You are browsing content specific to your location, some treatments may not be available:

Call for an appointment:

1800 103 7555

What is a gene?

The basic physical and functional unit of inheritance is “the gene.” A gene comprises the information required to identify characteristics. Genes are arranged (one after another) into structures referred to as chromosomes.

What is a chromosome?

A chromosome is composed of a single, extensive DNA molecule. Hundreds to thousands of genes are present in each chromosome. Every normal human cell contains 23 pairs of chromosomes for a total of 46 chromosomes. The exception exists for egg and sperm cells.

How is the sex of an individual defined?

One of the 23 chromosome pairs is known as the sex chromosome, while the other 22 pairs are called autosomes. Usually, an individual has two sex chromosomes. A normal female has two X chromosomes (XX), while a male has one X and one Y chromosome (XY).

What is a genetic disorder?

A genetic disorder refers to a condition that results from an alteration or variation within a gene/genes. A gene variant is inherited from either one or both parents.

What are the various types of genetic disorders?

Genetic disorders can be categorized depending on their mode of inheritance from one generation to the next.

·       Single-gene/monogenic disorders refer to a specific disease or disorder resulting from a change/variant in a particular gene. For example, Sickle Cell Anaemia or Thalassaemia result from variants in the HBB gene

·       Chromosomal disorders involve alterations (change in number or structure) affecting entire chromosome(s) or part(s) of chromosomes. For example, Down Syndrome results from an extra copy of chromosome 21.

·       Complex or multifactorial disorders result from combined genetic modifications in multiple genes and may be influenced by a person’s lifestyle and environmental factors. For example, diabetes, heart problems, obesity, blood pressure, Alzheimer’s, and cancers. 

What are the probabilities of inheriting a genetic condition?

The mode of inheritance is typically applied to Mendelian or Monogenic disorders.  It is quite complex to establish an individual’s risk of inheriting a complex or multifactorial disorder. Monogenic conditions can be categorized depending on their transfer from one generation to the next.
·       Autosomal Dominant conditions. are passed down from an affected parent with a 50% risk for each child. For example,  Myotonic dystrophy, Huntington’s disease, Polycystic kidney disease (PKD), Marfan syndrome, Neurofibromatosis, . Autosomal dominant disorders can also result from new (de novo) variants that may arise during the formation of egg or sperm cells or in early embryonic development.

Autosomal Recessive conditions require the inheritance of two abnormal copies of the gene. The statistical risk for each child of carrier parents is as follows:
25% probability that two abnormal copies of the gene are inherited (child is affected)
50% probability that one normal and one abnormal copy of the gene are inherited (child is a carrier just like his parents)
25% probability that two normal copies of the gene are inherited (child is unaffected by the condition).

·       X-Linked Dominant conditions result from genes located on the X chromosome. Generally, men are more seriously affected by such disorders. The possibility of transmission of the X-linked dominant disorder varies in males and females. The trait never gets transmitted to the sons by a male and all daughters would be affected. There is a 50% probability for an affected female of having an affected child in each pregnancy.
·       X-Linked Recessive conditions result from genetic modifications on the X chromosome. Men are more often affected in comparison to females. An affected female has a 50% probability of having an affected son or carrier daughter. An affected male has a 50% probability of having a carrier daughter but cannot pass the condition on to his sons. Examples include Duchenne Muscular Dystrophy, Hemophilia A, and Lesch-Nyhan syndrome.
·       Y-linked conditions are only transmitted from males to their sons (100% probability), as women can never be affected since they lack the Y chromosome.

What are the probabilities of inheriting a trait?

The statistical probability in each child of affected parents is as follows:

  • 25% probability that two normal genes are present in the in born child (normal)
  • 25% probability that two abnormal genes are present in the in born child (at risk)
  • 50% probability that one normal and one abnormal gene is present in the child (carries the disorder but not influenced).

State some examples of some genetic disorders?

X-Linked Dominant- In this condition, the X chromosome carries the trait. Generally, men are more seriously affected, and few being more deadly. The possibility of the transmission of the X-linked dominant disorder varies in males and females. The trait never gets transmitted to the sons by a male, while all daughters are a carrier. There is a 50% possibility in an affected female of having an affected embryo in each pregnancy.

X-Linked Recessive- Results due to some genetic mutations on the X chromosome. Men are more often affected in comparison to females. An affected female has a 50-50probability of having sons affected and daughters as a carrier. Examples include Duchenne Muscular Dystrophy, Hemophilia A, and Lesch-Nyhan syndrome.

Y Linked- This condition only transmits from males to their sons as women can never be affected. This is due to the reason that women lack aY sex chromosome.

Genetic abnormalities due to numerous other factors:

  • Multifactorial inheritance may result in some genetic problems. This includes one or more genes along with exposure to factors like the environment.
  • There is no single genetic cause found in certain medical conditions like diabetes, heart problems, asthma, obesity, or cancers.
  • They are often linked to the effects of multiple genes together with certain environmental or lifestyle factors. Hence, it is quite complex to establish an individual’s risk of inheriting these disorders.

Types of treatment related to this article

IVF means in vitro fertilization.  In vitro means in the laboratory ( outside the body)  and fertilization refers to conception (joining of a woman’s egg and a

Learn More

Intracytoplasmic sperm injection (ICSI) is a technique developed to overcome male infertility attributed to impaired semen quality.  ICSI is one of the most

Learn More

Preimplantation genetic testing for aneuploidies (PGT‐A), formerly known as preimplantation genetic screening (PGS), is an alternative method to select embryos

Learn More

PGT-SR is a genetic test for detecting inherited chromosomal structural rearrangements in embryos prior to their transfer and enhancing the chance of a

Learn More

We are here to help