DNA Replication Protein Synthesis DNA Deoxyribonucleic Acid DNA

DNA Replication & Protein Synthesis

DNA Deoxyribonucleic Acid (DNA) is found in what part of the cell? Nucleus

What is DNA made of? Monomers called Nucleotides (Biochemical group Nucleic Acid: 3 parts: Sugar (deoxyribose) Phosphate group Nitrogen base

NUCLEOTIDES Named for the base it contains Looks like: Sugar------Adenine | phosphate THIS IS AN ADENINE NUCLEOTIDE

A nucleotide

DNA Structure � 2 Nucleotide monomers are linked by a bond between the SUGAR of one nucleotide & the PHOSPHATE of the next nucleotide. (Dehydration Synthesis using an enzyme) �More monomers are added on the end to form a long polymer

Monomers are linked on the end to form a Single Long Strand This “backbone” formed by linking sugar to phosphate forms the “sides” of the DNA ladder: the STRONG, backbone of the DNA strand (polymer)

But DNA is double stranded- How are the 2 DNA strands held together? �Pairing of nitrogenous bases(by hydrogen bonds)! �The “steps” of the ladder are the same distance across- ALWAYS a purine (2 ring) with a pyrimidine (1 ring) �Adenine (pur) pairs with thymine(pyr); Guanine (pur) pairs with cytosine (pyr)

Bases Bond to Join 2 DNA Strands (polymers) Joined pairs of nucleotides are called “base pairs” (PO 4) | Sugar----A---T----Sugar | (PO 4)

MORE ABOUT THE BASES… Adenine always bonds to thymine Cytosine always bonds to guanine

Adenine – Thymine (A-T) Cytosine. Guanine (C-G)

DNA is a Double Stranded Molecule The four bases (ATGC) form complementary pairs in the double helix. This means that: A always pairs with T. G always pairs with C.

Double stranded DNA…. . If one strand is ACGCAATTGCATT The other is TGCGTTAACGTAA This also makes it possible for DNA copy it’s self…

BUT THERE’S MORE… The DNA molecule isn’t flat, it’s 3 -D!!! The whole thing coils to look like a “spiral staircase”

What are Chromosomes? �Structures the DNA forms (with proteins) to allow ALL of it to fit in the nucleus �All the DNA from 1 of our cells is 61/2 FEET long!!! �Our cells have 23 different pairs of chromosomes- 46 total. �These store ALL the genetic information to make YOU!!!!

What has to happen before a cell divides? All the DNA has to be copied, so there will be 2 sets of chromosomes in the cell This way, BOTH daughter cells (after division) will contain the SAME genetic information as the parent cell.

How does Replication happen? DNA strands separate at the ‘origin’ & the DNA ‘unzips’ Enzymes (protein machines) match free nucleotides to each ‘parent strand’ & bonds them to the backbone of the newly synthesized strand.

Initiation of Replication

Semi-conservative Replication is like making a second identical copy of each DNA strand. The 2 strands separate, and each is copied separately. This makes 2 double stranded molecules that have one parent strand one new strand.

This is called Semi. Conservative Replication. Each new ‘Daughter’ DNA has 1 copy of parent DNA (dk blue) and one new strand of DNA (light blue).

Summary: DNA replication results in 2 identical copies from 1 original. Each ‘daughter’ DNA contains 1 ‘parent’ strand 1 ‘new’ strand Because base pairing is always complimentary (A-T; G-C), replication enzymes can use the parent strand as a ‘template’.

Fill in the Newly synthesized Strand. A T C G T G G C T A ATTGGCC…. T CCGG….

What is the role of DNA? Store ALL the information The material genes are made of… Gene - segment of DNA that carries the information necessary to make a protein. How is the information stored? - The order of the DNA bases!!

Genes, cont… A gene is usually thousands of bases long! Because a gene is a series of DNA bases that codes for a protein, the information for the protein is encoded in the sequence (order) of the four DNA bases, ATGC.

The DNA in a single human cell = 3, 000, 000 bases (3 billion) However, scientists were surprised that there are only about 30, 000 genes!!

How is the information used by the cell? It needs to change languages to a form the cell uses to do work- PROTEINS But first, the gene needs to be COPIED!

Transcription Genetic information in DNA is copied to m. RNA. Where does it happen? What is m. RNA? Why is it necessary?

Answers: Nucleus messenger RNA Needed to transport coding info from the nucleus to the ribosomes.

How is RNA different from DNA? RNA= ribonucleic acid; Ribose sugar; phosphate; nitrogen base Adenine, Guanine, Cytosine, and URACIL (base pairs= C-G; A -U) Single Stranded

Transcription has three main phases: 1. Initiation 2. Elongation 3. Termination

1. Initiation – RNA polymerase binds to DNA at the START sequence (Promoter) & DNA uncoils 2. Elongation – Complimentary nucleotides are added along the sense strand

3. Termination – When it reaches the stop sequence in the DNA, the RNA polymerase is released from DNA

Transcription Animation http: //www. johnkyrk. com/DNAtranscription. html http: //www. stolaf. edu/people/giannini/flashanimat/ molgenetics/transcription. swf

m. RNA Splicing – Non-coding sequences (introns) are removed and coding (exons) are spliced together to make mature m. RNA

Overview of Protein Synthesis

Transcribe! Write the DNA sequence of a gene (at least 36 nucleotides long. ) Transcribe the sequence of the gene into m. RNA

What happens next. TRANSLATION What do you do when you go from one language to another? You TRANSLATE! Languages? nucleic acid is translated to amino acid (protein)

Translation, cont. Key “Players”: m. RNA t. RNA (transfer RNA) Ribsosomes Amino acids Where does it happen? The CYTOPLASM

m. RNA is the instructions for building the protein How is the info stored? In the order of the bases!!! (A, C, U, G) Translation takes place on the ribosomes (machine that makes the protein) t. RNA (transfer RNA) “reads” the nucleic acid and supplies the CORRECT, corresponding amino acid

CODON These serve as the “words” in the genetic code A codon is made up of three nucleotide bases (A, U, G, C). Each codon specifies an amino acid (MONOMER) in the protein being made (POLYMER) The codon is “read” by the t. RNA anticodon and the correct amino acid is linked to the growing polypeptide chain

Quick Quiz 1. The process where genetic information is copied from DNA to m. RNA is called ______. 2. List 3 differences between DNA and RNA 3. List the 3 phases of transcription. 4. Write the complimentary RNA sequence for the following DNA sequence: AAGGCCTTAGACTGT

Quick Quiz, cont… 5. The process of synthesizing a protein FROM the m. RNA is called ________. 6. How many nucleotides in a codon? 7. The anticodon is part of the _____. 8. The codon is part of the ______. 9. What “machine” is necessary for translation to take place? 10. What is the monomer of a