Breeding and Genetics Exam 1

Chromosome

A thread like structure of nucleic acid (DNA) and protein that harbors genetic information

Locus

Location in the DNA

Gene

A DNA sequence that encodes a biologically important molecule

Allele

A variant in the DNA in a population

Dominance

When one allele at a locus masks expression of the other allele

Complete Dominance

Occurs when one allele at a locus completely masks expression of the second allele

Partial Dominance

When 1 allele at a locus partially masks expression of the second allele

No Dominance

Occurs when neither allele at a locus masks expression of the other allele

Over Dominance

Occurs when a heterozygous is superior or inferior to both homozygotes

Mendel’s First Law

At a locus, each allele has an equal chance of being inherited

Mendel’s Second Law

At 2 loci, the allele inherited at one locus is independent of which alleles are inherited at other loci

Linkage

When two loci on the same chromosome have a recombination rate less than 50%

Parental gamete

AB, ab

Recombinant Gamete

aB, Ab

Recombination Frequency

The probability that you produce a recombinant gamete between 2 loci

Double Recombinant

When two recombination events occur between two loci

Chromosomal interference

When the presence of one recombination event prevents nearby recombination events from happening

Haplotype

A group of alleles inherited together from a single parent

Sex-linked inheritance

A phenotype that is affected by a locus on a sex chromosome

Sex-influenced inheritance

A phenotype determined by the interaction between genotype and sex

Sex-limited inheritance

Phenotype is expressed only in one sex