Animal Science with Professory Larson Week 6 at MSU
Animal Science with Professory Larson Week 6 at MSU ADS 1113
Popular in Animal Science
Popular in Animal and Dairy Science
This 4 page Class Notes was uploaded by Kaitlyn Notetaker on Sunday September 25, 2016. The Class Notes belongs to ADS 1113 at Mississippi State University taught by Dr. Larson in Fall 2016. Since its upload, it has received 28 views. For similar materials see Animal Science in Animal and Dairy Science at Mississippi State University.
Reviews for Animal Science with Professory Larson Week 6 at MSU
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 09/25/16
Animal Science Chapter 12: Genetics Learning Objectives o Describe the formation of gametes o Define the role of DNA and RNA o Describe the six fundamental mating types o Calculate genotypic and phenotypic outcomes o Illustrate various forms of dominance o Discuss the role of biotechnology in the livestock industry Probably won’t talk about. Won’t ask about on exam Genetics o Understanding of inheritance began with Mendel in 1856 o Watson and Crick suggested the model of DNA in 1953 o Chromosomes contain the genetic code and occur in pairs in somatic cells Somatic cells are body cells o Sex cells (spermatozoa and oocytes) contain half the chromosomes, and thus each cell contributes half the genetic code to a new embryo Mitosis and Meiosis o Mitosis=replication of somatic cells Each parent cell divided into two identical daughter cells that each carry all the chromosomes o Meiosis=the formation of gametes (sex cells) Each newly formed gamete contains only 1 member of each of the chromosome pairs, thus half the original chromosome The production of sex cells is called spermatogenesis and oogenesis o In both cases, chromosomes replicate so that there is double the number In mitosis, each set goes into a different cell so there are 2 new cells generated In meiosis, each set stays separated so there are 4 new cells generated In females, only 1 of these 4 become a viable oocyte Fertilization o Union of the sperm and the oocyte o Each sex cell contributes one chromosome to each pair of chromosomes in the fertilized oocyte (now called a zygote) o Father is called the sire and mother is called the dam o Genetic diversity is created because which chromosomes end up in which gamete is random, so no two identical individuals are genetically the same Exception is identical twins, because they were generated from the same zygote DNA o Each chromosome in a pair is alike in size and shape and carry genes that affect the same hereditary characteristics These chromosomes are homologous Genes for the coding system that directs enzyme and protein production and thus the expression of a specific trait or characteristic o Chromosomes are composed of deoxyribonucleic acid (DNA) Shaped as a double helix Segments of DNA are genes Each gene is specific DNA sequence that codes for a particular protein DNA is composed of a few molecules but the bases (A, T, G, and C) are the parts that control inheritance During cell division, this DNA unwinds and each strand replicates and then a new strand is formed RNA o Transcription and translation are the processes where by the code is “read” and protein is synthesized o The DNA template codes for RNAs Messenger RNA, transfer RNA, and ribosomal RNA o 1 step is transcription which transcribes DNA to create a mRNA molecule mRNA then leaves nucleus and travels to ribosome, where protein synthesis happens mRNA attaches to a ribosome for translation into a protein Inheritance o Genetic inheritance is based on chromosomes occurring in pairs and that genes carry the genetic code that influences traits Each gene is located on a specific locus So each chromosome pair has two alternative forms of a gene… alleles These alleles may be homozygous (same) or heterozygous (different) If one gene overpowers the other, it is dominant The overpowered allele is then recessive Many traits of interest are either Qualitative: discrete (color, polled/horn) Quantitative: exists along a continuum (height, weight) o Being able to predict how these genes are inherited is really what livestock producers care about Simple Inheritance o 6 mating types: BBxBB, BBxBb, BBxbb, BbxBb, Bbxbb, bbxbb o Coat color in cattle-controlled by an allele Black is dominant (B) while red is recessive (b) Each animal has two alleles and they can be homozygous or heterozygous BB (black), Bb (black), bb (red) o Punnett square- can be used to predict which alleles the offspring might inherit (genotypic ratio and phenotypic ratio) Multiple Gene Pairs o Note everything is so simple… o Sometimes we care about 2 traits that are controlled by 2 independent pairs of genes o For example, coat color and polled or horned (P or p) Phenotypic ratio: 9 black polled, 3 black horned, 3 red polled, and 1 red horned (9331) a dihybrid cross will always have a ratio of 9:3:3:1 (you can thank me later) Genotypic ratio: page 197 in book Gene Interactions o Genes can interact with other genes o Linear interaction: genes in the same chromosome, does not exist in livestock species Is an option but won’t talk about o Allelic Interaction: corresponding genes in a homologous chromosome 4 categories included in this interaction Complete dominance: only effect of the dominant genes is expressed o Horned vs polled (heterozygous is same phenotype as homozygous dominant) A lack of dominance: heterozygous animals have different phenotype that either homozygous dominant or homozygous recessive o Ear length: LL have long ears, Ll have short ears, ll have no ears o This can be called additive genes action (quantitative traits) Overdominance: heterozygous is “better” than either homozygous option (Heterosis) o Hybrid vigor: greater productivity of crossbreds Partial dominance: heterozygous is intermediate but more closely resembles homozygous-dominant o Epistatic: genes in non-homologous chromosomes Epistatic: a gene that interacts with other genes that are not allelic to it is said to be epistatic to them A gene or one pair of genes in one pair of chromosomes may influence many other genes in many pair of chromosomes o Coat color in horses- this is why horse coat color is very complicated Genes and the environment o Genes also interact with external and internal environments Temperature, light, altitude, humidity, disease, feed supply o All these interaction (allelic, epistatic, environmental) affect the degree to which genetic improvement can be made via selection o If environmental has a large effect, genetic improvement is low (because there is so much out of our control) Summary o Cells contain several pairs of chromosomes that are composed of DNA. Genes are segments of DNA that are the basic unit of inheritance o 2 chromosomes (X and Y) determine the sex of animals. In livestock, XX and XY is female and male, respectively. In birds, XX and XY is male and female respectively. The parent carrying the XY determines sex of offspring. o Genetic variation and genetic change occur through chromosome (gene) segregation and chromosome (gene) recombination resulting from sex cell formation and fertilization. o Genes produce their effects through dominance, over-dominance (heterosis), lack of dominance (additive), or epistasis (interactions between pairs of genes) o Biotechnology and genetic engineering are bringing changes and challenges to both humans and domestic animals Questions: 2, 3, 4, 5, 7, 8, 9 Possible Essay Questions: 7 and 8 together (use Punnett square to help answer 7 and derive phenotypic and genotypic ratios)
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'