DNA. Essential Question: How does the structure of the DNA molecule allow it to carry information?

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1 DNA Essential Question: How does the structure of the DNA molecule allow it to carry information? Fun Website to Explore!

2 DNA History Griffith Experimented on mice and observed some harmless strains of bacteria could change into harmful strains. He called this transformation. Avery Repeated Griffith experiment and discovered that DNA stores and transmits genetic information from one generation to the next.

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4 More DNA History Hershey-Chase Concluded that the genetic material in bacteria was DNA not proteins Watson & Crick created the double helix model for DNA after viewing the work of Rosalin Franklin

5 DNA is a polymer made up of monomers called nucleotides. Backbone Deoxyribose Sugar and Phosphate Rungs of the ladder Nitrogenous bases Structure of DNA

6 Nucleotides Monomers of the DNA molecule Each nucleotide is made up of three parts: a 5-carbon sugar called deoxyribose a phosphate group and 1 of 4 different nitrogenous bases

7 Nucleotide Bonding in the DNA Molecule Nucleotide bonding Covalent between the sugar, phosphates and nitrogen base Hydrogen bonds between the bases of opposing nucleotides Nitrogenous bases can occur in any order

8 Nitrogenous Bases of Nucleotides 4 kinds Divided into two classes: 1) Purines 2 ring structure Adenine & Guanine 2) Pyrimidines 1 ring structure Thymine & Cytosine

9 Chargaff s Rules Base Pairing Rules The proportion of : Adenine and Thymine is always the same Adenine always bonds with Thymine Cytosine and Guanine is always the same Cytosine always bonds with Guanine Question? A DNA sample contains 28% Adenine What are the % s of Thymine, Guanine and Cytosine?

10 Prokaryotes & DNA DNA is located in the cytoplasm a single circular molecule

11 In Eukaryotes Eukaryotes & DNA DNA is 1000 x s more than prokaryotes located in the nucleus in the form of chromosomes

12 DNA Length Bacteria have about 1.6mm of DNA They are only 1.6µm in diameter Eukaryotes have over a meter of DNA in each cell. How do you stuff this all in a little cell?

13 DNA Packaging Chromatin consists of DNA and protein. The DNA helix is wrapped around nucleosomes, an octamer of histone proteins.

14 DNA Replication During DNA replication, DNA molecule separates into 2 strands each strand serves as a template new complimentary strands are built following the base pairing rules Process is semiconservative New DNA has one new strand and one original strand

15 How It Occurs DNA replication regulated by a series of enzymes DNA polymerase is the main enzyme Two jobs Add nucleotides proof read the new strands

16 Replication Forks and Bubbles Locations where Nucleotides are added by DNA polymerase Strands separate for replication original strand (blue) Replication fork Replication fork DNA polymerase Newly made complementary strand (red)

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18 Writing Complementary Strands If you start with this template strand A T C T A A G What is the sequence of bases on the complementary strand?

19 DNA Essential Question: How does the structure of the DNA molecule allow it to carry information?

20 Types of Nucleic Acid DNA RNA Nucleotide Sugar Deoxyribose Ribose Bases A, T, G, C A, U, G, C Strands 2 1 Polymer Types 1 3 Messenger RNA (mrna) Ribosomal RNA (rrna) Transfer RNA (trna)

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22 From Genotype to Phenotype Protein Synthesis Process that converts genotype (gene make-up) into phenotype (physical appearance) 2 Steps 1. Transcription literally means to write out 2. Translation literally means to change to another language

23 Step 1 - Transcription genetic info in DNA is transcribed into a strand of messengerrna (mrna) Occurs in the nucleus Regulated by RNA Polymerase

24 Starting and Stopping mrna DNA carries directions Promotors start signal for RNA polymerase Terminators stop signal for RNA polymerase

25 Making mrna Chromosome coils loosen RNA polymerase (enzyme) separates the 2 strands of DNA exposing base pairs matches unattached RNA bases to their complement on the DNA strand Covalently bonds RNA nucleotides

26 Writing RNA Strands If you start with this DNA template strand A T G T A C A G G What is the sequence of bases on the mrna strand?

