Gene Expression, Translation & Mutations – Lecture Vocabulary

Chapter 7

• Finishing chapter 7.

• RNA polymerase binds to the promoter with the help of what.

• One race opens up the DNA (separates the two strands).

• Going to pay attention to one strand and not pay attention to the other.

  • The template is the guide to make the RNA.

  • No template strand.

• mRNA.

RNA Transcript Modifications

• RNA transcript.

• Add five five cap.

  • Modified guanine.

  • The cap changes the shape of that end of the transcript so enzymes in the cytoplasm do not recognize it as nucleic acid and do not destroy it.

  • Protects the beginning end from degradation in the cytoplasm by those nuclease enzymes, hydrolytic nuclease enzymes.

• Add a polyhalide tail.

  • Three prime poly HCl.

  • A long series of a's is added to this.

  • Does not prevent the nuclease enzymes from digesting, breaking down, or hydrolyzing this molecule; just slows it down.

  • The a's are flying over its shoulder as it goes through.

  • Slowly breaks down the covalent bonds between the nucleotide and separating them.

  • Eventually, it will get to the gene and degrade the gene, and you can't make any more proteins out of it.

  • If you have a longer tail, the transcript will persist longer, and you can make more protein out of it.

  • If you have a shorter tail, it persists for a brief period of time, and you can make less protein out of it.

  • It is one way that the cell can regulate how much protein it makes from each transcript.

Exon or Intron Removal

• mRNA now.

• Some sections of this are not going to be used.

  • AGCPUs.

• The parts we don't use are going to be cut out.

• Those units that are removed are called introns.

  • Stands for intervening region.

  • In the way region.

• Remove the introns.

• The parts that are left are called exons.

  • Exon stands for expressed region.

• Exon a b c d and intron one two three.

• Remove the three one, two, and three parts and splice back or glue back the other parts, third a, b, c, and d.

• Generally, about 90% of the transcript is actually gonna be removed in the steps.

• It is possible for one transcript to be edited differently.

  • Variable splicing that can occur to make different proteins out of the same transcript.

• Human Genome Project.

Translation

• Transcript (mRNA) leaves the nucleus and goes to the cytoplasm due to translation.

• Addition of the modified cap also enables it to bind with transporters in the nuclear envelope, the nuclear membrane, and help it be exported.

• It won't be exported until it's been modified.

Players

• We've got the mRNA.

• Ribosomes.

• Other RNAs.

  • tRNA.

  • rRNA.

  • mRNA.

• Leader sequence or untranslated section or region mRNA.

  • Translation will begin a little bit further.

  • First part.

  • Role:

    • Helps it exit the nucleus.

    • Helps it bind to a ribosome that binds its way, but it's not going to be translated.

• The first one that starts off as AUG.

  • The ribosome is going to translate this mRNA three bases at a time.

  • Three bases are sometimes called a triplet.

  • Codon - Your book uses that term codon.

  • The first codon that is translated reads AUG, a start codon.

TRNA

• Piece of RNA.

• Hairpin moving up one side.

• Another hairpin moving another side.

• Comes back, has another hairpin move, another side, and it kinda comes back.

• There is complementary base pairing that occurs along those hairpin moves.

• Holds it together but then it folds over on itself.

• Not very rigid because they are very flexible.

• Two of these ends are important, and the others do not.

  • This end up here that's still kinda sticky that we haven't started with.

    • This part here finds an amino acid.

    • Another name for amino acid is peptide Binding site.

  • At the other end, we've got more RNA bases in here.

    • Those don't actually bind anything.

    • These three are kind of twisted on the outside the binding on the small one.

    • These three are referred to as the anticodon.

The Code of Life

• A list of all the codons (not anticodons) and their corresponding amino acid that would be on the tRNA with the complementary anticodon.

• Codons

  • AUG
    *AUU, AUC, and AUA
    *CCU, CCC, CCA, CCG

• Redundancy.

• Start codon - AUG

• Stop codons: UAA, UAG, and UGA.

• 64 different possible combinations of four different letters taken three at a time (20 amino acids).

• Wobble: The flexibility of that third base.

Protein Synthesis

• Initiation, elongation, and termination.

  • the beginning, middle, and end.

  • The first thing that's gonna happen is the ribosome, which I haven't talked about yet, has two parts to it.

