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Chapter 11: Problem 12

Contrast the various categories of repetitive DNA.

Short Answer

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Question: Compare and contrast the different categories of repetitive DNA, including satellite DNA, minisatellite DNA, microsatellite DNA, and dispersed repetitive DNA. Answer: Satellite DNA consists of large blocks of tandem repeats found mainly in centromeric and heterochromatic regions, playing a role in chromosome stability and segregation. Minisatellite DNA refers to tandem repeats of 10 to 100 base pairs distributed throughout the genome and are highly polymorphic, making them useful as genetic markers. Microsatellite DNA consists of short tandem repeats (2-6 base pairs) and is highly polymorphic, used as genetic markers in various studies. Dispersed repetitive DNA includes mobile genetic elements like retrotransposons and DNA transposons, which contribute to genomic variation and evolution.

Step by step solution

01

Define satellite DNA

Satellite DNA is a category of repetitive DNA that consists of large blocks of tandem repeats. These sequences can range from 100 to several hundred base pairs in length and are found mainly in the centromeric and heterochromatic regions of the chromosome. Satellite DNA plays a role in chromosome stability and segregation during cell division.
02

Define minisatellite DNA

Minisatellite DNA, also known as variable number tandem repeats (VNTRs), is another category of repetitive DNA that consists of tandem repeats of 10 to 100 base pairs in length. These sequences are found throughout the genome and are known for their high degree of polymorphism due to variation in the number of repeat units. This feature makes them useful as genetic markers in various fields, including forensics, genealogy, and population genetics.
03

Define microsatellite DNA

Microsatellite DNA, also known as short tandem repeats (STRs), is a category of repetitive DNA that comprises tandem repeats of short sequences, usually 2 to 6 base pairs in length. These sequences are widely distributed in the genome and are characterized by high mutation rates, resulting in a high degree of polymorphism. They are often used as genetic markers to study genetic heritability, population structure, and evolution.
04

Define dispersed repetitive DNA

Dispersed repetitive DNA is a category of repetitive DNA that includes transposable elements, which are sequences that can move within the genome. There are two main types of transposable elements: retrotransposons and DNA transposons. Retrotransposons are widespread in eukaryotes and replicate through an RNA intermediate, while DNA transposons move directly as DNA and are less common in eukaryotes. Dispersed repetitive DNA sequences can cause mutations and contribute to genomic variation and evolution.
05

Contrast the categories of repetitive DNA

In summary, the categories of repetitive DNA can be differentiated based on their structure, distribution, and role in the genome: 1. Satellite DNA: large blocks of tandem repeats, mainly found in centromeric and heterochromatic regions, involved in chromosome stability and segregation. 2. Minisatellite DNA: tandem repeats of 10 to 100 base pairs, distributed throughout the genome and highly polymorphic, used as genetic markers in various fields. 3. Microsatellite DNA: tandem repeats of short sequences (2-6 base pairs), widely distributed and highly polymorphic, used as genetic markers in genetic heritability, population structure, and evolution studies. 4. Dispersed repetitive DNA: mobile genetic elements (retrotransposons and DNA transposons), contribute to genomic variation and evolution.

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Most popular questions from this chapter

Mammals contain a diploid genome consisting of at least \(10^{9}\) bp. If this amount of DNA is present as chromatin fibers, where each group of 200 bp of DNA is combined with nine histones into a nucleosome and each group of six nucleosomes is combined into a solenoid, achieving a final packing ratio of \(50,\) determine: (a) the total number of nucleosomes in all fibers. (b) the total number of histone molecules combined with DNA in the diploid genome. (c) the combined length of all fibers.

In this chapter, we focused on how DNA is organized at the chromosomal level. Along the way, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, propose answers to the following fundamental questions: (a) How do we know that viral and bacterial chromosomes most often consist of circular DNA molecules devoid of protein? (b) What is the experimental basis for concluding that puffs in polytene chromosomes and loops in lampbrush chromosomes are areas of intense transcription of RNA? (c) How did we learn that eukaryotic chromatin exists in the form of repeating nucleosomes, each consisting of about 200 base pairs and an octamer of histones? (d) How do we know that satellite DNA consists of repetitive sequences and has been derived from regions of the centromere?

Describe the transitions that occur as nucleosomes are coiled and folded, ultimately forming a chromatid.

What are the molecular composition and arrangement of the components in the nucleosome?

What genetic process is occurring in a puff of a polytene chromosome?
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