9-RNA Transcription & Translation

Question 1

Which is the flow of genetic information?

Answer 1

DNA→RNA→protein

Question 2

Where does translation take place?

Answer 2

In ribosomes (cytosol)

Question 3

Where does transcription takes place?

Answer 3

In the nucleus

Question 4

What is the function of the ribosomal RNA (rRNA)?

Answer 4

It is a structural component of ribosomes

Question 5

What small nuclear RNA (snRNA) consist of?

Answer 5

RNA and proteins

Question 6

From which side of a tRNA is the amino acid located?

Answer 6

It is located in the 3’ end

Question 7

How does a polypeptide start and end?

Answer 7

It starts with an amino gorup (H3N) and finishes with a carboxyl grouo (COO-)

Question 8

Does the mRNA come out of the nucleus maturated or not?

Answer 8

It comes out maturated.

Question 9

What is alternative Splicing?

Answer 9

It is like the original ‘splicing’process. However in this case except from the introns, an exon can be rremoved too, so a different protein is created. It is an answer to the question: How is it possible that there are millions of human
antibodies when there are only about 30,000 genes

Question 10

What is a Poly-tail and where can be found?

Answer 10

It is a sequence that protects the mRNA from degradation, it can be found in the 3’ end of an mRNA:

• It aids in the export of the mRNA to the cytoplasm
• Is involved in binding proteins involved in initiating translation

Question 11

What is a Cap and where can be found?

Answer 11

It can be found in the 5’ end of a mRNA molecule.

• Protects the new-made mRNA from degradation
• Iniatiation factors involved in translation recognise the cap to help initiate translation by ribsosomes

Question 12

How many are the codons and the amino acids?

Answer 12

64 codons and 20 amino acids.
**There are 61 codons for 20 amino acids
( 3 codons are stop signals and they do not correspond to any amino acids)

Question 13

These codons are universal, what does this mean?

Answer 13

That these codons appear in all living organisms

Question 14

How many fates does a codon have?

Answer 14

It has 3 fates:

• Initiate translation
• Code an amino acid
• Terminate translation

Question 15

How many sites does a large ribosomal unit have and which are their function?

Answer 15

A large ribosomal unit has two sites ( A and P site):

A site: Is the site where the amino acids will wait in order to be linked to the peptide chain.

P site: Is the site for the growing polypeptide chain

Question 16

How many and which parts does translation have?

Answer 16

It has 3 parts:

• Initiation
• Elongation
• Termination

Question 17

What happens in the initiation part of the translation?

Answer 17

The initiation phase of protein synthesis requires
over 10 eukaryotic Initiation Factors (eIFs): Factors
are needed to recognize the cap at the 5’end of an
mRNA and binding to the 40s ribosomal subunit.

▪Binding the initiator Met-tRNAiMet (methionyltRNA) to the 40S small subunit of the ribosome.

▪Scanning to find the start codon by binding to the 5’cap of the mRNA and scanning downstream until they find the first AUG (initiation codon).

▪The start codon must be located and positioned correctly in the P site of the ribosome, and the initiator tRNA must be positioned correctly in the same site.

▪Once the mRNA and initiator tRNA are correctly bound, the 60S large subunit binds to form 80s initiation complex with a release of the eIF factors.

Question 18

In which direction do the amino acids move during elongation?

Answer 18

They move from the A to P site in order to be connected with the polypeptide chain.

Question 19

What does the termination state of a translation process require in order to occur (signals)?

Answer 19

It requires a stop codon and specifing releasing factors (RFs)…………..eRFs in euakryotes.

Question 20

How final proteins are formed?

Answer 20

Polypeptides fold spontaneously into their active
configuration, and they spontaneously join with other
polypeptides to form the final proteins.

Question 21

What type of mileculesa can be attached to proteins?

Answer 21

-sugars
ilipids
-phosphatases etc…

All of these have a special function to the protein.

Question 22

What proteolytic enzymes are? Name a category of them and the enzymes this category consists of.

Answer 22

Proteolytic enzymes are aenzymes that cleave proteins. One category is the serine proteases that include dugestive enzymes:

• trypsin
• chymotrypsin
• elastase

Question 23

Where does chymotrypsin prefer to cut?

Answer 23

prefers an aromatic side chain on the residue whose carbonyl carbon is part of the peptide bond to be cleaved

Question 24

Where does Trypsin prefer to cut?

Answer 24

Trypsin prefers a positively charged Lys or Arg residue at this position.

Question 25

What do lysosomes contain?

Answer 25

contain a large variety of hydrolytic enzymes that degrade proteins & other substances taken in by endocytosis.

Question 26

What is ubiquitination?

Answer 26

Is the process in which proteins are tagged for selective destruction by covalent attachment of ubiquitin

Question 27

What is ubiquitin?

Answer 27

It is a small, compact, highly conserved protein.

Question 28

Are all proteins degraded by after ubiquitination?

Answer 28

no

Question 29

How ubiquitins are attached to each other? (bonds)

Answer 29

Carboxyl group- ε-amini group of Lys29 or Lys48 residue.

Question 30

What proteasomes are and where do they function in?

Answer 30

They are responsible for protein degradation and they function in the cytosol and the nucleus.

Question 31

What does the proteasome complex consist of?

Answer 31

The proteasome core complex, with a 20S sedimentation coefficient, contains 2 each of 14 different polypeptides.

 7 a-type proteins form each of the two a rings, at the ends of the cylindrical structure.

 7 b-type proteins form each of the 2 central b rings.

Question 32

Which are the “categories” of mutations?

Answer 32

• harmful
• lethal
• helpful
• silent