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🧬DNA, GENES AND PROTEIN SYNTHESIS🧬 (Genes and Genetic Code (Features of…
🧬DNA, GENES AND PROTEIN SYNTHESIS🧬
Genes and Genetic Code
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Features of Genetic Code
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The code is universal; all living organisms share the same triplet code system, which is indirect evidence for evolution.
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DNA in prokaryotic cells is short, circular and not associated with any proteins
DNA in eukaryotic cells is much longer than in prokaryotic cells, linear, and associated with proteins called histones
mtDNA and cpDNA is similar to that of prokaryotic DNA, which is indirect evidence of evolution
The function of histones is to package the DNA into nucleosomes, by acting as spools around which DNA winds
The start of a DNA sequence is always the same triplet, methonine, although this triplet is an intron (removed before the final polypeptide is formed)
The triplets are stop codes, which mark the end of a polypeptide chain
Some sections are non-coding, and are made up of repeats of the base sequences.
DNA and Chromosomes
A chromosome is a thread-like structure made of DNA and histones by which hereditary information is passed from one generation to the next
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Each thread of a chromosome is called a chromatid, the chromatids are held together by a centromere
Homologous chromosomes are a pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features
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Structures of RNA
RNA is made up of a ribose pentose sugar, a base (A, G, U, C) and a phosphate group
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The genome is the complete set of genes in a cell or organism, mtDNA and cpDNA
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mRNA is a long strand of RNA which is arranged in a single helix. Once formed, mRNA leaves the nucleus via the nuclear pores and goes to the ribsomes where it acts as a template for protein synthesis.
tRNA is a smaller molecule than mRNA that is made up around 80 nucleotides in a single strand, which is folded into a clover type shape.
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Each tRNA molecule is specific to one amino acid; the anticodon is complementary to the base sequence of the codon.
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