Gene to protein to phenotype

Question 1

What is a prion and what disease is a result of prions?

Answer 1

Prions are normal proteins that ref old into different dangerous infectious structures that kill brain and nervous cells. This is the case in Creutzfeld-Jakob disease vCJD or mad cow disease as its more commonly known.

Question 2

A child who’s newborns urine turns black in air suffers from what disease and how is it inherited?

Answer 2

Alkaptonuria, an autosomal recessive trait linked to the inability to produce enzymes needed to metabolise homogentisic acid so their urine turns black.

Question 3

Genes produce changes in … Through proteins

Answer 3

phenotype

Question 4

The amount of genetic information held in a cell is a function of the number of nucleotides in a cell on the 46 chromosomes the cell holds. How many genes roughly are on a chromosome and how many nucleotides make up a gene?

Answer 4

Hundreds or thousands of genes on a chromosome. Genes are typically made up of several hundred to several thousands of nucleotides.

Question 5

What is a protein?

Answer 5

A linear sequence of amino acid subunits folded into a specific 3D structure related to its function.

Question 6

How many amino acids are commonly found in humans?

Answer 6

20

Question 7

How many nucleotides code for an amino acid?

Answer 7

3

Note several different 3 nucleotides sequences may code for the same amino acid.

Question 8

When you write the nucleotide code for amino acids do you write the DNA code or the RNA code for convention?

Answer 8

RNA code

Question 9

What are the 4 special codons?

Answer 9

Start codon AUG (also codes for methionine)

Stop Codons UAA UAG UGA

Question 10

A group of 3 nucleotides coding for an amino acid is called?

Answer 10

A codon

Question 11

Transcription is…

Answer 11

The gene in the DNA being encoded into pre-messenger RNA in the nucleus.

Question 12

Translation is…

Answer 12

In the cytoplasm the messenger RNA is converted into a sequence of amino acids in a polypeptide chain to from a protein.

Question 13

What determines the structure and thus the function of a protein?

Answer 13

The amino acid sequence.

Question 14

What is pre-messenger RNA?

Answer 14

The transcript made by the DNA template that will go on to be modified to messenger RNA.

Question 15

What is messenger RNA?

Answer 15

A single stranded complementary copy of the amino acid coding nucleotide sequence of a gene.
(Modified pre-mRNA)

Question 16

Where is pre-mRNA modified to mRNA?

Answer 16

In the nucleus.

Question 17

Where does transcription initiation start?

Answer 17

The promoter region of the DNA sequence.

Question 18

What is the name of the stage of transcription where the gene is read and complementary pre-mRNA is made?

Answer 18

Elongation

Question 19

Describe transcription

Answer 19

RNA polymerase binds to the promoter region, one strand of DNA is used to make pre-mRNA. The polymerase moves along the DNA unwinding it and linking complementary RNA nucleotides into a strand . Opened DNA at the site of transcription is called the transcription bubble. Transcription is terminated at the 3’ termination sequence where the RNA polymerase dissociates.

Question 20

What are the tree stages of transcription?

Answer 20

Initiation
Elongation
Termination

Question 21

Define Introns

Answer 21

Nucleotide sequences in genes that do not code for amino acid sequences in proteins.

Question 22

What are exons?

Answer 22

What is left in mRNA after introns have been spliced out. The sequence of bases that correspond to the amino acid chain of the protein.

Question 23

What happens when pre-mRNA is converted into m-RNA?

Answer 23

Introns are spliced out leaving just the exon sequence.
A nucleotide cap is added to the 5’ end.
Poly-A tail is added to the 3’ end, this is a tail of 30-100 nucleotides.
The final product is a mature mRNA molecule.

Question 24

How does mRNA leave the nucleus for translation?

Answer 24

Through nuclear pores

Question 25

What is alternative splicing?

Answer 25

Exons can be retained or removed during splicing, allowing processed mRNA to contain different exon sequences- this allows one gene to code many different forms of a protein. 95% of pre-mRNA splicing has alternative slicing.

Question 26

What are the three acteristic parts of amino acids?

Answer 26

``` Amino group (NH3) Carboxyl group (COOH) R Group- the side chain. ```

Question 27

Where does a peptide bond form between amino acids?

Answer 27

Carboxyl group to amino group- forms in translation.

Question 28

What is the free amino group at the end of a polypeptide known as?

Answer 28

N-terminus

Question 29

What is the free carboxyll group at the end of a polypeptide known as?

Answer 29

C-terminus

Question 30

By convention which way do we write poly peptide sequences?

Answer 30

N-terminus to C terminus

Question 31

Peptide bond link a what to a what covalently?

Answer 31

C-N the OH on the C and the H on the N are lost as water.

Question 32

Describe the role of rRNA in translation

Answer 32

The rRNA in the rage subunit acts as an enzyme linking amino acids together in the order specified by the mRNA codons.

Question 33

What is transfer RNA?

Answer 33

Transfer RNA molecule bring amino acids to the mRNA ribosome complex for translation. There are two parts to a tRNA molecule -The anticodon (complementary 3 RNA bases to the codon on the mRNA) -Site for amino acid attachment specified by the mRNA codon.

Question 34

Describe translation.

Answer 34

The m-RNA binds to the small ribosomal subunit at the start codon for methionine AUG. Transfer RNA coding the anticodon for methionine binds and then the large ribosomal subunit binds. Transfer RNA carries amino acids with the anticodon dictated by the mRNA into the Ribosome at the A site of the ribosome. The large ribosome subunit contains rRNA which acts as an enzyme linking amino acids by making peptide bond in the P part of the ribosome. The transfer RNA then exits at the E site. The ribosome moves along the mRNA in this fashion throughout elongation. Termination occurs at the end codon which doesn't code for any amino acids. Release factors (proteins) bind instead to the stop codon. The polypeptide, mRNA and tRNA release from the ribosome.

Question 35

What is the first amino acid in all transcription?

Answer 35

Methionine

Question 36

The initiation complex is

Answer 36

The tRNA blinded to the mRNAcodon for methionine in the ribosome- both small and large units.

Question 37

What is a polysome?

Answer 37

After initiation has occurred new initiation complexes can form on the mRNA. One mRNA molecule with many ribosomes attached is called a polysome.

Question 38

What does RNA stand for?

Answer 38

Ribo Nucleic Acid

Question 39

Why do we cap pre-mRNA?

Answer 39

Protect against degradation

Question 40

What is and why do we add polyAtails to pre-mRRNA

Answer 40

Lots of A's added to protect from degradation

Question 41

What is capping?

Answer 41

5' to 5' linking by 3 phosphates covalently bonded. This protects and has a function in translation.

Question 42

What is a ribosome made up of?

Answer 42

Proteins and rRNA with two subunits. We have a 40 subunit and a 60 subunit. We have 80s ribosomes Prokaryotes have 30S and 50S known as 70S ribosome

Question 43

What is the wobble position and what does it exhibit?

Answer 43

3' of codon base and thus the 5' anticodon on base is the wobble position. In translation and inosine on the tRNA may bind to a U, C or A on the mRNA. This allows a singe tRNA to recognise multiple codons.

Question 44

Does elongation in translation require energy?

Answer 44

Yes, in translocation