1. DNA – Life’s Code
Chapter 12

2. DNA: “The code of life” makes up genes determines traits
passes an organism’s instructions from
generation to generation
“deoxyribonucleic acid”

3. Structure: twisted spiral; “double helix”
single DNA molecule in a human cell:
about 100 million rungs (steps)

4. Feature of DNA two main sides (ladder uprights)
sides made of 2 chemical: sugar (deoxyribose) and acid (phosphate)….alternate along the sides
rungs (steps) of the ladder
nitrogen bases make up the rungs
4 nitrogen bases: A, T, C, G
A only fits with T- AT TA
C only fits with G- CG GC

6. Where is DNA? makes up parts of the chromosomes found in the nucleus
define “gene”:
-a short piece of DNA
-a certain number of bases on the DNA
molecule
-a short section of a chromosome that
determines traits
p.590 mice experiment

7. Experiment showed that DNA controls traits!
Scientists inject mouse
Living harmless bacteria
Living harmful bacteria
Dead harmful bacteria
Living harmless and dead harmful bacteria
Results
Mouse lived
Mouse died
Meaning
Living harmless bacteria don’t kill mice
Living harmful bacteria kill mice
Dead harmful bacteria don’t kill mice
Living harmless exchanged DNA with bacteria that was harmful
Experiment showed that DNA controls traits!

8. How DNA Works DNA has the directions for building protein in the cell.
DNA’s code (or directions) is carried in the nitrogen bases (A, T, C, G)
The order of the nitrogen bases gives different directions for different amino acids
ex. ATG TAG
GTA GAT
AGT TGA

9. ex. normal blood cells vs sickle cells
* a change in just one pair of DNA bases can change traits

10. DNA Replication

12. Protein
DNA directs the making of proteins which are made in the ribosomes.
Ribosomes are in the cytoplasm.
DNA is in the nucleus- and stays there!
transcription: process during which RNA picks up message from DNA and carries it out of the nucleus to the ribosomes
-RNA is a single strand
-RNA has bases A, U, C, G

13. Transcription

14. http://www. youtube. com/watch

15. translation: process by which the correct amino acids are hooked together based on RNA’s directions
genetic code: code that translates the DNA language into the protein language (the order of the nitrogen bases)
*traits show up in a cell because of the kinds of proteins made at the ribosome

16. Translation

17. http://www. youtube. com/watch

18. mutations: change in copying the DNA message…the bases (A T C G) join incorrectly
A mutation causes a change in a child’s trait only when it takes place in the parent’s sex cells
causes of mutations:
-copying mistakes
-chemicals
-radiation (x-rays)

19. Cloning identical twins: splitting of one fertilized egg -same genes
-same DNA
-exact copies
fraternal twins: two separate eggs fertilized by two separate sperm
-not clones

20. Plant/Animal Breeding
cloning: produces living things with identical desired traits
breeding: bringing together two living things to produce offspring
*selective breeding brings out desired traits of living things: often used to get the best traits of both parents

21. Gene Splicing inserting or joining genes
Genes of one living thing can be joined with the genes of another living thing because the genetic code for all living things is the same! (All have A C T G)

22. recombinant DNA: formed when DNA from one organism is put into the DNA of another organism
ex. -making insulin in large amounts; benefits diabetics
-making human growth hormone
*may help cure genetic diseases