2.7b, 7.2, 7.3 (protein synthesis, Transcription & Translation)

Question 1

3 Structural difference between DNA and RNA

Answer 1

RNA has Uracil instead of thymine
RNA has 1 strand instead of 2
DNA = Deoxyribose acid
RNA = Ribonucleac acid

Question 2

3 types of RNA

Answer 2

mRNA = carries messages between DNA to ribosome
rRNA = Ribosome made of RNA
tRNA = carries amino acids to the ribosome based on instructions from mRNA

Question 3

Transcription

Answer 3

2. Occurs before translation
3. occurs in a 5’ to 3’ direction
4. DNA allows the mRNA to code for different Amino acids in your body with the help of ribosomes.
5. RNA polymerase binds to the promotor region of the DNA strand and separates the DNA strands.
6. RNA polymerase covalently binds the nucleoside triphosphates (NTP) while releasing 2 phosphates.
7. Complementary base pairing for RNA occurs (A-U & C-G)
8. When Terminator signal is reached, the RNA polymerase stops and detaches from the DNA.
9. RNA then detaches from DNA template and the double helix reforms by supercoiling.
10. The introns are then removed from the RNA in eukaryotes to form mRNA, which is for later use in translation.

Question 4

Operons

Answer 4

• is a sequence of DNA containing a cluster of genes under the control of a single promoter

Question 5

Components of an Operon

Answer 5

P.R.O.G

• Promoter (RNA polymerase binds to)
• Repressor
• Operator (Segment of DNA to which a repressor protein binds)
• Genes

Question 6

Lac Operon

Answer 6

Section of DNA working together to form lactase
1. Lactose binds w repressor removing it from the operator, changing its shape allowing RNA polymerase to make lactase and break down lactose

Question 7

Example of how the environment of a cell and of an organism has an impact on gene expression

Answer 7

Melanin in the skin
- More sun exposure = more melanin
- Darker skin = more natural sunscreen

Question 8

Nucleosomes

Answer 8

• Regulate transcription in eukaryotes
• Chemical tags outside histones coiled with DNA = epigenome
• Epigenomes up-regulate or down-regulate gene expression
• Epigenomes are flixible and react to the outside environment

Question 9

Analysis of changes in the DNA methylation patterns

Answer 9

Increased methylation of DNA decreases gene expression
- Consequently, genes that are not transcribed tend to exhibit more DNA methylation than genes that are actively transcribed

Question 10

Translation

8 Mark

Answer 10

Sites = EPA
1. mRNA binds to small subunit of a Ribosome inside the cytoplasm and reads the mRNA in 3 bases long (1 codon) at the P-Site
2. **INITIATION OCCURS: **tRNA comes along with an amino acid and binds to codon with the anticodon on the P-site
3. Start codon is always AUG, and anticodon is UAC
4. **ELONGATION OCCURS: **Second tRNA comes with a new amino acid and binds to the A site
5. **TRANSLOCATION OCCURS: **The 2 tRNA move along to the next sites, A to P and P to E, the first tRNA amino acid breaks off and binds to the second tRNA amino acid with a peptide bond
6. The cycle is repeated, new tRNA comes to A site pushing the tRNAs along forming a long polypeptide
7. **TERMINATION OCCURS: **When a stop codon appears on the A site, a releasing factor is signaled, translation stops and polypeptide forms a protein
8. rRNA finds a new mRNA, and the mRNA then breaks apart into nucleotides and goes into the nucleous.

Question 11

Using a table of mRNA codons and their corresponding amino acids to deduce the sequence of amino acids coded by a short mRNA strand of known base sequence

Answer 11

Example: (mRNA) GUAUGCACGUGACUUUCCUCAUGAGCUGAU

Answer: (codons) GU AUG CAC GUG ACU UUC CUC AUG AGC UGA U

Answer: (amino acid) Met His Val Thr Phe Leu Met Ser STOP

Question 12

Answer 12

Question 13

Using the table, tranlate the mRNA into a polypeptide

mRNA: U G C A A U G C C U A A U G U C A G G G U U U G A U G

Answer 13

Question 14

Free ribosomes

Answer 14

• synthesize proteins for use primarily within the cell.
• Float around cytoplasm and protuce proteins

Question 15

Bound ribosomes

Answer 15

• synthesize proteins primarily for secretion or for use in lysosomes.
• Produce proteins into golgi apparatus which get packed into vessicles to be shopped out of cell

Question 16

Protein structures

Answer 16

Question 17

The tertiary protein structure is the further folding of the polypeptide stabilized by interactions between R groups.

Answer 17

• Polar & nonpolar amino acids are relevant to the bonds formed between R groups in the tertiary structure
• Some ‘R’ groups are polar, some are non-polar

Question 18

quaternary structure

Answer 18

• exists in proteins with more than one polypeptide chain.
• multiple polypeptides come together to form quaternary structure

Question 19

RNA Splicing

8 mark

Answer 19

1. DNA transcribed into mRNA with transcription
2. before mRNA is a thing, introns interrupt coding regions by seperating the exons
3. The process of RNA splicing removes introns, joining the exons into a contiguous sequence (solid line)
4. RNA splicing begins with assembly og helper proteins at the intron/ exon boarders, defining the section to be cut out.
5. A spliceosome is assmebled with splicing factors bringing the exons together ready to cute the intron
6. The spliceosome cuts the 5’ end of the intron causing the intron to loop back on itself.
7. Spliceosome then cuts the 3’ releasing the intron and the exons bind together
8. Intron is broken down, splicesosome is disassembled and ‘mature’ mRNA is formed
9. This ‘mature’ mRNA is then ready to be translated into a protein through translation