DNA and RNA

Add to Table of Contents p. 10 DNA/RNA Vocabulary p. 11 DNA/RNA Structures p. 12 Complementary Base-Pairing

DNA Deoxyribonucleic Acid Double-stranded Double-helix structure Made of nucleotides - each nucleotide has 3 parts (remember PBS) Phosphate group Bases – Adenine (A), Guanine (G), Cytosine (C), Thymine (T) Sugar – 5-carbon sugar called deoxyribose Only one type of DNA

RNA Ribonucleic Acid Single-stranded Made of nucleotides also Phosphate group Bases – Adenine (A), Guanine (G), Cytosine (C), Uracil (U) Sugar – 5-carbon sugar called ribose Three types of RNA mRNA – messenger RNA tRNA – transfer RNA rRNA – ribosomal RNA

On the back of your notes: Turn the page sideways, and complete a Venn Diagram summarizing the similarities and differences between DNA and RNA. DNA DNA RNA

Complementary Base-pairing Adenine pairs with Thymine; Cytosine pairs with Guanine In RNA, Adenine pairs with Uracil

Base pairing rules Erwin Chargaff (Chargaff’s Rule) determined that the amount of Adenine is equal to the amount of Thymine and the amount of Cytosine is equal to the amount of Guanine. So… %A = %T %C = %G A+T+C+G = 100%

A = 23 If A = 23, then T = 23 T C + G 100 A = 23 T = 23 Do some math… If Adenine makes up 23% of the DNA, how much Cytosine is there? A = 23 If A = 23, then T = 23 T C + G 100 A = 23 T = 23 46 100 – 46 = 54 54 ÷ 2 = 27 Answer: 27% Cytosine

Replication Copying DNA Where? In the nucleus When? S phase of Interphase 1 Strand  2 Complementary Strands Remember: A pairs with T G pairs with C

Replication - Remember: A pairs with T G pairs with C TTA CGG TAG AAT CCC CGG AAT GCC ATC TTA GGG GCC

Replication – Check Your Answers 1. TTA CGG TAG AAT CCC CGG AAT GCC ATC TTA GGG GCC 2. ATA GTA TTG ACC CGT AAG TAT CAT AAC TGG GCA TTC 3. CCG GAA AAT CGA AGT ATA GGC CTT TTA GCT TCA TAT 4. TAG CAT AAC TAC GAT GGA ATC GTA TTG ATG CTA CCT 5. GGA GTA CCA TAT GAT CCT CCT CAT GGT ATA CTA GGA

History of DNA James Watson and Francis Crick Discovered the 3- dimensional structure of the DNA molecule. Called it the Double Helix Rosalind Franklin: Provided x-ray evidence of the DNA helix structure.

Double Helix 2 strands twisted together like a ladder. Complementary strands– fit together but are opposites.

Differences DNA RNA Double strand Sugar: Deoxyribose Location: ONLY in the nucleus. Job: A list of instructions Nitrogen-containing bases: Adenine Guanine Cytosine Thymine RNA Single strand Sugar: Ribose Location: Throughout the cell Job: Carries out instructions of DNA Nitrogen-containing bases: Adenine Guanine Cytosine Uracil

DIFFERENCES (CONT) There is only ONE type of DNA There are 3 types of RNA… Messenger RNA (mRNA): RNA strand created from the original DNA strand. Ribosomal RNA (rRNA): Makes up ribosomes. Transfer RNA (tRNA): carries amino acids from the cytoplasm to the ribosome during protein synthesis.

What holds DNA together? There are weak hydrogen bonds that hold the base pairs together. They are broken to allow the molecule to replicate or be transcribed.