Nucleic Acids NUCLEIC ACIDS AND DNA

Standard Biology What did we learn from POGIL? GOT NEED

Rosalind Franklin First to discover that DNA must be 3-D Not in notes Rosalind Franklin First to discover that DNA must be 3-D Used X-ray diffraction and chromatography

The Double Helix

Watson and Crick 1953 – Discovered the structure of DNA (double helix model) - DNA is made of two chains of nucleotides joined at the nitrogen bases by hydrogen bonds Double Helix Model (twisted ladder)

Nucleotide Structure DNA (a nucleic acid) is a polymer made up of repeating sub-units called NUCLEOTIDES Three Parts of nucleotides: Nitrogen BASE Deoxyribose Sugar Phosphate group

TYPES OF SUGARS Two types of sugars in the nucleic acids are: DNA: Deoxyribose RNA : Ribose Nucleic Acid Nucleic Acid

Nitrogen Bases 4 Possible Base pairs in DNA Adenine Cytosine Guanine Thymine RNA base!

BASE PAIRING RULE The amount of A=T and amount of G=C In double stranded DNA weak hydrogen bonds connect G - C and A - T

Complementary Base Pairing Parent Strand: A T G G G C C A A G G G C Complementary Strand ______________________________________________ “The “Complementary” strand is the opposite side of a DNA ladder. In DNA, A is always opposite T, and G is always opposite C. WATCH ME! If a DNA strand contains 20% Thymine, then… how much Adenine will it contain? how much Cytosine will it contain? how much Guanine will it contain?

WHITE BOARD - Practice Again 2) If a DNA strand contains 30% Guanine, then… how much Adenine will it contain? how much Cytosine will it contain? how much Thymine will it contain?

WHITE BOARD – Practice Last Time 3) f a DNA strand contains 15% Thymine, then… how much Adenine will it contain? how much Cytosine will it contain? how much Guanine will it contain?

Let’s check our POGIL

Phosphate Group In a DNA nucleotide, the Phosphate group is composed of one atom of PHOSPHORUS surrounded by four atoms of OXYGEN

Shape of DNA Double Helix Twisted Ladder Sugar-Phosphate Backbone

Essential Questions WHITE BOARD! 1. What is the shape of DNA? 2. Who discovered DNA’s structure? 3. What are the sub-units of DNA called? 4. What are the 3 parts to a nucleotide? 5. Which nucleotides bind together in DNA?

Essential Skill WHITE BOARD! DRAW and LABEL a nucleotide and its 3 parts without looking at your notes!

Clear your Board!

Essential Questions Write it Down! 1. What is the shape of DNA? 2. Who discovered DNA’s structure? 3. What are the sub-units of DNA called? 4. What are the 3 parts to a nucleotide? Which nucleotides bind together in DNA? DRAW and LABEL a nucleotide and its 3 parts.

Video

DNA REPLICATION DNA replication involves making an exact copy of DNA. Happens during Interphase of cell cycle, BEFORE cell division (before mitosis or meiosis)

DNA REPLICATION Process of DNA reproducing an exact copy of itself Enzymes (helicase) break the hydrogen bonds and DNA molecule “unzips” Free nucleotides in the cytoplasm binds to the single strands by base pairing (A-T and G-C) An enzyme (DNA polymerase) binds the new base pairs together to form 2 new identical strands Proofreading enzymes then check the new DNA for mistakes

DNA Replication is Semi-conservative Semi = “half” Conserve = “to save” When DNA makes a copy of itself, it uses the parent strand (“old” DNA) as a template to make the “new” strand. End Result = 2 identical DNA molecules each with ½ old (parent) DNA and ½ new

Semi-conservative Replication

Mutations Mistakes made in the genetic code (either during DNA replication or protein synthesis) 2 specific types of mutations: POINT mutation- one base is substituted for another Original: GGT ATC GGA TTA Replicated: GGC ATC GGA TTA 2. FRAME SHIFT mutation- one base is added or deleted and it shifts sequence Original: GGT ATC GGA TTA Replicated: GGA TCG GAT TA - T was deleted thus causing the whole molecule to shift Which type of mutation has the greater effect on the DNA?

Essential Questions Write it Down! What is Replication? What are the steps to replication? What organic molecule controls all steps in the replication process?

Worksheet Practice Complete BOTH sides of the worksheet to review DNA structure and the process of DNA replication.