DNA, RNA Replication, Transcription, Translation

What is DNA? Deoxyribonucleic acid Subunits: nucleotides Contains: genetic code Structure: double helix.

NUCLEOTIDES - the subunits of DNA Parts of a nucleotide: Phosphate group Sugar (ribose or deoxyribose) Nitrogen base

DNA’4 Nitrogen Bases Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Thymine and Cytosine are PYRIMIDINES (one-ring base) Adenine and Guanine are PURINES (two-ring bases)

BASE PAIRING RULES: A binds with T G binds with C There are 3 hydrogen bonds holding G and C together There are 2 hydrogen bonds holding A and T together.

DNA STRUCTURE: DOUBLE HELIX DNA is like a twisted ladder Rails of the ladder: alternating deoxyribose and phosphate. Rungs of the ladder: base pairs (cytosine–guanine or thymine– adenine)

3-D Animation of DNA DNA Video

Stop & Review What is the smallest subunit of DNA? List 3 parts to #1? What are the side chains of DNA made of? What are the “rungs” of DNA made of? What are the base pairing rules of DNA? Describe the structure of DNA in 2 words.

ANSWERS Nucleotide Sugar, phosphate and a nitrogen base Sugar and phosphate Nitrogen base A-T, C-G Double Helix

Comparing eukaryote & prokaryote DNA Circular Linear

How are genes, chromosomes and DNA related? Genes: portions of DNA that code for proteins. DNA: Contains the genetic code, tightly packed into chromosomes

How are genes, chromosomes and DNA related? Think of chromosomes as socks and genes as stripes on the socks.

Place in order from smallest to largest. 1. Chromosomes 2. Genes 3. DNA Smallest to Largest: Genes -> DNA -> Chromosomes

DNA RNA There are THREE main differences between DNA & RNA NAME Deoxyribonucleic acid Ribonucleic acid SUGAR Deoxyribose ribose NO. OF STRANDS double single NITROGEN BASES A,T,G,C A,U,G,C (U = Uracil) NITROGEN BASE PAIRS A – T G – C A – U G - C TRANSPORT IN AND OUT OF NUCLEUS Stays in nucleus Goes in and out of nucleus CONTAINS A CHEMICAL MESSAGE OR CODE Yes yes

Semi-conservative replication Part 2

DNA Replication Duplication of DNA: DNA copies itself! Happens during the S-phase of Interphase, before cell division.

“Semi-Conservative” Replication results in 2 new DNA molecules “Semi-Conservative Replication: Each “new” DNA molecule will contain an “original” DNA strand and a “new” DNA strand, made of added free nucleotides.

The Process of Replication STEP 1: Enzyme HELICASE unwinds DNA at “replication fork” by breaking hydrogen bonds between two complementary strands of DNA (It “unzips” the helix) “Antiparallel”: DNA strands run in opposite directions: ” 3’to 5’ and 5’to 3’.

RNA primase adds a RNA primer to free 3’ end STEP 2: RNA primase adds a RNA primer to free 3’ end The direction of synthesis is from 5’ to 3’. Base Pairing Animation

STEP 3: DNA Polymerase attaches to Primer and adds new nucleotides to 3’ end of a growing DNA chain, following base-pair rules: Adenine - Thymine Guanine – Cytosine Forms the LEADING STRAND, Made continuously from primer. helicase polymerase Leading strand primer 3”

DNA Polymerase can only add new nucleotides to a 3’ end! Lagging Strand (5’ to 3’): made discontinuously on opposite DNA strand, near replication fork. DNA Polymerase can only add new nucleotides to a 3’ end! Contains Okazaki fragments: “pieces of DNA”, later mended by enzyme LIGASE to form new DNA strand Replication animation 5” 3” helicase primer Lagging strand polymerase Leading 3” 5” 5” 3”

Replication fork

Protein synthesis

Warm-Up Quiz: DNA 101 DNA is a double stranded sequence of ___________ (smallest unit of DNA). DNA is a code of instructions for building ___________ (molecule). DNA is stored in the _________ (control center of the cell). The DNA code must be transmitted to the ___________ where proteins are built. Today we’ll see how this happens.

