AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

TERMINOLOGY

• Mendel used letters of the alphabet as symbols for factors (genes).
• The character that expresses itself in all the offspring of a monohybrid cross is termed dominant and the trait that fails to express is termed recessive.
• A capital letter signified a dominant and a lowercase letter a recessive member of a pair of alleles.
• The female parent is written first in genetic crosses.
• A female and a male gamete combine in fertilization to produce a zygote.
• Zygotes or individual organisms carrying two units of one allele (Example DD or dd) are homozygous and those with two alleles (Example: Dd) are heterozygous.
• A gene can have many different versions, called alleles.
• Phenotype : observable physical characteristics or visible expression of a trait .
• Genotype: actual gene constitution .
• Hybrids: The F1 progeny produced by two pure line parental generations are called hybrids.
• Monohybrid cross: A cross involving contrasting expression of one trait is called Monohybrid cross.
• Dihybrid: have two pairs of different characters.
• Polyhybrid: have more than two pairs of different characters.