Mendelian Genetics and Biotechnology OBJECTIVE: 12.01 Define key genetic terms related to agriscience research and biotechnology.

Terms DNA Deoxyribonucleic Acid- the major nucleic acid in organisms carries genetic information, and is responsible for the transmission of traits.

Terms Gene- segment of DNA that codes for a specific trait in an organism.

Terms Allele- an alternative form of a gene / trait. Ex: eye color- alleles = blue, green, hazel, brown, etc. Homozygous- organism with identical alleles for a given trait- can be dominant or recessive. Ex: TT or tt Heterozygous- organism with different alleles for a given trait. Ex: Tt

Terms Phenotype- Genotype- the physical appearance of a trait in an organism- determined but not always indicative of the genetic makeup of the organism. Ex: tall or short Genotype- the genetic composition of an organism for a given trait- often cannot be determined by looking at an organism. Ex Tt or TT

Terms Recessive Gene / Allele- variation of a trait that can only be expressed in the absence of a dominant allele. Heterozygous individuals are carriers for recessive alleles.

Terms Dominant Allele / Gene- variation of a trait that is expressed over other variations of the same trait. Most common forms in natural populations. Some traits can be co dominant or exhibit incomplete dominance.

Terms Chromosome- long condensed strand of DNA forming in the nucleus of a cell prior to cell division. Form pairs that when split, create an exact copy of DNA in the daughter cell.

Terms Chromatid pairs- X-shaped structures that serve as the mechanism for the transmission of genetic material during cell division. They are pulled apart in the process of mitosis and meiosis.

Punnett Squares method utilizing the known genotypes of parent organisms to predict the expression of a given trait or traits in offspring. Must know the genotype of parents and the inheritance pattern of the trait.

Punnett Squares Conducting Tests A box should be drawn with one space for each allele expressed by both parents. (in simple heredity, like pea height, boxes are 4x4) The alleles for one parent should be placed above each column at the top, with the alleles for the other placed beside each row on one side. The alleles of each parent should be distributed across and down the box.

Punnett Square Example 1   T TT Homozygous Dominant t Tt Heterozygous Tt hereozygous Genotype Ratio-2:2:0 Phenotype Ration- 4:0

Punnett Square Example 2   TG Tg tG tg TTGg TTgg TtGg Ttgg Genotype Ratio- 0:4:4:4:4:0 Phenotype Ratio- 0:8:8:0

Process of Simple Heredity Definition- heredity is best described as the manner in which inheritable characteristics (traits) are passed from parents to offspring. Heredity is a direct outcome of the RANDOM genetic recombination resulting during sexual reproduction. ***ONLY FUNCTIONS IN SEXUAL REPRODUCTION ***ENSURES GENETIC DIVERSITY Heredity determines the genetic potential of an animal, but… HEREDITY & ENVIRONMENTAL INFLUENCES determine the overall quality of an animal.

Types of Heredity Simple Heredity Complex Heredity One gene controls one trait- alleles are either dominant or recessive. Ex: height & color in pea plants Complex Heredity Polygenic Inheritance- one trait is controlled by several genes and possibly environmental factors- genes may even be located on different chromosomes. This is a slow process requiring many generations to achieve desired results. Ex: height in humans Codominance - multiple alleles for a given trait are not expressed over one another, but in combination. Ex: RR (Red Flower) x WW (White Flower) = RW (Red & White Striped Flower) Incomplete Dominance - similar to codominance, except characteristics of alleles blend instead of remaining distinct. Ex: RR (Red Flower) x WW (White Flower) = RW (Pink Flower)

Heredity in Agriscience Huge factor in successful agricultural selective breeding programs. Processes of heredity manipulated to create high quality HYBRID offspring. Plants and animals are inbred through several generations to isolate a specific trait or traits. NO MORE THAN 7 GENERATIONS TO PREVENT GENETIC DISORDERS The final generation of two different lines inbred for different traits are crossed producing offspring with the beneficial traits of both lines. Resulting offspring possesses hybrid vigor. Hybrid vigor usually lasts only one generation, as hybrid organisms rarely express traits true to type in offspring. Alternative forms of the gene resurface in the new cross.