Chapters 16 & 17 (Chapter 17- Gene Expression: From Gene to Protein ( …
Chapters 16 & 17
Chapter 17- Gene Expression: From Gene to Protein
Genes specify proteins via transcription and translation
Evidence from Studying metabolic Defects
Basic Principles of transcription and translation
The genetic code
Transcription is the DNA-directed synthesis of RNA
Molecular Components of transcription
Synthesis of an RNA transcript
Definition: The synthesis of RNA using a DNA template.
Elongation: The polymerase moves downstream, unwinding the DNA and elongating the RNA transcript 5′ → 3′. In the wake of transcription, the DNA strands re-form a double helix.
Termination: Eventually, the RNA transcript is released, and the polymerase detaches from the DNA.
Initiation: After RNA polymerase binds to the promoter, the DNA strands unwind, and the polymerase initiates RNA synthesis at the start point on the template strand.
Eukaryotic cells modify RNA after transcription
Split Genes and RNA Splicing
Alteration of mRNA ends
Enzymes in the eukaryotic nucleus modify pre-mRNA in specific ways before the genetic message is dispatched to the cytoplasm. During this RNA processing, both ends of the primary transcript are altered
the introns are cut out and the exons spliced together
Mutations of one or a few nucleotides can affect protein structure and function
Types of Small-Scale mutations
New mutations and mutagens
What is a Gene? Revisiting the Question
Translation is the RNA-directed synthesis of a polypeptide
Molecular Components of translation
Making multiple Polypeptides in Bacteria and eukaryotes
Building a Polypeptide
Completing and targeting the Functional Protein
Definition: The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of “language” from nucleotides to amino acids.
Using ATP, the synthetase catalyzes the covalent bonding of the amino acid to its specific tRNA.
The tRNA, charged with its amino acid, is released by the synthetase.
The amino acid and the appropriate tRNA enter the active site of the specific synthetase.
Chapter 16- The Molecular Basis of Inheritance
DNA is the genetic material
the Search for the Genetic material: Scientific Inquiry
Building a Structural model of DNA : Scientific Inquiry
Each DNA nucleotide monomer consists of a nitrogenous base (T, A, C, or G), the sugar deoxyribose, and a phosphate group.
Nitrogenous bases: Guanine (G), Cytosine (C), Adenine (A), Thymine (T)
Many proteins work together in DNA replication and repair
The Basic Principle: Base Pairing to a template Strand
Proteins involved in DNA replication and repair
Primase: synthesizes RNA primers, using the parental DNA as a template.
Topoisomerase: breaks, swivels, and rejoins the parental DNA ahead of the replication fork, relieving the strain caused by unwinding.
Helicase: unwinds and separates the parental DNA strands.
Proofreading and repairing DNA
Evolutionary Significance of altered DNA nucleotides
Replicating the ends of DNA molecules
A chromosome consists of a DNA molecule packed together with proteins
DNA: A nucleic acid molecule, usually a double-stranded helix, in which each polynucleotide strand consists of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of being replicated and determining the inherited structure of a cell’s proteins.
Chromatin: when a eukaryotic DNA is precisely combined with a large amount of protein
Chromosomes:is a strand of DNA that is encoded with genes