Central Dogma DNA  RNA  Protein

…..Which leads to  Traits

How Does DNA produce traits? 1. Genes control proteins which determine traits 2. Order of nucleotides in the DNA determines amino acid sequence RNA's act as 'go-between' for DNA RNA's act as 'go-between' for DNA Gene- a sequence of DNA with a specific function Gene- a sequence of DNA with a specific function

RNA Single strand of nucleotides (unlike DNA) Single strand of nucleotides (unlike DNA) Contains 5-C sugar ribose Contains 5-C sugar ribose Uracil replaces Thymine Uracil replaces Thymine 3 types of RNA produced 3 types of RNA produced 1. Messenger RNA (m-RNA) - code for order of amino acids 2. Transfer RNA (t-RNA) - carry amino acids and fit them in proper place 3. Ribosomal RNA (r-RNA) - major component of ribosome; large and small subunits a. P site: carries the growing polypeptide chain b. A site: delivers the next amino acid to the growing chain

Codons Codons – 3 nucleotide sequences coded from the original DNA strand onto a mRNA strand. Codons – 3 nucleotide sequences coded from the original DNA strand onto a mRNA strand. Each codon corresponds to an amino acid or a stop/start signal Each codon corresponds to an amino acid or a stop/start signal The codon on a mRNA strand is complementary to an anti-codon on tRNA The codon on a mRNA strand is complementary to an anti-codon on tRNA

Codons in mRNA

Going from DNA  RNA Transcription - Formation of m-RNA molecule from a DNA template – occurs in the nucleus. Transcription - Formation of m-RNA molecule from a DNA template – occurs in the nucleus. Occurs in three steps: Occurs in three steps: 1. Initiation 2. Elongation 3. Termination

Initiation RNA polymerases bind to DNA at regions called promoters (initiation site, also called TATA box); the enzyme then separates the 2 DNA strands and transcription begins. RNA polymerases bind to DNA at regions called promoters (initiation site, also called TATA box); the enzyme then separates the 2 DNA strands and transcription begins. RNA polymerase reads DNA from 3’ to 5’ RNA polymerase reads DNA from 3’ to 5’

Elongation RNA polymerases move along the DNA and: RNA polymerases move along the DNA and: -untwists and opens a short segment of DNA (DNA template) - links incoming RNA nucleotides to the 3' end of the elongating strand; RNA grows one nucleotide at a time in the 5' to 3' direction

Termination Transcription proceeds until RNA polymerases reaches a termination site on the DNA; RNA molecule is then released and leaves the nucleus. Transcription proceeds until RNA polymerases reaches a termination site on the DNA; RNA molecule is then released and leaves the nucleus. The DNA strand then joins back together – unchanged.

Translation Translation – using the mRNA strand made during Transcription and tRNA and rRNA to build a protein. Translation – using the mRNA strand made during Transcription and tRNA and rRNA to build a protein. Occurs at the site of protein synthesis – the ribosome. Occurs at the site of protein synthesis – the ribosome. Occurs in three steps – the same but different than transcription – initiation, elongation, and termination. Occurs in three steps – the same but different than transcription – initiation, elongation, and termination.

Initiation 1. the small ribosomal subunit attaches to the 5' end of the mRNA ('start' codon -AUG) 2. a tRNA (with anticodon UAC) carries the amino acid methionine to the mRNA

Elongation 1. the next tRNA binds to the ribosome; the new amino acid is attached to first one 2. the first tRNA is released and binds again with other amino acids (repeated deliveries) 3. a new tRNA attaches to the ribosome and repeats the process, thereby increasing the polypeptide chain length

Termination 1. Occurs when the ribosome encounters a 'stop' codon. 2. The resulting protein formed is now released and is used by the cell.