Melanin Bio Notes

DNA

Deoxyribonucleic Acid, located in the nucleus, codes for your genes, double helix

Nitrogen bases are held by

Hydrogen bonds

DNA nucleotide structure

Deoxyribose (5-C Sugar, Pentagon), Phosphate group (circle), Nitrogen bases (A,T,C,G,)

Sides or handrails of ladder are composed of alternating

phosphate and deoxyribose sugar molecules

Rungs are composed of 2 bases

Purine and pyrimidine joined by hydrogen bonds

Purines

Double-ringed (Adenine & Guanine)

Pyrimidines

Single-ringed (Thymine & Cytosine)

Melanin

Protein makes brown hair

Order of nitrogen bases

(A,T,C,G) determine the type of protein that is assembled

If order of bases is changed…

Then mutations occur which can change the proteins that need to be made

Ribosome

In the cytoplasm, tiny organelles where proteins are assembled

mRNA

Instruction get from the DNA to the ribosome using messenger RNA. From nucleus to the ribosomes in the cytoplasm.

mRNA

Single stranded, carries the DNA message from the nucleus to the ribosomes, Has URACIL (U) instead of Thymine (T)

Codon

Set of three nitrogen bases that code for an amino acid

Protein

Created is determined by the base arrangement in DNA (code sentence)

DNA

Transfers information to mRNA

tRNA

mRNA carries code to ribosome where tRNA decodes it, tRNA anti-codons base pair with mRNA’s codons

rRNA

Forms peptide bonds between amino acids to form a protein

Step: Transcription

DNA transfers (rewrites) the code to mRNA, takes place in nucleus

Step 2: Translation

mRNA is decoded and forms a protein, takes place at ribosome

Point Mutation

The substitution, addition, or removal of a single nucleotide

Substitution

Letters switch, one nucleotide in a codon is replaced with a different one, resulting in a new codon

Insertion

Letter gets insterted, one or more nucleotides are added to a gene

Deletion

Letter gets deleted, one or more nucleotides are lost from a gene

Silent mutation

Substitution has no effect, the new codon codes for the same amino acid as the original codon.

Missense Mutation

New codon changes the amino acid being coded for, the entire protein may be different and defective.

Nonsense Mutation

If mutation changes a codon that specifies an amino acid to one of the STOP codons (UAA, UAG, UGA). Stop prematurely

Frameshift Mutation

Insertion or deletion when number of nucleotides inserted is not a multiple of three. Causes remaining codons to be grouped incorrectly. Alter the protein as there will be a different amino acid sequence.