MicroBio Chapter 9
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Polymers of repeating units- composed of three smaller units.
- DNA contains everything but uracil
- RNA contains everything by thymiine
Basic unit of DNA stucture: composed of phosphate, deoxyribose sugar, and nitrogenous base.
Define/Describe Purines and Pyrimidines
- Purines: Adenine (A) & Guanine (G)
- Pyrimidines: Thymine (T) & Cytosine (C) & Uracil (U)
- Purines: Two rings of nitrogen base
- Pyrimidines: One ring
Describe the differences between DNA and RNA
- DNA contains all nitrogen bases except uracil
- RNA contains all nitrogen bases except thymine
- RNA is a single strand containing ribose sugar instead of deoxyribose, and uracil instead of thymine.
- DNA is a double-helix, sugar-phosphate backbone represents the rails and paired nitogen bases represent the steps.
What are the three main types of RNA and what are their functions?
- mRNA: Messenger RNA is transcribed from DNA and is translated=code to make protien. It is the sequence of amino acids in a protien
- tRNA: is needed for translation, and carries amino acid to ribosome, is transcribed from DNA
- rRNA: major component of ribosomes, is transcribed from DNA. forms the major part of a ribosome and participates in protien synthesis.
- Sum total of genetic material of a cell.
- Genomes of cells are composed exclusively of DNA
- A discrete cellular structure composed of a neatly packaged DNA molecule.
- Chromosomes of all cells are subdivided into basic information packets called genes.
- Site on the chromosome that provides information for a certain cell function.
- It is a certain segment of DNA that contains the necessary code to make a protien or RNA molecule.
- Three basic categories of genes.
- Structural genes: code for protien
- RNA coding genes: code for RNA
- Regulatory genes: control gene expression
- Sum of all types of genes that constitutes an organisms destinctive genetic makeup
- The expression of the geneotype creates traits reffered to as the phenotype
- Phenotypes can change depending on which genes are turned on
Distinguish between eukaryotic and prokarotic chromosomes
- Eukaryotic Chromosomes: DNA molecule tightly wound around histone proteins
- -located in the nucles
- - vary in # from few to hundreds
- -can occur in pairs (diploid) or singles (haploid)
- -appear linear
- Prokaryotic chromosomes: condensed and secured into a packet
- -single: circular double stranded chromosome
How is DNA "unzipped"
The paired nitrogenous bases are aligned as to be joined by hydrogen bonds. These weak bonds can be easily broken by Helicase.
What is the purpose of DNA replication, and at what point in a cell's life does it occur?
- For the language of the DNA to be preserved for a very long time.
- Duplicated and passed on to offspring
- It occurs in binary fission -the metabolic machinery of a bacterium initiates the duplication of the chromosome.
What are the three constrains of DNA Polymerase
- 1. Nucleotides are buried deep, so the DNA molecule must be unwound & two strands of helix seperated from each other
- 2. DNA Polymerase is unable to begin synthesizing a chain of nucleotides, but can only continue to add nucleotides to an already existing chain.
- 3. Can only add nucleotides in one direction, from 5'-3'
- Leading Strand: continuous, complete strand 5'-3'
- Lagging Strand: goes from 3'-5'. DNA polymerase adds nucleotides few at a time, in direction ---> away from fork.
- Okazaki Fragments: 1 Strand containing short fragments and are connected by the enzyme ligase.
What is the second role of DNA Polymerase?
- It can correct the mistakes made
- the incorrect unmatching bases, excise them, and replace them with the correct base
Describe the relationship between DNA, RNA, proteins, transcription, and translation.
- The stored information of DNA is converted to RNA molecules which carry out instructions. Genetic information flows from DNA to RNA to protein.
- The master code of DNA is first used to sinthesize an RNA molecules via transcription, and the information used to produce protiens is known as translation.
List the three points that connect DNA to an organism's traits
- Proteins primary structure, order, and type of amino acids in the chain determines its charateristic shape & function.
- Protiens ultimatley determine phentotype, expression of all aspects of cell function/structure.
