Causes of Mutations: Recombination & Translocation

Instructor: Lisa Roundy

Lisa has taught at all levels from kindergarten to college and has a master's degree in human relations.

DNA can be exchanged between chromosomes through the processes of translocation and recombination. Learn more about these processes and how they differ from one another in this lesson.

Homologous vs. Nonhomologous

It's laundry day and you have dumped all of the clean socks into a basket for sorting. Unless you have lost one somewhere, each sock should be part of a matching pair. You find the mate for each sock and roll them up into a ball so they will stay together in your drawer.

You could think of each sock as one of a pair of homologous chromosomes. A chromosome is a ropelike strand of DNA that contains genetic material. Chromosomes come together to form matching (homologous) pairs, just like our socks. One chromosome from the homologous pair will come from each parent.

Now imagine you have two pairs of chromosomes. Just like when we match red socks with red socks and blue socks with blue socks, each chromosome only has one mate. Any chromosomes from different matched pairs (a red sock with a blue sock) are considered nonhomologous.

Why is understanding this difference important? Understanding the differences in chromosomes will help you understand the differences in two types of genetic exchange that we will be discussing in this lesson: recombination and translocation.

Recombination

Remember that in each pair of homologous chromosomes we have one chromosome from each parent. Like a pair of socks, each chromosome is basically the same chromosome. When DNA is exchanged between this homologous pair we call it recombination. In other words the genetic material is recombined so that you may have a bit of the mother and father's DNA on each chromosome in the pair.

This would be like taking a pair of socks, cutting the top off of each sock, then sewing the top back on to the sock's mate. You would have two matching socks, even though some of the parts have moved around.

Recombination is the exchange of genetic material between chromosomes that are paired together.
recombination

Translocation

The prefix 'trans' means 'across', so it makes sense that translocation would involve the movement of genes from one location to the next. Translocation occurs when DNA is exchanged between two nonhomologous chromosomes. In other words, a section of genes on one chromosome is broken off and replaced by a section of genes from a non-paired chromosome.

Thinking back to the sock pairs again, we could imagine the top of one of a pair of blue socks being cut off. If the top is replaced by the top of a red sock from another pair we would have translocation. If this only happens to one sock in the pair, your socks will no longer match.

Translocation is the exchange of genetic material between chromosomes that are paired separately.
recombination

Effects of DNA Exchange

Why are the processes of recombination and translocation important? When translocation or recombination take place it results in a chromosome that differs from the original. This new chromosome has a mutation, or a change in genetic material. When a mutation occurs and DNA is exchanged between chromosomes, genetic variability is increased.

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