The role of DNA is to store and transmit genetic information DNA RNA PROTEINS PHENOTYPE YOU

What is RNA?? RNA, like DNA, is made up of nucleotides However, there are 3 differences between DNA and RNA: RNA has ribose instead of deoxyribose RNA has uracil instead of thymine RNA is single-stranded instead of double- stranded

How do DNA & RNA compare? Deoxyribose sugar & phosphate “backbone” N-bases: A, C, G, T Double helix RNA Ribose sugar & phosphate “backbone” URACIL replaces thymine Single-stranded, globular, hairpin (huh? Hairpin???)

Warm-up What’s the difference between RNA and DNA?

mRNA is written in the form of codons. Types of RNA Messenger RNA (mRNA) The original DNA code is transcribed then carried from the nucleus to the ribosome. mRNA is written in the form of codons.

Transfer RNA (tRNA) Types of RNA The anticodon that matches the codon found on mRNA. It transfers an amino acid in order to assemble a protein chain.

RNA & proteins that make up ribosomes where proteins are made. Types of RNA RibosomalR NA (rRNA) RNA & proteins that make up ribosomes where proteins are made.

Base Pairing in DNA vs. RNA A - T C - G RNA A - Uracil C - G

Check your understanding… Decide with your partner whether the following describes DNA or RNA or Both: Involves Uracil Single-stranded Double-stranded Involves codons Polymerase Master Plan Blueprint copy Stays in nucleus Goes to ribosome Involves Thymine

Step 1 Transcription Step 2 Translation PROTEIN SYNTHESIS Step 1 Transcription Step 2 Translation

Why? Because mRNA can leave the nucleus whereas DNA cannot. Step 1: TRANSCRIPTION DNA is transcribed to create a strand of nucleic acid called RNA (ribonucleic acid) The RNA codes are “read” 3 nucleotides at a time called a codon Occurs in the nucleus Why? Because mRNA can leave the nucleus whereas DNA cannot.

TRANSCRIPTION Enzymes unzip helix RNA polymerase assembles mRNA nucleotides but base pairing rules changes slightly Thymine in DNA pairs with Adenine Adenine in DNA pairs with Uracil Cytosine still pairs with Guanine

T - - A - - C - - G - - DNA A T G C U A C G mRNA - - A - - T - - G Step 1: Helicase enzyme “unzips” double helix by weakening H-bonds T - - A - - C - - G - - DNA A T G C U A C G mRNA - - A - - T - - G - - C Write the complementary codon sequence. Slide  Copy the following DNA sequence. Write the complementary nucleotide sequence. Step 2: RNA polymerase enzyme forms complementary mRNA strand

Step 2: TRANSLATION The language of DNA is translated into the language of amino acids Occurs in the cytoplasm on a ribosome

TRANSLATION The mRNA travels to the ribosome where each codon is read The codon of mRNA matches an anticodon on tRNA When the codon and anticodon match the amino acid being carried by the tRNA is transferred to a growing protein chain.

Let’s use your foldable from before. A T G C DNA U A C G mRNA  Open the foldable and translate the mRNA code into the correct amino acid sequence.

The translation… A T G C DNA U A C G mRNA Tyrosine Lysine Leucine STOP

Protein Synthesis Animation http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120077/micro06.swf::ProteinSynthesis

YOU NEED TO UNDERSTAND THIS!!! DNA codes for RNA, which guides the synthesis of proteins. DNA  RNA  Protein DNA is unzipped RNA polymerase uses DNA as a template for making mRNA (Uracil is incorporated instead of thymine) mRNA moves out of nucleus to ribosome tRNA carries amino acids to ribosome where they are assembled into a peptide chain Upon reading a STOP codon, the complete protein chain is released

Now consider this… On a sheet of paper, write the word CATS. Try rearranging the letters to form as many 3- letter words as you can. Write each word on your paper, and then add a definition for each word. Did any of the codes you formed have the same meaning?

Like CATS, there are only 4 nitrogen bases in the DNA alphabet. Like the CATS activity, DNA “words” are only 3-letters. These triplet base sequences are called codons.

= 64 possible codon combinations. BRAIN TEASER How many codons can be made using the four letters of the four different bases? Hint: A codon is made up of 3 nucleotides. So there are 3 spots and a possibility of 4 bases in each. 4 bases x 4 bases x 4 bases = 64 possible codon combinations. Since the nitrogen base is the only unit to change, the sequence of bases makes up the code.

How is DNA like Morse code?

How is DNA like Morse code? It is a series of single repeating units (sounds or symbols) that make up a message. The repeating units are the nucleotides of the DNA molecule. The message is the final protein that is produced. Proteins can be structural, enzymatic, hormones, etc.