Genetics: The Science of Genetics: The Science of HeredityHeredity

A guide to Chapter 5A guide to Chapter 5

History of GeneticsHistory of Genetics

»Genetics:Genetics: The study of The study of heredity, or the passing on heredity, or the passing on of traits from an organism of traits from an organism to its offspring.to its offspring.

»Trait:Trait: Characteristic Characteristic

Gregor MendelGregor Mendel

• 1860’s1860’s• Austrian monk and biologist who Austrian monk and biologist who

experimented with pea plants.experimented with pea plants.• The “Father of Genetics”.The “Father of Genetics”.

Dominant & RecessiveDominant & Recessive

• Genes:Genes: Units of heredity. Each Units of heredity. Each organism carries two genes for organism carries two genes for each characteristic. each characteristic.

• Dominant:Dominant: the trait that is the the trait that is the stronger of the two. (D)stronger of the two. (D)

• RecessiveRecessive: The weaker of the two : The weaker of the two traits that is masked by the traits that is masked by the dominant trait. (d)dominant trait. (d)

Symbols of Genetics:Symbols of Genetics:

• Geneticist:Geneticist: a scientist who studies a scientist who studies heredity. heredity.

• P1 GenerationP1 Generation: Parental or 1: Parental or 1stst generation.generation.

• F1 GenerationF1 Generation: Filial or 2: Filial or 2ndnd generation. generation.

• F2 GenerationF2 Generation: 3: 3rdrd generation. generation.

Principals of GeneticsPrincipals of Genetics

• Traits are passed from one Traits are passed from one generation to the next.generation to the next.

• Traits are controlled by genes.Traits are controlled by genes.• Organisms inherit one gene from Organisms inherit one gene from

each parent.each parent.• Some genes are dominant and Some genes are dominant and

some recessive.some recessive.

Continued:Continued:

• Dominant genes hide recessive Dominant genes hide recessive genes. (Dd)genes. (Dd)

• Some genes are neither dominant Some genes are neither dominant or recessive. They have or recessive. They have Incomplete Incomplete DominanceDominance (RW). (RW).

• Purebred:Purebred: (PP or pp) same genes (PP or pp) same genes• Hybrid:Hybrid: (Pp) different genes. (Pp) different genes.

Probability:Probability:

• The possibility, or likelihood, that a The possibility, or likelihood, that a particular event will take place. It is particular event will take place. It is used to predict the results of used to predict the results of genetic crosses. genetic crosses.

Punnett SquarePunnett Square

• A special chart is used to show the A special chart is used to show the possible gene combinations in a possible gene combinations in a cross between two organisms.cross between two organisms.

• Developed by Reginald C. Punnett, Developed by Reginald C. Punnett, an English geneticist. an English geneticist.

A white rabbitA white rabbit

• PhenotypesPhenotypes: physical appearance : physical appearance or what an organism looks like or what an organism looks like (white).(white).

• Genotypes:Genotypes: The gene make-up of The gene make-up of the organism. BB or Bb or bb.the organism. BB or Bb or bb.

• A white rabbit: Phenotype? A white rabbit: Phenotype? Genotype?Genotype?

ChromosomesChromosomes

• Walter SuttonWalter Sutton: an American : an American graduate student. graduate student.

• Developed the Developed the Chromosome Chromosome Theory of GeneticsTheory of Genetics..

• Genes are carried from parents to Genes are carried from parents to offspring on chromosomes.offspring on chromosomes.

• They are found in the nucleus and They are found in the nucleus and produce proteins.produce proteins.

Mitosis: Cell DivisionMitosis: Cell Division

• MitosisMitosis: One cell divides into two : One cell divides into two identical cells. This happens in 4 identical cells. This happens in 4 phases or steps.phases or steps.

MeiosisMeiosis

• A process of cell division that A process of cell division that produces sex cells: egg and sperm. produces sex cells: egg and sperm.

• Each cell contains half the number Each cell contains half the number of chromosomes as the original of chromosomes as the original cell. cell.

DNADNA

• Deoxyribonucleic acidDeoxyribonucleic acid• Stores and passes on genetic Stores and passes on genetic

information from one generation to information from one generation to the next. the next.

• James Watson & Francis CrickJames Watson & Francis Crick (1962) discovered it. (1962) discovered it.

• Chromosomes are made up of DNA. Chromosomes are made up of DNA. DNA contains the genes.DNA contains the genes.

Structure of DNAStructure of DNA

• A twisted ladder, the steps are the A twisted ladder, the steps are the nitrogen bases. nitrogen bases.

• Adenine (A)Adenine (A)• Guanine (G)Guanine (G)• Cytosine (C)Cytosine (C)• Thymine (T)Thymine (T)• A only pairs with T.A only pairs with T.• G only pairs with C.G only pairs with C.

DNA ReplicationDNA Replication

• The process of DNA forming exact The process of DNA forming exact copies or duplicates.copies or duplicates.

• The DNA ladder unzips at the two The DNA ladder unzips at the two nitrogen bases. nitrogen bases.

• Free nitrogen bases match up with Free nitrogen bases match up with the pairs to make an exact copy. the pairs to make an exact copy.

Inherited DiseasesInherited Diseases

• Sometimes a structure of a gene Sometimes a structure of a gene contains an error. contains an error.

• Sickle Cell Anemia, Muscular Sickle Cell Anemia, Muscular Dystrophy.Dystrophy.

• Sex-linked traits carried only on the Sex-linked traits carried only on the X chromosome. X chromosome.

Hemophilia & ColorblindnessHemophilia & Colorblindness