24.Applied Genetics done.doc.docx

Applied Genetics Selective Breeding is the process of breeding animals or plants with desirable traits and concentrating those desirable traits in their offspring. Vital to ensure a profitable farm. Also known as artificial selection. Selective breeding is also done to eliminate any undesirable trai...

Applied Genetics Selective Breeding is the process of breeding animals or plants with desirable traits and concentrating those desirable traits in their offspring. Vital to ensure a profitable farm. Also known as artificial selection. Selective breeding is also done to eliminate any undesirable traits. This type of breeding is divided into two types: Inbreeding and Crossbreeding. 1. Inbreeding The mating of closely related animals, which increases the chances of the offspring being affected by undesirable recessive traits. Inbreeding is advantageous sometimes for fixing desirable traits such as high milk yields in pure-bred dairy cattle (Holsteins) and creating uniformity among offspring. Inbreeding produces pedigree animals whose ancestry is known. 2. Crossbreeding The mating of animals or plants from two different breeds, varieties or species. The offspring can inherit favourable genes from both parents leading to improved qualities over both parents. This is called hybrid vigour. While crossbreeding reduces the risk of harmful recessive genes, hybrid vigour is generally reduced with subsequent crossing of hybrids. Crossbreeding is extensively used to produce F1 hybrid seed varieties. Artificial Insemination (AI) AI allows farmers to target areas in their herd that they want to improve. Traits that farmers might want to improve: Milk yield, Milk composition, Fertility and Conformation Preparation of an AI straw After being collected, the bull’s semen it is diluted with an extender. This extender protects and nourishes the sperm during storage. AI of a Cow The AI Straw is thawed in warm water. It is placed in a catheter (insemination gun). The AI technician places hand into cow’s rectum and guides the straw through the cervix into the uterus, Semen is deposited in the uterus of the cow. Laparoscopic AI is a Method used on ewes. A small incision is made in the abdomen of the ewe, Semen is inserted into the left and right horns of the uterus. Advantages of AI Don’t have to keep a stock bull on the farm Bulls are aggressive and can be dangerous. Expensive to keep, requiring additional fencing. Farmers have a variety of choices of bulls. All bulls used for AI are performance and progeny tested. Lower risk of inbreeding. Disadvantages of AI heat detection is crucial. More labour intensive Lower conception rates compared to a fertile stock bull. Semen must be stored properly. Genotyping Is the study of animal DNA. It controls certain traits like milk production and carcass weight. By comparing it to sequence of other animals we can see the variations in genetic codes Embryo Transplantation This is when superior quality pedigree females have been mated or AI and produce embryos at the start of pregnancy. These females act as donors. The donor’s embryos are taken and implanted into another female with a lower genetic quality. Procedure the donor is given hormone injections to cause super ovulation. The donor is then mated by AI to a top-class bull and the semen fertilises the eggs. The embryos are flushed-out of the donor and implanted into the surrogate, she will then give birth to a top-class pedigree calf. Super Ovulation: the production of more than the normal number of mature eggs at one time Cloning Procedure somatic cell was removed from the udder of sheep 1. Egg cell was removed from sheep 2 and the nucleus was removed from it. These cells were then fused together using an electrical current which caused the egg to start dividing. The dividing blastocyst is then implanted into another sheep. Blastocyst: an embryo 5 – 6 days after fertilisation The main advantage of cloning is that it makes it possible to produce identical copies of genetically superior animals. Micropropagation is known as tissue culturing. It produces many plants asexually from small pieces of plant tissue that are genetically identical. It is often used for potato seeds. Procedure: 1. Small pieces of a plant (single cells) are cut. 2. Placed on sterile growth medium like agar. 3. Forms a clump referred to as a callus. 4. Callus is placed on a new growth medium. 5. Plant hormones speed up the process. These will develop into plants. Transgenic Species: any organism that has had part of the DNA of another species transferred into its own DNA by genetic engineering. Example of a GMO Genetically modified maize plant contains a gene taken from a type of bacteria which allows the maize to produce a poison for a corn borer caterpillar. This makes the crop resistant to these pests. Polyploidy describes a cell that has more than 2 sets of chromosomes, example 3n, 4n 10n. Most organisms are diploid (2n). Polyploidy occurs due to abnormal cell division and is most found in plants. Some polyploidy crops are sterile/infertile (especially odd sets of chromosomes – 3n), which leads to the fruit being seedless, example seedless grapes.