Molecular marker

Key takeaways

Molecular marker belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Molecular marker to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Molecular marker from memory before moving on to harder problems.

Reference excerpt

In molecular biology and other fields, a molecular marker is a molecule, sampled from some source, that gives information about its source. For example, DNA is a molecular marker that gives information about the organism from which it was taken. For another example, some proteins can be molecular markers of Alzheimer's disease in a person from which they are taken. Molecular markers may be non-biological. Non-biological markers are often used in environmental studies.

Genetic markers

In genetics, a molecular marker (identified as genetic marker) is a fragment of DNA that is associated with a certain location within the genome. Molecular markers are used in molecular biology and biotechnology to identify a particular sequence of DNA in a pool of unknown DNA.

Types of genetic markers There are many types of genetic markers, each with particular limitations and strengths. Within genetic markers there are three different categories: "First Generation Markers", "Second Generation Markers", and "New Generation Markers". These types of markers may also identify dominance and co-dominance within the genome. Identifying dominance and co-dominance with a marker may help identify heterozygotes from homozygotes within the organism. Co-dominant markers are more beneficial because they identify more than one allele thus enabling someone to follow a particular trait through mapping techniques. These markers allow for the amplification of particular sequence within the genome for comparison and analysis. Molecular markers are effective because they identify an abundance of genetic linkage between identifiable locations within a chromosome and are able to be repeated for verification. They can identify small changes within the mapping population enabling distinction between a mapping species, allowing for segregation of traits and identity. They identify particular locations on a chromosome, allowing for physical maps to be created. Lastly they can identify how many alleles an organism has for a particular trait (bi allelic or poly allelic). Genomic markers as mentioned, have particular strengths and weakness, so, consideration and knowledge of the markers is necessary before use. For instance, a RAPD marker is dominant (identifying only one band of distinction) and it may be sensitive to reproducible results. This is typically due to the conditions in which it was produced. RAPD's are used also under the assumption that two samples share a same locus when a sample is produced. Different markers may also require different amounts of DNA. RAPD's may only need 0.02 ug of DNA while an RFLP marker may require 10 ug of DNA extracted from it to produce identifiable results. currently, SNP markers have turned out to be a potential tool in breeding programs in several crops. Some commonly used types of genetic markers are:

RFLP (or Restriction fragment length polymorphism) SSLP (or Simple sequence length polymorphism) AFLP (or Amplified fragment length polymorphism) AAD (or Arbitrarily amplified DNA) RAPD (or Random amplification of polymorphic DNA) DAF (or DNA amplification fingerprinting) AP-PCR (or Arbitrarily primed PCR) VNTR (or Variable number tandem repeat) SSCP (or Single-strand conformation polymorphism) SSR Microsatellite polymorphism, (or Simple sequence repeat) SNP (or Single nucleotide polymorphism) STR (or Short tandem repeat) SFP (or Single feature polymorphism) DArT (or Diversity Arrays Technology) RAD markers (or Restriction site associated DNA markers) STS (using Sequence-tagged sites)

Mapping of genetic markers Molecular mapping aids in identifying the location of particular markers within the genome. There are two types of maps that may be created for analysis of genetic material. First, is a physical map, that helps identify the location of where you are on a chromosome as well as which chromosome you are on. Secondly there is a linkage map that identifies how particular genes are linked to other genes on a chromosome. This linkage map may identify distances from other genes using (cM) centiMorgans as a unit of measurement. Co-dominant markers can be used in mapping, to identify particular locations within a genome and can represent differences in phenotype. Linkage of markers can help identify particular polymorphisms within the genome. These polymorphisms indicate slight changes within the genome that may present nucleotide substitutions or rearrangement of sequence. When developing a map it is beneficial to identify several polymorphic distinctions between two species as well as identify similar sequences between two species.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Molecular marker

Start with the simplest possible case. Write down what Molecular marker claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Molecular marker before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Molecular marker ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Molecular marker

In research: Molecular marker appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Molecular marker in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Molecular marker is common in secondary-school and first-year university syllabi. It links to neighbouring topics Authentication methods, Chemical compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Molecular marker outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Molecular marker in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Molecular marker means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Molecular marker out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Molecular marker in simple terms?

In molecular biology and other fields, a molecular marker is a molecule, sampled from some source, that gives information about its source. For example, DNA is a molecular marker that gives information about the organism from which it was taken.

Why does Molecular marker matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Molecular marker?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Molecular marker.