DNA
What are the benefits of the redundancy in the genetic code? List two functions of the triplet AUG.
Genetic code the set of rules that relate codons in RNA to amino acids in proteins. The triplet AUG has dual function: it codes for the amino acid methionine (MET) and also can provide a signal for the start of a polypeptide chain. In 10.8 A there is redundancy in the code but no ambiguity, for example although codons UUU and UUC both specify phenylalanine (redundancy) neither of them ever represents any other amino acid (no ambiguity) There are more codons than amino acids so if one is damaged they still can produce amino acids
Identify the question that Hershey and Chase were trying to answer. What was the significance of this experiment
Hershey and Chases question was how do we know that DNA is the genetic/ hereditary material? The hershey-chase experiment indicate the DNA and not protein was the genetic material of viruses. By tagging DNA with heavy phosphorous and the protein capsule with heavy sulphur they were able to trace where each molecule went when the virus infected a bacterium. they discovered that the DNA ended in the bacteria but the protein did not. DNA was actually the carrier of hereditary information. They wanted to see what is used to transmit genetic material
How serious are the consequences of each of these types of mutations to the affect of protein? to the cell/organism
Silent mutation will cause no change in the protein produced. Missense mutations do change the amino acid coding. Some of these have little effects on the protein while others like sickle- cell disease prevent the protein from performing its normal function nonsense mutation change an amino acid codon into a stop codon. and not function properly
Distinguish between base substitution mutations and insertion/deletion mutations
Substitution is the replacement of one nucleotide and its base-pairing partner with another pair of nucleotides. Insertion/deletion- one or more nucleotides in a gene often have disastrous effects. because mRNA is read as a series of nucleotide triplets (codons) during translation, adding or subtracting nucleotides may alter the reading frame (triplet grouping) of the message.
How and when do these types of gene mutations typically arise
it starts when a person is developing.
Distinguish between tRNA, rRNA, and mRNA in terms of their origins, structures, and roles in translation.
mRNA- is called messenger RNA because it conveys genetic messages from DNA to translation machinery of the cell. tRNA- to covert the words of nucleic acids (codes) to the amino acid words of proteins a cell employs a molecular interpreter. rRNA- a ribosome consists of two subunits each made up of proteins and a kind of RNA called ribosomal RNA
What are two main sources of mutations in cells
mutagenesis- can occur in a number of ways. Spontaneous mutations are due to errors in DNA replication Mutagens- physical or chemical agents such as x-ray or uvlights
Why are changes in the 3rd position less serious than changes in the 1st of 2nd positions
the third position is less harmful because there's still possibility that there will be the same codon
Explain the structure of a nucleotide in terms of its 3 component parts. How does nucleotide structure participate in the structure of a DNA molecule?
A nucelotide is the building blocks of nucleic acid. they are made up of three parts- nitrogenous bases, sugar and phosphate group. DNA in a cell is really a pattern made up of four different parts called nucleotides
For the DNA sequence TTACGGGATTCT, what would be the sequence of nucleotides in the complementary DNA strand?
AATGCCCTAAGA
What is mutation
Any change in the nucleotide sequence of DNA
What is complementary base paring? What are the "rules" of complementary base pairing? What evidence did Chargaff present for these rules?
Complementary base pairing is the standard arrangement of bases in nucleotides in relation to their opposite pairing, such as thymine being paired with adenine and cytosine paired with guanine. Erwin Chargaff's rules on base pairing are explained by the fact that A on one of DNA's polynucleotide chains always pairs with T on the other polynucleotide chair, and G on one chair pairs only with C on the other chain
Describe the role of complimentary base pairing in protein synthesis
Complimentary base pairing for protein synthesis just means a=u c=g. Those pair and then protein synthesis happens to make the amino acids
How can mutations in DNA lead to a genetic disease
Complimentary pairs don't match
How is DNA replicated? Include an explanation of why the two resulting DNA double helices are identical. Describe and contrast 'continuous' and 'discontinuous' DNA synthesis, as seen on complementary strands in a given region during replication. What aspects of DNA structure and of DNA polymerase specificity account for this?
DNA Replication - An enzyme called helicase unwinds the double stranded DNA and breaks hydrogen bonds - several small proteins called single strand binding proteins (SSB) temporarily bind to each side and keep them separated. -An enzyme complex called DNA polymerase "Walks" down the DNA strands and adds new nucleotides to each strand. The nucleotides pair with the complementary nucleotides on the existing strand ( A with T. G with C) - a subunit of the DNA polymerase proofreads the new DNA -An enzyme called DNA ligase seals up the fragments into one long continuous strand - new copies automatically wind up again
Why is DNA referred ti as a "double helix"? what is double about DNA. What is helical about DNA? in your response, clearly distinguish between one DNA strand (nucleotide chain) and the whole DNA molecule.
DNA has two strands referring to its two adjacent polynucleotides strands interwound into a spiral shape. The double helix describes the appearance of double stranded DNA. Which is composed of two linear strands that run opposite to each other or anti-parrel and twist together.
What is DNA and what is a genome?
DNA is a double stranded helical nucleci acid molecule consisting of nucleotide monomers with deoxyribose sugar and the nitrogenous bases adenine, cytosine, guanine and thymine, capable of replicating DNA is an organism's genetic material. A genome is an organism's complete set of DNA including all of its genes each genome contains all of the information needed to build and maintain that organism.
