BIOLOGY 111 1st Edition Lecture 16 Outline of Last Lecture I Meiosis II Sexual Reproduction III Phases of Meiosis IV Genetic Variation Outline of Current Lecture I Mendelian Genetics II Segregation of Alleles III Phenotype and Genotype IV Law of independent assortment V Probability Formulas Current Lecture Mendelian Genetics cross fertilization the cross of two different specimens instead of selffertilization parental generation first original generation F1 first generation offspring of parentals F2 second generation offspring of F1 experiment o Parental cross fertilization of purple and white flowers o F1 there was a dominance in purple so all offspring were purple He self fertilized to create F2 o F2 white shows back up in small ratio to purple Alleles are different variations of the same gene encoding the same character account for variations inherited o for each character an organism inherits two alleles one from each parent o different individuals can have different alleles at this locus o dominant alleles masks the presence of another allele A AA These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute or Aa o recessive alleles are masked and reveal themselves only when the organism has two copies of that allele aa o heterozygous individual has two different alleles Aa o homozygous individuals alleles are identical AA or aa locus is the address or location of a particular gene allele on a chromosome segregation of alleles two alleles for a heritable character segregate separate from each other so that only one allele is carried by each sperm or egg o inheriting even one copy of a dominant allele is effective o if offspring showed the recessive trait they would have two copies of the recessive allele o this explains the 3 1 segregation ratio in the F2 generation phenotype is the physical appearance genotype is genetic composition Monohybrid cross focuses on one character o a cross between parents that differ in a single gene pair AA X aa o phenotype is 3 1 3 dominant 1 recessive i e 3 purple to 1 white flower o genotype is 1 2 1 1 homozygous dominant 2 heterozygous dominant 1 homozygous recessive a test cross is a way of testing if a genotype was homozygous dominant or heterozygous law of independent assortment each pair of alleles segregrate independently of each other pair of alleles during gamete formation this law only applies to genes on different nonhomologous chromosomes dihybrid cross based on two characteristics o cross parents that differ by two pairs of alleles AABB X aabb o phenotype is 9 3 3 1 9 double dominant 3 recessive and dominant 3dominant and recessive 1 double recessive i e 9 yellow round peas 3 green round peas 3 yellow wrinkled peas 1 green wrinkled pea combination of gametes is o YyRrTtPP o 2 2 2 1 8 o or 2 n n is number of possible gametes Laws of probability P number of times an event occurs total number or possible outcomes Product rule multiply the possibilities of each product AND is keyword o probability that two or more independent events will occur is equal to the product of their individual probabilities o ex what is the probability of having 3 girls in a row the chances of having a girl is 1 2 chances of having three girls is 1 2 1 2 1 2 1 8 o ex 2 an offspring with Aadd if the parents are AaDd X AaDd Aa 1 2 dd 1 4 1 2 1 4 1 8 Sum rule add up the possibilities of each event OR is keyword o probability that one of two or more mutually exclusive events will occur is the sum of probabilities of possible outcomes o add the probabilities 1 4 1 4 1 2 o probalbility of having YYRR or yyrr from a YyRr X YyRr cross YY 1 4 RR 1 4 YYRR 1 16 yy 1 4 rr 1 4 yyrr 1 16 1 16 1 16 2 16 1 8 o probability of having aaDd or aaDD Mendels interpretation o Heritable factor genes responsible for character inheritance Mendels Laws o Law of segregation for monohybrid cross Phenotype ratio 3 1 Genotype 1 2 1 o Law of independent assortment for dihybrid cross Phenotype ratio 9 3 3 1 incomplete dominance o traits appear to blend in F1 generation o ex crossing a red and white flower gives pink offspring o not enough encoding to signal for complete dominance co dominant allels o 2 alleles affect the phenotype equally and separately o instead of blending both characteristics appear in equal amounts o ex in red blood cells there are four types that each give a different phenotype A is dominant could be homozygous or heterozygous dominant B is dominant could be homozygous or heterozygous dominant AB codominant A and B are equally dominant neither masks the other universal recipient because it has all the markers allowing it to recognize type A B or O blood O is homozygous recessive for both A and B considered a universal donor because it does not have any markers allowing it to be recognized by all types of blood BUT only type O blood can donate to type O blood Rh factor genes are inherited in dominant recessive fashion Rh Rh is present dominant Rh Rh is absent recessive Polygenic characters characters controlled and expressed as a combined expression of two or more genes o quantitative characters that vary continuously throughout a population i e skin color height are usually encoded Multifactorial character in addition to genetic factors there are environmental factors i e diet as well o depression exhibits multifactorial inheritance genes plus stressful environment altered protein function can affect phenotype