Part 2 DNA structure

Learning Target 1. Compare and contrast the structure of eukaryotic and prokaryotic chromosomes. 11. Know what a plasmid is and the types of organisms that have them.

Prokaryotes Prokaryotes lack true nucleus and membrane-bound organelles Prokaryotic DNA Found in Cytoplasm 1 circular chromosome Consists of only DNA & plasmids Copies  then immediately divides Plasmids Circular strands of DNA Separate of Chromosomal DNA

Eukaryotes Eukaryotes have a membrane bound nucleus and organelles Eukaryotic DNA Found in Nucleus Many linear chromosomes Consists of DNA and histones Copies then cell continues to grow  then mitosis (organizes chromosomes)  and then divides

Pro DNA vs Eu DNA Prokaryotic DNA Eukaryotic DNA Don’t write this! You already have it!!!! Prokaryotic DNA Found in Cytoplasm 1 circular chromosome Consists of only DNA Copies  then immediately divides Eukaryotic DNA Found in Nucleus Many linear chromosomes Consists of DNA and histones Copies then cell continues to grow  then mitosis (organizes chromosomes)  and then divides

Learning Target 3. Recognize the structure of a nucleotide. 4. Describe the chemical and structural properties of DNA. 5. Understand base pairing and its role in replication, transcription and translation.

Structure of DNA C Monomer = nucleotides Phosphate group 5 C sugar (Deoxyribose in DNA) Nitrogen base- 4 possible Adenine and guanine- purine bases- double ring structure Cytosine and thymine- pyrimidine bases -single ring structure C

Structure of DNA (cont.) DNA molecule consists of 2 chains of nucleotides Arranged in a “ladder” configuration Alternating phosphate and sugar groups Rungs composed of paired nitrogen bases Complementary base pairing-purine with pyrimidine A with T G with C “Ladder” coils to form a helix

Why A-T/C-G? N H O CH3 Sugar Adenine (A) Thymine (T) Guanine (G) Cytosine (C)

Why purine/pyrimidine? Purine + Purine: too wide Pyrimidine + pyrimidine: too narrow Purine + pyrimidine: width Consistent with X-ray data