Classwork Series and Exercises {Basic Science – JSS2}: Genetics

Topic: Family Traits (Genetics)

Meaning of Genetics, heredity and Variation

Genetics: is defined as the study of heredity and variation in living things.The study of heredity, or how the characteristics of living things are transmitted from one generation to the next. Every living thing contains the genetic material that makes up DNA molecules. This material is passed on when organisms reproduce. The basic unit of heredity is the gene.

Genetics is the process of a parent passing certain genes to their children. A person’s appearance — height, hair color, skin color, and eye color — is determined by genes. Other characteristics affected by heredity are:

• Likelihood of getting certain diseases
• Mental abilities
• Natural talents

An abnormal trait (anomaly) that is passed down through families (inherited) may:

• Have no effect on your health or well-being — for example, the trait might just cause a white patch of hair or an earlobe that is longer than normal
• Have only a minor effect — for example, color blindness
• Have a major effect on your quality or length of life

Heredity (Inheritance): is defined as the transmission of characters from parents to offspring via genes. It is responsible for the similarity and small differences between parents and offspring. Heredity is the sum of the qualities and potentialities genetically derived from one’s ancestors. It is also defined as the transmission of traits from ancestor to descendant through the molecular mechanism lying primarily in the DNA or RNA of the genes. Heredity is the passing of phenotypic traits from parents to their offspring, either through asexual reproduction or sexual reproduction. This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism.

Variation: is defined as the differences which exist between parents and offspring as well as among the offspring.Variation, is any difference between cells, individual organisms, or groups of organisms of any species caused either by genetic differences (genotypic variation) or by the effect of environmental factors on the expression of the genetic potentials (phenotypic variation).

Therefore, family traits are those inherited characters, which show variations among members of a family. Some characters that are genetically transferred from parents to offspring include skin, colour, height, size of nose and some genetic disease conditions such as albinism, sickle cells anaemia, colour blindness, etc.

Meaning of Dominant and Recessive Traits

Dominant Traits: These are trait that keeps appearing in each successive generation.

Recessive Traits: These are trait present in a living organism, yet they do not appear physically because of the dominant trait in the offspring, but may suddenly appear in successive generation.

For example, a dominant tall man (AA) who married a recessive short woman (aa) may not produce any short child or children. But the children having the recessive traits or genes may produce short child or children by the second generation.

Comparison between Dominant and Recessive Traits

Dominant Traits	Recessive Traits
Traits are manifested outwardly	Traits are not manifested outwardly
Traits are controlled by dominant genes	Traits are controlled by the recessive genes

Importance of Family Traits

a) Intelligence: Intelligent parents usually give birth to intelligent children. This trait (character) seems to be continuous in most family generations.

b) Diseases: The study of family traits has helped in the understanding of some genetic diseases like albinism, sickle cell anaemia, colour blindness, etc. Prospective spouses are counseled to check their genetic make-up before entering into marriage to avoid transmitting genetic diseases.

c)  Resemblance: Family trait also helps to identify a member of a particular family.

d) Family Genealogy: One can easily trace a person’s ancestor (lineage) and predict his present and future characteristics through the family traits.