Gene expression

Question 1

Describe RNA

Answer 1

Single stranded
composed of RNA nucleotides

Question 2

Structure of an RNA nucleotide

Answer 2

Consists of a phosophate group ribose sugar and A base

• includes uracil

Question 3

State the three types of RNA

Answer 3

RRNA
MRNA
TRNA

Question 4

State the function of MRNA

Answer 4

carries a complementary copy of DNA code from the nucleus to ribosome
MRNA is transcribed from DNA in the nucleus and translated into proteins in the cytoplasm.

Each triplet of bases on the MRNA codes for a codon and codes for one amino acid

Question 5

Describe TRNA

Answer 5

folds due to complementary base pairing TRNA also has a triplet of bases exposed known as an anticodon at one end of the TRNA molecule

At the other end of the TRNA molecule is the specific amino acid attachment site. The TRNA molecule carries its specific amino acid to the ribosome.

Question 6

State function of RRNA

Answer 6

together with protein forms the ribosome

Question 7

State the transcription process

Answer 7

RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between bases. RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complementary base paring.

the mrna produced is called a primary transcript

Question 8

Describe RNA splicing

Answer 8

During RNA splicing regions known as introns, or non-coding regions, are removed from the primary transcript and the exons or coding regions remain and are spliced together.

As

The exons when spliced together form a mature (mRNA) transcript. It is important to remember that during the process of splicing the order of the exons remains unchanged.

Question 9

Describe the translation process

Answer 9

The mRNA mature transcript leaves the nucleus to the ribosome for the process of translation into a polypeptide.

NA S

(A polypeptide chain is a sequence of amino acids that will eventually become part of a functioning protein).

nor between

not to

Translation starts at a START codon and ends at a STOP codon. This is very important to ensure the entire polypeptide chain is produced without any amino acids missing.

rma

way

The ribosome exposes one codon on the mRNA allowing tRNA to bring a specific amino acid to the ribosome. The correct anticodon on the tRNA will complementary base pair with the codon on the mRNA, bringing the correct specific amino acid with it. The ribosome exposes the next codon where another tRNA and its amino acid will complementary base pair with that codon.

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How many

Aligning amino acids are joined together by a peptide bond, allowing the tRNA to leave the ribosome as the polypeptide is formed. This happens throughout the length of the mRNA until it reaches a STOP codon.

Question 10

describe alternative splicing process

Answer 10

Different proteins can be expressed from one gene as a result of alternative RNA splicing. Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained.

Question 11

describe the formation of proteins

Answer 11

Amino acids are bonded together by peptide bonds to form polypeptide chains.

Polypeptide chains fold to form the three-dimensional shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids.

Proteins have a large variety of shapes which determines their functions.

Remember that a phenotype is a physical expression of a gene/characteristic. This is determined by the protein produced as a result of gene expression.

Environmental factors can also influence phenotype.