27 Editing mrna mrna must be SPLICED Before leaving the nucleus introns are removed (stay inside) exons are linked together (exported) INTRONS noncoding sections of nucleic acid EXONS code for proteins in nucleic acid

28 Alternative splicing allows for a single gene to be used for more than one polypeptide RECENT DISCOVERY

29 The Genetic Code Language of mrna Read 3 bases at a time 3 bases = 1 codon = 1 amino acid AUGCGAUACUCGUGA AUGAGGUAUAGCUAA

30 Codons 64 possible codons for 20 amino acids 1 is the start codon AA Methionine 3 are stop codons UGA, UAA, UAG Do not code for amino acids

31 From Genotype to Phenotype Essential Question: How does the structure of the DNA molecule allow it to carry information?

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33 Step 2 - Translation The process of making proteins from mrna Occurs in the cytoplasm Need 3 things mrna, trna, ribosome, free amino acids

34 Ribosomes

35 trna carries amino acids RNA molecule that folds into a special structure Each trna carries one type of AA Each has a specific anticodon that matches the mrna codon

36 Translation - Begins Setting up the RNA / Ribosome complex mrna attaches to small ribosome subunit trna with Methionine attaches to mrna Large ribosome subunit attaches

37 Translation - Elongation trna s continue to bring in AA AA bond to one another and are released from the first trna Ribosome moves along the mrna Process of growing the AA chain is called elongation

38 Translation - Stops Stop codons signal release factor Ribosome releases polypeptide, mrna

39 Translation A continuous process

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41 Proteins can be described according to their large range of functions in the body, listed in alphabetical order: Examples of protein functions Function Description Example Antibody Antibodies bind to specific foreign particles, such as viruses and bacteria, to help protect the body. Immunoglobulin G Enzyme Enzymes carry out almost all of the thousands of chemical reactions that take place in cells. They also assist with the formation of new molecules by reading the genetic information stored in DNA. Phenylalanine hydroxylase Messenger Structural component Transport / storage Messenger proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues, and organs. These proteins provide structure and support for cells. On a larger scale, they also allow the body to move. These proteins bind and carry atoms and small molecules within cells and throughout the body. Growth hormone Actin Ferritin

42 From Genotype to Phenotype Essential Question: How does the structure of the DNA molecule allow it to carry information?

43 12.4 Mutations Unit Essential Question: How does the structure of the DNA molecule allow it to carry information?

44 Mutations When mistakes are made during the copying of DNA it causes changes to the genetic material and potentially to the message 2 Major Types of Mutations 1) Gene Mutation 2) Chromosomal Mutation

45 Mutations When mistakes are made during the copying of DNA it causes changes to the genetic material and potentially to the message 2 Major Types of Mutations 1) Gene Mutation (impacts a single gene) 2) Chromosomal Mutation (impacts the whole chromosome)

46 Gene Mutations Point Mutations A change in a single DNA base can lead to a mutation in a single gene or a number of genes depending upon location 3 General Types Insertion Deletion result in Frameshift Mutations Substitution may or may not cause a change

47 Point Mutations Insertion and Deletion Insertions and deletions are referred to as Frameshift Mutations because they change the reading frame of the codons

48 Frameshift Mutations

49 Point Mutation - Substitution A single base is substituted Because of code redundancy, this sometimes results in no change to the amino acid sequence Therefore it may be a silent mutation Or can change the code to a STOP codon and fail to produce a protein and we call this a nonsense mutation

50 Mutations When mistakes are made during the copying of DNA it causes changes to the genetic material and potentially to the message 2 Major Types of Mutations 1) Gene Mutation (impacts a single gene) 2) Chromosomal Mutation (impacts the whole chromosome)

51 Chromosomal Mutations Changes in chromosomes can occur in 4 basic types 1) Deletion 2) Duplication 3) Inversion 4) Translocation

52 Polyploidy Sometimes ENTIRE sets of chromosomes are duplicated Most common in plants, but can be found in fish, insects, amphibians and reptiles Only one report in mammals a rat species Triploids (3n) and Tetraploids (4n) are the most common forms

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54 Daylily Tetraploids Larger flowers Taller plants Thicker flower stalks ALL of these traits are desirable in the horticulture industry