newly formed RNA.
What is the promoter in transcription?
The promoter is a sequence of nucleotides that is responsible for determining when the transcription process begins.
What is the terminator in transcription?
The terminator is a specific sequence of nucleotides that signals the end of the transcription process.
Why is the process of splicing ,capping and tailing necessary?
The newly formed RNA strand is not readily usable for translation. It needs to undergo splicing to transform into a mRNA.
Capping/ tailing is to signal the cytoplasm that the mRNA is not foreign. If the cyctoplasm thinks an mRNA is foreign it will be digested by enzymes.
An mRNA conveys genetic messages from the DNA to the translation process.
What is splicing, capping and tailing?
Splicing is the process in which the introns
( uncoded parts of RNA) get spliced off and the exons (expressed parts of a gene) get spliced together.
A cap and a tail is also added.
What is the code for RNA nucleotides to become 1 amino acid?
3 RNA nucleotides = 1 amino acid
(A codon)
Name the start and stop codons.
Start codon : AUG (codes for methionine)
Stop codons : UAG, UGA, UAA
Name the types of RNA and their functions.
mRNA (messanger RNA) : Coding RNA used as code to make protein
tRNA (transfer RNA) : Structural RNA that carries amino acids to the ribosome during translation
rRNA( ribosomal RNA) : Structural RNA that makes up subunits of ribosome
