Honors Biology Notes Grade 10 Highschool Unit 3:

U 3: DNA/RNA/Protein Synthesis

DNA

 \n DNA function: to store and transmit the genetic information that tells cells which proteins to make and when to make them. Proteins form the structural units of cells and help control chemical processes within cells.

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DNA = Deoxyribose Nucleic Acid

\n \n \n DNA Structure
  • DNA is a nucleic acid
  • DNA is made of nucleotides which are composed of a phosphate group, a 5-carbon sugar called deoxyribose, and a nitrogenous base
  • DNA is a double helix
  • DNA has a sugar-phosphate backbone with nitrogen bases in the middle

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Visual Representation

 

 \n Nitrogenous Bases

Four types:

==Adenine (A)==

@@Thymine (T)@@

<strong>Cytosine(C)</strong><strong>Cytosine (C )</strong>

%%Guanine (G)%%

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==Adenine (A)== and %%Guanine (G)%% __have two rings of carbon and nitrogen atoms.  These bases are ^^called purines.__^^

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<strong>Cytosine(C)</strong><strong>Cytosine (C )</strong> and @@Thymine (T)@@ have only one ring of carbon and nitrogen atoms.  These bases are ^^called pyrimidines.^^

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Complementary Base Pairing Rules

 \n ==Adenine (purine)== hydrogen ^^bonds^^ (2) only with @@Thymine (pyrimidine)@@  A = T

 \n %%Guanine (purine)%% hydrogen ^^bonds^^ (3) only with <strong>Cytosine(pyrimidine)</strong><strong>Cytosine (pyrimidine)</strong>  G = C

\n \n \n \n DNA Replication

^^WHAT IS IT?^^

<strong>ProcessinwhichDNAiscopied</strong><strong>Process in which DNA is copied</strong>

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^^WHY?^^

<strong>DNAreplicationmustoccursothatwhenthecellreproducesthenewcellwillhaveacopyofthegeneticinformation</strong><strong>DNA replication must occur so that when the cell reproduces the new cell will have a copy of the genetic information</strong>

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^^WHEN?^^

<strong>DNAreplicationoccursintheSphaseofInterphaseofthecellcycle.</strong><strong>DNA replication occurs in the S phase of Interphase of the cell cycle.</strong>

 

^^WHERE?^^

  1. <strong>[ProkaryoticCells(inthecytosol)]()</strong><strong>[Prokaryotic Cells (in the cytosol)]()</strong>
  2. <strong>EukaryoticCells(inthenucleus</strong><strong>Eukaryotic Cells (in the nucleus</strong>)

Major Events of DNA Replication \n

1st:  DNA is separated by enzymes called helicases at the replication fork;

hydrogen bonds break as Helicase moves along DNA

2nd:  Nucleotides are joined to the new chains by covalent bonds between deoxyribose sugars and phosphate groups using DNA Polymerase

3rd:  Nucleotides are joined to original DNA strand by hydrogen bond

Results:  two copies of DNA (each copy with ONE parental DNA and ONE new DNA - semiconservative)

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The problem in DNA replication

 \n A mutation is a change in the DNA sequence

 \n \n \n \n \n DNA and RNA Venn Diagram

DNABothRNA
[[Name:  Deoxyribonucleic AcidSugar = deoxyriboseDouble-strandedBases: ATCG1 type[[ \n \n \n \n \n \n \n \n<strong>BothareorganicmoleculesbotharemadeoftheelementsC,H,O,N,botharenucleicacidscomposedofnucleotides(seenextslide)BothuseAdenine,Guanine,andCytosineasnitrogenousbasesBothcarry“code”intheformofbasesforthecell</strong><strong>Both are organic molecules both are made of the elements C, H, O, N, both are nucleic acids composed of nucleotides (see next slide)Both use Adenine, Guanine, and Cytosine as nitrogenous basesBoth carry “code” in the form of bases for the cell</strong> \n \n ==A pairs with T (DNA)== \n %%A pairs with U (RNA)%%%%Name:  Ribonucleic Acid Sugar ribose Single-strandedBases: AUCG“U” = Uracil and it is similar to T and pairs with Adenine.3 types (mRNA, tRNA, and rRNA)%% \n \n \n \n

DNA and RNA Visuals

DNA —> RNA —-> Protein

Transcription   Translation \n

RNA
DNA

\n RNA

\n \n \n \n Transcription

^^WHAT IS IT?^^

<strong>transcribe”means“tocopy”</strong><strong>transcribe” means “to copy”</strong>

<strong>TheDNAmessageiscopiedintomRNAandbroughtfromthenucleustothecytoplasm.(rRNAandtRNAarealsomade,andsentouttothecytoplasm)</strong><strong>The DNA message is copied into mRNA and brought from the nucleus to the cytoplasm. (rRNA and tRNA are also made, and sent out to the cytoplasm)</strong>

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^^WHY?^^

The DNA can’t leave the nucleus because it needs to be protected (bad if it was damaged), and it’s too big. So, we make a copy of what we need.  That “copy” is the RNA, which is just a different version that is the actual code to make protein.

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HOW?

<strong>TheprocessofTranscription</strong><strong>The process of Transcription</strong>

  1. <strong>DNAunzips(H−bondsbroken!)(HELICASE!!)</strong><strong>DNA unzips (H-bonds broken!)(HELICASE!!)</strong>
  2. <strong>RNAbasespairwithcomplementaryDNAbases(ononlyonechainofDNA)</strong><strong>RNA bases pair with complementary DNA bases (on only one chain of DNA)</strong>

−RememberUinsteadofT!!!- Remember U instead of T!!!

  1. __RNA polymerase__ (an enzyme) links the RNA nucleotides together and an mRNA is made
  2. <strong>mRNAunzipsfromtheDNAstrand,andDNArejoins</strong><strong>mRNA unzips from the DNA strand, and DNA rejoins</strong>
  3. <strong>mRNAmovestothecytoplasm</strong><strong>mRNA moves to the cytoplasm</strong>

 \n Results:  a strand of mRNA

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Types of RNA Involved in Protein Synthesis(making proteins):

  • mRNA (messenger RNA): brings the DNA message into the cytoplasm
  • tRNA (transfer RNA): transfers amino acids to the growing protein chain by reading the mRNA instructions
  • rRNA (ribosomal RNA): holds all the parts together while making a protein

Visual Representation:

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Moving from DNA to Protein

  • The chromosomes are the wound up DNA that will be used in the cell to make proteins
  • Proteins are responsible for our phenotypes! (Physical Characteristics)

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Example of Transcription of DNA into mRNA

(DNA) TAC CGG TAA CGT ACT

(mRNA) AUG GCC AUU GCA UGA

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