Micro ch.8

Describe two ways mutations can be repaired

-enzymes that cut out and replace the damaged portion of DNA ex: in UV radiation damage -base repair by enzymes ex: photoreactivation enzymes that repair thymine dimers in the presence of visible light

outline the procedure for the Ames test

1. two cultures are prepared of Salmonella bacteria that have lost the ability to synthesize histidine. 2. The suspected mutagen is added to the experimental sample only; rat liver extract is added to both samples. 3.Each sample is poured onto a plate of medium lacking histidine. The plates are incubated at 37 degrees C for two days. Only bacteria whose histidine-dependent phenotype has mutated back to histidine-synthesizing will grow into colonies. 4. The numbers of colonies on the experimental and control plates are compared. The control plate may show a few spon histidine-synthesizing revertants. The test plates will show in increase in the number of histidine-synthesizing revertants if the test chemical is indeed a mutagen. The higher the concentration of mutagen used, the more revertant colonies will result.

Describe the process of DNA replication

1.one "parental" double-stranded DNAmolecule is converted to two identical "daughter" molecules. Replication begins by relaxing the supercoiled double helix with topoisomerase, and the two strans are unwound and separated by the heliase. 2. Free nucleotides present in the cytoplasm are matched to the exposed bases of the single strand DNA. 3. Once aligned, the newly added nucleotide is joined to the growing DNA strand by an ezyme called the DNA polymerase.

Silent Mutation

A mutation that changes a single nucleotide, but does not change the amino acid created.

Nonsense mutation

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

Missense mutation

A point mutation in which a codon that specifies an amino acid is mutated into a codon that specifies a different amino acid.

Gene

A segment of DNA on a chromosome that codes for a specific trait

Define operon.

A set of operator and promoter sites and structural genes they control.

Chromosome

A threadlike structure located in a cells nucleus contains DNA and is passed from one generation to the next

Genome

All the genetic information in a cell

Describe how inducible operons work.

An inducible gene is a gene that is expressed in the presence of a substance (an inducer) in the environment

Genotype

An organism's genetic makeup

Phenotype

An organism's physical appearance, or visible traits.

What is Horizontal gene transfer

Being able to pass genes laterally, to other microbes of the same generation.

Describe DNA replication, including the functions of DNA ligase, and DNA polymerase

DNA ligase: Makes covalent bonds to join DNA strands; joins the Okazaki fragments and new segments in excision repair. DNA polymerase: Synthesizes DNA; proof and repairs DNA.

Discuss how genetic mutation and recombination provide material for natural selection to act upon.

Diversity is the precondition of evolution, and the above described methods all contribute to genetic diversity. Genetic mutation and recombination provide for diversity of organisms by altering the core of "who they are" (the DNA). The process of natural selection allows the growth of those best adapted to the environment.

How does mRNA production in eukaryotes differ from the process in prokaryotes?

Eukaryotes mRNA: Transcription and translation are spatially and temporally separated in eukaryotic cells; that is, transcription occurs in the nucleus to produce a pre-mRNA molecule. The pre-mRNA is typically processed to produce the mature mRNA, which exits the nucleus and is translated in the cytoplasm. Prokaryote:In a prokaryotic cell, transcription and translation are coupled; that is, translation begins while the mRNA is still being synthesized.

2. Describe how DNA serves as genetic information.

Genetic information that is encodes in a sequence of bases along the of DNA

Describe the effect of mutagens on the mutation rate

If a mutagen is present, it will usually increase the spontaneous rate of mutation, which is approximately 1 in 106 replicated genes, by a factor of 10-1000 times. This is a 1 to 3 order of magnitude increase, meaning a mutation rate of 10-6 becomes 10-5 or possibly 10-3.

Compare protein synthesis in prokaryotes and eukaryotes

In eukaryotes, transcription takes place in the nucleus. The mRNA must be completely synthesized and moved through the nuclear membrane to the cytoplasm before translation begins. Along with that, they have regions of genes that code for protein that are interrupted by noncoding DNA calles introns (intervening regions).

Describe protein synthesis, including transcription, RNA processing, and translation

In the process of transcription, genetic info in DNA is copied, or transcribed, into a compementary base sequence of RNA. The cell then uses the info encoded in this RNA to synthesize spacific proteins thru the process of translation.

Compare conjugation between the following pairs: F+ ´ F-, Hfr ´ F-.

It's a horizontal transfer of DNA. A F+ microbe has a F factor plasmid which can conjugate a F- which does not have a F factor. F- becomes a F+ once conjugated. Sometimes a F+ conjugates a microbe, but the plasmid integrates with in the chromosome and becomes a Hfr cell.

Frameshift mutation

Mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

What is the role of the promoter, terminator, and mRNA in transcription?

Promoter: The startting site on a DNA strand for trnascription of RNA by the RNA polymerase. Terminator: The site on a DNA strand at which transcription ends. mRNA: The type of RNA molecule that directs the incorporation of amino acids into proteins.

Nagative (indirect) selection

Selects a cell that cannot perform a certain function, by using a technique of replica plating.

Genomics

Study of an organism's genome

Identify the purpose of the Ames test

The Ames test has about a 90% reported positive associative ratio for identifying mutagens to be carcinogenic.

Describe how repressible operons work.

The structural genes are transcribed until they are turned off, or repressed.

Genetics

The study of what genes are , and how they carry information, how information is expressed, and how genes are replicated

What types of genes do plasmids carry?

conjugative plasmids (as mentioned), dissimilation plasmids (genes for the destruction of molecules), plasmids carrying genes for toxins or bacteriocins (toxins that kill other bacteria), and resistance factors (R factors).

Positive (direct) selection

involves the detection of mutant cell by rejection of the unmutated parent cells.

What is Vertical gene transfer

occurs when genes are passed from parental organism to offspring organism.

Compare the mechanisms of genetic recombination in bacteria

the exchange of genes between two DNA molecules to form new combinatins of genes on chromosome