Protein synthesis
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Protein Synthesis. Honors Biology (grab a textbook). Protein Synthesis. Sometimes proteins need to be made but DNA is trapped inside nucleus How does the “ code” for making proteins get out ?. DNA ---> RNA---> Protein.

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Protein Synthesis

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Protein synthesis

Protein Synthesis

Honors Biology (grab a textbook)


Protein synthesis1

Protein Synthesis

  • Sometimes proteins need to be made but DNA is trapped inside nucleus

  • How does the “code” for making proteins get out?


Dna rna protein

DNA ---> RNA---> Protein

  • 1. Transcription - DNA is a template or pattern for making RNA

  • 2. RNA moves outside nucleus through pores

  • 3. Translation– RNA directs assembly of amino acids to form proteins


Transcription step 1

Transcription Step 1

  • RNA polymerase binds to a “promoter” on the DNA; says where to “start”

  • DNA starts unwinding


Transcription step 2

Transcription Step 2

  • RNA polymerase adds free RNA nucleotides (bases that are complementary to those on DNA strand)

  • A mRNA strand forms

  • Only involves a specific gene on DNA strand, not entire strand


Transcription step 3

Transcription Step 3

  • RNA polymerase reaches a “termination” signal; says “stop”

  • RNA is released and DNA rewinds


Questions don t copy

Questions (don’t copy)

  • Where does transcription take place in the cell?

  • What is the product of transcription?

  • How much of the DNA strand is copied?


Types of rna

Types of RNA

  • Messenger RNA (mRNA) - carries “code” from DNA out of nucleus to a ribosome

  • Ribosomal RNA (rRNA) - makes up ribosome; the place where proteins are made

  • Transfer RNA (tRNA) - carries amino acids to the ribosome so protein can be made


The genetic code

The genetic code

  • The sequence of bases on mRNA determines how amino acids are put together

  • Genetic code - 3 bases together determine a specific amino acid

  • 3 bases on a mRNAcalled a “codon”


How it works

How it works

  • Page 207

  • AUG on mRNA means “start”

  • If next bases are CAC, this codes for Histidine

  • If next bases are AGC, this codes for Serine

  • Are 3 “stop” codons


Translation making proteins

Translation (making proteins)

  • mRNA comes from nucleus and goes to a ribosome

  • If DNA code is: ATACGG

  • Then mRNA code is: UAUGCC (remember U is found in RNA, not T)

Chargaff’s Rule:

A pairs with T (or U)

C pairs with G


Translation step 1

Translation – Step 1

  • mRNA moves along a ribosome

  • A tRNA arrives - on one end is the amino acid, on other end is anti-codon

  • codonof mRNA matches up to anticodon of tRNA (complementary)


Translation step 2

Translation – Step 2

  • Codon & anti-codon meet; tRNA releases amino acid

  • Next tRNAarrives; codon & anti-codon meet; another a.a. is released and forms peptide bond with adjacent a.a.


Translation step 3

Translation – Step 3

  • Enough amino acids bind together to form a polypeptide chain until a “stop” codon is reached

  • Chain falls off and a protein is made


Example

Example

  • Original DNA = A-A-T-T-C-C-A-T-G

  • mRNA = U-U-A-A-G-G-U-A-C

  • tRNA= A-A-U-U-C-C-A-U-G

  • Amino acids the mRNA codon codes for:

    • UUA = leucine

    • AGG = lysine

    • UAC = tyrosine


Now you try

Now you try…

  • Original DNA = G-C-T-T-A-G-C-T-A

  • mRNA =

  • tRNA =

  • Amino acids the mRNA codon codes for:?


Answers

Answers

  • Original DNA = G-C-T-T-A-G-C-T-A

  • mRNA = C-G-A-A-U-C-G-A-U

  • tRNA = G-C-U-U-A-G-C-U-A

  • Amino acids the mRNA codon codes for:

    • C-G-A = arginine

    • A-U-C = isoleucine

    • G-A-U = aspartic acid


Another one

Another one…

  • Original DNA =

  • mRNA = C-U-U-A-A-G-C-A-C

  • tRNA =

  • Amino acids the mRNA codon codes for:?


Answers1

Answers

  • Original DNA = G-A-A-T-T-C-G-T-G

  • mRNA = C-U-U-A-A-G-C-A-C

  • tRNA = G-A-A-U-U-C-G-U-G

  • Amino acids the mRNA codon codes for:

    • C-U-U = leucine

    • A-A-G = lysine

    • C-A-C = histidine


One more

One more…

  • Original DNA =

  • mRNA =

  • tRNA = C-C-G-U-U-A-U-G-A

  • Amino acids the mRNA codon codes for:?


Answers2

Answers

  • Original DNA = C-C-G-T-T-A-T-G-A

  • mRNA = G-G-C-A-A-U-A-C-U

  • tRNA = C-C-G-U-U-A-U-G-A

  • Amino acids the mRNA codon codes for:

    • G-G-C = glycine

    • A-A-U = asparagine

    • A-C-U = threonine


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