* Trait- a character/gene shape, * Monk in Austria at age 21 * At 30, went to University of Vienna to study science and math * After graduating he returned to the monastery and became a high school teacher * Famous for work with pea plants and study of heredity transmission of characters from parents to offspring * Gregor Mendel was the first person to realize that traits are * He didn t know about DNA though! * His work was forgotten until 1906 self-pollination or crosspollination and can be controlled * Pollen (male gamete) from the stamen fertilizes the pistil (carpel) parents) generation 1
* height (tall or short) * Monohybrid Cross - A cross looking at only one trait *requires a box with four squares * Mother s possible gametes (eggs) are put on one side. The father s are put on the other side. * Each box represents a possible offspring. * R = round peas r = wrinkled Determine the genotypic and a heterozygous plant and a homozygous dominant plant Mendel's first law The Law of Segregation: the alleles of a gene/trait separate when an individual makes gametes. * - likelihood that an event will occur (scale of 0-1) # of times an event is expected to occur total # of chances * Example * Probability of Heads = 5 10 trials * Deviation Deviation = total # of trials * Example * 10 tosses of coin *100 tosses of coin Heads Observed 4 6 Heads Observed 55 45 Probability of two independent events happening together: multiply the probabilities of the individual events. Tossing two coins probability that both will come up heads: ½ x ½ = ¼ The multiplication rule. Example: Joint probability that a seed will be spherical and yellow: ¾ ¾ = 9/16 The probability of an event that can occur in two different ways is the sum of the individual probabilities. In F2, there are two ways to get a heterozygote; thus ¼ + ¼ = ½ The addition rule. Example: Probability that F2 seed will be spherical is ¾ = probability of heterozygote + probability of homozygote or ½ + ¼ = ¾ 2
Dihybrid cross * EX: pea color and pea shape. square with 16 boxes. * Mendel set up these crosses in the same manner as monohybrid crosses: P, F1 and F2 * Flower Color: r = white * Height: t = short * Complete the Punnett Square for one plant that is heterozygous for flower color and homozygous short for height. The other plant is homozygous red for flower color and homozygous recessive for height. * When two double heterozygous individuals are crossed, it will always produce a 9:3:3:1 ratio. **Dihybrid crosses support Mendel's Second Law- LAW OF INDEPENDENT ASSORTMENTtraits are inherited separately * Special type of inheritance where the one allele is not completely dominant over the * Codominance - more than one allele is dominant (no blending) *This produces a blended * A and B are codominant (RR) with a white snapdragon (rr) the heterozygous * Because there is no truly dominant used and superscript letters indicate * Ex: C R C W * C R C R * C R C W = pink * C W C W 3
* When more than 2 alleles for a gene exist within a population on an organism's phenotype. * i A = Antigen A * i B = Antigen B * i = No antigen * color pattern (light body, dark extremities) 44% 16% 36% - when genes contribute to a phenotype. expression of another gene. * One gene codes for the presence or absence of pigmentation. * The other gene determines the color of * B = black * C = pigment b = agouti * c = no pigment * This causes phenotypes that are not * EX: The height of a plant is a result of 4 genes, each of which adds 2 cm. to the the plant is 6 cm. with a base height plant (aabbccdd) what is the height of the F1 plants? * C=pigment * c=no pigment. * black (BB or Bb) * chocolate (bb) * What is the coat color? * CCBB= * Ccbb= * ccbb= * Humans and many other animals that determine their gender compared to males * When a gene is located on a sex chromosome, certain genders are more likely to inherit that gene. * Their yellow and black colors are caused by a gene on one x chromosome * Example - eye color in fruit flies * Gene is carried on X chrom. only * X R * X r = white eyes 4
Linked Genes * Punnett squares can correctly predict inheritance when two genes are on different chromosomes and separate independently into gametes. * When two genes are on the same chromosome, we say they are linked. * Linked genes do not separate independently into gametes * They are more likely to be inherited together. * If two traits are linked, the offspring will look more like the parents, rather than the way you would predict using a Punnett Square which assumes completely random separation * Linkage can be undermined by crossing over Thomas Hunt Morgan is credited with the discovery and understanding of Linkage. He studied fruit flies (Drosophilia melanogaster), a model organism, and noticed that the recessive white eye showed up more than expected. Linkage refers to genes that are located on the same chromosome. They tend to be inherited together and fewer genetic combinations of their genes are possible. Linkage is indicated in a genetic cross when a greater proportion of the parental type exists. Steps to determine crossover frequencies and map relative positions of genes on a chromosome: 1. Identify the offspring genotype frequencies (usually provided) *Offspring similar to parents *Offspring recombinants (non- parental phenotypes) 2. Calculate the crossover value: Crossover Value % = No. of recombinant types / Total no. of offspring 3. Map the genes- using the crossover value each percent of crossover is equivalent to one genetic map unit (Centimorgan or cm) *10% would = 10 cm Linked Genes Linked Genes * When a mutated gene is carried only on a sex chromosome (X or Y) * Males are affected more than females (only have 1 X chromosome) * Females are often carriers * EX: Red-green Color-blindness * recessive X-linked disorder * EX: Hemophilia * recessive X-linked disorder * impairs the ability of the blood to clot * EX: Duschene Muscular Dystrophy * recessive X-linked disorder 5
Germ-cell mutations organism s gametes * Environment also affects phenotype; Light, temperature, nutrition, etc., can affect expression of the genotype. Siamese cats and certain rabbit breeds enzyme that produces dark fur is inactive at higher temperatures. A normal healthy Karyotype will include all 46 chromosomes where Males have XY and Females have XX. To notate/describe the chromosomes you would list the total number of chromosomes, gender and location of abnormal chromosome. fetus, amniotic fluid from the sac that surrounds the Chorionic villi sampling * Shaded shape has the trait in question, unshaded does not 6