biology test 3

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biology test 3
2012-11-10 18:24:19
biology test

biology 3
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  1. Name and describe 3 types of RNA?
    mRNA- messanger RNA carries genetic material copied from DNA to the translation machine.

    tRNA-transfer RNA it codes for the specific amino acids

    rRNA- ribosomal RNA it is found in the ribosomes
  2. Describe transcription and translation in terms of DNA, RNA and polypeptides. where does each occur in the cell?
    transcription- is where DNA is coded onto RNA inside the nucleus. then the mRNA takes it onto the cytoplasm where it attaches to a ribsome. then it goes to the translation machine where tRNA codes for certian amino acids, these amino acids form polypeptides.
  3. What is one gene one polypeptide theory?
    each polypeptide is specified by its own gene. we now know this is not entirely accurate because many genes now code for a set of polypeptides.
  4. Describe 3 kinds of genetic recombination which occur naturally in bacteria?
    • 1) transformation- where a cell will take up some foreign DNA from its surrounding causing genotypes and possibly the phenotypes to change
    • 2) transduction- phages carry prokaryotic genes from one host to another
    • 3) Consugation- DNA is transferred between two prokaryotic cells that are temperally joined.
  5. Describe the reproductve cycle of a retrovirus?
    RNA virus that replicates by trnscribing its RNA into DNA and then inserting the DNA into a cellular chromosome

    Important class of cancer causing viruses
  6. Name and describe 2 diseases caused by prions?
    1) mad cow disease- degenerative brain disease

    2) Cruetz feldt jakob- another brain disease

    • Food borne illness with long incubation periods
    • Propagate by convertings normal protiens into the prion version
  7. Describe one type of control of of gene expression in bacteria?
    bacteria often responds to changes in the enviroment by regulating transcription. Natural selection has chosen the bacteria that only produce the products they need. In bacteria they're operons which are clusters of functionally related genes that can be cordinated by an on/ off switch called an operator. the operon can then be turned off by a protien repressor.
  8. Why does a DNA molecule have a constant width?
    A DNA molecule has a certain width because the base pairs A and T are amines and C and G are pyrines. A pyrine is a certain site and so is a amine so since it pairs T/C with G. a pyrine is always attached to a amine, keeping the DNA molecule a certain width.
  9. Name 3 ways RNA and DNA differ?
    1) DNA- has dioxyribose sugar, RNA has ribose sugar

    2) DNA has a double helix and RNA is a single strand

    3) DNA has a thiamine base and RNA has a uracil base
  10. Name and describe 5 hereditary patterns which vary from the classical medelion Dominant recessive genetics?
    • 1) Alleles arent completly dominant or recessive, resluts in offspring that are amix between two parents
    • 2) Genes have more than 2 alleles
    • 3) Genes have more than 1 phenotype, which means one gene can have multiple visual differences
    • 4)Incomplete dominace
    • 5) Pleiotrophy, where most genes have multiple phenotypic effects. Incomplete dominace is where the dominant allel isnt strong enough to fully express the trait¬†
  11. Describe the effects on polypeptide amino acids and sequence resulting from base substitution and base deletion. Which produces the most serious consequences?
    • -A base solution is where a polypeptide is replaced with another. this could result in one amino acid changing, but not always. For this reason this is the least harmful.
    • - When a polypeptide is deleted that means there is a frame shift. this is bad because it will change the coding for every amino acid from here on, this is the worst mutation.
  12. Allele
    the alternative version of a gene.
  13. Phenotype

    and organisms observable traits or appearance

    the genetic make up
  14. Pleiotrophy

    when a gene has multiple phenotypic effects

    when the phenotypic expression of a gene at one locus alters that of a gene at a second locus
  15. Exon

    part of the coding regions, eventually translated into amino acids sequence

    changes to the genetic information of a cell or virus
  16. mutagens

    physical and chemical agents that interact with DNA in ways that cause mutations

    a unit of genetic function found in bacteria and phages, consisting of a promotor, operator and a coordinately regulated cluster of genes whose products function in a common pathway.
  17. transposon

    a transposable genetic element that moves within a genome by means of a DNA intermediate

    referring to a diploid cell that has three copies of a particular chromosome instead of the normal two
  18. restriction enzyme

    an endonuclease that recognizes and cuts DNA molecules forgien to a bacterium. 

    a small protien with high proportion of positivly charged amino acids that bind to negatively charged DNA plays a key role in chromatin structure