LIFE SCIENCES
FOR GRADE 12
GENETICS –
NUCLEIC ACID
RNA
WHAT IS RNA
> RNA is made up of:
Ribose sugar (a pentose sugar with 5
carbons),
Phosphate and
A nitrogenous base; e.g. Pur...
> The RNA strand is made up of alternating
molecules of ribose sugar and phosphate.
> The nitrogen bases are attached to t...
TYPES AND LOCATION OF RNA
> mRNA (MESSENGER RNA) –
> tRNA (TRANSFER RNA)
> rRNA (RIBOSOMAL RNA)
> cRNA (catalyticRNAs)
> s...
mRNA
> Single strand RNA nucleotides.
> A polynucleotide strand synthesized
according to the code of the DNA.
> It carries...
tRNA
> A single RNA strand folded in the shape of a
clover leaf.
> It carries a specific amino acid on one end
and transfe...
rRNA
The two ribosomal subunits (large and small)
are made of proteins and ribosomal RNA
(rRNA)
The single-stranded molecu...
PROTEIN SYNTHESIS
> PROTEIN SYNTHESIS CONSIST OF 2
DISTINCT STAGES:
TRANSCRIPTION
TRANSLATION
TRANSCRIPTION
The 3 stages of transcription:
> Initiation
> Elongation
> Termination
TRANSCRIPTION:INITIATION
> RNA-polymerase attaches to the beginning
of the DNA code called the promotor.
> It unwinds the ...
TRANSCRIPTION:ELONGATION
> Free nucleotides in the nucleus bonds to the
complementary bases of the DNA template
strand. (U...
TRANSCRITION:TERMINATION
> The mRNA will detach from the DNA
template.
> The RNA polymerase detaches and starts
all over a...
TRANSLATION
> A cell translates an mRNA message into
protein
WHAT IS NEEDED TO DO THIS?
> mRNA (Carries the code)
> tRNA (...
THE THREE STAGES OF
TRANSLATION
> Initiation
> Elongation
> Termination
TRANSLATION:INITIATION
> Small ribosomal subunit binds with mRNA
Small subunit moves along mRNA until it
reach the start c...
TRANSLATION;ELONGATION
> More tRNA anticodons attach to mRNA
codons.
> The amino acids attached to the tRNA’s
attach to on...
TRANSLATION:TERMINATION
> Termination occurs when a stop codon in
the mRNA reaches the A site of the
ribosome
> The A site...
REFERENCES
http://www.slideshare.net/dreyngerous/rna
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Presentation4

  1. 1. LIFE SCIENCES FOR GRADE 12 GENETICS – NUCLEIC ACID RNA
  2. 2. WHAT IS RNA > RNA is made up of: Ribose sugar (a pentose sugar with 5 carbons), Phosphate and A nitrogenous base; e.g. Purines (Adenine and Guanine) and Pyrimidines (Cytosine and Uracil). RNA exists largely as single nucleotide chains in living cells.
  3. 3. > The RNA strand is made up of alternating molecules of ribose sugar and phosphate. > The nitrogen bases are attached to the sugar molecules in the strand and ’stick out’ laterally as in DNA. > A sugar, a nitrogenous base and a phosphate together form a ribonucleotide. > An RNA molecule is a polymer of ribonucleotides.
  4. 4. TYPES AND LOCATION OF RNA > mRNA (MESSENGER RNA) – > tRNA (TRANSFER RNA) > rRNA (RIBOSOMAL RNA) > cRNA (catalyticRNAs) > snRNA (Small Nuclear RNA) > snoRNA (Small Nucleolar RNA)
  5. 5. mRNA > Single strand RNA nucleotides. > A polynucleotide strand synthesized according to the code of the DNA. > It carries the code in base triplet (codon) form, from the DNA to the ribosomes. > Found in the nucleus of the cell.
  6. 6. tRNA > A single RNA strand folded in the shape of a clover leaf. > It carries a specific amino acid on one end and transfers it to the ribosomes. > Has an anticodon on the other end; the anticodon base-pairs with a complementary codon on mRNA. > Found in the cytoplasm of the cell.
  7. 7. rRNA The two ribosomal subunits (large and small) are made of proteins and ribosomal RNA (rRNA) The single-stranded molecule of rRNA is variously folded and twisted upon itself in certain regions forming a secondary structure. Constitutes 50% of a ribosome. Help to bond mRNA to protein of the ribosome. Found in the ribosomes in the cytoplasm of the cell.
  8. 8. PROTEIN SYNTHESIS > PROTEIN SYNTHESIS CONSIST OF 2 DISTINCT STAGES: TRANSCRIPTION TRANSLATION
  9. 9. TRANSCRIPTION The 3 stages of transcription: > Initiation > Elongation > Termination
  10. 10. TRANSCRIPTION:INITIATION > RNA-polymerase attaches to the beginning of the DNA code called the promotor. > It unwinds the DNA molecule and breaks the weak hydrogen bonds between the complementary strands – a “bubble forms” > The one strand now acts as a template for the formation of the mRNA strand.
  11. 11. TRANSCRIPTION:ELONGATION > Free nucleotides in the nucleus bonds to the complementary bases of the DNA template strand. (Uracil replaces Thymine in mRNA) > More free nucleotides bond to their complementary bases, to elongate the mRNA strand, until the entire code has been transcribed.
  12. 12. TRANSCRITION:TERMINATION > The mRNA will detach from the DNA template. > The RNA polymerase detaches and starts all over again at a different location where needed. > Now the pre-mRNA strand has to undergo a modification and RNA splicing before it can leave the nucleus
  13. 13. TRANSLATION > A cell translates an mRNA message into protein WHAT IS NEEDED TO DO THIS? > mRNA (Carries the code) > tRNA (pick up amino acid and takes it to the mRNA > Amino acid (connect to form protein) > Ribosome (Location for protein synthesis)
  14. 14. THE THREE STAGES OF TRANSLATION > Initiation > Elongation > Termination
  15. 15. TRANSLATION:INITIATION > Small ribosomal subunit binds with mRNA Small subunit moves along mRNA until it reach the start codon (AUG) > The matching anti-codon of the tRNA (with amino acid Methionine)bonds with the start codon. > Add the large subunit which completes the translation initiation complex.
  16. 16. TRANSLATION;ELONGATION > More tRNA anticodons attach to mRNA codons. > The amino acids attached to the tRNA’s attach to one another by means of peptide bonds. > Amino acids form a long polypeptide chain. tRNA releases amino acid to pick up more amino acids
  17. 17. TRANSLATION:TERMINATION > Termination occurs when a stop codon in the mRNA reaches the A site of the ribosome > The A site accepts a protein called a release factor. > The release factor causes the addition of a water molecule instead of an amino acid. > This reaction releases the polypeptide, & the translation assembly then comes apart
  18. 18. REFERENCES http://www.slideshare.net/dreyngerous/rna

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