Genetics Flashcards
Define genetics
The study of how genetic characteristics are passed down from parents to the child
Define genus locus
The exact position of a gene on a chromosome
Define allele
Different forms of a gene which occur in the same locus on homologous chromosomes
Mendel’s Law of Dominance
When two homozygous organisms with contrasting characteristics are crossed, all the individuals of the F1 generation will display the dominant trait
An individual that is heterozygous for a particular characteristic will have the dominant trait as the phenotype
Define genotype
The genetic composition of an individual
Define phenotype
The physical appearance of an organism based on the genotype and the environment; how the genes are expressed in that individual
Define homozygous
Two alleles for a characteristic are the same
Define heterozygous
Two alleles for a characteristic are different
What is the dominant allele?
An allele that is expressed in the phenotype when found in both heterozygous (Tt) and homozygous (TT) conditions
What is the recessive allele?
An allele that is masked in the phenotype when found in heterozygous (Tt) conditions and only expressed in homozygous (tt) conditions
Mendel’s Principle of Segregation
An organism possesses two factors (alleles) which separate/segregate so that each gamete contains only one of these factors (alleles)
Half the gametes carry one allele and the other half carry the other allele
Mendel’s Principle of Independent Assortment
The various ‘factors’ controlling different characteristics are separate entities, not influencing each other in any way, and sorting themselves out independently during gamete formation
(The allele a gamete receives for one gene does not influence the allele received for another gene)
Complete dominance
The dominant allele completely masks expression of the recessive allele in heterozygous conditions
Incomplete dominance
Neither one of the two alleles of a gene is dominant over the other, resulting in an intermediate phenotype in heterozygous conditions
Co-dominance
Both alleles are expressed equally in the phenotype (patchy cow example)
Multiple alleles
Genes which have more than two alternatives at the same locus
What type of dominance is seen in inheritance of blood groups
Partly co-dominance and partly complete dominance
Define polygenic characteristics
Characteristics which are the result of multiple genes
What are gonosomes?
X and Y sex chromosomes
What are sex-linked genes?
Genes carried by the gonosomes
Is the allele for colour-blindness dominant or recessive?
Recessive
On which sex chromosome, X or Y, is colour-blindness carried?
X chromosome
Is the allele for haemophilia dominant or recessive?
Recessive
On which sex chromosome, X or Y, is haemophilia carried?
X chromosome
What is a mutation?
A permanent change to the DNA of a cell
The two types of mutations
Gene mutations and chromosomal mutations
What is the function of a pedigree diagram?
Used to study/trace the inheritance of a characteristic over many generations
