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**Gene-Tics**
Chapter Review Directory 13. Meiosis and Sexual Life Cycles 14. Mendel and the Gene Idea 15. The Chromosomal Basis of Inheritance 16. The Molecular Basis of Inheritance 17. From Gene to Protein 18. The Genetics of Viruses and Bacteria 19. The Organization and Control of Eukaryotic Genomes 20. DNA Technology and Genomics 21. The Genetic Basis of Development *All images and videos were taken from other sites. Click on the images to receive the urls. |
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The Connection Between Genes and Proteins
- Genes specify proteins
- DNA controls metabolism by directing cells to make specific enzymes and other proteins
- A gene determines the amino acid sequence of a polypeptide chain
- The two main processes in making a protein from a gene is transcription and translation
Transcription
- Transcription is the transfer of information from DNA to RNA (nucleotide to nucleotide)
- Translation is the transfer of information from nucleotide sequence in RNA to amino acid sequence in a polypeptide
- A nucleotide triplet is called a codon. They are used as a genetic code to specify amino acids
- When a start codon is recognized translation begins until it reaches a stop codon that signals it to terminate
The Synthesis and Processing of RNA
- RNA synthesizes by using a strand of DNA after it is catalyzed by RNA polymerase
- RNA uses the same base pairing method except that instead of using thymine they use uracil
- At the start of a gene there are specific nucleotide sequences called promoters to signal the initiation of RNA synthesis
- In Eukaryotic cells RNA molecules are modified after transcription. Their ends are modified and RNA splicing occurs
- In RNA splicing introns are removed because they are non-coding regions unlike the exons that remain
- If exons are shuffled during this process it may contribute to protein diversity
The Synthesis of Protein
- Translation is directed by RNA to synthesize polypeptides
- tRNA transfers amino acids from the cytoplasm’s amino acid pool to a ribosome. The ribosome then adds each amino acid brought to it to the end of the polypeptide chain its creating
- tRNA molecules bear different amino acids at one end and anticodons on the other. The anticodon base-pairs with a com
- There are three parts in translation: initiation, elongation, and termination
- Ribosomes perform all stages of translation and are made of protein and rRNA. They have binding sites for mRNA called P and A sites that hold tRNA’s as amino acids are linked in the growing polypeptide. The E site releases tRNA.
- Free ribosomes in the cytosol initiate the synthesis of all proteins but proteins that are made for membranes or export from the cell become attached to the endoplasmic reticulum
- In a prokaryotic cell translation of mRNA can begin while transcription is still taking place but in a eukaryotic cell the nuclear envelope separates the processes.
- Point mutations are changes in one base pair of DNA which can affect protein structure and function.
- Base pair substitutions, insertions, or deletions can occur and cause frameshift mutations that disrupt the mRNA reading