Why do we need RNA molecule for coding?. Nucleus membrane has small pores which let small molecules through to the cytoplasm. Double helix DNA molecule is too big to move through the pores. Amino acids and ribosome occur only outside the nucleus in the cytoplasm of the cell.
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Why do we need RNA molecule for coding?
Nucleus membrane has small pores which let small molecules through to the cytoplasm.
Double helix DNA molecule is too big to move through the pores.
Amino acids and ribosome occur only outside the nucleus in the cytoplasm of the cell.
Have to use small molecules with the same codes as the DNA to form the correct protein in the ribosome. This small molecule is RNA.
Study the next slide.
Diagrammatical presentation of some parts of a cell (Not drawn to scale)
Pore in nucleus membrane
Ribosome – ‘protein fabric’
From the DNA template a mRNA is formed in the nucleus
Single strand mRNA moves through the pores in the nucleus membrane into the cytoplasm of a cell
Single strand – No complementary bases
Uraciel replaces Thymine
A simplified diagram of a part of a mRNA molecule.
Three types of RNA molecules
Messenger RNA (mRNA).
Move from the nucleus to the ribosome in the cytoplasm. Carrying the genetic codes from DNA.
Ribosomal RNAs (rRNA)
They combine with proteins to form a subunit of a ribosome.
Transfer RNA (tRNS)
Is a single strand that is folded to form loops. At one of the looped ends it has three exposed bases, called anticodon. At the opposite end an amino acid is attached.
tRNA are used to transfer amino acids to the ribosome during protein synthesis.
Diagrams to show mRNA and rRNA
Comparison between DNA and RNA
Both have the same phosphate groups
Sugar-phosphate bond joins the adjacent sugars of the nucleotides