DNA and RNA Chapter 12

Types of Nucleic Acids DNA (Deoxyribose Nucleic Acid) RNA (Ribose Nucleic Acid)

DNA Structure DNA consists of two molecules that are arranged into a ladder- like structure called a Double Helix. A molecule of DNA is made up of millions of tiny subunits called Nucleotides.

Nucleotides are composed of: 1.A sugar 2.A phosphate group 3.A nitrogenous base

Nucleotides Phosphat e Pentose Sugar Nitrogenous Base

Nucleotides The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. There are four types of nitrogenous bases.

Nucleotides A Adenine T Thymine G Guanine C Cytosine

Nucleotides Each base will only bond with one other specific base. Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Form a base pair.

DNA is a molecule of nucleic acid that stores and transfers genetic information. Nitrogenous Bases Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Chargaff’s Rule Percentages of guanine and cytosine and percentages of adenine and thymine are almost equal in any sample of DNA. A = T and C = G

Question If 32% of the bases in a certain sample of DNA were thymine, what would be the percentages of adenine, cytosine and guanine?

DNA Replication DNA duplicating before a cell divides A pairs with T and G pairs with C In the diagram, the complementary strand would be: GTAGGC

G G A T T A A C T G C A T C

RNA A messenger between DNA and ribosomes “Decodes” the genetic message contained in the DNA molecule

3 Types of RNA: Messenger RNA (mRNA) - copies information from DNA and carries it to the ribosomes in the cytoplasm Ribosomal RNA (rRNA) - makes up the major part of the ribosomes Transfer RNA (tRNA) - carries amino acids to the ribosomes where the amino acids are joined to form a polypeptide

Transcription Information in a DNA molecule is transferred to an mRNA molecule (DNA  RNA). Guanine pairs with Cytosine Adenine pairs with Uracil Thymine pairs with Adenine

Practice Transcribing DNA CUAGGA

Translation Decoding mRNA into a chain of amino acids (RNA  proteins) Groups of 3 RNA nucleotides, called codons are “decoded” into amino acids

Translation Section 12-3

Translation Section 12-3

DNA RNA Deoxyribose (sugar) Double stranded Nitrogenous bases: –Guanine –Cytosine –Adenine –Thymine Ribose (sugar) Single stranded Nitrogenous bases: –Guanine –Cytosine –Adenine –Uracil

Codon Three-nucleotide sequence on mRNA that codes for a single amino acid

The Genetic Code

Mutation Change in a DNA sequence that affects genetic information

Blueprint DNA is the blueprint of an organism DNA tells an organisms how to construct it self

Genetic Mutations Point Mutations – change involving one or a few nucleotides –Substitution of one base for another –Insertion or deletion of a base Frameshift Mutations – shifts the reading of the genetic message by inserting or deleting a nucleotide

SubstitutionInsertion Deletion Genetic Mutations: Substitutions, Insertions, Deletions Section 12-4

Chromosomal Mutations involve a change in the number or structure Deletion – loss of chromosome Duplication – produce extra copies of parts Inversions – reverse direction of parts Translocations – part breaks off and attaches to another part

Deletion Duplication Inversion Translocation Chromosomal Mutations Section 12-4