protein synthesis

Question 1

genes definition

Answer 1

is a portion of DNA which holds genetic information to code for a protein or RNA molecule

Question 2

exon definition

Answer 2

are segments of a gene that codes for the synthesis of a protein

Question 3

intron definition

Answer 3

segments of a gene that do not code for the synthesis of a protein and is spliced out of the gene through RNA splicing

Question 4

RNA splicing

Answer 4

in transcription the entire gene is copied into mRNA, the molecule before RNA splicing is called pre-mRNA, RNA splicing removes introns forming mature mRNA, the splicing is carried out by a protein RNA complex called a spliceosome. The mature mRNA contains only exons

Question 5

Transcription

Answer 5

occurs in the nucleus, and copies the gene to mRNA

Question 6

transcription stage 1

Answer 6

the enzyme RNA polymerase binds to the beginning of the gene called the promoter, unwinding the DNA

Question 7

transcription stage 2

Answer 7

free RNA nucleotides are attracted to the exposed complementary bases on the template strand of the DNA molecule

Question 8

transcription stage 3

Answer 8

RNA polymerase joins the sugar and phosphate groups of adjacent RNA nucleotides creating the backbone of the mRNA molecule

Question 9

transcription stage 4

Answer 9

mRNA is cut by enzymes to remove the introns (RNA splicing) ligase enzymes join the exons together to form mature mRNA

Question 10

direction of transcription

Answer 10

RNA polymerase reads the template strand in the 3’ to 5’ direction and the RNA is formed in the 5’ to 3’ direction

Question 11

codon

Answer 11

every 3 nucleotide base in the mRNA molecule which codes for one amino acid

Question 12

mRNA

Answer 12

synthesised during transcription, enables a protein to be formed, mRNA can travel outside the nucleus to the ribosome

Question 13

rRNA

Answer 13

ribosomal RNA. The rRNA functions as an enzyme by catalysing the formation of the protein molecule

Question 14

Ribosomes made up of and subunits etc

Answer 14

ribosomes consist of a small and large subunit, the small subunit reads the mRNA and the large subunit joins the amino acids to form a protein. Ribosomes are composed of 60% rRNA and 40% protein.

Question 15

tRNA

Answer 15

transfer RNA, transfers amino acids to the ribosome during translation

Question 16

anticodons

Answer 16

binding region on the tRNA, which are a sequence of 3 bases complementary to the mRNA codon which codes for the attached amino acid

Question 17

translation stage 1

Answer 17

the ribosome binds to the beginning of the mRNA and position itself at the first codon

Question 18

translation stage 2

Answer 18

a tRNA with an amino acid attached with complementary base pair to the codon through its anti-codon

Question 19

translation stage 3

Answer 19

the mRNA molecule moves so that the next codon is now covered by the ribosome. The large ribosomal unit catalyses a chemical reaction that joins the amino acids together

Question 20

translation stage 4

Answer 20

the process is repeated until a stop codon is reached on the mRNA. The newly synthesised protein molecule moves to the rough endoplasmic reticulum

Question 21

triplet

Answer 21

3 bases in a gene on DNA coding for an amino acid

Question 22

template strand

Answer 22

single strand of DNA from which a single stranded molecule of mRNA is made from in transcription (closest to RNA strand)

Question 23

coding strand

Answer 23

the strand of DNA which has the correct sequence to produce a protein, the same as the mRNA strand (furthest from RNA strand)