    • One's big, one's small.

    • It is going to come in and clamp on to where that start going on is.

    • That first tRNA is also going to bind.

• Ribosome.
  *Ribosome is protein

• Ribosome is basically just a really big enzyme. And enzymes tend to be protein.

• Ribosome is made up of a lot of protein (a bunch of amino acid chains that have been folded up).

• Ribosome also has a bunch of RNA into it.

• Combination of protein and nucleic acid.

  • Made up of 50% DNA and 50% protein- Chromosome.

• Move down the mRNA three bases at a time.
  *Ribosome has a couple of binding sites with two active sites. The ribosome can accommodate two different tRNAs at a time.

Terminology

• tRNA stands for transfer RNA.

  • Transfer RNA transfer the amino acid.

• mRNA

  • Messenger RNA.

  • The message is that RNA is the instructions.

  • It's gluing the message of instructions for the sequence.

• rRNA

  • Ribosomal.

  • The RNA that's in the red zone.

Regulation of Gene Expression

• Transcription factors.

• Poly A and L.

• How the DNA is folded can make certain genes available and unavailable.

• Developmental genes when you're an embryo that were being utilized and now you don't use those anymore.
  *Chromatin is just the wrapped-up DNA.
  *Chromatin is actually divided into two different types of chromatin
  *Euchromatin is more open
  *Heterochromatin is more closed.

• Another way of making genes available or unavailable is called methylation. Add methyl groups such as that c h three functional group to the outside of the DNA, and that prevents the transcription factors from binding. The transcription factors can't bind.

• Methylating a region of DNA can prevent transcription from occurring.

• These are modifications that occur to the outside of the DNA, we call this epigenetics.

• Changes outside of the DNA sequence.

• Epigenetic changes can persist from one generation to the next.

• Alternative splicing.

• RNA export.

• Make little RNAs or microRNAs.

• The cell can make little RNAs or microRNAs.

  • They don't go for a protein.

  • They're not part of tRNA.

  • They're not part of RNA.

  • They're their own thing called microRNA.

  • MicroRNAs are complementary to a region on an RNA, so they're specific to an RNA.

  • If the cell makes those, they will bind to the mRNA in the cytoplasm and block the ribosomes, essentially turning that gene off. No protein will be made to block translation.

  • MicroRNAs; They will bind to the mRNA in the cytoplasm and block the ribosomes, essentially turning that gene off. No protein will be made to block translation.

• Degrade some faster than others; The polyatail

Mutations

• A mutation is simply a change to the DNA.

  • Interested in changes to DNA that will affect the protein of the backside of translation.

  • Interested in in changes to the DNA that affect the proteins.

  • It is when we say affect protein, we mean the amino acid sequence is altered.

• Mutations are a natural part of of life.

• Selective breeding for these different grapes.

• Two different types of mutations.

  • Point mutations

    • A point mutation is when a single amino acid has been changed; A single nucleotide has been changed.

• Wild type is the one that's the most common (the version that's most common in the population).

• Mutant type is any of the versions that are not the most common version.

• Black is wild type for humans, black hair.

Subtypes

• Substitution (one base is changed for another)

• Insertion (a is added)

• Deletion (would be removed)

• A substitution tends to change one amino acid in the sequence.

• An insertion will change every amino acid downstream from the insertion of the deletion point (alot of different amino acids).
  *One amino acid, the protein may work. It may work better. It may work worse. It may work well enough. A bunch of them change, that thing's not gonna work. That protein's not gonna work.

Terminology

• Silent mutation:

  • No change to the amino acids.

• Missense mutation:

  • Change one amino acid.
    *Sickle cell anemia is caused by substitution and one single amino acid is different in the chain of about a thousand, and that's enough to cause the red blood cells, the hemoglobin, and the red blood cells to form a sickle shape from the wash. So it's a missense mutation.

• Nonsense mutation:

  • Premature stop codon that shows up, and ends translation at that point.

• Frameshift mutation:

  • When you change the reading frame and you mess up all your amino acids downstream.

Fox p

• Two gene, Sometimes called language gene.

• Humans have a duplication of that gene.

• Humans can talk.

• Neanderthals also have a duplication.
  *It has to do with the brain development in the broca region, which is where you kinda communication the language part of your brain.