Genetics: Heredity & Traits
Genetics is the study that focuses on the transfer of traits from parents to the offspring. Knowledge of Punnett squares, DNA, and genes would be fundamental in the understanding of how traits are inherited to subsequent generations and how genetic diversity is developed within living organisms.
1. Punnett Squares
A Punnett square is a diagram used to establish the likelihood of certain traits in offsprings to be passed on by their parents. It is used in picturizing the way the offspring combine alleles.
How Punnett Squares Work:
The square is divided into boxes that express potential genotypic variation from the parents.
Going around the square, the alleles are listed down for each parent.
As observed in the boxes, the possible combinations of alleles that the offspring may inherit are presented.
Dominant and Recessive Traits:
The dominant alleles are denoted with capital letters (e.g., A), and only one copy is sufficient for expressing the trait.
Recessive alleles are denoted by small letters (e.g. a) and both have to be present for them to be expressed.
Example:
In case a parent is Aa (heterozygous) and the other is Aa, then the Punnett square will report 25% possibility for the offspring to be AA, 50% ability of Aa, and 25% possibility of aa.
2. DNA (Deoxyribonucleic Acid)
DNA is the instructional substance for life itself. It is present in every cell of an organism and is important in inheritance and cell function.
Structure of DNA:
DNA takes the form of a double helix, in the form of a twisted ladder. The rungs of the ladder are composed of pairs of nitrogen bases. Adenine (A) binds with Thymine (T) while Cytosine (C) binds with Guanine (G).
Function of DNA:
DNA includes instructions required in constructing proteins that are behind most of the functions in a cell.
It also has information on genes that can be transferred from one generation to the other, hence offspring acquire their parent’s traits.
3. Genes
Genes are parts of DNA to specify certain traits. They give instructions concerning the manufacture of proteins that regulate the manner in which cells operate and how traits are portrayed.
Gene Expression:
There are genes that are not active all the time. The practice that leads to the expression of a gene to transform it to the corresponding protein is referred to as gene expression.
Alleles and Trait Inheritance:
There exist different variants of a gene known as alleles. They can be dominant or recessive alleles, and the combination of both parent’s alleles determines which trait is passed down to the offspring.
Example:
The eye color gene has various modes, including brown-eye allele (B), and blue-eye allele (B). One with BB or Bb will have brown eyes, whereas if it is bb, then the person will have blue eyes.