3 What is DNA? DNA stands for deoxyribonucleic acid DNA determines the traits of organisms by determining the structure of proteins.Think of it as a “blueprint”.The proteins carry out all of the work in the cell and essentially carry out all of the actions of life!Remember: Ribosomes make proteins!
4 Where Do I Find DNA? Chromosomes are in the nucleus of every cell. Chromosomes are madeup of DNA.Genes are pieces of DNAthat contain the instructionsfor building a protein.
5 The Structure of Nucleotides DNA is made up of repeating nucleotide subunits.One nucleotide = phosphate group, sugar (deoxyribose), and one of four nitrogenous bases
6 The Structure of Nucleotides The four nitrogenous bases ultimately give the nucleotide its “identity”Adenine (A)Thymine (T)Cytosine (C)Guanine (G)Purines- A, GPyrimidines- T, C
7 The Structure of DNADNA is made up of two strands of nucleotides coiled up into a double helix or “twisted ladder” shapeThe sugar and phosphatecreates the backbone ofthe DNA molecule
8 The Structure of DNAThe bases attach to the sugar on the DNA molecule and base pair to a partner with a hydrogen bond. This creates the “rungs” of the twisted ladder.The bases of one nucleotide strand will base pair to the bases on the other nucleotide strandA always pairs with TC always pairs with G
9 The Structure of DNA T pairs with A C pairs with G Sugar and phosphate forms the “backbone”Order of the bases holdsthe information
10 The Importance of Nucleotide Sequences The order of the bases holds the genetic information as a “code”Just like the letters of the alphabet make up words!Example: ATTGAC means something completely different than TCCAAAThe more similar two organisms’ DNA sequences are, the more related the organisms are!
11 DNA ReplicationAll new cells (made by mitosis and meiosis) need a complete copy of the DNAThis is completed during S phase of InterphaseDNA must be copied so each cell can have its own copy.This process is called DNA replication.semiconservative replication – the process in which the DNA molecule uncoils and separates into two strands. Each original strand becomes a template on which a new strand is constructed, resulting in two DNA molecules identical to the original DNA molecule.
12 How DNA replicatesEnzyme breaks the bonds between the bases that holds the two strands together. This is called “unzipping” the DNA.Another enzyme (DNA polymerase) assembles a complementary nucleotide chain for each original nucleotide strand. The newly added nucleotide strand is called the complementary strand.At the end you are left with two identical copies of the DNA.
17 RNARNA and DNA are both nucleic acids that are made out of nucleotidesThree main differences:RNA is single stranded;DNA is double strandedRNA’s sugar is ribose;DNA’s sugar is deoxyriboseRNA contains uracil (U);DNA contains thymine (T)
18 Types of RNAThere are three main types of RNA that carry out important roles in the cell:mRNA – brings instructions from the DNA in the nucleus to the cytoplasmrRNA – makes up part of the ribosometRNA – brings amino acids to the ribosome to build proteins
19 Transcription-The process in which a strand of mRNA is synthesized by using the genetic information found on a strand of DNA as a template.-RNA polymerase reads the complementary DNA strand and attaches complementary RNA bases.Occurs in the nucleusAn RNA copy of a portion of DNA is madeHappens similar to replication except:One strand of RNA (single-stranded) is madeRNA polymerase is the enzyme that carries out transcriptionA pairs with U (rather than T)G pairs with C
21 Practice Transcription Complementary/non-codingDNA strand T A C G G A C T G A T TmRNA strand -A U G C C U G A C U A A
22 Translation-the process in which the mRNA molecules is decoded to produce a sequence of amino acids for protein synthesismRNA is read in codons (groups of 3 bases)Each codon has a particular amino acid that goes with itThe genetic code is universal; all organisms use the same code
23 Translation Occurs on the ribosomes in the cytoplasm mRNA is “read” by the ribosomes (either “free” in the cytoplasm or on the rough endoplasmic reticulum) and tRNA molecules bring amino acids to the ribosome to be assembled into a polypeptide chainRough ER is responsible for transporting the newly synthesized proteins to the Golgi apparatus where carbohydrates are added to it and it is packaged in a vesicle for transportation to the cell membrane.polypeptide chain- chain of amino acids joined together by peptide bondsproteins are polypeptide chains folded into specific shapes
25 Write in the 3-letter code in your handbok on page 12!!!!
26 Practice Reading the Genetic Code What amino acid is coded for by the following codons?CCCGUAAUCAUGUAAWhat codons stand for serine?Proline (Pro)Valine (Val)Isoleucine (Ile)Methionine (Met)/ StartStopUCU, UCC, UCA, UCG, AGU, AGC,
27 Practice Transcription and Translation Using the following DNA sequence, transcribe it into mRNA and then translate it into an amino acid sequence:Coding DNA: A T G T T T A C C T A T G A C T A AComplementary DNA:mRNA:amino acid sequence :T A C A A A T G G A T A C T G A T TA U G U U U A C C U A U G A C U A ATyrAspStopPheThrMet