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DNA – life’s code molecule that makes up genes and determines the traits of all living things.

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Presentation on theme: "DNA – life’s code molecule that makes up genes and determines the traits of all living things."— Presentation transcript:

1 DNA – life’s code molecule that makes up genes and determines the traits of all living things

2 Importance of DNA Controls by: producing proteins
Proteins are important because All structures are made of protein Skin Muscles Bones All actions depend on enzymes (special kind of protein) Eating Running Thinking All life activities Structure contains the complete instructions for making all proteins

3 DNA Structure Stands for deoxyribonucleic acid
Double helix = twisted ladder = linked nucleotides

4 DNA Structure - nucleotide
Made of 3 things: Deoxyribose Phosphoric acid Nitrogen bases

5 DNA Structure – nitrogen bases
Four types: Adenine Cytosine Guanine Thymine A nucleotide is named for the nitrogen base it contains

6 Linking Nucleotides Nucleotides join together to make DNA – complementary base pairing Adenine fits with Thymine A – T Cytosine fits with Guanine C – G

7 How DNA is packaged

8 Figure 12-10 Chromosome Structure of Eukaryotes
Human cells contain over one meter of DNA! How? Section 12-2 Nucleosome Chromosome DNA double helix Coils Supercoils Histones Wrapped around proteins (histones and nucleosomes) Go to Section:

9 Interest Grabber A Perfect Copy
Section 12-2 A Perfect Copy When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells. Go to Section:

10 Interest Grabber continued
Section 12-2 1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2. Hold the papers side by side, and compare the lines. Do they look the same? 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4. How could you use the original paper to draw exact copies of the line without tracing it? 5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original? Go to Section:

11 Section Outline 12–2 Chromosomes and DNA Replication
A. DNA and Chromosomes 1. DNA Length 2. Chromosome Structure B. DNA Replication 1. Duplicating DNA 2. How Replication Occurs Go to Section:

12 DNA Replication Making a chromosome copy
One strand  two identical strands Steps: DNA “unzips” Free nucleotides attach to complementary bases Bonds form between nucleotides creating two identical strands

13 Figure 12–11 DNA Replication
Section 12-2 Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand Go to Section:

14 DNA replication

15

16 RNA vs. DNA

17 Bring amino acids to ribosome
Concept Map Section 12-3 RNA can be Messenger RNA Transfer RNA also called which functions to also called which functions to Bring amino acids to ribosome mRNA Carry instructions tRNA from to DNA Ribosome

18 Protein Synthesis Make proteins Two steps:
Transcription: copying your DNA (genes) into messenger RNA (mRNA). Translation: turning messenger RNA (mRNA) into proteins-proteins make up cells.

19 Transcription Section 12-3 RNA polymerase DNA RNA
Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA

20

21 The Genetic Code Section 12-3 :

22 Translation mRNA : Nucleus Messenger RNA mRNA Lysine Phenylalanine
Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Methionine Ribosome mRNA Start codon :

23 Translation (continued)
The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Translation direction Ribosome

24 DNA Splits In nucleus “Unzipping”
Transcription DNA Splits In nucleus “Unzipping” Messenger RNA (mRNA) copies DNA and DNA reforms ladder Translation Travels to ribosome Transfer RNA (tRNA) copy mRNA and make proteins

25

26 Transcription Animation

27 Translation

28 Gene Mutations: Substitution, Insertion, and Deletion
Section 12-4 Substitution Insertion Deletion Point mutation- mutations that affect one nucleotide; generally change one amino acid in a protein (ex: substitution) Frameshift mutations (Insertion and Deletion) cause much bigger changes since the sequence is read in 3 base codons, everything is now moved over one spot Go to Section:

29 Figure 12–20 Chromosomal Mutations
Section 12-4 Deletion Duplication Inversion Translocation - Involve changes in the number or structure of chromosomes - May change the location of genes and even the number of copies of some genes Go to Section:

30 Typical Gene Structure
Section 12-5 Promoter (RNA polymerase binding site) Regulatory sites DNA strand Start transcription Stop transcription At first glance- a DNA sequence is a bunch of jumbled letters, but soon patterns emerge. Some sequences serve as promoters: binding sites for RNA polymerase Some sequences are stop and start signals for transcription Regulatory Sites: places where other proteins, binding directly to the DNA at that site, can regulate transcription. These help determine if a gene will be turned on or off A typical gene includes start and stop signals, with the nucleotides to be translated in between Go to Section:

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