- DNA is mainly a blueprint that tells cells which kinds of protiens and RNA to make & how.
mRNA and tRNA, the association of the two molecules with codons and anticodons
- mRNA: the copy of structural genes in DNA
- the message of this transcribed strand is later read as a series of triplets called Codons.
- tRNA: uniform in length, tRNA is a copy of specific region in DNA
- contains sequences of bases that form hydrogen bonds with complimentary sections of the same tRNA strand. converts RNA language into protien language.
Describe the structure of a ribosome
- rRNA: the ribosomal RNA and protien-long polynucleotide molecule
- 2 subunits: engage in final translation of genetic code
- Takes a gene on DNA and converts it into a strand of RNA
- RNA Polymerase: huge enzyme system converting DNA code to RNA.
- Transcription is initiated when RNA polymerase recognizes the segent of DNA called promoter region. Its allowed to begin when DNA helix begins to unwind @ second sequence.
- As polymerase advances & synthesizes RNA molecule complimentary to temperate strand of DNA
5'-3' mRNA is assembled by addition of nucleotides complimentary to DNA temperate strand.
Polymerase gets another signal that signals seperation and release of mRNA strand now called the transcript.
- Particular amino acid can be coded for by more than a single codon. SO
- One cannot predict from protein structure what the exact mRNA codons are because of redundancy.
What does wobble mean? *ask teacher.
thought to permit some variation or mutation without altering the message.
Why can prokaryotic transcription and translation occur at the same time?
- Because the prokaryotes do not contains a nucleus holding the DNA.
- The mRNA transcript does not have to pass through pores in the nuclear membrane
- Coordinated sets of genes, all regulated as a single unit.
- They are either inducible or repressible
- The category they fall into is determined by how transcription is affected by the envoirnment surrounding the cell.
Explain association between catabolic and anabolic operons and induction and repression.
- Catabolic operons: are inducible oprerons that are turned on by the substrate of the enzyme needed for which the structural genes code
- Repressible operons: contains genes for coding anabolic enzymes
List three important feautres of the lactose operon
- 1. Regulator: composed of the gene that codes for a protein capable of repressing the operon.
- 2. the control locus: promoter and the operator acts as an on/off switch for transcription
- 3. Structural locus: made up of three genes each coding for a different enzyme needed to catabolize lactose
Describe assoiation of glucose with lactose operon
- Lac operon only functions in the absense of glucose or if the cells energy needs are not being met by the available glucose
- When glucose is present, a second regulatory system ensure that the lac operon is inactive, regardless of lactose levels.
Differentiate between spontaneous and induced mutations
- SPONTANEOUS: random change in DNA arising from errors in replication that occur randomly
- INDUCED: result from exposure to known mutagents, which are primarly physical or chemical agents that interact with DNA in a distruptive manner
Addition, deletion, or substitution of single bases
- Any change in the code that leads to placement of a different amio acid
- it can create a fault nonfunction protein
- it can produce a protein that functions in a different manner
- cause no significant alteration in protein function
- Changes a normal codon into a stop codon that does not code for an amino acid and stops the production of the protein
- Always results in a nonfunctional protien
Alters the base but does not change the amino acid, thus having no effect.
When a gene that has been mutated or undergone mutation reverses (mutates back) to its original base composition
- One or more bases are inserted into, or deleted from a newly synthesized DNA strand.
- The reading frame of the mRNA has been changed
- Nonfunctional protein=result
- Bacterial "sex"
- Plasmid or other genetic material is transferred by a donor to a recepient cell
- Transfer of naked DNA and requires no special vehicle
- From enviornment
DNA transfer mediated through the action of a bacterial virus!
Explain how conjugation works using terms plasmid, fertility F factor, pilus, f+ and f-
- In gram - cells, donor has the plasmid (Fertility or F factor) that allows the synthesis of a conjugative pilus.
- A cells role in the conjugation is denoted by F+ factor for the cell that has the plasmid
- F- for cell that doesn not
What is the significance of high frequency recombination?
Cells can transmit its chromosomal genes at a higher frequency than other cells.
The F factor can direct a more comprehensive transfer of part of the donor chromosome to a recipient cell.
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