Gene Expression

Question 1

Phenotype

Answer 1

A cell’s phenotype (it’s physical state) is determined by the proteins that are synthesised when the genes are expressed

Question 2

Gene Expression

Answer 2

Gene expression is controlled by transcription and translation.

Only a fraction of the genes in a cell are expressed

Question 3

RNA

Answer 3

-RNA nucleotides join together into a permanent strand
-exists only as a single strand

Question 4

mRNA

Answer 4

Carries a complimentary copy of the genetic code from the DNA in the nucleus to the ribosome, where proteins are assembled from amino acids. Carries a mature strand. The order of the bases in the DNA determines the sequence of the amino acids in the proteins.

Question 5

tRNA

Answer 5

tRNA folds die to the complimentary base pairing. Each tRNA molecule carries its specific amino acid to the ribosome. It has three bases called an ANTICODON. It has an attachment site for a specific amino acid which is complimentary.

Question 6

rRNA

Answer 6

Ribosomal RNA and proteins form the ribosome where translation takes place.

Question 7

Transcription

Answer 7

1. DNA containing gene to be transcribed in identified
   2.RNA polymerase moves along the DNA breaking the hydrogen bonds and separating the DNA strands
   3.RNA nucleotides pair with DNA bases
2. Guanine pairs with cytosine and adenine pairs with uracil
3. Sugar phosphate backbone forms, this requires ATP/enzymes/RNA polymerase
   6.Introns are removed from the mRNA/primary transcript to make the mature strand
   DNA winds up into a double helix

Question 8

Requirements

Answer 8

DNA(gene)
Free RNA nucleotides
RNA Polymerase
ATP

Question 9

RNA Splicing

Answer 9

RNA splicing forms a mature transcript from the primary mRNA transcript
-Introns are removed from the primary transcript
-the exons are joined together to form mature RNA transcript
-The order of exons is unchanged during splicing
-Mature mRNA travels to ribosome from nucleus through cytoplasm

Question 10

Introns

Answer 10

non coding region of the primary transcript

Question 11

Exons

Answer 11

Coding regions of the primary transcript

Question 12

Why do you think RNA splicing might be of importance to the protein

Answer 12

Wrong or extra amino acids are not placed in the protein which would affect how it folds and functions and so the correct proteins is formed

Question 13

Translation

Answer 13

Starts at the start codon and ends at the stop codon
-mRNA attaches/moves to the ribosome
-tRNA carries amino acid to mRNA/ribosome
-each tRNA molecule is attached to a specific amino acid
-tRNA has an anticodon of three bases, mRNA has a codon of three bases
-Anticodon binds to/aligns with codon
-Order of codons/bases determines the order of amino acids
-Peptide bonds form between amino acids
-Ribosome moves along the mRNA strand
-each tRNA molecule leaves the ribosome to collect its specific amino acid in the cytoplasm.

Question 14

Alternative Splicing

Answer 14

Different mature mRNA molecules are produced from the same primary transcript.

This depends on which exons are retained.

Question 15

Protein Structure

Answer 15

The polypeptide chain folds to form the three dimensional shape of a protein.

Hydrogen bonds and other interactions between individual amino acids hold the protein in it’s three dimensional shape.

Question 16

Environmental factors

Answer 16

Environmental factors also influence phenotype by changing the order of the base sequence.
x-rays
UV radiation
mustard gas
nuclear radiation

Question 17

Phenotype

Answer 17

Phenotype is determined by proteins produced by proteins produced as a result of gene expression.