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RNA and Protein Synthesis

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1 RNA and Protein Synthesis
Chapter 13

2 What does DNA code for and how is the code read?

3 Differences Between RNA and DNA (3)

4 Types of RNA mRNA- carries coded instructions for polypeptide (protein) synthesis from nucleus to ribosomes in the cytoplasm. rRNA- part of the subunits of ribosomes. tRNA- carries amino acids to the ribosome and matches them to the coded mRNA message.

5 Transcription DNA segments are used as templates to produce complementary mRNA strands. Enzyme: RNA polymerase Sample transcription sequence- pg. 367

6 How RNA Polymerase Works
The enzyme binds only to promoters, or regions of DNA with specific base sequences. This enables RNA polymerase to know where to start transcription.

7 Introns and Exons Not all of the new RNA sequence is needed.
The needed parts are called exons. The not needed parts are called introns. The introns are removed and the exons are then spliced back together to form the final mRNA strand.

8 The Genetic Code The transcribed mRNA sequence contains a code for making proteins. Proteins are made by joining amino acids (20 exist) together into long chains called polypeptides. The amino acid sequence determines the properties of a protein, such as its shape and function.

9 Protein Review

10 Codons The genetic code is read three letters at a time so that each word (called a codon) that is three bases long corresponds to a single amino acid. 64 possibilities

11 How To Read Codons- pg. 367

12 Start and Stop Codons Start: Stop:

13 Translation The decoding of mRNA message into a protein on ribosomes.

14 Steps in Translation Initiation

15 Steps in Translation 2. Elongation

16 Steps in Translation 3. Termination

17 The “Central Dogma” of Molecular Biology
Information is transferred from DNA to RNA to protein. (gene expression)

18 Mutations Heritable changes in genetic information.

19 Point Mutations Change in one nucleotide (substitution).

20 Frameshift Mutations Shifts the “reading frame” of the genetic message (deletion and insertion).

21 Types of Mutations

22 Chromosomal Mutations
Changes in the number or structure of chromosomes.

23 Causes of Mutations Errors in genetic processes
Stressful environmental conditions Mutagens

24 Harmful Effects of Mutations
Most harmful mutations dramatically change protein structure or gene activity. Ex: sickle cell anemia


26 Beneficial Effects of Mutations
Mutations that produce proteins with new or altered functions that are useful to organisms in different or changing environments. Evolution (genetic variability) Example: polyploidy

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