Biology Unit 2: Introduction to Inheritance PDF
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This document provides definitions and examples of various genetic concepts, including homozygous and heterozygous traits, dominant and recessive traits, and phenotypes and genotypes. It also explains Punnett squares, and laws of inheritance. It touches on topics of co-dominance and incomplete dominance in regards to inheritance patterns, including blood and sex-linked inheritance.
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Unit 2- Introduction to Inheritance efinitions D Homozygote: having two identical alleles (ex. BB) Heterozygous: Genotype consisting of two differentalleles (ex. Bb) Genotype: The alleles that an individual carries ontheir chromosomes (ex. Bb, BB,bb) Phenotype: The out...
Unit 2- Introduction to Inheritance efinitions D Homozygote: having two identical alleles (ex. BB) Heterozygous: Genotype consisting of two differentalleles (ex. Bb) Genotype: The alleles that an individual carries ontheir chromosomes (ex. Bb, BB,bb) Phenotype: The outward appearance of an organism (ex.Blue eyes) Dominant: The stronger of two alleles that only needsto be present once in the genotype for it to be expressed in the phenotype (Ex. B) Recessive: The weaker of two allele that needs tobe present twice in the genotype for it to be expressed in the phenotype ifferent Alleles: D Alleles:different flavors of genes (B or b) ominant trait:is expressed whether there is oneor two copies (ex. B-brown eyes) D Recessive trait:only expressed if an individual hastwo copies of that trait since it is hidden by the dominant one (ex. Bb-blue eyes) henotypes & Genotypes P Phenotype (physical appearance):brown eyes, blueeyes Genotype (genetic code) :ex. BB, Bb, bb omozygous & Heterozygous H Homozygous:individuals with two of the same alleles(ex. BB, bb) Heterozygous:two different alleles (ex.Bb bB) Punnett Squares Father traits go on top Mother’s on the side Always remember to write let statements & genotypic/phenotypic ratios Let T represent the allele for tall plants Let t represent the allele for short plants G enotypic ratio: 1TT:2Tt:1tt Phenotypic ratio: 3 tall : 1 short 1 and F2 generations F P generation: parents of the cross, (one green podGG, and one yellow pod gg) F1 (1st filial generation):first generation of theoffspring, peas are all green pods with genotype Gg F2(2nd filial generation):produced by crossing twoindividuals from the first generation Example work of a F1 and F2 generation punnett squares: Laws of Inheritance 1. T he Law of Dominance: in a pair of genes one is stronger (dominant) 2. The Law of Independent Assortment: genes for different traits are inherited separately. (ex. If a plant has genes of height (tall or short) and flower color (purple or white) the height does not affect the flower color. Each trait is passed on independently. 3. The Law of Segregation:parents pass down just one of their two genes for a trait to their children Co dominance & Incomplete dominance omplete dominance:One allele is dominant and masksthe presence of the other allele C Codominance:both alleles are dominant, traits fromboth alleles show in the phenotype Incomplete dominance:Neither allele is dominant. Ablend of the two alleles is expressed in the phenotype odominance:is a non-mendelian inheritance pattern.The alleles of a gene pair in a C heterozygote are fully expressed and the phenotype shows both traits. (ex. Roan cows, flowers with red & white petals, speckled chickens, human AB blood type) RCR = red cow CWCW = white cow C CRCW or CWCR = roan cow (we usually write the traits in alphabetical order) I ncomplete:is a Non-Mendelian Inheritance pattern. The alleles of a gene pair in a heterozygote are both expressed as a blend of two phenotypes. (ex.palomino horses, flowers with pink petals, grey chickens, wavy human hair) Occurs when a mix of both traits are expressed, such as in the case of a person with wavy hair or a flower with pink petal colours. HCHC = curly hair HSHS = straight hair HCHS or HSHC = wavy hair (we usually write the traits in alphabetical order) olygenic:that is they are coded for by multiple genes (ex. Human height, weight & hair colour P are also polygenic) Blood Types lood type A: IAIA IAi B Blood type B: IBIB IBi Blood type AB: IAIB Blood type O: ii ominant : blood A & blood B D Codominant: blood AB Recessive: blood O Heterozygous: i Sex-linked Inheritance ales: XY M Females: XX Examples of superscripts: - X HXH(no hemophilia) - XHXh (carrier of hemophilia) - XhXh (has hemophilia) Extra things to remember! Blood type O is the universal donor Blood AB positive is known as the universal recipient
