Gene Expression

Question 1

What is Protein Synthesis?

Answer 1

It is the process where cells make proteins for the organism.

Question 2

Explain Transcription

Answer 2

Transcription is the process where DNA turns into mRNA in the nucleus of the cell. This occurs in the nucleus because that’s where the DNA is stored.

First the promoter region signals the enzyme RNA polymerase to unwind the section of DNA which codes or the polypeptide chain. This unwound piece is made into a copy called mRNA by attaching matching complementary base pairs (A,U,C,G).
The section of DNA then rewinds.

The mRAN will leave the nucleus via the nuclear pores to travel to the cytoplasm/ribosomes

Question 3

Explain Translation

Answer 3

Next the mRNA travels to the ribosomes in he cytoplasm to undergo translation. They do so because ribosomes read and assemble proteins.

The mRNA joins with a ribosome at a start codon. tRNA brings in the correct ANTICODONS. When two amino acids are side by side a peptide bond forms between them. The ribosomes keep on moving along a codon the first tRNA leaves the ribosomes

Then tRNA brings in its matching, amino acid, peptide bond forms and ribosome moves long.
This process continues until the ribosome meets a termination codon where the ribosomes leaves he mRNA.

Question 4

Explain Protein Folding

Answer 4

After the polypeptide chain has been produced it is still not a functional protein, as the chain needs to be folded in a specific way. Most proteins are either fibrous and are folded in regular secondary structures, where the polypeptide chain forms a zigzag, spire helix or are globular

GLOBULAR are folded into a tertiary or ternary structure
TERTIARY folding involves a polypeptide chan being folded into a irregular ball shape
QUATERNARY folding involves two or one polypeptide chains being loosely held together.

Question 5

Explain Protein Folding

Answer 5

After the polypeptide chain has been produced it is still not a functional protein, as the chain needs to be folded in a specific way. Most proteins are either fibrous and are folded in regular secondary structures, where the polypeptide chain forms a zigzag, spire helix or are globular

GLOBULAR are folded into a tertiary or ternary structure
TERTIARY folding involves a polypeptide chan being folded into a irregular ball shape
QUATERNARY folding involves two or one polypeptide chains being loosely held together.

Question 6

What is a Metabolic Pathway

Answer 6

A metabolic pathway is a series of enzyme controlled chemical reactions were the product of one chemical reaction is the reactant for the next.

Question 7

Explain what a PRECURSOR, INTERMEDIATE , and PRODUCT are in a Metabolic Pathway

Answer 7

A PRECURSOR in a metabolic pathway is a the STARTING MOLECULE or compound that starts the enzyme catalysed reactions

A INTERMEDIATE is the MOLECULES formed at various steps along the pathway, between the precursor and the final product.

A PRODUCT is the END RESULT or final molecule produced by the pathway.

Question 8

What is the difference between DNA and mRNA

Answer 8

DNA is a LONG LIVED, DOUBLE STRANDED molecule found in the NUCLEUS.
It is made up of DEOXYRIBOSE sugar.
Its base pairs are, A, T, C, G.
DNA is the BLUE PRINT to ALL GENETIC INFORMATION and INSTRUCTIONS.

MRNA is a SHORT LIVED, SINGLE. STRANDED molecule.
It is made up of RIBOSE sugar.
Its base pairs are, A, U, C, G.
MRNA is the copy of DNA.

Question 9

What is a Mutation?

Answer 9

A mutation is a permanent change in the DNA base sequence of a gene.

Question 10

What are the different types mutations?

Answer 10

There are two groups of mutations, POINT MUTATION, and FRAMESHIFT MUTATION.

The different type of POINT MUTATIONS include, silent, messiness and nonsense.
The different type of FRAMESHIFT MUTATIONS include, deletion and insertion.

Question 11

Explain what is mean by “degeneracy of the genetic code”

Answer 11

There are 20 AMINO ACIDS and 64 CODONS. Because there are more codons than amino acids, some amino acids are coded by MORE THAN ONE CODON. This is called DEGENERACY of the GENETIC CODE

Question 12

Explain what is a SILENT MUTATION

Answer 12

A SILENT MUTATION is a type of mutation that changes a codon in the DNA sequence but does not change the amino acids which it USED TO code for. This occurs due to the degeneracy and redundancy fo the genetic code. Since there are 64 codons and 20 amino acids, it means more than one codon will code for an amino acid, due to this degeneracy. This DOES NOT alter the protein FORMED

Question 13

Explain what a MISENSE MUTATION is

Answer 13

A MISENSE MUTATION is a type of mutation that changes a single codon in the DNA sequence, resulting in a DIFFERENT AMINO ACID being produced during protein synthesis. This occurs because the new codon codes for a different amino acid due to the change in the DNA sequence.

Question 14

Explain what a NONSENSE mutation is

Answer 14

A NONSENSE mutation is where a codon that originally coded for a amino acid gets changed to a stop codon due to a mutation in the DNA base sequence.
This causes the protein synthesis to stop prematurely, producing a SHORTENED and usually NON-FUNCTIONAL protein.

Question 15

Explain what a INSERTION mutation is

Answer 15

A INSERTION mutation is where a EXTRA BASE is added into the DNA SEQUENCE. The number of bases will no longer be in a three causing a FRAMESHIFT.
This leads to the production of a completely different amino acids from he point of insertion onwards resulting in a non-functional protein.

Question 16

Explain what a FRAMESHIFT is

Answer 16

A FRAMESHIFT occurs when the number of bases INSERTED or DELETED from a DNA sequence is NOT a MULTIPLE of THREE Since coding are read in groups of three during translating, adding or removing bases shifts the READING FRAME. This changes how every codon after the mutation is read, which can lead to completely different amino acids being produced.

Question 17

Explain what a DELETION mutation is

Answer 17

A DELETION mutation occurs when one or more bases are removed from the DNA sequence. If the number of deleted bases is not a multiple of three it causes a FRAMESHIFT, changing the a the codons are read. This leads to a completely different and usually non-functional protein.

Question 18

What happens AFTER a FRAMESHIFT

Answer 18

After a FRAMESHIFT mutation either of 3 things can occur.
1. Since the codons ae read incorrectly, the ribosomes assemble a completely different set of amino acids after the mutation, this produced a protein with a jumbled sequence, which likely will not function properly.

2. They can also introduce a premature stop codon which causes proteins synthesis too stop a lot sooner. This results in a shorter, incomplete protein that is nonfunctional.
3. Because he structure of the protein is crucial for its function, these significant changes in the amino acids sequence causes the protein to fold incorrectly further causing it to not perform its function.

Question 19

What is a MUTAGEN with EXAMPLES

Answer 19

A mutagen is something which can cause a CHANGE or MUTATION in the DNA.
Examples include chemicals and radiation.
These mutation will only get passed on to the offspring if they occur in the gametic cells but if they occur in the SOMATIC CELLS they will NOT be PASSED onto future generation.

Question 20

Explain how environmental factors influence the phenotype without changing the genotype

Answer 20

The environment influences the expression of the phenotype of an organism without changing its genotype to help it to adapt and survive in its niche, giving it a better chance at survival.

An example of this is sun exposure. Being exposed in more sunlight causes your skin to produce more melanin but it doesn’t change your DNA that controls the genotype for skin colour. The DNA remains the same but the environment changes how the body uses it to maximise survival.

Another example is diet. Flamingos genotype causes them to phenotypically express white but due to their DIET of salmon fish they are pink/orange. The build up of the pigment form the fish causes them to express the pigment in their own bodies without changing the genotype.