biologyfinalexamreview

Deletion occur when 1 or more nucleotides are removed

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3. Deletion- occur when 1 or more nucleotides are removed from the double helix o 4. Inversion- occurs when a piece of DNA is cut out of a chromosome, turned around, & re-inserted into the gap o 5. Translocation- occurs when a chunk of DNA (often very large) is removed from 1 chromosome & attached to another chromosome o Only time more than 1 chromosome is involve Chapter 12: Transcription - Transcription = the information in a gene is copied into RNA (DNA à mRNA) o 1 st step: transcription o In court, clerks transcribe spoken words to written words: different forms of the same language o DNA & RNA are both nucleic acids: different forms of the same “language” o Overview of transcription DNA à RNA Transcription has three stages Initiation- DNA helix is split near the start of the gene (unzipped): initiation o Short series of DNA bases called a promoter region signal the start of the gene Elongation- RNA polymerase (an enzyme) pairs RNA nucleotides with the DNA until the end of the gene o A with U, & C with G o Only 1 side of the DNA is copied (called the template strand ) Termination- Short series of DNA bases called the termination signal signals the end of the gene o mRNA strand is released and DNA re-zips RNA splicing- Exons = strands of DNA that truly code for amino acids in a protein
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Introns = “junk” DNA which is not part of the code & must be clipped out of mRNA after it is made RNA splicing = clipping out introns Translation - Translation = mRNA, tRNA, amino acids, & a ribosome synthesize a protein using the info carried by mRNA - 2 nd step: translation o RNA “translated” to proteins: changing from one kind of biological molecule (nucleic acids) to another (proteins) o RNA & proteins = different “languages” Codons, know how to go from DNA à RNA à amino acids (amino acid chart will be on the exam- no need to memorize) - Bases in mRNA are read by the ribosome in triplets called codons (e.g. AUG, ACG, CUG, GGC…) - Each codon specifies a unique amino acid in the genetic code (e.g. UAU = tyrosine) o Each mRNA also has a start codon (AUG) and 1 of 3 stop codons (UAG, UAA, and UGA) o So each single codon codes for either o Start protein here” o A specific amino acid to be added o Or “stop protein here” - Mutations: consequences, frameshift, redundancy - Mutations = changes in the DNA sequence caused by mistakes during replication or by various environmental factors (carcinogens) - Mutations fall into 5 categories - Inversions- Occur when chunks of DNA are broken apart & reattached (within a single chromosome or… - Translocations- to a different chromosome - Deletions- A deletion occurs when 1 or more nucleotides are removed from the gene sequence - Insertions- An insertion occurs when 1 or more nucleotides are added to the gene sequence o Deletions & insertions = a misreading of a gene’s codons during transcription or replication: frameshift mutations - Substitutions- When a substitution (point mutation) occurs, an incorrect nucleotide takes the place of a correct one Gene expression -
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