3.4.2 DNA and protein synthesis

Question 1

Transcription

• only about production of mRNA

Answer 1

*DNA helicase unwind the DNA double helix and separate the two strands *by breaking hydrogen bonds between complementary base pair
This expose unpaired base on the template strand *(Only one strand is used to code for mRNA = template)
*Free RNA nucleotide from the nucleoplasm come in and bind/ attracted to their *complimentary base pair on the template strand
The enzyme RNA polymerase binds to the template strand of the DNA at the start triplet
*RNA polymerase catalyses the formation of phosphodiester bond between adjacent RNA nucleotides one at a time
*splicing to remove intron

Behind RNA polymerase, the DNA strands rewind to form the double helix once again
Beyond the end of the gene there is a “stop” triplet code, where RNA polymerase leave DNA
MRNA detached from the DNA and can pass out from the nucleus through a nuclear pore into the cytoplasm

Question 2

Translation

Answer 2

Ribosome associate/ attached to mRNA
Ribosome find the start codon
TRNA carry specific amino acid
anticodon on trna complementary to codon on mrna
The process continue ribosome move along onto next codon
Peptide bond form between amino acid by condensation reaction or through used of energy from ATP

Question 3

defintion of genome

Answer 3

the complete set of genes in a cell

Question 4

the structure of molecules of mRNA and tRNA

Answer 4

a single-stranded chain of ribonucleotides (adenine, cytosine, guanine, and uracil) with a sugar-phosphate backbone

• no hydrogen bond / linear (straight)
  phosphodiester bond between adjacent bases
  -no aa binding site
  -more nucleotides (long)
  different length
  -codon

hydrogen bond /cloverleaf shape
peptide bond between amino acid
aa binding sites
less nucleotides (short)
all same length
anticodon

Question 5

difference in transcription result in prokaryotes and eukaryotes

Answer 5

prokaryotes
directly in production of mRNA from DNA
There is no intron in prokaryotic cell

Eukaryotes
produce pre-mRNA. then spliced

Question 6

why does the lack of nuclear envelope in prokaryotes required their genes to lack introns?

Answer 6

prokaryotes don’t have a nuclear membrane surrounding the DNA
thus translation before transcription has even begun
no time for splicing
in eukaryotes the membrane seperate transcription and translation

Question 7

definition of proteome

Answer 7

the full range of protein/ different amino acid that a cell is able to produce

Question 8

advantage of showing the genetic code as base sequence on mRNA rather than triplet on DNA

Answer 8

ribosome assembles polypeptide using mRNA code
DNA have 2 strand each with different bases

Question 9

why mRna of a particular gene is shorter than original gene

Answer 9

DNA contain introns
after splicing
mRNA contain only exons

Question 10

exam Q : why error in precise location of splicing in dna molecule can lead to mutations

Answer 10

change in base sequence of exons
deletion of exons/ bases

Question 11

DNA vs tRNA vs mRNA

Answer 11

1. Deoxyribose v ribose v ribose
2. Double-stranded v single-stranded v single-stranded
3. Many nucleotides v few v X
4. Thymine v uracil v uracil
5. Linear/double helix v clover leaf (structure) v linear
6. Does not bind to amino acid v does bind to amino acid v doesn’t bind to amino acid
7. No exposed bases v anticodon v codon
8. Long vs (no comment) vs short
9. hydrogen bond vs hydrogen bond vs no hydrogen bond