GENETICS
,Genetics: branch of biology that studies inheritance and variation in organisms
Gegor Mendel (1822-1884) - father of genetics
● Austrian monk
● Investigated the transfer of characteristics from one generation to the next
● Experiments on pea-pants
, Concepts of inheritance - results in similarities and differences between parents and their
offspring
● Chromosomes - long, intertwined threads made up of a strand of DNA wound around
histones. Only visible when a cell is dividing
● Chromatic network - network of intertwined chromosomes. Visible even when the cell is
not dividing
● Genes - a section of DNA that controls a hereditary characteristic
- Genome - the complete set of genetic instructions necessary to create an organism
- Different genes are activated in different cells e.g) genes making proteins are active in
many types of cells and some are non-coding
● Alleles - variation of a gene
- Control different versions of a characteristic found in the same position on the
homologous chromosomes
- Only 2 possible versions of alleles for each gene - one from mother and one from father
- Passed on by the chromosomes in the gametes
● Dominant alleles
- This characteristic is expressed in the phenotypes of the offspring
● Recessive alleles
- This characteristic is suppressed in the presence of the dominant allele and not
expressed in the phenotype of the offspring. Only expressed when there is no dominant
allele present.
● 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.
● Genotype - genetic makeup of an organism
● Phenotype - physical appearance of an organism. Shaped by its genotype and external
factors like diet, exercise and environment
● Homozygous - the pair of alleles at a locus (place) are the same
● Heterozygous - the pair of alleles at a locus are different. Called a hybrid
,Genetics: branch of biology that studies inheritance and variation in organisms
Gegor Mendel (1822-1884) - father of genetics
● Austrian monk
● Investigated the transfer of characteristics from one generation to the next
● Experiments on pea-pants
, Concepts of inheritance - results in similarities and differences between parents and their
offspring
● Chromosomes - long, intertwined threads made up of a strand of DNA wound around
histones. Only visible when a cell is dividing
● Chromatic network - network of intertwined chromosomes. Visible even when the cell is
not dividing
● Genes - a section of DNA that controls a hereditary characteristic
- Genome - the complete set of genetic instructions necessary to create an organism
- Different genes are activated in different cells e.g) genes making proteins are active in
many types of cells and some are non-coding
● Alleles - variation of a gene
- Control different versions of a characteristic found in the same position on the
homologous chromosomes
- Only 2 possible versions of alleles for each gene - one from mother and one from father
- Passed on by the chromosomes in the gametes
● Dominant alleles
- This characteristic is expressed in the phenotypes of the offspring
● Recessive alleles
- This characteristic is suppressed in the presence of the dominant allele and not
expressed in the phenotype of the offspring. Only expressed when there is no dominant
allele present.
● 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.
● Genotype - genetic makeup of an organism
● Phenotype - physical appearance of an organism. Shaped by its genotype and external
factors like diet, exercise and environment
● Homozygous - the pair of alleles at a locus (place) are the same
● Heterozygous - the pair of alleles at a locus are different. Called a hybrid
