Presentation on theme: "Molecular Genetics Chapter 12"— Presentation transcript:
1Molecular Genetics Chapter 12 12.1 DNA: The genetic master12.2 Replication of DNA12.3 DNA, RNA and Protein
2Comprehension Check What organic compound group does DNA belong to? What are the building blocks (monomers) of DNA?
3History of DNAEarly scientists knew that there was something in cells that controlled the genetic informationThey did not know what that was!
4History of DNAFrederick Griffith was studying bacteria (in 1928) and realized that one bacteria could change another, this is called: transformation.He believed proteins, NOT DNA, controlled this genetic informationHe mixed good and bad bacteria in mice to see what would happenNon-harmful Bacteria: Mouse livedHarmful Bacteria: Mouse diedNon-harmful Bacteria and Dead Harmful Bacteria mixed together: Mouse died
5History of DNAOswald Avery designed an experiment (in 1944) to further test Griffith’s findingHe made a solution of the dead harmful bacteria and treated the solution with enzymes that destroyed all organic compounds except DNA.Transformation (change) still occurred so he concluded that genetic information was controlled by DNA
6History of DNAAlfred Hershey and Martha Chase (in 1952) used viruses called bacteriophages (a virus that makes bacteria sick) to confirm that DNA is the genetic materialRadioactive DNA: Cell infected by these viruses glowedRadioactive Protein: Cell infected byt these viruses did not glow
7History of DNAJames Watson and Francis Crick (in 1953) develop the double-helix model of the structure of DNATheir model looks like this:
8Current Research Human Genome Project, finished Gene Chips Identifying new speciesIdentifying new genes/Treating diseasesTracing your heredity
9Comprehension CheckWhat was the first major question scientists had to answer about genetic information?What was the second major question?
10Structure of DNA (Monomers) DNA is made up of many repeating units (monomers) called: NUCLEOTIDESDNA holds the code for making proteins in your body.The order of the nucleotides determines which proteins will be madeA nucleotide is a three-part unit made up of . . .1. Sugar(Deoxyribose)2. Phosphate group3. Nitrogen-carrying base
11Structure of DNA (Monomers) There are 4 different nitrogen bases in DNA: Adenine, Guanine, Cytosine, ThymineThe bases are classified into two main group based on their size:Purines have two nitrogen ringsPyrimindines have one nitrogen ringBases always pair in the same way:ADENINE binds with THYMINE GUANINE binds with CYTOSINEPurinesPyrimidinesAdenineGuanineCytosineThymineGo to Section:Go to Section:
12Structure of DNA (Polymer) DNA (the polymer) is a double strand of nucleotides joined by their basesThe phosphate of one nucleotide connects to the sugar of the next nucleotide (forming the sides). EXAMPLE:Some people think that DNA looks like a ladder, with the bases being the steps and the sugar/phosphates being the sides
13DNADNA molecules contain four bases: adenine (A), guanine (G), cytosine (C) and thymine (T). Instead of thymine, RNA molecules that are constructed from DNA contain uracil (U). If the sequence of bases in an RNA molecule is GUCUCA, what was the base sequence of DNA molecule from which it was constructed?CTGTGACAGAGTGTCTCAACTCTG
14DNADNA molecules contain four bases: adenine (A), guanine (G), cytosine (C) and thymine (T). Instead of thymine, RNA molecules that are constructed from DNA contain uracil (U). If the sequence of bases in an RNA molecule is GUCUCA, what was the base sequence of DNA molecule from which it was constructed?CTGTGACAGAGTGTCTCAACTCTG
15Chromosomes There are two different types of cells Prokaryotic Cells: Bacteria Cells with no nucleusEukaryotic Cells: More complex cells with a nucleusThe cells of all organisms contain DNA, but some cells contain more than othersEukaryotic Cells have 100,000 times more DNA than Prokaryotic Cells…..so how does it all fit inside that tiny nucleus???Chromosomes, only found in eukaryotes, help the DNA pack into the nucleusChromosomes are made of two organic compounds: DNA, Proteins (called Histones)Go to Section:Go to Section:
16Comprehension CheckWhat is the difference between a prokaryote and a eukaryote?The nucleus of a human cell contains 1 meter of DNA. How does all of this DNA fit into a cell’s nucleus?
17Comprehension Check What does the word replication mean? What must be occurring in DNA Replication?Do you think that this will be a complicated process?
18DNA ReplicationThis is the process by which a DNA molecule makes an EXACT copy of itself.This is important so the “code” can be passed from one generation to the next.This has to happen every time that a cell dividesThis process has to be exact so that mutations do not occurIn humans, the entire replication process takes about 4 hours.
20Steps of DNA Replication Step #1: The two sides of the strand are broken apartStep #2: The two inside parts of the strand are assembledStep #3: The new strands are proofread by the cell and mistakes are fixed
21Comprehension CheckA section of DNA has the following sequence of bases:G A C C T A G G C T T A A CDetermine the complimentary sequence:C T G G A T C C G A A T T G
22Comprehension CheckWhat does DNA do?/Why do you need DNA?
23THE CENTRAL DOGMA TRANSCRIPTION TRANSLATION Remember, the order to amino acids is determined by the RNA code which is determined by the DNA code:DNA RNA PROTEINS
24What does DNA really do?DNA is found in the nucleus. It codes for the production of proteins.Proteins are the keys to almost everything that living cells do!Proteins are actually put together on the ribosomes.The problem is getting the code out of the nucleus to the ribosome.
25RNA RNA gets the codes in the DNA out to the ribosome There are three types of RNA, each has a special job in sending the message and making the protein1. mRNA = Messenger RNA2. tRNA = Transfer RNA3. rRNA = Ribosomal RNA
26Processes of Protein Synthesis There are two processes that must occur to make a protein:1. TRANSCRIPTION: DNA’s code in the nucleus is “copied” by mRNA and is then taken to a ribosome.2. TRANSLATION: With the help of rRNA, tRNA brings the correct amino acids to the mRNA and the protein is assembled.
27Comprehension Check Why can’t the DNA leave the nucleus? How does the “code” get to the ribosomes?
28Reading the CodeRemember that RNA is a copy of the code found in DNA, its like a encrypted messageIt is NOT single bases in RNA that are important – but groups of 3 called CODONS.Each codon on mRNA codes for a specific amino acid. (REMEMBER THAT AMINO ACIDS ARE THE MONOMERS OF PROTEINS)