Protein Synthesis

Question 1

What is a gene

Answer 1

Sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chain

Question 2

What is the genome

Answer 2

The complete set of genetic information in an organism

Question 3

What are the two stages of protein synthesis

Answer 3

Transcription
Translation

Question 4

What occurs during transcription

Answer 4

-enzyme helicase attaches to DNA causing H bonds between paired bases to break and DNA to unwind
-the sequence on one of the strands is transcribed to make mRNA molecule with same base sequence as DNA coding strand
-free complementary RNA nucleotides align themselves into position with template DNA strand and RNA polymerase causes phosphodiester bonds to form between adjacent RNA molecules to produce mRNA molecule
-mRNA leaves nucleus through pore in nuclear envelope and DNA zips up

Question 5

What occurs during translation

Answer 5

-mRNA attaches to ribosome in cytoplasm
-first codon exposed on ribosome is always start codon which the tRNA carrying complementary anticodon for binds to
-ribosome moves along mRNA strand to expose next codon
-tRNA with anticodon complementary to this next codon brings next amino acid
-ribosome holds mRNA and tRNA in place while peptide bonds form between the amino acids
-translation continues until stop codon is reached which no tRNAs have complementary anticodon for so no amino acid is transferred
-completed polypeptide chain dissociated from ribosome

Question 6

Structure of a tRNA molecule(transfer RNA)

Answer 6

-at one end is a three base sequence(anticodon) which is complementary to the mRNA codon for a particular amino acid
-at opposite end is a binding site for an amino acid
-within cytoplasm free amino acids become attached to the correct tRNA molcules

Question 7

What is mRNA and why is it made

Answer 7

-messenger RNA
-sequence of bases with same sequence as DNA sense strand needed to make required protein
-made as it is small enough to leave the nucleus to attach to a ribosome in the cytoplasm

Question 8

How many bases codes for one amino acid and what is this called

Answer 8

-three bases codes for one amino acid, called a codon

Question 9

Why is the genetic code degenerate

Answer 9

There are more codon codes than amino acids so more than one codon can code for the same amino acid