Searching for the “Secret of Life” Pre-lecture review 1.Fundamental unit of all living things? The cell 2.Organelle that controls the cell? Nucleus 3.Structures found in the nucleus that carry hereditary information? Chromosomes 4.What are chromosomes made of? DNA wrapped around histones (proteins) 5.What molecule carries “the code of life”? DNA 6.How does DNA control the activity of the cell? Producing proteins that regulate cell fuctions or become part of the cell

Nucleic Acids DNA & RNA Chapter 12

I.DNA A.Discovery * Read section 12-1 in your textbook and summarize the following sections: 1.Griffith and Transformation 2.Avery and DNA 3.The Hershey-Chase Experiment

B.Components 1.DNA is made of repeating sub-units called nucleotides 2.Nucleotides have 3 parts: a.A nitrogenous base b.5-carbon sugar (deoxyribose) c.A phosphate group What does DNA stand for? Deoxyribonucleic Acid

Phosphate group Deoxyribose Nitrogenous base DRAW: Nucleotide Structure Why are they called nitrogenous bases?

Purines Pyrimidines AdenineGuanine CytosineThymine Phosphate group Deoxyribose What is the difference between purines and pyrimidines? Draw Fig pg Two types of bases: a.Purines (Adenine and Guanine) b.Pyrimidines (Cytosine and Thymine)

C. Base Pairing and DNA Structure 1.Chargaff’s Rule of Base Pairing a.Opposing bases always pair the same:  Adenine (A) pairs with Thymine (T)  Guanine (G) pairs with Cytosine (C) What would be the complementary base sequence for the strand of DNA below? A C G G T T A C A A T G A TGC C AAT G T TAC T

2.Structure a.The overall shape of DNA is described as a double helix (a twisted ladder) What force holds the two strands together? Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

b.The sugar-phosphate backbone is held together by covalent bonds Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) DRAW Fig. 12-7, pg 294

DNA Nucleotide and Bonding Movie

D.Discovery of DNA Structure 1.In the early 1950’s British scientist Rosalind Franklin discovered the helical structure of DNA using x-ray diffraction 2.In 1953, James Watson and Francis Crick (using Franklin’s images) developed the double helix model for DNA and won the Nobel Prize

E.How does DNA control living systems? 1.Genes are segments of DNA that code for proteins that control traits 2.DNA codes for the amino acid sequence in proteins 3.Every three bases codes for one amino acid = codon Examples: TTT codes for phenylalanine GAA codes for leucine TGG codes for tryptophan DRAW

F. DNA Replication 1.Controlled by series of enzymes 2.Helicase enzymes are produced and “unzip” the parent DNA by breaking the hydrogen bonds. 1.Controlled by series of enzymes 2.Helicase enzymes are produced and “unzip” the parent DNA by breaking the hydrogen bonds. DRAW

3.DNA polymerase starts to form two new daughter strands by base pairing free nucleotides with those on the exposed parent strands, then “proofreads” the new strands DRAW

4.Finally, two new strands form. Each is made of one strand of parent and one strand of daughter DNA. DRAW

Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Replication fork Original strand New strand Nitrogenous bases DRAW FIG.12-11, pg 298

DNA REPLICATION SONG

II. RNA: The Other Nucleic Acid What does RNA stand for? Ribonucleic Acid  Differences between DNA and RNA 1.RNA contains ribose instead of deoxyribose. 2.RNA can be in single-stranded or double-stranded forms. 3.RNA is found in both the nucleus and cytoplasm. DNA is only in the nucleus.

4.RNA contains uracil (U) instead of thymine (T)

B. Three Kinds of RNA 1.Messenger RNA (mRNA) a.Copies the DNA code in the nucleus and carries the message to the ribosomes b.Single stranded

2. Transfer RNA (tRNA) a.Each tRNA consists of ~90 nucleotides b.It transfers amino acids to the ribosome and places them in the correct position in the protein

3.Ribosomal RNA (rRNA) a.Part of the ribosome involved in the synthesis of tRNA  Draw Fig. 12-2, pg 300

fromtoto make up also calledwhich functions toalso called which functions to can be RNA Messenger RNA Ribosomal RNA Transfer RNA mRNACarry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome DNARibosomeRibosomes DRAW: RNA Concept Map