Lab Exercise 18 Classical Genetics Problems

F2 generation

offspring of the F1 generation The ratio of F2 represent a 3:1 ratio due to its physical appearance.

What are heterozygous alleles?

not identical

Each allele

is separated by separate gametes.

Genotype

Genetic Makeup; in F2 example, its written in a 1:2:1 ratio. 1PP:2Pp:1pp, one was homozygous dominant, two were heterozygous, and one was homozygous recessive.

What is meant by a sex-linked trait?

X-linked

F1 generation

hybrid offspring of the P generation

What are homozygous alleles?

identical

Homozygous

A pair of identical alleles for one of its characters; true-breeder. It can be dominant or recessive.

Character

*An inherited feature that varies among individuals. *Example: A character for a plant would be its flower color.

Gene

*defined as a specific sequence of nucleotides on the nucleic acid DNA that codes for a protein, or an RNA product; section of DNA. * Location: Chromosomes * Approximately 20,000 genes have been identified on human DNA.

What is the genotype of an organism?

The genetic Makeup.

Phenotype

The physical appearance of the trait.

What is the phenotype of an organism?

The physical appearance of the trait.

Genetic Cross

A breeding experiment in which two varieties of a plant are mated, or hybridized.

Monohybrid Cross

A breeding experiment that uses parental varieties that differ in one character, such as flower color. *Example: Two true-breeding parents being used.

Allele

An alternative form of a gene. Example: *AA same allele *aa same allele *Aa Diff Allele

P generation

Are the true-breeding parents

Trait

Each variant for a character; what the gene represents. *Example: The specific flower color being either purple or white. *Eye color gene

Monohybrid Cross Example

One has the purple flower color trait, and the other a white flower color. One of the flowers is dominant (purple) being fully expressed and one of the flowers is recessive (white), meaning that it is not expressed in the flower.

Problems Illustrating Sex-Linked Inheritance Patterns

Problem 1. A man with normal vision (C) marries a color-blind woman (c). The genotypes of the parents are: XCy x XcXc List the gametes of the parents. List the genotypes for both sexes. List the percent of the phenotypes for both sexes.

Problems Illustrating Incomplete (Dominant) Inheritance Patterns

Problem 1. Assume the following three genotypes of flowers: RR = red flower color, Rr = pink flower color, and rr = white flower color Two parents, one red (male) and one white (female), are mated. What are the genotypes of the parents? List the gametes for the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Classical Dominant-Recessive Inheritance

Problem 1. Assume two plant parents of Japanes maple trees, tall and dwarf: Their genotypes are Tt (male) x tt (female) List the gametes for male. List the gametes for female. List the percent of each genotype. List the percent of each phenotype, tall and dwarf.

Problems Illustrating Incomplete (Dominant) Inheritance Patterns

Problem 2. Assume two flowers, one pink (male) and one white (female). They are mated. What are the genotypes of the parents? List the gametes for the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Sex-Linked Inheritance Patterns

Problem 2. A heterozygous woman carrying the recessive gene for color-blindness marries a man who is color-blind. List the gametes of the parents, male and female. List the percent of the genotype for both sexes. List the percent of the phenotype for both sexes.

Problems Illustrating Classical Dominant-Recessive Inheritance

Problem 2. Assume two plant parents of Japanese maple trees, both tall phenotype, but hybrid genotype. They are: Tt (male) x Tt (female). List the gametes for male. List the gametes for female. List the percent of each genotype. List the percent of each phenotype, tall and dwarf.

Problems Illustrating Incomplete (Dominant) Inheritance Patterns

Problem 3. Assume that two pink flowers are mated. What are the genotypes of the parents? List the gametes of the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Sex-Linked Inheritance Patterns

Problem 3. A heterozygous woman carrying the recessive gene for hemophilia marries a man who is not a hemophiliac. Assume the dominant gene is XH, and recessive is Xh. List the gametes of the parents, male and femalee. List the percent of genotypes, for both sexes. List the percent of phenotypes, for both sexes.

Problems Illustrating Classical Dominant-Recessive Inheritance

Problem 3. Assume two human parents, both with type AB blood. What are the genotypes of the parents? List the gametes for the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Incomplete (Dominant) Inheritance Patterns

Problem 4. An example of incomplete dominance in humans is inheritance of the sickle-cell trait. This is an abnormal shape of the red pigment in blood, hemoglobin. It has a sickle shape with sticky ends, and has a tendency to clump together as it travels through the blood stream. The capillaries, the site of gas exchange, are very small in diameter, and red blood cells with this type of hemoglobin cannot travel through and clump up, prohibiting oxygenated blood from reaching tissues. This causes tissue death and multiple symptoms. Genotype SS stands for an all that doesn't code the sickle-shaped hemoglobin, & individuals with this trait is normal. Genotype Ss is heterozygous, & represents carries for the sickle cell trait. Their phenotype is not as severe than those that are homozygous recessive for the sickle cell trait. Genotype ss have sickle cell anemia. Assume the following parents: SS (male) x ss (female) List the gametes of the male. List the gametes of the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Classical Dominant-Recessive Inheritance

Problem 4. Assume two guinea pig parents, both with rough coat phenotype, but one is homozygous dominant (male). and one is heterozygous (female). Assume that rough coat (R) is dominant over smooth coat (r). What are the genotypes of the parents? List the gametes for the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Classical Dominant-Recessive Inheritance

Problem 5. Assume two guinea pig parents, with genotypes: Rr (male) x rr (female). List the gametes for the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Incomplete (Dominant) Inheritance Patterns

Problem 5. Assume two parents, both of who are carriers for sickle-cell anemia. What are the genotypes of the parents? List the gametes for the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Incomplete (Dominant) Inheritance Patterns

Problem 6. Assume two parents, one has sickle-cell disease (male), and the other is a carrier (female). What are the genotypes of the parents? List the gametes for the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

Problems Illustrating Classical Dominant-Recessive Inheritance

Problem 6. Assume two guinea pig parents, both true-breeding, one for the dominant coat of fur (male), and the other for the recessive coat of fur (female). What are the genotypes of the parents? List the gametes for the male. List the gametes for the female. List the percent of each genotype. List the percent of each phenotype.

How can one tell by looking at the results from a Punnett square that the trait displays incomplete dominance.

The heterozygous alleles will display a third phenotype, a blend between the two homozygous extremes.

Dominant & Recessive Trait

These two traits are the alleles, or alternative versions of genes, that account for variations in inherited characters.

What is a gene?

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Heterozygous

alleles are not identical in hybrids (F1 generation of P generation of purple and white flower)

Punnett Square

diagram showing the gene combinations that might result from a genetic cross.

Hybridization

the mating, or crossing, of two true-breeding varieties

When offspring self-pollinate

the new offspring is called F2