6.3 Mendel and Heredity

13.1 Ecologists Study Relationships Fundamentals of Genetics Genetics – field of biology devoted to understanding how characteristics are transmitted from parents to offspring

6.3 Mendel and Heredity Father of Genetics Gregor Mendel Austrian Monk Heredity – transmission of characteristics from parents to offspring Garden Peas

6.3 Mendel and Heredity CharacteristicTraits 1.Plant HeightTallShort 2.Flower position AxialTerminal 3.Pod appearance Inflated Constricted 4.Seed TextureSmoothWrinkled 5.Seed ColorYellowGreen 6.Flower ColorPurpleWhite 7.Pod ColorGreen Yellow

6.3 Mendel and Heredity Mendel’s Methods Pollination – pollen produced in the male reproductive parts of the flower (anther) are transferred to the female reproductive part of a flower (stigma) Self-pollination – pollen is transferred from an anther to a stigma on the same plant Cross-pollination – involves flowers of two separate plants

6.3 Mendel and Heredity Mendel’s Experiments 1.He allowed plants to self-pollinate for several generations to obtain 14 pure strains: Parental Generation (P1) –Pure - always produce offspring with that trait –Strain - plants that are pure for a trait 2.Cross-pollinated these strains –one pure for one trait with another pure for the contrasting trait –P1 (tall) X P1 (short)  First Filial Generation (F1) 3.Then allowed F1 to self pollinate  second filial generation (F2)

6.3 Mendel and Heredity Mendel controlled the fertilization of his pea plants by removing the male parts, or stamens. He then fertilized the female part, or pistil, with pollen from a different pea plant.

6.3 Mendel and Heredity Mendel’s Results Only one of the two traits in P1 appeared in the offspring F1 The trait then reappeared in F2 in a ratio of 3:1

6.3 Mendel and Heredity Mendel’s Conclusions Factor – something is controlling the traits –Allele Pair of factors controls each trait –Gene Recessive & Dominant Traits - Dominant Allele – masked the other factor (appeared in F1) - Recessive Allele – is masked by the presence of another (reappeared in F2)

6.3 Mendel and Heredity Chromosomes and Genes Molecular genetics – study of the structure and function of chromosomes and genes Gene – segment of DNA on a chromosome that controls a particular hereditary trait Letters are used to represent alleles of genes - capital letters refer to dominant alleles T = tall - lowercase letters refer to recessive alleles t = short Genome - All of an organism’s genetic material

6.3 Mendel and Heredity Genotype – genetic makeup of an organism TTTttt Phenotype – appearance of an organism as a result of its genotype Tallorshort Homozygous – both alleles of a pair are alike TT or tt Heterozygous – two alleles in the pair are different Tt 6.4 Traits, Genes, and Alleles

6.3 Mendel and Heredity The axes represent the gametes of each parent. –The boxes show the possible genotypes of the offspring. 6.5 Traits and Probability

6.3 Mendel and Heredity Genotypic ratio – ratio of the genotypes that appear in offspring 1TT:2Tt:1tt Phenotypic ratio – ratio of the offspring's phenotypes 3 Tall:1 short 6.5 Traits and Probability

6.3 Mendel and Heredity A monohybrid cross involves one trait (12 points) 6.5 Traits and Probability Homozygous Dominant XHomozygous Recessive

6.3 Mendel and Heredity 6.5 Traits and Probability Heterozygous XHeterozygous

6.3 Mendel and Heredity How Mendel's pea plants helped us understand genetics helped-us-understand-genetics-hortensia-jimenez-diazhttp://ed.ted.com/lessons/how-mendel-s-pea-plants- helped-us-understand-genetics-hortensia-jimenez-diaz 6.5 Traits and Probability

6.3 Mendel and Heredity Testcross Determine the genotype of an individual whose Phenotype is dominant –TT or Tt (?) Individual of unknown genotype is crossed with a homozygous recessive individual T? Xtt 6.5 Traits and Probability

