DNA & GENES

What is DNA?  DNA (deoxyribonucleic acid) is a nucleic acid  It is composed of smaller units called nucleotides  These are:  A, T, C, and G  Shape—double helix

DNA

DNA Nucleotides

Complimentary Base Pairing

 AAA TCC GCT AAT CCG GGG  TTT AGG CGA TTA GGC CCC  Try another!  GCA TTA CCG AGA CCC TAA  CGT AAT GGC TCT GGG ATT

The Double Helix

Who discovered the Double Helix?  In 1953, James Watson and Francis Crick published an article on what DNA looked like.  Made of tow chains of nucleotides held together by nitrogen bases.  DOUBLE HELIX.

Hydrogen Bonds  How the nitrogen bases bond

What is DNA Replication?  The DNA in chromosomes is copied.  Enzymes break Hydrogen bonds  Add matching nucleotides  2 identical molecules made, each with 1 new, 1 old strand

 Chromosome

What is a GENE?  A sequence of DNA (nucleotides) that codes for a protein  Proteins = traits!

What is Protein Synthesis?  The process of making proteins from DNA instructions

What is mRNA?  mRNA is similar to DNA  Only one strand  Uses a “U” instead of a “T”  It brings the instructions from DNA in the nucleus to the cytoplasm.  Example:  DNA = AAT GGC CAT  mRNA=UUA CCG GUA

What is Transcription?  First part = TRANSCRIPTION  Enzymes separates DNA strand and “reads” the letters (nucleotides)  RNA copy of DNA is made  A molecule called mRNA is made

Transcription

What is Translation?  mRNA moves out of the nucleus and finds a ribosome  The information in the mRNA (nitrogen bases) is changed into a sequence of amino acids in protein.

Where and what happens during tranlation?  Ribosome uses instructions on mRNA to build one protein

Translation  Once at the ribosome, transfer RNA (tRNA) brings amino acids

Translation  tRNA drops off correct amino acid and adds it to the growing chain

What is tRNA?  Is the supplier RNA  It delivers amino acids to the ribosome to be assembled into a protein.

tRNA  Uses the same letters as mRNA; U’s instead of T’s.  U—uracil instead of thymine

How does mRNA and tRNA work in translation?  Each 3-letter chunk of mRNA is called a CODON (CUA)  Codons match the 3-letter chunk of tRNA called an ANTI- CODON (GAU)

How are codons and anti-codons coded?  Use a table to determine which amino acids are connected

Translation  There are about 20 different amino acids

What is rRNA?  Binds to the mRNA and uses the instructions to assemble the amino acids in the correct order.  Which are then transferred to the ribosomes by tRNA.

What are mutations?  Any change that occurs in the DNA sequence.  2 types –Point mutation –Frameshift mutation

What is a point mutation?  A change in a single base pair of DNA.  A has become a C (pt. mutation)

What is frameshift mutation?  Where a single base is added or deleted from DNA.

What causes mutations?  Caused by a mutagen.  Any agent that can cause a change in DNA. –Radiation –Cosmic rays –Ultraviolet light –Nuclear radiation –Alcohol

Mutagens

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