Inheritance Flashcards
Allele
Alternative form of a gene
Locus
the specific position of a gene on the chromosome
Phenotype
Observable characteristics of an organism which are the result of genotype and environment
Genotype
The alleles present within cells of an organism, for a particular trait or characteristic.
Dominant
Only a single allele is required for the characteristic to be expressed, that is the allele that is always expressed in the phenotype.
Recessive
the characteristic is only expressed if there is no dominant allele present.
Homozygous
Two identical alleles.
Heterogeneous
Two different alleles.
Codominance
both alleles contribute to the phenotype.
Linkage
Is the phenomenon where genes for different characteristics, located at different loci on the same chromosome are linked
Monogenic inheritance
When a phenotype or trait is controlled by a single gene. For instance, cystic fibrosis where individuals with doubly recessive phenotype are affected.
DiHybrid cross
Inheritance of two genes.
Sex linkage
Expression of an allele dependent on the gender of the individual as the gene is located on a sex chromosome.
Autosomal linkage
Genes which are located on the same chromosome and tend to be expressed together in the offspring
Codominace
When both alleles are expressed in a heterozygote, that is, both alleles contribute to the phenotype. Examples include blood type.
Epistasis
The interaction of different loci on the gene, one gene locus affects the other gene locus. One gene loci can either mask or suppress the expression of another gene locus.
Recessive epistasis
Occurs when the presence of a recessive allele prevents the expression of another allele at a second locus. Recessive epistasis gives the ratio 9:3:4.
Dominant epistasis
When a dominant allele at one locus completely masks the allele at the second locus. Dominant epistasis gives a ratio 12:3:1.
Carcinogen
A type of mutation that causes cancer.
Chi-Squared test
A statistical test used to determine whether a pattern of inheritance is statistically significant
Degrees of freedom
The number of categories minus one.
Down’s syndrome
A genetic disorder characterised by delayed development and learning difficulties. Due to non-disjunction, an affected individual possesses three copies of chromosome 21
Duchenne muscular dystrophy (DMD)
An X-linked recessive condition characterised by muscle degeneration and weakness. It is more common among males because they only inherit one X chromosome.
Sickle cell anaemia
A recessive genetic disorder caused by a substitution mutation on chromosome 11. This results in abnormal haemoglobin which distorts red blood cells.
