Chapter 16 Mendelian Genetics Flashcards
Why were peas used as Mendels experimental organism?
- They were easy to grow.
- They were available in many distinguishable varieties.
- Strict control over mating was possible to ensure the parentage of new seeds.
Define true breeding.
The physical appearance of the offspring in each successive generation is identical the to previous one.
What were the results of Mendels first experiment involving a cross between two true breeding pea plants that varied in colour?
F1 generation was all purple.
F2 generation had 3/4 purple plants and 1/4 white plants.
Define monohybrid cross.
A cross between teo individuals differing in a single character.
How are round and wrinkled peas formed?
The dominant allele (round) codes for an enzyme that makes seeds round, while the recessive allele (wrinkled) codes for a defective enzyme resulting in wrinkled seeds.
What is the Law of Segregation?
The Law of Segregation states that the two alleles for a heritable character separate during gamete formation and end up in different gametes.
Differentiate between phenotype and genotype.
Phenotype is the physical appearance (purple) and genotype is the genetic makeup (Pp).
What is happens in a testcross and what does it determine?
A testcross determines the genotype of an individual.
Breed the mystery individuals with a homozygous recessive individual. If any offsprings display recessive phenotype, the individual must be heterozygous.
What is the Law of Independent Assortment?
The Law of Independent Assortment states that the two copies of each gene segregate into gamete independently of the two copies of another gene.
What is a dihybrid cross?
A cross between F1 dihybrids. Crossing two true-breeding parents differing in 2 characters produces dihybrids (i.e. Heterozygous for both characters) in the F1 generation.
E.g. AaBb x AaBb
What phenotypic ratio does a dihybrid cross give?
Phenotypic ration 9:3:3:1.
How many genotypes are produced in a dihybrid cross?
9 different genotypes.
What is a dihybrid cross equivalent to?
Two monohybrid crosses.
When do you use the multiplication rule?
In calculating the chances for various genotyopes, each character is considered separately and then the individual probablities are multiplied together.
What is incomplete dominance?
The phenotype of F1 hybrids is somewhere between the ohenotyoes of the two parental variaties.
What is epistasis?
Genes that modify the phenotypic expression of other genes.
If the phenotypic ratio in the F2 generation from a dihybrid cross is 9:3:4 its most likely Epistasis.
What are the 4 indicators for a dominant allele?
- Affected individuals are equally likely to be females or males.
- Most matings that produce affected offsprings only have one affected parent.
- Among mating in which one parent is affected, half the offsprings are affected.
- Two affected parents can produce an unaffected child.
What are the indicators of a recessive trait.
- The trait may skip one or generations.
- Females and males are equally likely to be affected.
- Affected individuals often result from mating between relatives, typically first cousins.
- Two unaffected parents can produce an affected child.
