Semester 2, Day 7

Transcription & Translation

Agenda Study for DNA, RNA, Proteins,

Semiconservative Replication Quiz Turn in homework: Section 11.1-11.3 Quiz for DNA, RNA, Proteins, Semiconservative

Replication Translation and Transcription Lecture Translation and Transcription Activity Work Time

Central Dogma

Central Dogma: DNA codes for RNA which guides the synthesis of proteins. DNA: “master blueprint”, contains all genetic info of an organism.

Must be protected; therefore it never leaves the nucleus. RNA: “temporary blueprint”, copies small portions of DNA and

can leave nucleus to synthesize proteins at the ribosome. Proteins: primary building block of organisms. A macromolecule

made of linked monomers called amino acids.

DNA RNA Protein

Transcription“copy”

Translation“interpret”

Central Dogma Transcription: DNA mRNA

“messenger”

Image Source: biology.about.com

1. DNA helicase (enzyme)

unwinds DNA strands.

2. RNA polymerase (enzyme)

“reads” DNA template

strand & synthesizes mRNA

• Matches nitrogen

bases on DNA to

complementary RNA

bases

3. mRNA leaves nucleus

through nuclear pore to the

cytoplasm

DNA RNAA = UT = AC GG C

template strand

nontemplate strand

DNA Helica

se

Usually T in

DNA, but RNA uses U

instead!

Central Dogma Translation: mRNA

Protein

1. mRNA travels through

cytoplasm to ribosome

(made of rRNA)

2. tRNAs bring amino acids

to the ribosome

3. The ribosome matches

tRNA anticodons to

mRNA codons, which

links amino acids

together, creating a

polypeptide (unfolded

protein)

**Note: 20 different

tRNA (one for each

amino acid)

codon

Image Source: hyperphysics.phy-astr.gsu.edu

Central Dogma

Image Source: nnhsbiology.pbworks.com

Transcription“copy”

Translation“interpret”

Central Dogma How do you know what amino acid is brought

by tRNA?

Image Source: waynesword.palomar.edu

Genetic Code Chart(uses codons from mRNA!)AUG: methionine

(START)•Begin decoding; start with methanine amino acidUAA, UAG, UGA: STOP•End decoding; no additional amino acids**Note: Many

types of codons (64 codons), but only 20 amino acids. Important when we learn about mutations!

Central Dogma Example:

DNA Non-Template Strand A C G A A T G T C T C A C A A A G A G T A G A T C

DNA Template Strand T G C T T A C A G A G T G T T T C T C A T C T A G

mRNA Strand A C G A A U G U C U C A C A A A G A G U A G A U C

Polypeptide x x x x Met Ser His Lys Glu STOP x x x

Folded into complex 3D shape Protein!

Image Source: www.contexo.info

What would the tRNA anticodons have been?

Remember!**The Genetic CodeChart uses CODONS,not anticodons.

Central Dogma

Image Source: en.wikipedia.org

mRNA: A U G U C U C A C A A A G A G

Met

tRNA: U A C A G A G U G U U U C U C

Ser His Lys Glu

Anticodon

Codon

Amino Acids

tRNA is a type of RNA, so it uses U, not T!

Gummy DNA Supplies:

Red Licorice = Deoxyribose sugar and phosphate backbone

Purple Licorice = Ribose sugar and phosphate backbone

Gummy Bears = Nitrogen bases

Hard Candies = Amino Acids to build Proteins

You should have 18 toothpicks

Break them in half

Choose 9 gummy bears with different colors

Red=Adenine, Yellow=Thymine, Orange=Cytosine, Green=Guanine

Don’t choose white!

Put 9 half-toothpicks in red licorice and attach gummy bears. This is one DNA strand.

Make the complementary DNA strand. A=T, CG

Attach strands together. This is what DNA looks like!

Gummy Transcription

Transcription = “Copy”

Take your purple licorice and add 9 half-toothpicks

“Unzip” your DNA and take one of the strands

Find the matching RNA bases (not DNA)!

Red=Adenine

White=Uracil

Orange=Cytosine

Green=Guanine

Build the mRNA strand

Gummy Translation Translation = “Change” Using your mRNA strand, find the codons

(nitrogenous base triplets) Use the genetic code chart to “translate” to

amino acids Have your tRNA bring in a hard candy

representing the amino acids. If you have different amino acids, you should have different colors of hard candy.

Put amino acids together into a strand = Protein!

Work Time Annotate the packet Sections 11.4-11.5

Do all concept checks Chapter 11 Review

#3-6, 12, 14, 15, 19, 20, 22-24