DNA – Life’s Code Chapter 12

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

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

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

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

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!

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

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

DNA Replication

http://www.youtube.com/watch?v=zdDkiRw1PdU

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

Transcription

http://www. youtube. com/watch http://www.youtube.com/watch?v=OtYz_3rkvPk&safety_mode=true&persist_safety_mode=1

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

Translation

http://www. youtube. com/watch http://www.youtube.com/watch?v=1NkLqjQkGHU&safety_mode=true&persist_safety_mode=1

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)

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

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

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)

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