Unit 6: DNA and Protein Synthesis Guided Notes

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1 Unit 6: DNA and Protein Synthesis Guided Notes 1 DNA Nucleic Acid review: Nucleic Acids are made of nucleotides. There are two types of nucleotides have 2 rings. They are and They look like: have 1 ring. They are and They look like: In DNA, the nucleotides are always paired in the same way: This matches 1 purine to 1 pyrimidine. Watson & Crick (& Franklin) figured out DNA looks like a twisted ladder, its shape is a: Label the phosphate, sugars, and bases on this DNA Model (note the uprights and rungs ): Note how the complimentary pairs of nucleotides are facing in opposite directions. One end of the molecule begins with the 5 th carbon on Deoxyribose, so it is called the end. The other side begins with the 3 rd carbon so it is called the end. RNA is another Nucleic Acid. It is different from DNA because: 1) 2) 3) 4)

2 2 DNA Replication In DNA replicates to pass on genes and genetic traits. First the chromosome unwinds and stretches out. The DNA unzips and splits open separating at the bases. The enzyme facilitates this. Another enzyme, matches new nucleotides to their complement on the old strand. joins these pairs together to form new strands of DNA. Therefore, each new DNA molecule is one half old and one half new. Therefore, DNA replication is considered (because half is conserved). In bacteria, there is only 1 piece of DNA so this process occurs rather quickly and easily. In eukaryotes, there are many strands of DNA. Therefore, the DNA opens at many replication points so that replication can occur quickly. Remember that the two sides of DNA are in opposite directions. If the DNA is being unzipped, one strand runs from the 3 end to the 5 end and the other runs from the 5 end to the 3 end. DNA Polymerase is a very specific enzyme and can only add DNA to the end of the strand. It reads the old DNA starting with the 3 end towards the 5 end. It adds complimentary DNA so that it runs from the 5 end to the 3 end (because it can only add onto the 3 end). This half of the DNA is called the strand. The strand that runs in the other direction (5-3 ) has to replicate in small pieces so it proceeds more slowly. These pieces are called, and the strand is the: At the end of DNA replication, each chromosome has 2 sister chromatids.

3 Protein Synthesis 3 DNA is important in genetics and heredity. The code of DNA is related to the genotype ( ) and phenotype ( ). Genes on chromosomes carry the directions for building, which determine an organism s phenotype. When a gene goes through this process, we say it is. Most genes start with a genetic sequence called a and end with one of three sequences called. DNA is first into RNA in the nucleus, and then the RNA is into a protein by ribosomes. Transcription DNA is in the nucleus and it cannot leave. But proteins are made in the: So RNA is used to carry the message out of the nucleus. DNA is transcribed into a specific type of RNA called mrna or. It will take the message of the DNA code to the ribosome. Transcription cannot occur without the enzyme If your DNA is: T A C G T G G A C A G T T T G A A T C C G C G A A T T Your mrna would be: Remember there is instead of Thymine in RNA. In other words, U instead of T. Translation mrna leaves the nucleus and goes to the ribosome. The ribosome is made of protein and: The ribosome has two parts and resembles a burger bun. Here the code of the mrna is read 3 nucleotides at a time. These 3 nucleotides are collectively called a, and each codes for a specific. The promoter of the gene translates into a start codon, and the terminators of a gene translate into stop codons. Amino Acids are the monomers for proteins. There are only 20 Amino Acids and organisms use them to make millions of different proteins, just like our 26 letters make millions of words. Scientists determined which codon codes for which amino acid and wrote that down as the. It is the same code for all living organisms. The genetic code is on page 192 of your textbook. The start codon is AUG and codes for the Amino Acid. The codon UUA codes for the Amino Acid Leucine. That is the only Amino Acid UUA codes for, but other codons also code for Leucine: Convert the mrna into the appropriate Amino Acids: AUG CAC CUG UCA AAC UUA GGC GCU UAA

4 4 The proteins that you eat are broken down into Amino Acids, which end up in your cytoplasm around the ribosomes. Special RNA molecules called or trna transport the Amino Acids to the ribosome so they can be linked together to form the new protein. In order to match correctly with the mrna molecule, the trna has an that is complementary to the codon. Write the anticodons for the mrna: AUG CAC CUG UCA AAC UUA GGC GCU UAA Cells can regulate the entire protein synthesis process. There are nucleotides that can act as a switch and can turn on or off the expression of the gene. Proteins can block the switch or the gene. Transcription factors may interact with the RNA Polymerase - they help the enzyme bond with the DNA to start transcription, but they may only facilitate the transcription of certain parts of the DNA. They can act as an activator or a repressor. The ribosome can change the speed of translation. Sometimes the mrna is altered before it is translated. Certain regions are removed and are not translated into the final protein. They are called introns. The mrna nucleotides that are spliced together and are eventually translated are called exons. Sometimes the DNA stays compacted around the histones. When this happens the DNA is not expressed. Once the DNA is expressed, the cell will become set. This means that its type is determined and only certain genes will be used and expressed. We call this process cell Mutations Mutations are permanent changes in or chromosomes. They can be changes in chromosome or. Structural changes are usually errors in replication that code for new When nucleotides are substituted or exchanged it is a. This is usually a small error and because of the redundancy in the genetic code may not be harmful (a mutation). Sometimes it can be serious. When a nucleotide or a piece of DNA is added it is an: When a nucleotide or a piece of DNA is removed it is a: When a piece of DNA is removed, flipped, and placed in backwards it is an: When two non-homologue chromosomes exchange pieces it is: When a piece of DNA that is deleted attaches to a different chromosome or to the other member of the homologous pair, it is a. This may be why we have more than one allele for a trait.

