DNA (Deoxyribonucleic acid) Instructions for life Makes proteins/enzymes DNA Structure Polymer: Nucleotide subunits Nucleotides have 3 parts Sugar (deoxyribose) + Phosphate = Strands Nitrogen Bases = Rungs Adenine  Thymine Guanine  Cytosine What did we learn last time?

Double Helix Helix is a spiral DNA double helix Complementary bases (A, T, C, G) hydrogen bonded to each other to form double helix Strands are anti-parallel DNA Replication During Interphase (S phase) 4 main steps 1) Separate the strands (break H bonds) 2) Free “floating” nucleotides pair up with complement 3) Bases bond with new Sugar-Phosphate backbone 4) Result = 2 molecules of DNA More

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Genes and Proteins Proteins are polymers of ? AMINO ACIDS Proteins make our muscle fibers, walls of blood vessels, etc… Genes are a sequence of DNA that will go on to make a specific protein From DNA to Protein

mmons/3/37/Difference_DNA_RNA- EN.svg Nucleic Acid (Ribonucleic) Different than DNA 1) Single Stranded 2) Sugar is RIBOSE 3) Uracil replaces Thymine 3 Types of RNA 1.Messenger RNA (mRNA) Brings info from DNA to the cytoplasm 2.Ribosomal RNA (rRNA) Clamp onto mRNA 3.Transfer RNA (tRNA) Transports amino acids RNA

H466lqk 1)Enzymes unzip DNA 2)Free RNA nucleotides pair with complement (U’s replace what would be T’s) 3)mRNA breaks away as the DNA rejoins 4)mRNA leaves the nucleus TRANSCRIPTION

zb6r1MMTkc Order of Nitrogen Bases on mRNA determines proteins (remember no T’s on RNA!) Translating genetic code on mRNA into amino acids Codons: 3 “letter” sequences on mRNA Each will make a specific amino acid Page 298 Translation

Remember: DNA controls the structure and function of our cells based on… sequence DNA nucleotides A mutation is a change in the sequence (or random error) Mutations

Mutations might occur in reproductive cells (sperm & egg) Passed on to offspring 1.Offspring might have problems with cells 2.If severe=offspring will not survive Rare = mutation is a benefit Mutations and Reproduction

If a mutation occurs in NON- sex cells = not passed on The damaged gene might affect the function of the cell and will be passed on to cells that go through mitosis If they are in genes that control cell division = CANCER Mutations in body cells

Change in a single nitrogen base Might change the entire structure by changing a single amino acid Example Point Mutations

Adding a single base or deleting one will cause a mutation for that amino acid and all the ones after = more harm (generally) Frameshift Mutations

Spontaneous Mutations just happen Others are caused by mutagens (env. Factors) High energy radiation Chemicals High temp Asbestos, formaldehyde Cyanide, benzene Occurs on chromosomes Include: Deletions and Insertions Inversions and Translocation Occur in all living organisms but esp. common in plants Most not passed on because zygote does not survive Some mutations are repaired (repair mechanisms) Chromosomal Mutations