Glossary of Bio 181: Genetics

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Definition of Genetics
Study of heredity and variation in organisms.
Inherited traits are specified by discrete factors. What are the properties of these factors?
1. Factors assort independently during gamete (egg and sperm) formation.
2. New combinations of factors forc during fertilization (zygote formation).
3. Traits are specified by genes, which are parts of chromosomes.
Inbred (true-breeding)
Homozygous for both alleles.
What are the names of the three first generations of crosses?
1. parent
2. F1
3. F2
Monohybrid cross
Cross involving parents differeing in only one trait.
Dominant trait
A trait expressed preferetially over another trait.
Recessive trait
The opposite of dominant. A trait that is preferentially masked.
Reciprocal cross
Using male and female gametes for two different traits, alternating the source of gametes.
Ex. white-male & purple-female, to white-female & purple-male.
F1 Generation
Offspring of a cross between true breeding plants.
F2 Generation
Offspring of a cross involving F1 generation.
What is the phenotypic ratio for a monohybrid heterozygous cross?
In what type of cell division and phase do cells become haploid?
Meiosis 1, Anaphase
What does diploid mean?
2 copies of each chromosome, and thus two versions of each gene (different alleles).
The physical representation of a genetic trait.
The genetic representation of a trait (the genetic constitution).
The differing forms of a gene.
Ex. Y and y, for Y=yellow, y=green.

Alleles occupy the same locus, or position, on chromosomes.
Bothe alleles for a trait oare the same. They can be homozygous dominant (YY), or homozygous recessive (yy).
Differing alleles for a trait, such as Yy.
What tool is commonly used to solve genetic problems?
Punnett Square
Test Cross
A cross used to determine the genotype (homozygous or heterozygous) of an individual with the dominant phenotype. The unknown genotype is crossed with homozygous recessive plants. The F1 genotype can then be determined by the phenotypes obtained.
What is an example of the monohybrid cross?
1. Human Rh-factor (Rh+ and Rh-)

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