Dna Structure

-double helix

-sugar-phosphate backbone, covelant bond

-Nitrogen bases, hydrogen

What are the 4/5 Nitrogen Bases?

-Adenine, Thymine, Uracil, Guanine, Cytocine

Steps in Dna Replication & Where

1. Parent Dna untwists

2. strands seperate

3. N bases (in cytoplasm) attach to complementary base

-occurs in nucleus

-uses Dna polymerase

What are the 3 types of Rna?

-trna-transfer

-mrna-messanger

-rrna-ribosomal

Transcription

1. Initiation- Rna polymerase attaches to the Dna promoter nucleotide sequence on Dna. Rna is synthesized.

2. Elongation- Rna grows longer. Peels aways from Dna, Dna strands come back together.

3. Termination- Rna polymerase reaches the terminator. Polymerase molecule detaches from Rna molecule and the gene.

Translation/Protein Synthesis

-mRNA goes to a ribosome

-small subunit has binding sites for mRNA

-large subunit for tRNA

1. Initiation- mRNA binds to small ribosomal subunit. tRNA with attached amino acid binds to start codon. Large subunit bind to small one, creating funcional ribosome.

2. Elongation- amino acids are added one by one to the first amino acid.

3. Termination- a stop codon tells the translation to stop.  Polypeptide is freed and ribosome splits into sub units.

 -change in nucleotide sequence of Dna

- Base Substitutions- replacement of one base for another

-Base insertion or deletions- adding or subtracting nucleotides

-mutagens-physical & chemical elements

-usually bad, but can lead to diversity

-In Eukaryotes add in cap and tail to protect Rna from enzymes and help ribosomes recognize it as mRNA

-Introns are removed before Rna leaves the nucleus and exons (coding regions) kept in

Promoter

the site which makes the 3 (could be lactose) enzyme genes

-part of gene regulation and rna polymerase attaches to it