Gene Expression<br />How a gene goes from being “just DNA” to showing up as a trait<br />
RNA	<br />Ribonucleic acid is similar to DNA in many ways:<br />Nucleotides<br />polymer<br />RNA is also different from D...
Codons<br />DNA (and RNA) codes for specific amino acids.<br />There are 20 amino acids, but only four nitrogen bases in e...
Transcription<br />The DNA “code” is transcribed (copied) as a messenger RNA molecule (mRNA) during transcription.<br />DN...
Read everything, but copy what’s in black – I’ll put the chart back up for you to complete (or use page 186 in your book)<...
Mutations<br />Chromosomalmutations involve large portions, or even entire chromosomes.<br />
Point Mutations occur at just one point in the DNA<br />Substitutions<br />Insertions & Deletions are often referred to as...
TranslationUsing the information on mRNA to complete a polypeptide<br />Introns are spliced out, mRNA leaves the nucleus a...
rRNA<br />Many types…<br />Complex….<br />May fold back on itself (bonding with complementary bases) <br />
mRNA actually goes through a ribosome <br />
Transfer RNA (tRNA) brings the correct amino acid to the ribosome to create a chain of amino acids in the prescribed seque...
The ribosome acts as an enzyme and catalyzes the linking of the amino acids together into a polypeptide.<br />            ...
Example of an inducer:  lac operon (page 190-191)<br />When lactose is present around some bacteria, it acts as an inducer...
Enhancers<br />Enhancers are proteins in eukaryotic DNA that increase transcription.<br />Example (pg 193): Steroid hormon...
Other factors affect eukaryotic gene expression…<br />Eukaryotic DNA is a double helix.  Transcription occurs in areas whe...
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Gene expression

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  • ANIMATION - YouTube
  • ANIMATION……………http://www.youtube.com/watch?v=vJSmZ3DsntUpromoter regions, like a TATA box (25-30 TATA repeats)… ‘start’ codon = AUGTranscription occurs in the 3’  5’ direction only
  • Practice some codons
  • ‘start’ – alanine – phenylalanine – arginine – (stop)
  • ACTIVITY
  • ANIMATION – translation – 3 minutes YouTube http://www.youtube.com/watch?v=5bLEDd-PSTQ
  • Operon = a cluster of genes that code for proteins with related functions ONLY IN PROKARYOTES
  • Enhancers aren’t removing repressors, they are stimulating transcription.
  • Gene expression

    1. 1. Gene Expression<br />How a gene goes from being “just DNA” to showing up as a trait<br />
    2. 2. RNA <br />Ribonucleic acid is similar to DNA in many ways:<br />Nucleotides<br />polymer<br />RNA is also different from DNA:<br />Ribose (instead of deoxyribose)<br />No thymine (instead it has uracil)<br />RNA is a single-strand<br />
    3. 3. Codons<br />DNA (and RNA) codes for specific amino acids.<br />There are 20 amino acids, but only four nitrogen bases in each nucleic acid. How can we work the code?<br />Sequences of THREE nitrogen bases will code for an amino acid. These triplets are called “CODONS”.<br />
    4. 4. Transcription<br />The DNA “code” is transcribed (copied) as a messenger RNA molecule (mRNA) during transcription.<br />DNA is unwound at one transcription bubble.<br />RNA polymerase adds RNA nucleotides to one side of the DNA molecule, starting at a promoter region or ‘start’ codon.<br />Base pairing is the same except RNA doesn’t have thymine. Uracil takes its place.<br />When it reaches a ‘stop’ codon, mRNA is released and the DNA rewinds. <br /> http://www.youtube.com/watch?v=vJSmZ3DsntU<br />
    5. 5.
    6. 6. Read everything, but copy what’s in black – I’ll put the chart back up for you to complete (or use page 186 in your book)<br />Write the sequence of amino acids that would result from the following sequence:<br />AUGGCAUUUCGAAUG<br />Write out a sequence of nucleotides on a mRNA strand that would code for:<br />Threonine – alanine – glycine – lysine<br />
    7. 7. Mutations<br />Chromosomalmutations involve large portions, or even entire chromosomes.<br />
    8. 8. Point Mutations occur at just one point in the DNA<br />Substitutions<br />Insertions & Deletions are often referred to as “frameshift” mutations<br />
    9. 9. TranslationUsing the information on mRNA to complete a polypeptide<br />Introns are spliced out, mRNA leaves the nucleus and ends up at a ribosome. <br />Ribosomes have 2 subunits. They are made partially of protein, but also contain RNA, called ribosomal RNA (rRNA)<br />
    10. 10. rRNA<br />Many types…<br />Complex….<br />May fold back on itself (bonding with complementary bases) <br />
    11. 11. mRNA actually goes through a ribosome <br />
    12. 12. Transfer RNA (tRNA) brings the correct amino acid to the ribosome to create a chain of amino acids in the prescribed sequence.<br />tRNA has two important ends:<br />Anticodon, which is a complementary sequence to the mRNA codon<br />End that attaches to an amino acid<br />
    13. 13.
    14. 14. The ribosome acts as an enzyme and catalyzes the linking of the amino acids together into a polypeptide.<br /> --------------------------<br />There are regions of prokaryotic DNA that allow RNA polymerase access to the gene. These are called “operators”. <br />There are proteins that act as “repressors” when bound to the DNA.<br />Molecules that can remove a repressor are called “inducers”.<br />http://www.youtube.com/watch?v=5bLEDd-PSTQ<br />
    15. 15. Example of an inducer: lac operon (page 190-191)<br />When lactose is present around some bacteria, it acts as an inducer. It binds to the repressor so that it falls off the operator. This means transcription can occur.<br />Transcription, followed by translation, will produce the enzyme to break down lactose.<br />When lactose is absent, the repressor binds to the operator so that the genes can’t be transcribed.<br />
    16. 16. Enhancers<br />Enhancers are proteins in eukaryotic DNA that increase transcription.<br />Example (pg 193): Steroid hormones like estrogen and testosterone are lipids that bind to enhancer proteins in the nuclear membrane. <br />This binding will stimulate RNA polymerase to transcribe certain genes.<br />
    17. 17. Other factors affect eukaryotic gene expression…<br />Eukaryotic DNA is a double helix. Transcription occurs in areas where it has uncoiled, which will change and are different in different types of cells.<br />Gene expression can be regulated at many spots in the process – before or after transcription.<br />

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