Bio 120-Gene expression

Gene expression

How genetic information goes from genotype to phenotype

DNA to RNA to Protein

what is one gene hypothesis?

The belief that one gene controls the synthesis of a singe enzyme

Explain Central Dogma

Info flow of genetics

DNA guides transcription of RNA which creates the Protein by translation

RNA molecules

sometimes, cd does not always follow that order. Can go from RNA to DNA

Describe a gene

It’s a small organized portion of DNA that transcribes into RNA to make a functional product

What are genes composed of?

• Promotor

• Regulatory sequence

• Transcribed region

• Terminator

What is the promotor

Site where RNA polymerase binds for transcription

The beginning of transcription.

Usually found on 5’ end

What is the regulatory sequence?

Site bonding to regulatory proteins that control whether gene is turned on or off

What is the transcribed region

the whole part of DNA that is transcribed into RNA

what is the terminator?

The sequence that causes RNA to release from the transcription complex.

Stops transcription at the AAUAAA code

What are transcription factors?

They bind to promotor with RNA polymerase

What is the RNA sequence of transcription factor found in prokaryotes?

Pribnow boxTATAAT

What is the RNA sequence of transcription factor found in eukaryotes?

TATA box

How many strands are called template strands for DNA synthesis?

Only one strand

When does transcription end?

At the termination site

For eukaryotes, how many proteins/factors are needed for the start of transcription?

5 general transcriptional factors

A typicall eukaryotic protein-coding gene has both introns and exons.

A typical eukaryotic protein-coding gene has both ______ and exons.

What are the different roles of introns?

• can merge to other intron and code for other protein

• jumping gene which is not good cuz that means it goes with an exon

• genetic diversity

• regulate gene expression

What is RNA splicing?

Removing an intron to join it with an exon to form an mRNA molecule with continuous sequence

Whwre does mRNA splicing happen?

in a spliceosome (protein complex) befire mRNA matures

What is a cap?

A methylguanosine atttached to mature mRNA 5’ end

what is tailling?

Basically a tail made of poly “A”( legit five As ) tail attached to 3’ end

Describe structure of a mature eukaryotic mRNA transcript

• 5’ cap

• 5’ UTR (untranslated region)

• Coding region

• 3’UTR

• 3’ poly A tail

What are codons foR?

They are triplets of base pairs

Specifies an amino acid

Is a signal for the stop/ start of translations

What are the three stop codons?

• UAA

• UGA

• UAG

"The genetic code is ________ as it can be transcribed after being transplanted from one species to another."

"The genetic code is universal as it can be transcribed after being transplanted from one species to another."

What are ways to call the DNA strand that does not participate in replication?

• Non- template strand

• Coding strand

• Sense strand

What are ways to call the DNA strand that participates in replication?

• Template strand

• Antisense strand

Which strand is identical to mRNA strand?

• Non- template strand

• Coding strand

• Sense strand

What is a gene mutation?

A permanent alteration of nucleotide sequence within the genome

What are ways common mutations happen?

• A base substitution

• Insertion or deletion

Base pair substitution/ point mutation

When one nucleotide and its complementary partner changes with another pair

Missense mutation

A single nucleotide change results in a codon that codes for a different amino acid

Silent mutation

When the change in codons does not affect amino acid specified by a gene

Nonsense mutation

A sense codon that codes is changed to a chain termination codon

Frameshift mutation

Insertion or deletion of a number of nucleotides in a DNA sequence not divisible by three (completely changes the way we read)

What does Translation require to take place?

• 20 AA Amino acids

• ATP and GTP (requires energy cuz endergonic)

• Enzymes and proteins

• All three RNA

How do the three RNAs work in protein synthesis?

• -rRNA makes the polypeptide chains

  -mNA carries info from out the nucleus and changes it to RNA language

  -tRNA reads mRNA it and brings it to Ribosomes

Which ends binds to amino acids in tRNA?

the 3’ end that corresponds to anticodon

What is aminoacylation?

Adding an amino acid to tRNA

Which RNA is the most important for peptide bond formation and for ribosomal structure?

rRNA

What is the best template to use for taxonomy?

Sequencing rRNA because it is very conservative for each species

What are the three stages of Translation?

1. Initiation

2. Elongation

3. Termination

WHat happens in initiation?

• Met-tRNA with energy-rich molecule(GTP) bind and form a complex

• Complex binds to 5’ end cap of mRNA

• GTP is hydrolised (GDP)

• Start of chain with AUG codon from N_ terminus to C-terminus (5’ to 3’)

What happens in elongation?

• mRNA enters A site and meets tRNA

• P site catalyse the reaction 3 nucleotides at the time

• A P E site

What happens in Termination?

• The elongation stops at A site with codon : UAA,UAG,UAG

• A factor binds in the a site since tRNA has no match codon

• the chain is released as the components disassemble