Linkage and Recombination

Linkage and Recombination Definition

Linkage and recombination are the phenomena that are responsible for the inheritance of genes and characteristics.  Linkage refers to the inheritance of two DNA segments as they reside in the same chromosome for more than two generations. Recombination is a phenomenon which results in the formation of an offspring with combined characteristics as a result of the separation of genetic material during crossing over (at the time of meiosis). We hope that we are able to define linkage and recombination clearly. But linkage recombination is a pretty vast concept in the field of genetic inheritance. Thus, just defining the concepts is not enough. We will be moving towards our next concert related to linkage and recombination i.e. differences between linkage and crossing over.

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We have seen the definition of linkage and recombination in the previous section. Now, in order to explain linkage and recombination, let’s look at the difference between linkage and crossing over in the field of genetics. 

Differences Between Linkage And Crossing Over

Linkage

Crossing-Over

Responsible for keeping the genes in a chromosome for inheriting together

Responsible for the separation of genes and segregation into different gametes.

The strength of linkage is inversely proportional to the distance between the genes in the chromosomes.  

The chance of crossing-over is directly proportional to the distance between the genes in the chromosomes.


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We hope that the difference between linkage and crossing over is very much clear. The next section talks about an important experiment that led to a transition in the field of genetics.

Did You Know About Morgan’s Experiment?

Thomas Hunt Morgan experimented in 1910 at Columbia University. Morgan’s experiment aimed at proving the fact that sexual reproduction produces variations in the off-springs. For experimenting, Morgan started breeding fruit flies (Drosophila). In his experiment, he found that among thousands of red-eyed fruit flies, there was one fly with white-eye and that too, a male fly. After several observations, Morgan inferred that:

Eye color and sex were determined by the same chromosome and thus, chromosomes carry the genes for the inheritance of parental traits in the offspring.

Morgan’s experiment was published in an article, titled “Sex Limited Inheritance in Drosophila”. 

Fruit flies were the best alternative for Morgan’s experiment because of the following reasons: 

  • Males and females could be easily differentiable.

  • Fruit-flies had a short lifespan i.e. 2 weeks.

  • Many off-springs could be produced by a single mating.

  • They were easy to cultivate.

  • Males and females could be easily differentiated. 

Thomas Hunt Morgan's experiment also noticed that the white-colored eyes were only present in males. The reason behind this was that the white-colored trait was found only on their X-chromosome and thus, proved that the inheritance of traits can differ by sexes. Females didn’t show white eyes because it was only present on one of their X-chromosome. Thus, Morgan’s experiment was the perfect explanation of linkage and crossing over.

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Types of Linkages

Let’s get to the next topic of the discussion, what are the different types of linkages in the genetic inheritance proposed by the Morgan linkage experiment. 

So, there are two types of linkages: 

Complete Linkage

Complete linkage is a type of linkage where two or more traits are inherited and are visible in two or more further generations. These types of linkages are found together in the chromosomes of the same type.

Incomplete Linkages

Incomplete linkages produce some portion of non-parental combinations. These types of linkages are found at a distance and result in occasional destruction of chromosomal segments while crossing over.             

We hope that the concept of types of linkages is very much clear. We’ll be heading towards our next section.  

3 Types of Genetic Recombination

We are proceeding towards our next section i.e. what are the different types of recombinations in genetic inheritance.

There Are 3 Types of Recombination

Homologous Recombination: 

Homologous recombination is one of the types of recombinations where nucleotide sequences are interchanged two identical nucleic acids (DNA/ RNA)

Non-Homologous Recombination: 

Non-homologous recombination is a type of recombination by which chromosomal double-strand breaks in the DNA of somatic cells get repaired. 

Site-Specific Recombination: 

Site-specific recombination is a type of recombination where DNA strands interchange DNA strands among the segments having a certain degree of homology.  

We hope that we were able to explain linkage and combination, types of linkage mechanisms, and types of genetic recombinations. Now, we are heading towards our final topic of the discussion i.e. recombination of linked genes.

Recombination of Linked Genes

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This is the final topic of the discussion. We will understand the recombination of the linked genes with an example. 

The character traits of blonde hair and patchy skin appear on a person because both of these attributes are present in the same chromosome. Homologous recombination leads to a rare splitting of two genes. 

The chance of inheritance of the two mentioned attributes is very low in homologous recombination. As a result, most of these traits are inherited at the same time. 

FAQ (Frequently Asked Questions)

1. Why did Morgan Choose Fruit Flies for his Experiment and What was the Result of the Experiment?

Morgan chooses fruit flies for his experiment due to the following reasons: 

  • Males and females could be easily differentiable.

  • Fruit-flies had a short lifespan i.e. 2 weeks.

  • Many off-springs could be produced by a single mating.

  • They were easy to cultivate.

  • Males and females could be easily differentiated. 

After several observations and studies, Morgan’s experiment led him to the following result:

“Eye color and sex were determined by the same chromosome and thus, chromosomes carry the genes for the inheritance of parental traits in the offspring.”

The experiment was published in an article, titled “Sex Limited Inheritance in Drosophila”, which was a transition in the fields of gene linkage and recombination. 

2. What are the Different Types of Linkages? 

There are basically two kinds of linkages, which have been defined adequately below: 

Complete Linkage: The complete linkage is a type of linkage where two or more traits are inherited and are visible in two or more further generations. This type of linkage is basically found together in the chromosomes of the same type.

Incomplete Linkages: The incomplete linkages produce some portion of non parental combinations. This type of linkage is found at a distance and results in an occasional destruction of chromosomal segments while getting crossover.   

These are the two types of linkage that you should know about.