Genetics and Heredity Chapter 8

Mendel Studied 7 Characters in the Garden Pea (Pisum sativum) Flower color. Flower position. Seed color. Seed shape. Pod color. Pod shape. Stem length.

Mendel’s Methods Cross-pollination- the transfer of pollen from one plant to the stigma of another. –Self-pollination –Artificial cross-pollination Monohybrid crosses- an experimental cross between individuals that differ by a single trait. First (F 1 ) and second (F 2 ) generations.

Mendel’s F 1 Observations One of the traits could be seen in the F 1 generation= Dominant One of the traits could not be seen in the F 1 generation= Recessive 100% Purple

Genetic Terminology Phenotype- an organisms traits. Genotype- an organisms genetic makeup. Homozygous- identical alleles for a gene. Heterozygous- two different alleles for a gene.

Genetic Terminology #2 Allele- one of 2 or more alternative forms of the same gene. Gene- a sequence of DNA that codes for a protein. Locus- the position on a chromosome occupied by a gene. W w

Mendel’s F 2 Observations Flower color –Purple:white 705:224 3:1

Mendel’s Dihybrid Cross 315:108:101:32 = 9:3:3:1

Mendel’s Work Yielded These Genetic Rules Alternative versions of genes (different alleles) account for variations in inherited characters. For each character an organism inherits two alleles, one from each parent. If two alleles differ, then one, the dominant allele is fully expressed in the organism’s appearance. The two alleles for each character segregate during gamete production. Alleles of a gene segregate independently of the alleles of other genes.

Punnett Squares and the Testcross Punnett square- a diagram used to predict the result of a genetic cross. Testcross- a genetic experiment used to determine an organisms genotype. ? ? w w w w W w W W Ww ww Ww

Incomplete Dominance Incomplete dominance- type of inheritance in which the F 1 is intermediate in phenotype between the parents. Neither allele is dominant. Self-pollination of the F 1 yields a 1:2:1 F 2 population.

Continuous Variation Continuous variation- a gradation in phenotype; indicates that a trait is controlled by two or more genes. –Polygenic inheritance.

Linkage Linkage- the tendency for certain genes to be inherited together, owing to the fact that they are located on the same chromosome. Linked genes- genes that are inherited together.

Genetically Engineered Rice

Genetically Modified Rice

Genetic Engineering Genetic Engineering- the technique of removing, modifying, or adding genes to a DNA molecule. –Improvements in crops Longevity Resistance to insects Resistance to herbicides

Transgenic Plants Tomato with BT gene and without. Transgenic tomatoes with and without etr1-1 gene. Petunia with and without etr1-1 gene. Tobacco with and without a cytokinin gene.

Transfer of Genes

Agrobacterium tumefaciens

Genomics Genomics- a field of genetics that attempts to understand the content, organization, function, and evolution of genetic information in a whole organism.

Arabidopsis thaliana

Genome Genome- all of the genetic information of an organism.