6.3 Mendel and Heredity Testcross (12 points): Offspring 100% Dom 6.5 Traits and Probability

6.3 Mendel and Heredity Complete Dominance – one allele completely dominant over the other Incomplete dominance – two or more alleles influence the phenotype results in a phenotype in between the dominant and recessive R = red W = white RW  pink 7.2 Complex Patterns of Inheritance

6.3 Mendel and Heredity Incomplete Dominance: Homozygous (1 st trait) XHomozygous (2 nd trait) 7.2 Complex Patterns of Inheritance

6.3 Mendel and Heredity Codominance – both alleles for a gene are expressed in a heterozygous offspring neither is dominant or recessive R = Red W = White RW  red & white polka dots 7.2 Complex Patterns of Inheritance

6.3 Mendel and Heredity Codominance: HeterozygousXHeterozygous 7.2 Complex Patterns of Inheritance

6.3 Mendel and Heredity Multiple Alleles – 3 or more alleles of the same gene I A or I B or i Blood Types I A I A orI A i=Blood type A I B I B orI B i=Blood type B I A I B =Blood type AB ii=Blood type O 7.2 Complex Patterns of Inheritance

6.3 Mendel and Heredity Blood Type ABXBlood Type O 7.2 Complex Patterns of Inheritance

6.3 Mendel and Heredity Sex-linked Inheritance Traits controlled by genes located on the sex chromosomes (X or Y) X-linked traits – found on X chromosome Y-linked traits – found on Y chromosome –X-linked traits more common in males –Y-linked traits only in males 7.1 Chromosomes and Phenotype

6.3 Mendel and Heredity X-Linked Heterozygous Female XMale with recessive trait 7.1 Chromosomes and Phenotype

6.3 Mendel and Heredity Y-Linked FemaleXMale with Dominant trait 7.1 Chromosomes and Phenotype

6.3 Mendel and Heredity Female mammals have an XX genotype –X-inactivation – one X chromosome is randomly “turned off” in every cell –Ex: calico cats 7.1 Chromosomes and Phenotype

6.3 Mendel and Heredity Sex-Influenced – traits affected by how much sex hormones are present 7.1 Chromosomes and Phenotype

6.3 Mendel and Heredity A dihybrid cross involves two traits (12 points) Homozygous Recessive/HeterozygousX Homozygous Dominant for both 6.5 Traits and Probability

6.3 Mendel and Heredity Heredity patterns can be calculated with probability. Probability is the likelihood that something will happen Predicts an average number of occurrences, not an exact number of occurrences. Probability = number of ways a specific event can occur number of total possible outcomes 6.5 Traits and Probability

6.3 Mendel and Heredity Laws Law of Segregation – a pair of factors is separated during the formation of gametes 1 trait: Tall from short Law of Independent Assortment – factors for different characteristics are distributed to gametes independently All characteristics being separated from each other Ex: Tall plant from yellow peas

6.3 Mendel and Heredity Autosomal genetic disorders –Carrier - A heterozygote for a recessive disorder –Disorders caused by dominant alleles are uncommon. (dominant) 7.1 Chromosomes and Phenotype

6.3 Mendel and Heredity Epigenetics – study of changes in gene activity which are not caused by changes in the DNA The changes in gene expression or phenotype have other causesgene expressionphenotype Ex: environment, other genes, etc

6.3 Mendel and Heredity Genes can interfere with other genes Epistatic genes 7.2 Complex Patterns of Inheritance

6.3 Mendel and Heredity Phenotype is a combination of genotype and environment. EX: Height is another example of a phenotype strongly affected by the environment. EX: The sex of sea turtles depends on both genes and the environment 7.2 Complex Patterns of Inheritance

6.3 Mendel and Heredity Polygenic Inheritance Traits controlled by many genes ~250 genes have been described to control human height  up to 700

6.3 Mendel and Heredity Trihybrid Cross Hetero/Homo Rec/Homo DomX Homo Rec/Hetero/Homo Dom