Question

Explain why an insertion of three nucleotides is less likely to result in a deleterious effect than an insertion of a single nucleotide.

Short answer

DNA is read in 'codons' of three nucleotides, each coding for a specific amino acid. Inserting a single nucleotide changes the reading frame, likely causing a harmful protein to be produced. Inserting three nucleotides, an entire codon, just adds an extra amino acid. While it can be harmful, it's less likely to be as disruptive as a frameshift mutation caused by single nucleotide insertion.

Step-by-step solution

Understanding DNA and Codons

Genes in a DNA molecule are instructions for creating proteins. These instructions are read three nucleotides at a time, a unit known as a 'codon'. Each codon codes for a specific amino acid.

Understanding Insertion Mutations

An insertion mutation is when extra nucleotides are added to the DNA sequence. This can change how the sequence is read and thus alter the final protein produced.

Comparing the Effects of Single vs Triple Nucleotide Insertions

If a single nucleotide is inserted, it will 'push' all following nucleotides forward one position. This will change the reading frame from the point of insertion onwards, likely resulting in a protein that is nonfunctional or harmful to the organism. This is called a 'frameshift' mutation. On the other hand, if three nucleotides are inserted, they form an entire new codon, which means they just add a single, extra amino acid to the final protein. While this can still be harmful, it's less likely to be as disruptive as a frameshift mutation.

Key concepts

DNA and Genetics

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. It carries the genetic instructions used in growth, development, functioning, and reproduction. This tightly packed structure is made up of building blocks called nucleotides, each consisting of a sugar, a phosphate group, and a nitrogen base. Four types of nitrogen bases are present in DNA: adenine (A), thymine (T), cytosine (C), and guanine (G).

The sequence of these bases encodes genetic information. Within the DNA, sequences are structured into genes, which serve as templates for producing proteins. These proteins are crucial for various biological functions and traits. Genetic variations, such as mutations, can alter these instructions, leading to changes in protein function. Understanding DNA's role is fundamental in genetics, as it underpins concepts like mutation and inheritance.

Insertion Mutations

An insertion mutation occurs when additional nucleotides are introduced into the DNA sequence. This type of mutation can have significant consequences on gene function and, consequently, protein synthesis. Insertion mutations disrupt the integrity of the original DNA sequence, potentially altering the reading of the genetic code.

When nucleotides are inserted, the extra bases can impact the way information is converted from the genetic code into a protein. Depending on the number, position, and the specific sequence of nucleotides inserted, the effects can range from negligible to severe. These mutations can occur naturally or be influenced by environmental factors. Geneticists study insertion mutations closely to understand their impact on health and development.

Codon Reading

The process of codon reading involves interpreting the sequence of nucleotide triplets, known as codons, which make up the genetic code in DNA. Each codon specifies a particular amino acid that will be added to a growing protein chain or signals the end of protein synthesis.

The significance of codon reading lies in its precision; the genetic code is read in sets of three nucleotides without overlap. This is why changes affecting codon alignment can have substantial effects. In maintaining proper codon reading, the entire protein synthesis process runs smoothly, ensuring that proteins are built correctly. Errors in codon reading can lead to misformed proteins, which may not function properly or could be detrimental to the organism's health. Understanding codon reading is essential for comprehending how genetic information is translated into functional proteins.

Frameshift Mutation

A frameshift mutation is a genetic mutation caused by insertions or deletions of nucleotides in a DNA sequence that shifts the "reading frame" of the genetic message. The reading frame is how nucleotide sequences are divided into codons. For instance, insertion or deletion of a single nucleotide rearranges the downstream codons, altering the entire amino acid sequence from that point.

Frameshift mutations often lead to drastic consequences because they reconfigure the triplet grouping of the bases. This makes every subsequent codon different from the original coding sequence. As a result, frameshift mutations often produce proteins that are dysfunctional. They might cause diseases or lead to cellular malfunctions. Understanding the concept of frameshift mutation highlights why precise maintenance of reading frames is crucial for sustaining correct genetic and protein functions.