133182
Descrição
Mapa Mental por harry_bygraves, atualizado more than 1 year ago
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Criado por harry_bygraves
mais de 11 anos atrás
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Nucleic acids and
the genetic code
- DNA and mRNA are nucleic acids consisting of long chains of nucleotides. The nucleotides
are linked together by phosphodiester bonds fomed as a result of condensation reactions
- DNA contains the genetic information inherited by offspring from parents.
This information is transcribed into mRNA and used to synthesize
polypeptides which make the proteins and enzymes that ultimatly determine
every inherited physical and behavioural characteristic of an organism
- The polynuleotide chains of Dna and mRNA have four types of
nucleotide. DNA has guanine, cytosine, adenine and thyamine, but in
mRNA uracil replaces T. other differenced between DNa and mRNA are
that DNA consists of a double helix, while mRNA consists of only a single
strand, and mRAN contains the sugar ribose instead of deoxyribose
- A gene that carries the genetic information for a polypeptide occurs in DNA as a sequence of
bases. The information is transcrbed into mRNA by complementary base pairing on a DNA
template in the nucleus. The transcribed information takes the form of a code. The three most
important features of this genetic code are that it is; Triplet, non-overlapping, and degenerate
- After the mRNA is made, and in eukaroytes introns have been removed,
the single strand moves out into the cytoplasem where the information
encoded on the mRNA is translated into a polypeptide. Translation takes
place on ribosomes and involves another nucleaic acid called tRNA
- tRNA molecules transport specific ammino acids to ribosomes during polypetide synthesis. There are about 20
groups of tRNA, each is specific for one kind of amino acid and acts as an adaptor - one end of the molecule
combines with its particular amino acid and the other links with the mRNA codon specifying that amino acid
- To carry out its function tRNA must first attach an amino acid to itself and then
transfer that amino acid to a ribosome for incorporation into a polypeptide chain. An
amino acid is attached to its particular tRNA by a specific enzyme. The energy
required for this endergonic process comes from the hydrolysis of ATP
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