1. Transcription and Translation
Haileybury Astana IB Biology

2. Transcription and translation

4. Types of RNA
Messenger RNA is synthesised in the nucleus during transcription and carries the genetic code to the rough endoplasmic reticulum where translation occurs.
Transfer RNA attached to an amino acid. tRNA transfers specific amino acids to a polypeptide chain during the ribosomal site of protein synthesis during translation.
Ribosomal RNA consisting of small and large subunits. rRNA translates mRNA into amino acid peptide sequences known as proteins.

5. The synthesis of RNA on a DNA template
Transcription
The synthesis of RNA on a DNA template

6. Messenger RNA
Carries the genetic information from the nucleus to the site of protein synthesis (RER)
Three bases form a codon
Each codon is TRANSLATED into an amino acid

7. Transcription DNA acts as a template (antisense strand)
Synthesis of a mRNA molecule occurs in a 5’-3’ direction according to complimentary base pairing with the antisense strand.
The mRNA molecule has the same sequence as the sense strand except thymine is replaced by uracil.
The process is catalysed by RNA polymerase.
Introns are removed from the mRNA before it passes through the nuclear pores to the cytoplasm.
Copy figure on page 494 of Biology – A Functional Approach by MBV Roberts

8. Sense and antisense strands
The SENSE strand is the coding strand. Its nucleotide sequence is the same as the mRNA except thymine is replaced by uracil.
The ANTISENSE strand is the template strand.
The sense strand may not be the same for all genes!
3’ – 5’ direction

9. Transcription
Explain the process of transcription leading to the formation of mRNA.(8)

10. Explain the process of transcription leading to the formation of mRNA

11. unwinding the DNA strands; binding RNA nucleotides;
Transcription is the synthesis of a mRNA molecule from a DNA template/gene;
RNA polymerase;
unwinding the DNA strands;
binding RNA nucleotides;
to the antisense strand of DNA;
mRNA assembled in a 3’-5’ direction;
using complementary pairing/A-U and C-G;
mRNA detaches from the template and DNA rewinds;
RNA polymerase detaches from the DNA;
many RNA polymerases can follow each other;
mRNA leaves the nucleus via nuclear pores.
8 max

12. The Genetic Code (codons)

13. The Genetic Code (codons)

14. TRANSLATION

15. Question: complete the sequences....
Sense
DNA 5’
.... A T G C 3’
Anti-sense
Polypeptide
Anti-codons
tRNA
Codons ‘
mRNA

16. Question: complete the sequences....
Sense
DNA 5’
.... A T G C 3’
Anti-sense
Ser
Met
Ala
Try
Thr
Polypeptide
Anti-codons A G U
tRNA
Codons 5‘ A U G C 3‘
mRNA