Why is DNA replication said to be semi-conservative? What is the value of this to the cell?
DNA is semi-conservative because in DNA replication the term "Semi-conservative" means that after DNA replication half of the DNA molecules in the daughter DNA are original DNA. This means that during DNA replication, the original double stranded DNA is separated into two DNA strands and each strand served as a template for replications
Why is DNA the central molecule in biology? What are the 2 major functions of DNA in the cell?
DNA is the central molecule in biology because the study of heredity at the molecular level. Two main functions is hereditary and control. hereditary- DNA transmits genetic instructions from generation to generation control- gene expression
What is 'proofreading' in the context of DNA replication? What is the error rate before versus after proofreading? What is the value of this proofreading to the cell/organism?
DNA polymerase also proof reads DNA -1/10,000 base pairs mismatched -after proof reading 1/1billion base pairs mismatched -DNA polymerase- a large molecular complex that assembles DNA nucleotides into polynucleotides using a preexisting strand of DNA as a template -DNA polymerase carry out a proofreading step that quickly removes nucleotides that have base-paired incorrectly during replications
Using the lac operon in prokaryotes as an example, describe how a cell can regulate whether or not it expresses information in a gene(s). What ultimately controls whether or not the structural genes of the lac operon are transcribed? Why is gene regulation important to the cell? What researchers were responsible for first describing the lac operon?
On control sequence is a promoter, a site where the transcription enzyme, RNA polymerase attaches and initiates transcription, in this case transcription of all three lactose enzyme genes (as depicted in 11.1 B between the promoter and the enzyme genes a DNA control sequence called an operator acts as a switch. the operator determines whether RNA polymerase can attach to the promoter and start transcribing the genes. such a cluster of genes with related functions along with the control sequences is called an opera. with rare exceptions, operons exists only in prokaryotes. the key advantage to the grouping of related genes into operons is that the single " on-off" switch can control the whole cluster p210
What are the parts or components of a properly controlled scientific experiment?
Parts of controlled experiment include: -Variable: a factor that can change in an experiment -Independent Variable: manipulate variable the one we change -Dependent Variable: responding variable, one we measure -Constant: variable that does not change -Control: a sample that does not have an independent variable we compare our results to it.
What type(s) of macromolecule do genes code for directly? What type(s) of macromolecule do they NOT code for directly? How does the cell produce macromolecules not directly coded for in DNA?
Proteins code, sugars fats and lipids don't. Cells get the ones that don't code by eating sugars, fats, and lipids
What is RNA? How does the structure of RNA differ from that of DNA? Why is it that A=T and G=C in all DNA, regardless of source, length, etc.? Why, in RNA, does A≠U and G≠C?
RNA- type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogen bases adenine, cytosine, guanine, and uracil; usually single stranded; functions in protein synthesis, gene regulation, and as the genome of some viruses. RNA sugar is ribose, DNA is dexoyribose RNA has uracil instead of thymine RNA usually single stranded, DNA is double
What initiates scientific investigation? What are the sequential steps of this process?
The scientific method is a method for conducting an objective investigation. It involves making observations and conducting an experiment to test a hypothesis. Steps: 1. Make observations 2. Propose a hypothesis 3. Design an experiment to test the hypothesis. Includes controlled variables, independent and dependent. 4. Test hypothesis 5. Accept or reject hypothesis 6. Draw conclusions.
Distinguish between transcription and translation in terms of the molecules involved, the location and the products.
Transcription- the synthesis of RNA under the direction of DNA Translation- the synthesis of protein under the direction of RNA Transcription happens in the nucleus (DNA->RNA) Translation happens in the cytoplasm (Protein)
List at least 10 specific features of the structure of DNA as explained by Waston and Crick model. How did Watson and Crick come up with their model of the double helix? Describe 2-3 specific pieces of information about DNA that Watson and Crick gathered from other contributing scientists. What insights did Watson and Crick contribute to the model?
Watson and Crick DNA has: -2 chains -DNA to be a helix with uniform diameter of 2nm with nitrogen bases stacked 1/3 of nm apart. (Franklin) -Two polynucleotide strands- a double helix -Sugar phosphate backbones must be on the outside of the double helix forcing nitrogen bases to swivel to the interior of the molecule. - contains nucleotides -weak hydrogen bonds hold together base pairs -A-T -C-G -Base pairs are complimentary -Guanine is paired with cytosine by three h-bonds -adenine is paired with thymine by two h-bonds -Phosphodiester bond the covalent bond that links nucleotides within the same strand - Wastons and crick apparent that the double ringed base (purine) must always be paired with a single ringed bases (pyrimidine) on opposite strand
Explain how the sequence of nucleotides of DNA codes for the sequence of amino acids in a protein. How is the protein made? Why is "translation" a good name for protein synthesis?
When a protein is built each amino acid is attached to a tRNA molecule, which carries three nucleotides on one end, this is called anti-codon. every possible combination of three RNA nucleotides codes for a specific amino acid. During translation of mRNA every three nucleotides are called anti-codon. every codon has a complimentary anti-codon. so if a section of mRNA reads: AAGCAGAUUGCG the first codon to the left to the right is AAG the corresponding anticodon is UUC. so the tRNA with the mRNA and the amino acide that it carries will join with the next amino acid called for by the code. Is just how translation works. Translation is a good name because it translated genetic code.