Eagle Zone-8 minutes (write the question and complete the sentence with an answer from the word bank) 1.Mitosis makes __new nuclei. 2.______ coil and become condensed 3.Along the middle of the cell, called the _____, sister ________start to align. 4.When mitosis ends, _______ begins so cytoplasm can pinch in half to make new cells called ________. 5.Mitosis allows chromosomes to ________ and divide on their own. Word Bank: Reproducechromosomeschromatids Cytokinesistwoequatordaughters 1

2

3 DNA Why do we study DNA? We study DNA for many reasons, e.g., its central importance to all life on Earth, medical benefits such as cures for diseases, better food crops.

4 Chromosomes and DNA Our genes are on our chromosomes. Chromosomes are made up of a chemical called DNA.

5 The Shape of the Molecule DNA is a very long polymer. The basic shape is like a twisted ladder or zipper. This is called a double helix.

6 The Double Helix Molecule The DNA double helix has two strands twisted together.

7 One Strand of DNA The backbone of the molecule is alternating phosphates and deoxyribose sugar The teeth are nitrogenous bases. phosphate deoxyribose bases

8 Nucleotides CC C O Phosphate O C C O -P O O O O O O O One deoxyribose together with its phosphate and base make a nucleotide. Nitrogenous base Deoxyribose

9 One Strand of DNA One strand of DNA is a polymer of nucleotides. One strand of DNA has many millions of nucleotides. nucleotide

10 Four nitrogenous bases Cytosine C Thymine T Adenine A Guanine G DNA has four different bases:

11 Two Kinds of Bases in DNA Pyrimidines are single ring bases.Pyrimidines are single ring bases. Purines are double ring bases.Purines are double ring bases. C C C C N N O N C C C C N N N N N C

12 Thymine and Cytosine are pyrimidines Thymine and cytosine each have one ring of carbon and nitrogen atoms.Thymine and cytosine each have one ring of carbon and nitrogen atoms. C C C C N N O N cytosine C C C C N N O O thymine C

13 Adenine and Guanine are purines Adenine and guanine each have two rings of carbon and nitrogen atoms.Adenine and guanine each have two rings of carbon and nitrogen atoms. C C C C N N N Adenine N N C C C C C N N O N Guanine N N C

14 Two Stranded DNA Remember, DNA has two strands that fit together something like a zipper. The teeth are the nitrogenous bases but why do they stick together?

15 C C C C N N O N C C C C N N O N N N C Hydrogen Bonds The bases attract each other because of hydrogen bonds. Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. The bonds between cytosine and guanine are shown here with dotted lines

16 Hydrogen Bonds, Hydrogen Bonds, cont. When making hydrogen bonds, cytosine always pairs up with guanine Adenine always pairs up with thymine Adenine is bonded to thymine here C C C C N N N N N C C C C C N N O O C

17 Chargraff’s Rule: Adenine and Thymine always join together A T Cytosine and Guanine always join together C G

18 DNA by the Numbers Each cell has about 2 m of DNA. The average human has 75 trillion cells. The average human has enough DNA to go from the earth to the sun more than 400 times. DNA has a diameter of only m. The earth is 150 billion m or 93 million miles from the sun.

DNA Replication Video hill.com/olcweb/cgi/pluginpop.cgi?it=s wf::535::535::/sites/dl/free/ /120076/micro04.swf::DNA%20 Replication%20Forkhttp://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=s wf::535::535::/sites/dl/free/ /120076/micro04.swf::DNA%20 Replication%20Fork

Eagle Zone Replication Practice On your paper, complete the missing DNA strand by adding the complementary bases. A T C G T T G C C A T C T A G C A A C G G T A G

Making Proteins The process of making proteins is called PROTEIN SYNTHESIS There are several steps to make a protein –Replication (DNA only) –Transcription (RNA) –Translation (RNA) 21

Replication Copying of DNA Makes a complementary strand DNA CANNOT LEAVE THE NUCLEUS! Write the complementary strand for the DNA strand below using the base pairing rules learned earlier (Chargaff’s Rule) –GTA CCG ATC GGA Solution: –CAT GGC TAG CCT 22

TYPES OF RNA RNA CAN leave the nucleus! There are 3 main types of RNA –Messenger RNA- (mRNA) carry copies of the DNA instructions OUT of the nucleus –Transfer RNA- (tRNA) transfers each amino acid to the ribosome by coded messages from mRNA –Ribosomal RNA- (rRNA) assembles proteins 23

Transcription RNA polymerase (an enzyme) binds to DNA to separate the DNA strands The nitrogenous base thymine (T) now becomes uracil (U) in an RNA strand Use the complementary DNA strand from earlier (written below) to write the transcribed RNA strand (mRNA)- don’t forget the U’s! –CAT GGC TAG CCT Solution –GUA CCG AUC GGU 24

Translation (protein synthesis) pg in book The cell uses information from messenger RNA (mRNA) to produce proteins What happens? –mRNA comes out of nucleus into cytoplasm –tRNA carries amino acids to create anticodon (complimentary bases to mRNA) –Ribosomes join with rRNA to break bonds to send tRNA to work again Several amino acids in a chain make a protein 25