Transcript Genetics
Modified by Patrick Matous from the Georgia Agricultural Education Curriculum Office Is the science of heredity. Heredity is the transmission of genetic or physical traits from parent to offspring. Austrian Monk Considered the “Father of Heredity” He conducted plant breeding experiments in their monastery garden. In 1865 he made his work public, units of inheritance. Each of the 100 Trillion cells in our body except the red blood cells contains the entire human genome, in the nucleus of every cell is the genetic information “blueprint” to construct the individual. It is the Deoxyribonucleic acid (DNA) Function of DNA Genetic code for almost every organism. Provide template for protein synthesis. The structure of DNA was discovered by Watson and Crick in 1953. It is a twisted double helix molecule, containing sugar, phosphates, and nitrogenous bases. The sugar is deoxyribose and the phosphoric acid molecules are always the same and provides for the structure (side of the ladder). The only difference between us is the order and arrangement of the four bases (rungs of the ladder). Adenine= A Thymine= T Guanine= G Cytosine= C A always pairs with T C always pairs with G Adenine= A Uracil= U Guanine= G Cytosine= C G always pairs with C T from the DNA = A in the RNA A from the DNA = U in the RNA The DNA in every cell is located in rod like segments called chromosomes Chromosomes occurs in pairs in every cell of our body except in the sperm and ovum. Chromosomes numbers are the same for each specie. Species Cattle Swine Sheep Horse Human Chicken Goat Donkey Diploid # 60 38 54 64 46 78 60 62 Haploid # 30 19 27 32 23 39 30 31 There are 2 sex chromosomes included in the diploid number of the chromosomes. All of the other chromosomes are referred to as autosomes. In mammals if the sex chromosomes are alike, XX it results in a female. If the sex chromosomes are different, XY it results in a male. Females contribute an X chromosome towards the sex of their offspring. Males can contribute an X or a Y chromosome toward the sex of their offspring. Absence of an Y chromosome results in a the embryo developing into a female. Presence of an Y chromosome results in the embryo developing into a male. Gametogenesis = Formation of gametes through meiosis. Male = 4 viable spermatids Female = 1 viable ovum, 3 polar bodies. Meiosis Is the form of cell division which results reducing the chromosome number from the diploid # to the haploid #. Occurs only in the sex cells, sperm and ovum. Mitosis Is the form of cell division which results in the formation of identical daughter cells, keeps the chromosome number constant. Tissue growth and repair. Occurs throughout the body except in the sex cells. Genotype contains two copies of the gene. Gamete (sex cells) contains only one copy of the gene. AaBB AB Determine the possible gametes of AaBB AB aB State if its a gamete or genotype. Aa D DdEeFFgg sRtxyq AaBBeeFF adgEFT From the genotype AaBb AB Ab aB ab Chromosomes contains several units of inheritance “genes”. Genes usually occurs in pairs, one from each parent. Some traits are inherited directly from one set of genes. Some traits are inherited through several sets of genes. It was presumed that we were composed of about 100,000 genes to construct us. Today, research has proven that number is a lot less than 100,000. Extra credit for the student that can find an article about the current number of genes. Homozygous- contains 2 identical genes for the same trait, AA, BB, cc Heterozygous- contains 2 different genes for the same trait, Aa, bB, Cc Phenotype- Outward appearance of a trait, coat color, polled, horned. Genotype- Genetic classification of a gene, AA, Aa, aa. Allele- Location of a gene on the chromosome. F-one = First cross mating. F-two = Second cross mating. http://www.biology.arizona.edu/vocabulary/mendelian_genetics/ mendelian_genetics.html The gene that express itself, the powerful and dominant gene. It has the power to overshadow the recessive gene when there is complete dominance. Some examples are: White faced in cattle Droopy ears in swine Polled in cattle Black coat color in Angus cattle The gene that is overshadowed by a dominant gene Recessive genes can only express themselves in the absence of the dominant gene Polled vs Horned (Pp) (pp) Black wool vs white (Ww) (ww) Dwarfism vs normal size (dd) Albino Angus- Black coat color is dominant. BB = Homozygous Dominant and Black Bb = Heterozygous and is black bb = Homozygous recessive and red A heterozygous bull is mated to 50 homozygous recessive cows. How many calves are black? How many calves are red? What is the genotypic and phenotypic ratios? B b b Bb bb b Bb bb 2 heterozygous = Bb 2 Homozygous Recessive bb 25 Black, 25 Red Genotypic ratio = 0:2:2 Phenotypic ratio = 2 Black: 2 Red Some recessive genes are attached to the X and Y chromosomes Humans: Colorblindness and Baldness are on the X chromosomes In Men, traits expressed anytime present In Women, must have two recessives to show trait Children get baldness from mothers Y X B X X XX B XX B X Y XY X X B X XX B XX Y X BY XY X X B X B X X B X X B Y X BY XB Y If both genes express themselves Shorthorn Cattle: Red male mated to a White female = Roan calf RR crossed rr = Rr Shorthorn Cattle RR = Red rr = white Rr = roan If a red bull (RR) is mated to a white cow (rr), what color will the calves be? R R r Rr Rr r Rr Rr If a red bull (RR) is mated to a roan (Rr) cow, what color will the calves be? R R R RR RR r Rr Rr R r R RR Rr r Rr rr Noticed when a gene has more than 2 alleles that code for multiple phenotypes. This is the property of a gene that causes it to have multiple phenotypic effects. Pg. 262 A gene at one locus alters the effects of a gene at another locus. In many cases it is masked! A single characteristic that is controlled by two or more genes! http://www.indiana.edu/~oso/lessons/Genetics/figs/HairColor/browns.jpg http://facweb.bhc.edu/academics/science/robertsk/biol100/Patterns_files/image033.jpg http://www.google.com/imgres?imgurl=http://www.biology.arizona.edu/men delian_genetics/problem_sets/dihybrid_cross/graphics/13punnet.gif&imgrefurl= http://www.biology.arizona.edu/mendelian_genetics/problem_sets/dihybrid_cr oss/13t.html&usg=__0lXOAHlJKQyfZdIKnbTteDlksaU=&h=195&w=301&sz=6&h l=en&start=9&zoom=1&um=1&itbs=1&tbnid=8rHyQaubxSBvSM:&tbnh=75&tbn w=116&prev=/images%3Fq%3Depistasis%26um%3D1%26hl%3Den%26sa%3DN% 26rlz%3D1T4GGIH_en__266US273%26tbs%3Disch:1&ei=6l9ATeG7OMqr8AaA7qj vAw http://www.nature.com/scitable/nated/content/45524/human_height_illustrati on_MID_1.gif http://bioweb.wku.edu/courses/BIOL115/Wyatt/Ge netics/Meiosis.asp