5 5 A change in chromosome number happens with. This happens when chromosomes don t separate in anaphase. It can occur in either mitosis or meiosis. We can see these changes when we take a picture of the chromosomes in a cell this picture is called a. When a cell is missing a chromosome it is called a. This is mostly lethal, only one type is known to survive. When a cell has an extra chromosome it is called a. This is much more common. The only autosomal nondisjunction that involves somatic chromosomes is the most common syndrome and involves an extra chromosome #21. It is called or. The 21 st chromosome is small and doesn t contain many genes so it is not as lethal as having other extra chromosomes would be. It is more common as parents age because occurs more often in older eggs, and sometimes in older sperm. The characteristic traits of the syndrome are: Similar but much more severe disorders are Patau Syndrome (Trisomy ) and Edward Syndrome (Trisomy ) The rest of the Trisomys involve the sex chromosomes, where nondisjunction is much more common and the chromosomes don t have as many genes that can cause problems. Trisomy X females have the genotype, a mild disorder that sometimes causes physical deformities, mental abnormalities, and reproductive issues. The genotype is sometimes called Meta Male. These men tend to be taller and have below normal intelligence. At one point scientists said they were more criminally aggressive, but now that is not believed to be the case. Individuals with the genotype are males that have Klinefelter Syndrome. The symptoms can be mild to severe. In many cases it isn t noticed until puberty, when the men do not develop secondary sexual characteristics. The men are sterile, have physical and mental abnormalities. Some affected with Klinefelter s have extra X and Y chromosomes. The only Monosomy that survives is, or X chromosome. These women have Turner Syndrome, which is characterized by physical and mental abnormalities. They are sterile and often do not go through puberty. DNA Technology We can use our knowledge of DNA and mutations to our advantage Genetic Engineering is the use of to alter the genome of a living cell for medical or industrial use. It is a type of artificially enhancing or replacing body parts

6 Scientists use to cut DNA in specific places and cut out specific genes. They mix the genes with DNA Polymerase and many nucleotides to copy them using the process of PCR or. When the genes are added to DNA, the new DNA is called. Organisms that have this new DNA are called: This technology can be used for many things: 6 We can also use these enzymes to get certain unique genes that we use to identify people in the case of paternity or criminal cases. This is called DNA. In the process of, DNA is cut with restriction enzymes and placed in a gel-like matrix. Electric current is passed through the gel and it separates the DNA segments by size. The stained DNA looks like lines in the gel. mom child dad 1 dad 2 dad === === crime scene suspect 1 suspect 2 suspect 3 ===== ===== ===== ===== ===== ===== Scientists have used this to map the human genome in the: They know all the genes, where they are, and what nucleotide sequence they have. They are using this to help diagnose genetic disorders so they can learn about them and hopefully cure them. Stem cells are also being used to replace cells and treat disease. This is because the DNA has not completely expressed and the cells are not differentiated. Embryonic stem cells are easier to manipulate, but controversial in their sourcing. stem cells, such as the ones in our bone marrow, are harder to work with but easier to get. Viruses Viruses can be used as a vector to introduce recombinant DNA into a Transgenic Organism. Virus is poison in Latin they are non-living entities that are infectious. Label these viruses:

7 7 The genetic material for a virus can be either DNA or RNA. If it has RNA it is called a: When a virus attacks a cell, its is injected into the host cell. It directs the cell, using its genetic material to force the cell to make new Since a virus needs a host to replicate, a virus is not considered: There are two parts to the virus life cycle: In the cycle, the viral DNA forces the host cell to make new viruses, the cell will and release the viruses. In the cycle, the viral DNA inserts itself into the host s DNA, becoming a. The viral DNA inactivates and hides within the host s DNA as the host replicates. The viral DNA waits for the right conditions, and then activates and switches the cell to the cycle. These viruses may go dormant and then flare up over and over again. One of the proteins that the virus forces the host to make is DNA or RNA It then carries that polymerase to the next host. If a virus has DNA, it uses this polymerase to insert the DNA into the host cell s genome, make more polymerase, and continue the cycle. If it is a retrovirus, it must first perform reverse transcription to make, and then insert it into the host. Again, it uses its host to make the necessary proteins for this process. Sometimes inserting this DNA can alter other genes in the host cell. This is how viruses can lead to. Viruses are specific to a certain cell. Some are viruses only on bacteria and are called which is short for. Some only attack plants. Some only attack one species, maybe even one tissue. The virus only attacks white blood cells. This is probably because they stole their nucleic acids from these cells originally. Vaccines prevent viruses by building up the body s immune system. The body makes the necessary to fight off the virus, so the cells will be ready when the virus actually attacks. But viral nucleic acids are constantly, so for many viruses, yearly immunity is necessary. Medicines that are taken to destroy viruses usually stop DNA replication and protein synthesis, so they will harm the cell as well.