Gene Expression and Protein Synthesis

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Gene expression:

Gene expression When a gene is ‘switched on’ or expressed, it is TRANSCRIBED into an mRNA strand which is then TRANSLATED into a protein. Proteins, such as enzymes, control chemical reactions and determine how an organism grows, develops and functions. Only some of the many genes in a cell will be expressed at any one time. This is key to controlling development and cell differentiation.

Features of the genetic code:

Features of the genetic code

How are proteins synthesized from DNA?:

How are proteins synthesized from DNA? Protein synthesis involves the production of a chain of amino acids that forms the primary structure of a protein. The sequence of amino acids are coded for by a gene. 4. Modification of the protein. The stages of protein synthesis include: 1. TRANSCRIPTION of the gene in the nucleus – an mRNA strand is formed. 2. Processing of the mRNA. 3. TRANSLATION of the mRNA in a ribosome – a polypeptide chain is formed. transcription translation

Transcription of DNA:

Transcription of DNA

Translation :


Protein synthesis:

Protein synthesis

Protein synthesis in prokaryotes:

Protein synthesis in prokaryotes

Genetic mutations:

Genetic mutations A mutation is a change in the amount or structure of DNA. There are two types of mutation: A gene or point mutation – a change in the base sequence of a gene, which can cause a change in the polypeptide chain. It is caused by errors that occur during DNA replication . A chromosome mutation – a change in the number or structure of the chromosomes. It is caused by errors that occur during cell division .

Different types of point mutation:

Different types of point mutation

Mutagenic agents:

Mutagenic agents The natural spontaneous mutation rate is typically around one or two mutations per 100,000 genes per generation. The mutation rate can be increased by mutagenic agents , which include UV radiation and harmful chemicals. These disrupt the structure of DNA or interfere with transcription. Mutations provide the genetic variation needed for evolution, however they can produce harmful effects.

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