Why do we need rna molecule for coding
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Why do we need RNA molecule for coding? PowerPoint PPT Presentation


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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.

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Why do we need RNA molecule for coding?

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Why do we need rna molecule for coding

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.


Why do we need rna molecule for coding

Diagrammatical presentation of some parts of a cell (Not drawn to scale)

DNA

Nucleus

Nucleus membrane

Pore in nucleus membrane

Ribosome – ‘protein fabric’

Amino acids


Coding for proteins in the cytoplasm by a single strand molecule called rna

Coding for proteins in the cytoplasm by a single strand molecule, called RNA

  • The RNA molecule is a polymer, a long molecule that is made up of many monomers called nucleotides.

  • Three types of RNA are messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA).

  • mRNA molecules are formed from a DNA template in the nucleus. Will discuss the detail under protein synthesis.


Forming and movement of mrna

Forming and movement of mRNA

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


Coding for proteins by mrna

Coding for proteins by mRNA

  • Because mRNA has a single strand structure it can move through the small pores of the nucleus membrane into the cytoplasm of the cell.

  • It is the nitrogenous bases that is responsible for the coding of the proteins.

  • Threeconsecutive (next to each other) bases in mRNA are called a codon.

  • These three bases (codon) represent the code for a particular amino acid.


Coding for life mrna molecule

Coding for Life – mRNA molecule

Note:

Single strand – No complementary bases

Uraciel replaces Thymine

U

A simplified diagram of a part of a mRNA molecule.


Three types of rna molecules

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

Diagrams to show mRNA and rRNA

mRNA

rRNA

U

Codon


Diagram to show trna

Diagram to show tRNA


Comparison between dna and rna

Comparison between DNA and RNA

Differences

Similarities

Both have the same phosphate groups

Sugar-phosphate bond joins the adjacent sugars of the nucleotides

together


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