UNIT 7. DNA Structure, Replication, and Protein Synthesis

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1 UNIT 7 DNA Structure, Replication, and Protein Synthesis

2 Section 3 Objectives Describe the difference between DNA and RNA. Define transcription. Define translation. Apply to rules of base pairing to replicate, transcribe, and translate a strand of DNA.

3 RNA and Protein Synthesis Genes are coded DNA instructions that control the production of proteins in the cell. In order to decode genetic messages, part of the nucleotides must be copied from DNA to RNA WHY??? RNA are molecules that carry information for making proteins. Proteins help to display our genetic traits or, in other words, our genotype affects our phenotype.

4 What is RNA? RNA: ribonucleic acid Contains information for making proteins. A disposable copy of a segment of DNA In RNA, Uracil (U) replaces Thymine (T).

5 How are DNA and RNA Different? DNA Sugar is deoxyribose RNA Sugar is ribose double stranded single stranded A,C,G,T A,C,G,U

6 3 types of RNA: 1. Messenger RNA (mrna) -carries the instructions or message for making amino acids which will then become proteins. 2. Ribosomal RNA (rrna) -makes up ribosomes -remember that ribosomes make proteins! 3. Transfer RNA (trna) -RNA transfers each amino acid to the ribosome -these amino acids make up our proteins in the cell

7 Each type of RNA has a specific job in making proteins. Steps to making proteins: DNA RNA proteins

8 Transcription: DNA to mrna process in which a portion of the DNA strand is written (script means to write!) into a complementary strand of RNA (mrna) This occurs in the NUCLEUS!! remember U replaces T EXAMPLE: TRANSCRIBES INTO DNA says=a T T G C T A C G G mrna writes=u A A C G A U G C C

9 RNA polymerase is the enzyme that unzips the DNA during transcription so it can be read and allow a complementary mrna strand to be created. Transcription occurs from the 5 (said five prime ) to 3 direction.

10 Once the mrna has the information, it leaves the nucleus (because the DNA cannot) and enters the cytoplasm. Let's watch it in action! (video is 1:52)

11 The original DNA strand is transcribed into mrna. REVIEW: DNA to DNA = replication AAGCAT TTCGTA DNA to RNA = transcription AAGCAT UUCGUA

12 RNA!Proteins: Translation Translation: RNA to protein This is the decoding of an mrna message into a protein it is translated Occurs ON the Ribosomes which is IN the CYTOPLASM Ribosomes are responsible for reading the mrna sequence and assembling proteins.

13 The language of mrna is called the genetic code. How do you break the code? The code is read 3 letters at a time This is a codon: a three letter sequence of nucleotides that codes for an amino acid. Amino acids make up proteins.

14 Example: -the bases would be read 3 letters at a time. UCGCACGGU This would be read as.. UCG--CAC--GGU Each codon represents a different amino acid How do you determine the amino acid?

15 *to read start in the middle and work outwards. *EXAMPLE: UCA = Serine * notice there are stop codons *the start codon is AUG

16 Each codon of the mrna moves through the ribosome The proper amino acid is then brought into the ribosome by the trna.

17 Each trna carries one amino acid. Each trna has an anticodon: 3 base pairs that are complementary to one mrna codon.

18 As the ribosome moves down the mrna, each amino acid is attached in a chain called a polypeptide chain The old trna is released and a new trna is brought in. The amino acid chain grows until the ribosome reaches a stop codon. Let's watch! (2:04)

19 How much DNA is there and what is it all for? (1:02) Some sections of DNA code for a protein and some sections do not. Exons are sections of DNA that code for proteins. Introns are sections of DNA that DO NOT code for proteins. How do introns get "edited" out? (2:51)

20 REVIEW: DNA to DNA = replication AAG-CAT TTC-GTA DNA to RNA = transcription AAG-CAT UUC-GUA mrna to amino acids = translation mrna Strand- UUC GUA trna carrying Amino Acids-AAG (phenylalanine)-cau (valine)

21 Let s Check Transcribe and Translate the following DNA: TAC CCG---TAA---GAC---AAC----GTT mrna: AUG GGC---AUU---CUG---UUG---CAA Amino acid: methionine glycine---isoleucine---leucine---leucine---glutamine What would be the complementary strand of trna? UAC---CCG---UAA---GAC---AAC---GUU

22 Section 4 Objectives Define mutation. Describe the different mutations that can occur in our DNA

23 Mutations Mistakes can happen in the cell We call these mutations: changes in the genetic material. Almost all mistakes or mutations in our DNA are neutral or have little or no effect. Some mistakes can be beneficial for an organism Some, however, can cause serious genetic disorders

24 Types of mutations: 1. Point mutations - Occurs in one or a few nucleotides. - One base can be added, deleted, or substituted Examples of Point mutations: -Substitution: THE---FAT---CAT---ATE---THE---RAT THE---FAT---CAR---ATE---THE---RAT -Insertion/Addition: THE---FAT---CAT---ATE---THE---RAT THE---FAT---CAT---HAT---ETH---ERA---T -Deletion: THE - FAT CAT ATE THE RAT TEF ATC ATA TET---HER-AT

25 2. Frameshift mutations - When the reading frame of the sequence is changed due to addition or deletion of a nucleotide. Example: -Insertion/Addition: THE---FAT---CAT---ATE---THE---RAT THE---FAT---CAT---HAT---ETH---ERA---T -Deletion: THE - FAT CAT ATE THE RAT TEF ATC---ATA---TET---HER

26 3. Chromosomal mutations - Changes in the number or structure of chromosomes INVERSION ADDITION DELETION

27 Are you getting it? Use a separate sheet of paper and turn in! 1. The process of copying DNA is called. 2. Where does replication take place? 3. When would replication occur? 4. The process of copying DNA into RNA is called. 5. The process of making proteins from RNA is called. 6. Transcribe and translate the following DNA strand: TAG GGC---CAT---TAC mrna= amino acids= BONUS: Write your name in codon form example: MICHAEL would be MIC---HAE---L Then rewrite it showing a point mutation..