Chapter 9 Genetics: what is difference between eukaryotic and prokaryotic chromosome? Eucaryotes chromosomes consist of a DNA molecule tightly wound around histone proteins, whereas a prokaryotic chromosome is condensed and secured into a packet by means of histone-like proteins. (Histone proteins help to hold the shape of the chromosome). Eucaryotic chromosomes are located in the nuclues, vary in number for a few to hundreds; they can occur in pairs (diploid) or singles (haploid) and they appear elongate. Thechromosomes can contain thousands to hundreds of thousands genes. Prokaryotic have a single cicular chromosome, which contain a few thousand genes. How is DNA replicated? DNA replication happens during the process of normal cell division cycles.DNA copies itself just before cellular division in theprocess of semisconservative replication. DNA replication requires a careful orchestration of the actions of 30 different enzymes which seperate the strands of the existing DNA molecule, copy its template and produce two complete daughter molecules. Steps: 1) Uncoiling the parent DNA molecule 2) Unzipping the hydrogen bonds between the base pairs, thus seperating the two strands and exposing the nucleotide sequence of each strand to serve as templates 3) Synthesizing two new strands by attachment of the correct complemnetary nucleotide to each single stranded template. What does semiconservative mean? semiconservative means that each "parent" or "original" DNA molecule is preserved and used as a template. why is the codon Amino Acid code considered to be degenerative? The Condon Amino Acid code is considered to be degenerative because a particular amino acid can be coded for by more than one codon. It is important because it eliminates substitution problems. What major enzymes are involved in DNA replication and what is their function (see table 9.1)? Helicase- Unzipping the DNA helix Primase- Synthesizing an RNA primer (meaning, START here) DNA polymerase 3-Synthesizes the new daughter strand of DNA using the parental template. It adds bases to the new DNA chain; proofreading the chain for mistakes DNA polymerease 1- Removing primer, closing gaps, repairing mismatches Ligase- puts it back together again; Gyrase- Recoiling **Important. DNA polymerase 3 can only add nucleotides in one direction, so a new starnd is always synthesized 5 to 3. Why are there multiple enzymes involved in DNA replication? Enzymes are specific in their job and their a multiple steps in DNA replication that have to occur. What is DNA composed of and what does DNA look like (sructure-wise)? The base of DNA is a neocleotide. Each neucleotide is made up of 1) Nitrogen bases ( Purine and Pyrimidine) that pair up and attached by hydrogen bonds.. The Purines are adenine and guanine. The Pyramidines are thymine and cytosine. A always pairs with T and G always pairs with C. 2)Phosphate 3) Deoxribose sugar It is a gigantic molecule with two strands combined into a double helix. what is the general flow of genetics with an organism? (how do you get from DNA to protein?) DNA->RNA->Protein Information in DNA is converted to proteins by the process of transcription and translation. what is transcription? Transcription is the formation of RNA using DNA as a template. what is translation? Translation is the synthesis of proteins using RNA as a template. what is an intron, where is it found? An intron is the segements on split genes of eukaryotes that do not code for polypeptides. They can have regulatory functions.. They are found in the Pre-mRNA. The processing of pre-mRNA into mRNA involves the removal of introns. What are the major kinds of RNA and what is their function? Messenger RNA mRNA- carries the DNA master code to the ribisome so it can be translated. Transfer RNA tRNA- brings amino acids to ribosome during translation. Ribosomal rNA- forms the major part of a ribosome and participates in protein synthesis. How is the DNA interpreted and a protein synthesized? Step 1: DNA transcription (happens in the nucleus of eukaryotes) A single strand of RNA is transcribed from a template strand of DNA. The result is mRNA, which is the copy of the structural gene or genes of DNA. In it, T is replaced by uracil. The message contain codon for a specific amino acid. mRNA is single stranded. After transcription, the mRNA is transported out of the cell's nucleus through nuclear pores to go to the site of translation, (the rough endoplasmic reticulum in eurkaryotes) Step 2: RNA translation- Ribosomes bind at the 5´-beginning of the mRNA and start scanning the mRNA for a Start-codon (AUG), a place where the protein synthesis starts. The tRN anticodon with the correct attached amino acid binds to the start codon. Ribosomes move the next codon, allowing a new tRNA to bind and add another amino acid. These series of amino acids form peptide bonds. A stop condon terminates translation and there you have your protein! In general, describe 2 mechanisms of regulation Repressible- being made all the time unless you tell it to stop (ex: amino acids and nucleotides) Inducable- not there until you tell it to make it. (ex: insulin) what are the 3 categories of genes and what do they do? (structural, regulatory, encode RNA) Structural- let's make a protein Regulatory- control gen expression (make it or no, dont make it) Encode for RNA- genes that code for RNA what is a mutation? how are caused? are they good? bad? lethal? A mutation is any change made to the DNA. It can be good or Bad. Sometimes it is lethal, but sometimes not. There are positive effects for the cell which allow the cell to adapt. There are also negative effects for the cells, which can result in lose of function or death of the cell. Can you name a few things that result in mutation? (spontaneous, induced by mutagens) Spontanous- Random Change as a result of a mistake made in copying of DNA. Happens at a known rate of about in a million. Induced- caused by chemicals or radiation- examples are Agent Orange Nonsense- a change in a normal codon into a stop condon, therefore you get incomplete proteins. Very common. Frameshift- reading frame of the mRNA changes. If you knock out a base.. Back-mutation- mutation is reversed. Can you name a few mutagens and what they do? (see table 9.3) Acridine dyes- cause frameshifts due to insertion between base pairs X rays- form free radicals that cause breaks in DNA Ultaviolet radiation- causes cross links between adjacent pyrimidines what is bacterial conjugation and what does it accomplish? Bacterial conjugation is a type of recombination (sex for bacteria) where a plasmid (or other genetic material) is transferred by a dontor a receipiant via d direction connection. (via a pilus of donor cell that connects to a reciepient cell) what is transformation? nonspecific acceptance of free DNA (left around DNA) what is transduction? Donor is dead bacteria. Live recipient cell of same species. Bacteriophage infects host cells serve as the carrier of DNA from a dontor cell to a reciepent cell.