DNA: The Molecule of Heredity DNA- maintains genetic continuity through replication and controls cellular activity by regulating enzyme production. Cell Nucleus Chromosome DNA Nucleotide Nucleotides have three parts: Sugar Phosphate Nitrogen base A - adenine T - thymine C - cytosine G - guanine S P B

Thus, there are 4 different nucleotides found in DNA. The pairing of nitrogen bases in DNA is the key feature that allows DNA to be copied A=T C=G By bonding with a sugar (& phosphate), each of these bases forms a nucleotide. Thus, there are 4 different nucleotides found in DNA. (It is the order in which these nucleotides are arranged (the genetic code) that determines what proteins the cell will make.) P A S P C S P T S P G S

The phosphate groups and deoxyribose sugar form the backbone of the chain. Watson and Crick were the first to suggest DNA is the shape of a double helix. *Describe the process of replication. *Label the structure of DNA. The DNA in the chromosomes is copied in a process called DNA replication.

P C S G A T P A S P T S P G S P T S P A S P C S

From DNA to Protein An RNA molecule is a polymer composed of subunits called nucleotides There are 3 types of RNA: mRNA – messenger RNA carries DNA’s code from the nucleus to the ribosomes Follow exact directions from a double-stranded template During the process of transcription, DNA serves as the template for making mRNA which leaves the nucleus and travels to the ribosomes tRNA – transfer RNA picks up amino acids and carries them to the ribosomes to be assembled into proteins rRNA – ribosomal RNA makes up the structure of the ribosomes (as well as the nucleolus)

During transcription mRNA is formed. Each set of three nitrogen bases in mRNA coding for an amino acid is known as a codon These 3-letter words are read by the ribosome telling it which amino acids to assemble.

Translation The process of converting the information in a sequence of nitrogen bases in mRNA into a sequence of amino acids that make up a protein is known as translation. Translation is to protein as transcription is to ? mRNA *What is the difference between a codon and an anticodon? Fig 11.8 KNOW *Why is tRNA important in translation?

Genetic Changes Read pg 303-304 A point mutation is a change is a single base pair in DNA Ex. AATTAG to AAATAG A mutation in which a single base is added or deleted from DNA is called a frameshift mutation Ex. AATTAGAAATAG to ATTAGAAATAG A chromosomal mutation occurs when parts of chromosomes are broken off and lost during mitosis or meiosis

4 kinds of chromosomal mutations pg 306 Sometimes the detached piece attaches to the wrong chromosome (a non-homologous one) – this is termed translocation. When paired (homologous) chromosomes become entangled, an “arm” occasionally breaks off – if it does not reattach then all of its genetic information will be lost. This is chromosomal deletion. Inversion occurs when the section reattaches upside down – or in inverse orientation. Insertion occurs when a part of a chromatid breaks off and attaches to its sister chromatid. The result is a duplication of genes on the same chromosome.

Any of the following may act as a mutagen: radiation pollution viruses Any substance or stimulus that can affect a change in the DNA of a cell is termed a mutagen. Any of the following may act as a mutagen: radiation pollution viruses extreme high temperatures chemicals found in some foods