Classical Genetics Flashcards
What is a gene?
Unit of inheritance usually responsible for one or two traits
What is an allele?
The two alternate forms of a gene
What does homozygous mean?
Identical alleles for the same gene
What does heterozygous mean?
Having different alleles for the same gene
What is a genotype?
The allele composition
What is a phenotype?
The physical expression of allele composition
What is the dominant trait?
The trait that is expressed
What is a recessive trait?
Only expressed in homozygous condition
What is a monohybrid cross?
A cross involving one trait
What is a test cross?
Cross the individual of the unknown genotype with an individual with a recessive genotype
What are Mendel’s Laws of Inheritance?
1st Law: Law of Segregation
2nd Law: Law of Independent Assortment
3rd Law: Law of Dominance
What is the 1st Law: Law of Segregation?
During gamete formation, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene
What is the 2nd Law: Law of Independent Assortment?
Genes for different traits can segregate independently during the formation of gametes
What is the 3rd Law: Law of Dominance?
Some alleles are dominant while others are recessive
An organism with at least one dominant allele will display the effect of the dominant allele
What is incomplete dominance?
When two alleles are equally dominant they produce a new phenotype
RR is red
rr is white
Rr is pink
What is codominance?
Both dominant alleles are fully expressed but in different cells
RR is red
rr is white
Rr is red and white spots
What are polygenic traits?
A single trait is determined by multiple genes
What are epistatic gene?
A gene that masks the expression of another gene or genes
What does multiple alleles mean?
When traits are determined by more than two alleles
The most commonly seen trait is called the wild type
Non wild types are mutant
What are sex linked traits?
Traits that are determined by genes located on sex chromosomes
A male needs just one of the recessive alleles to display the phenotype
A female needs both recessive alleles to express the phenotype
What is a linkage group?
Group of linked genes on a chromosome
What is a locus?
A specific location along a chromosome there a particular gene is found
What is a marker gene?
A gene with an easily identifiable phenotype that is used to trace the inheritance of other genes that are difficult to identify
Must on the same chromosome and very close together