Inherited Traits

What are Inherited Traits?

Heredity is a process in which organisms acquire characteristics from their parents. These characteristics are known as traits. Every individual has a unique set of traits. The traits which are transferred by the parent to its offspring through the process of fertilization are called inherited traits. This inheritance is regulated by specific rules of heredity. Inherited traits are coded in our DNA and hence can be disseminated on to the next generation. Example: Eye color, height, Skin color, Colour of hair, etc.

For similar traits, there are two duplicates of genes in sexually reproducing individuals. In case the copies are not identical to each other, the characteristic or the trait is expressed as the dominant trait while the other is referred to as the recessive trait. These variations observed in the species can either impart survival benefits or lead to genetic drift.

However, if there are variations in the non-reproductive tissues that are due to ecological influences, these are not considered to be inherited. If the variation is linked with geographical isolation, then there are possibilities of speciation taking place. Evolutionary dynamics are evident in organisms when they are classified. Not only living species, but even the study of fossil fuels can help in the study of evolution.  The evolution of complex organs can be attributed to the survival benefits that take place at the transitional stages.

Evolution cannot be simply termed as progress to higher forms from lower forms, instead, it appears to have provided the biotic organisms with complicated body structures and designs at the same time when simpler structures are still thriving.

How Do Traits Get Expressed?

The proteins in the cell are made up of information coded in the cellular DNA. A segment of this DNA provides information for one protein and is called a gene for that protein. These genes influence traits. As per the Mendelian law, both parents equally support contribution of genes, and thus the child has a combination of a set of genes from both the parents. Gene sets are present as separate independent portions called chromosomes and not a single long thread of DNA. Therefore, each cell will have two copies of the chromosomal set, one from each parent. When germ cells combine, they will re-establish a normal number of chromosomes to ensure the stability of DNA in species.

Heredity Examples

Heredity is the passing of traits from parent to offspring. Molecules of DNA carry information that codes for various proteins.

 Heredity in Bacteria and Archaea

  • Bacteria and archaea reproduce with the help of binary fission. 

  • The procedure starts with the duplication of genetic material, followed by chromosome segregation, and then cytokinesis.

  •  In fundamental nature, the microbial or archaeal cell divides presenting rise to two cells, each devising the potential to grow to the size of the fundamental cell.

  •  Since reproduction is by binary fission, the offspring is a replica of the parent. 

  • This means that both the parent and the offspring are genetically the same.

  • Nonetheless, both bacteria and archaea can exchange genetic material in a process called conjugation. 

  • Conjugation is crucial to many bacteria as it provides a way for acquiring genes, and thereby helps in expanding the bacterial genome. 

  • The plasmid may contain genes that may be useful or not.

  •  A useful gene is one that carries a code for a protein with a desirable function, e.g. a protein that enables the recipient bacterial cell to persist in a condition that used to be lethal. 

Heredity in Sexually-Reproducing Organisms

  • Sexually-reproducing organisms comprise the eukaryotes.

  • It should be noted, however, that not all eukaryotes reproduce either sexually or asexually.

  • Some eukaryotes are proficient in reproducing both by sexual and asexual means whereas others reproduce only sexually. 

  • Fungi, for example, are eukaryotic organisms wherein some of them reproduce through both ways whereas others reproduce by either means.

  • The ones that are able to reproduce sexually carry out the process by producing spores, fragmentation, or budding,

  • the genomic content of parent is passed on as it is to the offspring in any organism which reproduces asexually like bacteria or archae 

Inherited Traits Examples

Although human beings are exclusive, there are a set of common features that we all share with the members of our family, with our ancestors, etc. We have a unique set of traits. While some traits are regulated by genes that are inherited from parents to the offspring, there are traits that are developed through observing, learning, most of which are determined by a combination of ecological factors and genes. Listed below are a few examples:

  • Tongue rolling

  • Curly hair

  • Freckles

  • Handedness

  • Earlobe attachment

  • Dimples

  • Hairline shape

  • Green/Red Colour blindness

  • Hand clasping

What is the Inheritance of Traits?

Both parents have an equal contribution to the genetic material of the child. The maternal and the paternal DNA both influence the genomics of the offspring. For every trait, one form comes from the mother, the other one comes from the father. Gregor Mendel experimented and formulated some rules which are universally applicable to inheritance of traits.

Mendel carried out his experiments using many physical characters of garden peas such as round/wrinkled seeds, white/violet flowers, tall/short plants, etc. He took pea plants, with tall and short characteristics to produce progeny by crossing them to arrive at the results. Following are his observations:

  • He perceived that there were no intermediate traits in F1 progeny, no plants with medium height were produced.

  • All plants produced were tall in height.

  • He Observed, F2 progeny(second-generation) attained by the above cross, are all not tall, a quarter of them was short in height.

  • He then deduced both tallness and shortness traits are inherited but only tallness was expressed.

  • Hence Mendel proposed that genes controlling traits are present in organisms who reproduce sexually.

  • This reproduction depends on the parents, it can either be different or identical.

Consider a plant with the following traits:

T – Tall plant

 t – short plant

TT X tt → Tt (F1 Progeny)

T t

T TT Tt

t Tt tt

(F2 progeny)

He then understood that:

A gene encompassing a single ‘T’ is enough to make a plant tall

While for a plant to be short, both its traits need to be ‘t’ i.e., ‘tt’

Dominant traits are traits like ‘T’

Recessive traits are traits like ‘t’

Mendel also went onto experiment with self and cross-pollination methods by taking tall plants with round seeds and short plants with wrinkled seeds, and all turned out to be tall and round seeded plants, thus stating that these were dominant traits. 

When F1 progeny was used to generate F2 progeny by self-pollination, he noticed that some F2 progeny are tall and round seeded plants while some are short and wrinkled seeded plants. It interestingly gave rise to new combinations as well such as tall wrinkled seeded plants and short round seeded plants, all these changes happen during zygote formation. He concluded that traits are independently inherited.