604731
AQA AS Biology DNA
- Nucleotides
- Nitrogen containing base - adenine, cytosine,
guanine and cytosine
- Deoxyribose/Pentose Sugar
- Phosphate group
- Nitrogen containing base - adenine, cytosine,
guanine and cytosine
- Bases
- Adenine and guanine -
pyramidine bases/double
ring structure
- Cytosine and thymine -
purine bases/single ring
structure
- Adenine is
complementary to
thymine - 2 hydrogen bonds
- Cytosine is
complementary to
guanine - 3 hydrogen bonds
- Adenine and guanine -
pyramidine bases/double
ring structure
- RNA
- Uracil replaces thymine
- There is a ribose sugar
instead of a
deoxyribose sugar
- It is single stranded whilst
DNA is double stranded
- Uracil replaces thymine
- Protein Synthesis
- Process by which
proteins are made in
cells
- Transcription
Nota:
- 1. Hydrogen bonds break between base pairs - DNA strands unzip 2. Free RNA nucleotides form complementary base pairs using one DNA strand as a template (produces mRNA strand)3. Newly formed mRNA strand leaves nucleus through nuclear pores.
- Translation
Nota:
- 1. mRNA strand binds to a ribosome 2. Amino acids in cytoplasm become attached to tRNA molecules (they are specific) 3. Anticodon on the tRNA binds to codon on mRNA molecule according to complementary base pairing. 4. Next codon from mRNA allows tRNA anticodon to bind. A peptide bond joins the amino acids. 5. Ribosome moves along the mRNA molecule until all amino acids are linked. 6. Polypeptide chain then dissociates from the ribosome.
- Process by which
proteins are made in
cells
- Triplet Code
- Code is degenerate as most
amino acids have 1+ triplet code
- Non - overlapping -
each base is only
read once
- Three triplet codes don't code for any
amino acid (stop codes). They mark
the end of a polypeptide chain
- Universal - the same in all organisms
- Code is degenerate as most
amino acids have 1+ triplet code
- DNA - triplet code
mRNA - codons
tRNA - anticodons
Recursos multimedia adjuntos
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