bio

• Before the 20th century, two concepts were the basis for ideas about heredity: heredity occurs within species and traits are transmitted directly from parent to offspring.
• Early plant biologists, such as Josef Kolreuter, produced hybrids with puzzling results.
• The black lab gene has two alleles: E (functional protein- will allow pigment to be deposited) and e (non-functional) that follow the complete dominance inheritance pattern.
• If heterozygous black labs (genotype BbEe ) are mated, we might expect the dihybrid F 2 ratio of 9:3:3:1.
• The phenotypic ratio of black labs from the F2 generation was: 9 black 3 brown 4 yellow (no pigment in hair).
• Epistatic interactions produce a variety of ratios, all of which are modified versions of 9:3:3:1.
• Gregor Mendel used pea plants for his experiments because other research showed that pea hybrids could be produced, many pea varieties were available, peas are small plants and easy to grow, and peas can self-fertilize or be cross-fertilized.
• The male anther contains pollen grains, which give rise to haploid sperm.
• The female carpel contains ovules, which give rise to haploid eggs.
• The stigma is the receptive tip of a carpel.
• The style is a narrow upward extension of the ovary.
• Cross-fertilization yields all hybrid seeds that give rise to purple flowers.
• Using pollen from a purple flower to fertilize a white flower gives the same result.
• Hybrids strain self-fertilizes.
• True-breeding strains are both sexual organs enclosed; contain both male anther (pollen) and female carpel (egg).
• Gregor Mendel usually had three stages in his experimental method: produce true-breeding strains for each trait he was studying by self-cross for several generations, cross-fertilize true-breeding strains having alternate forms of a trait, and perform reciprocal crosses.
• Mendel produced true-breeding pea strains for 7 different traits: flower color, seed color, seed texture, pod color, pod shape, flower position, plant height.
• Each trait had 2 variants.
• Probability and the rule of multiplication, also known as Product rule, states that the probability of two independent events both occurring is the product of their individual probabilities.
• When crossing 𝑃𝑝 × 𝑃𝑝, the probability of obtaining offspring is ½.
• The probability of obtaining p from father = ½.
• The probability of obtaining p from mother = ½.
• The probability of 𝑝𝑝=1/2 × 1/2=1/4.
• In dihybrid cross probabilities, alleles affecting seed shape and seed color are segregated independently.
• The probability of 2 independent events (particular pair of alleles for both traits) both occurring is the product of their each pair.
• The probability of
• rr yy = ¼
• rr x ¼ yy = 1/16
• rr yy.
• Mendel’s model of inheritance assumes that each trait is controlled by a single gene with only two alleles and there are no environmental effects.
• Polygenic inheritance occurs when multiple genes are involved in controlling the phenotype of a single trait.
• Pleiotropy refers to an allele which has more than one effect on the phenotype.
• Multiple alleles refer to 2 alleles in one individual (diploid) but may be more than 2 alleles for a gene in a population.
• Dominance is not always complete.
• Incomplete dominance is when the heterozygote is intermediate in phenotype between the two homozygotes.
• Codominance is when the heterozygote shows some aspect of the phenotypes of both homozygotes.
• The results for monohybrid crosses are the F2 generation.
• Each true-breeding parent makes only one type of gamete.
• F1 are all purple heterozygotes.
• Some human traits exhibit dominant/recessive inheritance.