DNA & Protein Synthesis - C5

Question 1

What is protein synthesis?

Answer 1

How DNA can lead to the making of a protein

Question 2

What are the two major steps of protein synthesis?

Answer 2

Transcription and Translation

Question 3

Where does transcription occur?

Answer 3

In the nucleus

Question 4

What are the first 4 steps of transcription?

Answer 4

1. Helicase unwinds the DNA (only unwinds at a particular gene, exposing nitrogenous bases to make a particular protein)
2. Free complimentary RNA is connected by RNA polymerase to one half of the DNA
3. The RNA then detaches from the DNA to form a single stranded mRNA (messenger RNA)
4. Ligase sews DNA back together

Question 5

Is Uracil or Thymine in RNA?

Answer 5

Uracil

Question 6

Can mRNA leave the nucleus?

Answer 6

Yes

Question 7

What are the first 3 phases of Translation?

Answer 7

1. mRNA leaves nucleus and attaches to a ribosome (makes proteins)
2. Then nitrogenous bases (A-U, G-C are read in groups of 3 = codons)
3. Each codon codes for a specific amino acid (20 of them0

Question 8

When will the ribosome start making amino acids?

Answer 8

When START codon is reached (see codon table for more info)

Question 9

What are the next 3 steps of translation?

Answer 9

4. tRNA (transfer RNA in ribosomes) is attracted to mRNA strand
5. an amino acid is brought by tRNA
6. these amino acids are joined together by ribosomes (with peptide bonds, catalyzed by ribosomes)

Question 10

What is tRNA?

Answer 10

transfer RNA (has a group of three bases on it, when it finds a section on mRNA that matches, it leaves its amino acid behind, making an amino acid chain (first step of making a protein)

Question 11

What is an anticodon?

Answer 11

A complimentary nitrogenous base sequence to the codon on mRNA

Question 12

When will ribosome finish protein?

Answer 12

When STOP codon is reached

Question 13

What bonds hold DNA together?

Answer 13

Weak hydrogen bonds

Question 14

4 complimentary base DNA pairs

Answer 14

A-T
G-C

Question 15

How does DNA replication work?

Answer 15

splits double strand into two single strands and each strand makes a new partner so that when cell divides each has full DNA set

Question 16

What are the first 3 steps of DNA replication

Answer 16

1. Helicase unwinds DNA
2. Single Stranded Binding (SSB proteins) hold two strands of DNA apart so they don’t re-join
3. DNA primase generates a short RNA primer (10-15 nucleotides) on each template strand (piece or original DNA) this gives the signal for DNA polymerase 3 to start

Question 17

What does semi conservative mean?

Answer 17

Some original DNA is kept, some is taken away

Question 18

What are the next 3 steps of DNA replication?

Answer 18

4. Free nucleotides align to complementary nitrogenous base (A-T, G-C)
   note: DNA strands are antiparallel DNA Polymerase 3 moves in different directions on each strand (on the leading strand - moves towards replication fork (up to where helicase unzipped) and synthesis continuously - all in one. On lagging strand moves away from replication fork and synthesis in pieces - bit by bit
5. DNA Polymerase 1 - as lagging strand is synthesised in short fragments = has multiple RNA primers along length. DNA Polymerase 1 removes them as it goes and replaces them with DNA nucleotides
6. DNA Ligase joins fragments on lagging strand together to form a continuous strand (does this by joining sugar-phosphate backbones together)

Question 19

What is an RNA primer?

Answer 19

RNA that begins DNA synthesis