Question Video: Defining the Term “Repetitive DNA” | Nagwa Question Video: Defining the Term “Repetitive DNA” | Nagwa

Question Video: Defining the Term “Repetitive DNA” Biology • Third Year of Secondary School

What is meant by repetitive DNA?

02:16

Video Transcript

What is meant by repetitive DNA? (A) Consecutive sequences of DNA that repeat themselves and that are found throughout the genome. (B) Copies of the genome repeated in a cell and found throughout the organism. (C) Genes that are repeated in several copies throughout the genome. (D) Nucleotides that are used more than once within DNA.

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic information in all living organisms. A molecule of DNA is most commonly composed of two strands, each of which is a chain of individual units called nucleotides. We can see these different nucleotides here and the corresponding nucleotide sequence of one of these strands as it coils around the opposing strand.

In humans, if we look at the complete sequence of DNA, or our genome, it’s over three billion nucleotides long. We discovered this after sequencing the human genome as part of the Human Genome Project, which was a worldwide effort by multiple scientists that took over 10 years to complete.

Besides learning about the size of the human genome, we also discovered that it contains over 20,000 protein-coding genes, which represents about one percent of our genome. This includes sequences that code for proteins, such as insulin or hemoglobin. The remaining 99 percent is made up of noncoding DNA. This is a DNA sequence that doesn’t code for proteins. These sequences can include structural RNAs like ribosomal or rRNA or regulatory RNA like microRNAs.

However, about half of our genome is made up of repetitive DNA sequences with no clear function. An example of this is called the Alu element, which is a 300-base-pair-long segment of DNA that is repeated over one million times in the human genome. In fact, about 10 percent of our genome is made up of these repeated Alu elements.

Getting back to our question, the option that best describes what is meant by repetitive DNA is given by answer choice (A): consecutive sequences of DNA that repeat themselves and that are found throughout the genome.

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