7.1: Inheritance Flashcards
Define what the phenotype is
The set of observable/measurable characteristics of an organism which results from the expression of the genotype and environmental influences
What does variation in phenotype in organisms lead to
leads to natural selection
Define what the genotype is
Complete set of alleles within an organism
Define what a dominant allele is
If present in the genotype, will always be expressed in the phenotype
Define what a recessive allele is
Only expressed in the phenotype when no dominant allele is present
Define what codominant alleles are
If both are present in the genotype, both are expressed in the phenotype
Define what monohybrid inheritance is
inheritance of a single pair of alleles, that codes for a single phenotypic characteristic
Define what dihybrid inheritance is
inheritance of two pairs of alleles, they may code for two different phenotypic characteristics, or they may only code for one due to epistasis
What is epistasis
Where two pairs of alleles code for only one phenotypic characteristic.
x -> y -> z
To get to z you need two pairs of alleles to code for two functional enzymes (page 7 in notes)
Describe what independent assortment is
occurs at metaphase 1 of meiosis
produces new combinations of alleles in the gametes where each allele from a pair can combine randomly with another allele from another pair
Describe the difference between non-linked and linked (autosomal linkage) dihybrid inheritance
In non-linked dihybrid inheritance, alleles of each gene is located on a separate pair of homologous chromosomes. Whereas in linked dihybrid inheritance, alleles of each gene (at least 2 genes) is located on the same autosomal chromosome
What does ‘autosomal chromosome’ mean
A numbered chromosome / not a sex chromosome
What is the significance of linked dihybrid inheritance compared to non-linked
with non-linked dihybrid inheritance, when two genes are on 2 different chromosomes, then there are four possible combinations of alleles. Whereas with linked dihybrid inheritance, when two genes are on the same chromosome, then there are only two possible combinations of alleles
Describe what crossing over is
Crossing over occurs at prophase 1 of meiosis, resulting in recombinant gametes, producing new combinations of alleles in the gametes. This is a rare event.
Describe what sex linked inheritance is
The expression of an allele dependent on the gender of the individual as the gene is located on a sex chromosome - X chromosome only
