Biology 3 Transcription, Translation, and Mutations

Size: px

Start display at page:

Download "Biology 3 Transcription, Translation, and Mutations"

Norma Rogers
7 years ago
Views:

1 Biology 3 Transcription, Translation, and Mutations Dr. Terence Lee Overview 1. DNA and RNA structure 2. DNA replication 3. Transcription makes RNA 4. Translation makes protein James Watson, Francis Crick, and Rosalind Franklin discovered the structure of DNA 1

2 Image of DNA DNA Structure Deoxyribonucleic acid (DNA) is a type of nucleic acid Three parts: 1. Sugar group (deoxyribose) 2. Phosphate group 3. Nitrogenous base Adenine Guanine Thymine Cytosine 2

3 DNA provides the instructions for building virtually every organism on earth! Central Dogma of Biology The protein, influenced by the environment and in some cases other genes, then produces the trait. 3

4 DNA Replication Process by which a cell makes another copy of its DNA Pairing Rules: A = T G = C The structure of DNA is a double helix Shaped like a twisting ladder 4

5 RNA Structure Ribonucleic acid (RNA) is a type of nucleic acid Three parts 1. Sugar group (ribose) 2. Phosphate group 3. Nitrogenous base Adenine Guanine Uracil Cytosine How is RNA different from DNA? 1. Ribose has OH group 2. RNA has uracil instead of thymine 3. RNA is a single strand 4. DNA stays in nucleus 5. RNA is made from DNA in nucleus and then moves to cytoplasm. 5

6 Inside nucleus DNA HOW GENES WORK: AN OVERVIEW TRANSCRIPTION The sequence for a gene is copied from DNA to a middleman molecule called mrna. Cytoplasm mrna TRANSLATION The sequence for a gene, now encoded in mrna, is used to direct the production of a protein. Genes Protein molecule Nuclear pore Grandmother s cookbook Copying cookie recipe to index card Index card with recipe Combining and baking ingredient Chocolate chip cookies Transcription Transcription is the process of using DNA as a template to synthesize RNA. 1.) The DNA strands separate. 2.) RNA Polymerase reads the DNA and builds the RNA strand. 3.) Three types of RNA can be made: 1. mrna messenger RNA 2. rrna ribosomal RNA 3. trna transfer RNA 6

7 Promoter sequence specific sequences of DNA that the RNA Polymerase recognizes. Protein code the DNA sequence that holds the genetic material to create each protein. Termination sequence Tells the RNA Polymerase to stop transcription. DNA TRANSCRIPTION 1 RECOGNIZE and BIND 2 TRANSCRIBE 3 Once RNA polymerase As the DNA strand is processed recognizes a promoter site, through the RNA polymerase, it binds to one strand of the the RNA polymerase builds a DNA and begins reading single-strand copy of the gene, the gene s message. called the mrna transcript. RNA polymerase RNA polymerase TERMINATE When the RNA polymerase encounters a code signaling the end of the gene, it stops transcription and releases the mrna transcript. RNA polymerase Promoter site mrna transcript Termination site mrna transcript UNWIND and REWIND As the RNA polymerase moves down the strand of DNA, the helix unwinds so that the DNA can be read. At the same time, the DNA that has already been transcribed rewinds back to its original double-helix form. Helix unwinds Cap Tail Non-protein-coding regions of mrna 4 CAPPING and EDITING Before the mrna transcript can be translated into a protein, a cap and tail are often added for protection and to promote recognition, and non-coding sections are removed. Helix unwinds mrna transcript leaves nucleus to be translated into a protein. Translation Translation is the process of using the information in mrna to direct protein synthesis. Relies on sets of 3 nucleotides called codons. Each codon codes for a specific amino acid. 7

8 Translation Ribosome 2 subunit non-membrane organelle Holds the mrna and trna during protein formation trna Transfer RNA Reads the codons and finds the correct amino acids. Translation 1. Initiation 2. Elongation 3. Termination Translation Initiation: 1. Ribosome small subunit binds to mrna 2. Finds the start codon 3. The trna binds to the codon and brings the first amino acid 4. The large subunit joins the small subunit and protein formation can begin. 8

9 Translation Elongation: 1. A new trna arrives and reads the codon. 2. The next amino acid arrives and binds to the previous amino acid. 3. The process continues until a polypeptide (protein) is formed. 9

10 Translation Termination: Occurs when the ribosome reaches a stop codon. The two subunits come apart. The mrna is released. Summary of Protein Synthesis 10

11 5.4 Not all DNA contains instructions for making proteins. The Proportion of the DNA That Codes for Genes 11

12 Introns and Exons Portions of the mrna are removed before translation. Mutations Point Mutation change in a single nucleotide of the DNA sequence. Insertions and Deletions changes one or more nucleotides in the DNA sequence. 12

13 A fastflush response 13

DNA Replication & Protein Synthesis. This isn t a baaaaaaaddd chapter!!!

DNA Replication & Protein Synthesis This isn t a baaaaaaaddd chapter!!! The Discovery of DNA s Structure Watson and Crick s discovery of DNA s structure was based on almost fifty years of research by other