Genetics Flashcards
What is a gene?
A discreet unit of DNA that codes for a protein.
Heritable factor.
What is a locus?
The position of gene on a chromosome.
What is an allele?
An alternative form of a gene that produces a distinguishable phenotypic effect.
What is a genotype?
The alleles contained in an organisms cells.
What is a phenotype?
The characteristics of an organism determined by it’s genotype and it’s environment.
What does homozygous mean?
An organism that possesses 2 identical alleles of the same gene.
What does heterozygous mean?
An organism that possesses 2 different alleles of the same gene.
What is a dominant allele?
Allele which is always expressed in the phenotype if it is present in the genotype.
What is a recessive allele?
Allele which is only expressed in the phenotype when the dominant allele is not present.
What is codominance?
When both alleles affect the phenotype of a heterozygous individual.
What is F1?
First filial generation, the first hybrid offspring of two pure breeding parents.
What is F2?
Second filial generation, the offspring from interbreeding the F1 generation.
• Crossing two true-breeding parents differing
in two characters produces dihybrids in the?
F1 generation, heterozygous for both
characters
What is the medelian law of segregation?
the members of a pair of homologous chromosomes segregate during meiosis and are distributed to different gametes.
When might Inheritance of characters by a single
gene deviate from simple Mendelian patterns?
— When alleles are not completely dominant or
recessive (incomplete dominance/codominance)
— When a gene has more than two alleles
— When a gene produces multiple phenotypes
What is epistasis?
In epistasis, a gene at one locus alters the
phenotypic expression of a gene at a second
locus
In mice and many other mammals, coat color
depends on two genes: one gene determines the
pigment color (with alleles B for black and b for
brown), the other gene (with alleles C for color
and c for no color) determines whether the
pigment will be deposited in the hair.
Crossing over between linked genes can
produce?
recombinant individuals
Alleles can show?
Complete dominance, codominance or incomplete dominance
