Plant Genetics

Genetics can be defined as A. the study of genes. B. the inheritance of physical traits. C. the study and inheritance of DNA. D. the study and inheritance of chromosomes E. all of the above.

Genetics can be defined as A. the study of genes. B. the inheritance of physical traits. C. the study and inheritance of DNA. D. the study and inheritance of chromosomes E. all of the above.

How are traits inherited from one generation to another?

The genetic mechanism that controls the trait is transferred through gametes from parents to their offspring.

How are gametes formed in the parents?

Meiosis

Do the gametes have the same number of chromosomes as regular somatic cells?

Gametes have half the chromosome number as regular somatic cells.

Meiosis Reduction of chromosome number by half Production of gametes - egg (ovary), pollen (anthers) Two divisions each with phases

If a root tip cell nucleus of onion has 16 chromosomes, how many chromosomes are in a pollen cell nucleus of onion? A. 0 B. 4 C. 8 D. 16 E. 32

If a root tip cell nucleus of onion has 16 chromosomes, how many chromosomes are in a pollen cell nucleus of onion? A. 0 B. 4 C. 8 D. 16 E. 32

Where are the genetic information stored?

Chromosomes

Character vs. Trait Seed color Plant height Alleles: codes for each trait

Dominant traits traits that always appear and that we see Recessive traits traits that disappear or recede into the background and only show up in a few generations.

These type of traits are controlled by two alleles. P (dominant) p (recessive) Homozygous PP or pp Heterozygous Pp or pP This combination is called the genotype

Phenotype The physical appearance of the plant is called the phenotype. One dominant allele is needed to show the dominant phenotype. Two recessive alleles is needed to show the dominant phenotype.

Flower color example Pink White

Punnett Square

Monohybrid Cross

Dihybrid Cross

9:3:3:1 ratio

Testcross

Review We know that P (purple flower) is dominant over p (white flower). We wanted to test the genotype of a plant with purple flowers. After a testcross experiment we counted 46 purple flowers and 48 white flowers. What is the genotype of interest? PP Pp pp

Review We know that P (purple flower) is dominant over p (white flower). We wanted to test the genotype of a plant with purple flowers. After a testcross experiment we counted 46 purple flowers and 48 white flowers. What is the genotype of interest? PP Pp pp

Review Monohybrid Cross 3:1 Dihybrid cross 9:3:3:1 Test Cross Homozygous dominant Heterozygous

No dominance, incomplete dominance Important for phenotype, phenotype ratios change

No dominance, incomplete dominance Important for phenotype, phenotype ratios change Genotypic ratios stay the same

No dominance, incomplete dominance Important for phenotype, phenotype ratios change Genotypic ratios stay the same F 1 phenotype is intermediate of both parents

No dominance, incomplete dominance Important for phenotype, phenotype ratios change Genotypic ratios stay the same F 1 phenotype is intermediate of both parents F 2 phenotypic ratios same as genotypic ratios - 1Red:2Pink:1White

Incomplete Dominance F1: all intermediate F2: 1R:2P:1W ratio

In a cross between a red flowered plant and a white flowered plant, what would be the color of the flowers in the progeny if red flower color was incompletely dominant to white color, flower color is controlled by a single locus, and both parents were completely homozygous for flower color?  A. Red  B. Pink  C. White  D. Red and white  E. None of the above

In a cross between a red flowered plant and a white flowered plant, what would be the color of the flowers in the progeny if red flower color was incompletely dominant to white color, flower color is controlled by a single locus, and both parents were completely homozygous for flower color?  A. Red  B. Pink  C. White  D. Red and white  E. None of the above

If I were to cross a sweet pea plant that had red flowers and round pollen grains with a plant that white flowers and long pollen grains, what would be the phenotype of the offspring? Assume that red flowers are dominant to white flowers and long pollen grains are recessive to round pollen grains. Also assume that both traits exhibit complete dominance and both parents are homozygous for both traits.  A.Red flowers, long pollen grains  B. Red flowers, round pollen grains  C. White flowers, long pollen grains  D. White flowers, round pollen grains  E. Pink flowers, round pollen grains

If I were to cross a sweet pea plant that had red flowers and round pollen grains with a plant that white flowers and long pollen grains, what would be the phenotype of the offspring? Assume that red flowers are dominant to white flowers and long pollen grains are recessive to round pollen grains. Also assume that both traits exhibit complete dominance and both parents are homozygous for both traits.  A.Red flowers, long pollen grains  B. Red flowers, round pollen grains  C. White flowers, long pollen grains  D. White flowers, round pollen grains  E. Pink flowers, round pollen grains

Law of Segregation Alleles segregate during meiosis and then come together randomly during fertilization.

Law of Independent Assortment Each pair of alleles segregate independently during meiosis.

Practice DominantRecessive Yellow (Y) Round (R) Green (y) Wrinkled (r) YYRr x YyRr yyRr x Yyrr