Question

1. define the following terms:

a. genetics -
b. heredity -
c. trait -
d. allele -
e. gene -

1. who was gregor mendel? what did he use in his experiments for genetics?
2. what is the difference between dominant and recessive allele? how is each expressed?
3. what is difference between genotype and phenotype?
4. what is the difference between homozygous and heterozygous?
5. a tt (tall) plant is crossed with a tt (short plant). what percentage of the offspring will be tall? (show your work!)
6. a tt plant is crossed with a tt plant. what percentage of the offspring will be short? (show your work!)
7. a heterozygous round seeded plant (rr) is crossed with a homozygous round seeded plant (rr). what percentage of the offspring will be homozygous (rr)? (show your work!)

Explanation:

a. Genetics is the study of genes, heredity, and variation in living organisms.
b. Heredity is the passing - on of traits from parents to their offspring.
c. A trait is a characteristic or feature of an organism.
d. An allele is one of two or more alternative forms of a gene.
e. A gene is a basic unit of heredity, made up of DNA.

1. Gregor Mendel was an Austrian monk known as the father of modern genetics. He used pea plants in his genetics experiments.
2. A dominant allele is expressed when present in either the homozygous or heterozygous state, while a recessive allele is only expressed when in the homozygous recessive state.
3. Genotype refers to the genetic makeup of an organism, while phenotype is the observable physical or biochemical characteristics of an organism resulting from its genotype and the environment.
4. Homozygous organisms have two identical alleles for a particular gene, while heterozygous organisms have two different alleles for a particular gene.
5. When a TT (tall) plant is crossed with a tt (short) plant, all offspring will have the genotype Tt. Since the T (tall) allele is dominant, 100% of the offspring will be tall.
6. When a Tt plant is crossed with a Tt plant, the Punnett - square shows genotypes TT : Tt : tt in a 1:2:1 ratio. Since the recessive short trait is only expressed in the tt genotype, 25% of the offspring will be short.
7. When a heterozygous round - seeded plant (Rr) is crossed with a homozygous round - seeded plant (RR), the genotypes of the offspring are RR and Rr in a 1:1 ratio. So 50% of the offspring will be homozygous (RR).

Answer:

a. The study of genes, heredity, and variation in living organisms.
b. The passing - on of traits from parents to offspring.
c. A characteristic or feature of an organism.
d. One of two or more alternative forms of a gene.
e. A basic unit of heredity made up of DNA.

1. An Austrian monk known as the father of modern genetics; pea plants.
2. Dominant allele is expressed in homozygous or heterozygous state, recessive allele is only expressed in homozygous recessive state.
3. Genotype is genetic makeup, phenotype is observable characteristics.
4. Homozygous has two identical alleles, heterozygous has two different alleles.
5. 100%
6. 25%
7. 50%