This document discusses different types of genetic markers that can be used to detect genetic variation, including single nucleotide polymorphisms (SNPs), insertions/deletions, microsatellites, restriction fragment length polymorphisms (RFLPs), random amplified polymorphic DNA (RAPDs), amplified fragment length polymorphisms (AFLPs), and expressed sequence tags (ESTs). It describes how these markers are classified as type I (associated with genes of known function) or type II (associated with anonymous genomic regions) and compares their properties such as polymorphic information content and usefulness in genetic analysis.
Gene mapping / Genetic map vs Physical Map | determination of map distance a...NARC, Islamabad
Mapping- determining the location of elements with in a genome, with respect to identifiable land marks.
Gene mapping describes the methods used to identify the locus of a gene and the distances between genes.
In simple mapping of genes to specific locations on chromosomes.
Two types
Genetic map
Physical Map
Construction of a Linkage Map or Genetic Mapping
Construction of a Linkage Map or Genetic Mapping
1. DNA MARKERS FOR GENETIC MAPPING
– Restriction Fragment Length Polymorphism (RFLP)
– Simple Sequence Length Polymorphism (SSLP)
– Single Nucleotide Polymorphism (SNP)
2. Determination of Linkage Groups(No. of Chromosomes)
Dihybrid cross
Trihybrid cross
3. Determination of Map Distance
Recombination fraction
4. Determination of Gene Order
5. Combining Map Segments
Current trends in pseduogene detection and characterizationShreya Feliz
This presentation gives the insight of the current trends in detecting and characterizing Pseudogenes. Pseudogenes detection by bioinformatics may enhance the understanding of Pseudogenes and take research to the next step.
this presentation is about the molecular markers as we all know the molecular markers are the DNA sequences it can be easily detected and its inheritance is easily monitored.so the main basics of the molecular markers is the polymorphic nature so it can used as molecular markers.and this will gives you the idea about AFLP, RFLP, RAPD, SNPS,ETC.
This ppt will provide you a brief yet effective information about major types of biomarkers, their definitions, their significance in disease dignosis & treatment, how they are being & are developed to be used as an effective dignostic tool for Cancer & their other future implications in other fields of medicine.
Gene mapping / Genetic map vs Physical Map | determination of map distance a...NARC, Islamabad
Mapping- determining the location of elements with in a genome, with respect to identifiable land marks.
Gene mapping describes the methods used to identify the locus of a gene and the distances between genes.
In simple mapping of genes to specific locations on chromosomes.
Two types
Genetic map
Physical Map
Construction of a Linkage Map or Genetic Mapping
Construction of a Linkage Map or Genetic Mapping
1. DNA MARKERS FOR GENETIC MAPPING
– Restriction Fragment Length Polymorphism (RFLP)
– Simple Sequence Length Polymorphism (SSLP)
– Single Nucleotide Polymorphism (SNP)
2. Determination of Linkage Groups(No. of Chromosomes)
Dihybrid cross
Trihybrid cross
3. Determination of Map Distance
Recombination fraction
4. Determination of Gene Order
5. Combining Map Segments
Current trends in pseduogene detection and characterizationShreya Feliz
This presentation gives the insight of the current trends in detecting and characterizing Pseudogenes. Pseudogenes detection by bioinformatics may enhance the understanding of Pseudogenes and take research to the next step.
this presentation is about the molecular markers as we all know the molecular markers are the DNA sequences it can be easily detected and its inheritance is easily monitored.so the main basics of the molecular markers is the polymorphic nature so it can used as molecular markers.and this will gives you the idea about AFLP, RFLP, RAPD, SNPS,ETC.
This ppt will provide you a brief yet effective information about major types of biomarkers, their definitions, their significance in disease dignosis & treatment, how they are being & are developed to be used as an effective dignostic tool for Cancer & their other future implications in other fields of medicine.
JOBS Act Rule 506(c) Federal Subpoena to Jason Coombs from Securities and Exc...Jason Coombs
Read the federal subpoena provided to Jason Coombs by the Securities and Exchange Commission (SEC) on December 18, 2013 relating to Regulation D Rule 506(c) securities offerings being advertised publicly in compliance with the JOBS Act by startups.
Molecular marker General introduction by K. K. SAHU Sir.KAUSHAL SAHU
Introduction
Molecular marker
Characterstics of molecular marker
Types of molecular marker
. Non PCR Based
. PCR Based
RFLP
RAPD
AFLP
SSR
SNP
Conclusion
References
Molecular markers- RFLP, RAPD, AFLP, SNP etc.Cherry
Molecular markers are identifiable DNA sequences used to locate genes associated with specific traits or genetic conditions.
A molecular marker is a specific gene fragment present at a specific position called ‘locus’ (pleural loci) in the genome of a cell.
In the pool of unknown DNA or in a whole chromosome, these molecular markers help in identification of particular sequence of DNA at particular location.
A genetic marker is a gene or DNA sequence with a known location on a chromosome and associated with a particular gene or trait. It can be described as a variation, which may arise due to mutation or alteration in the genomic loci that can be observed. A genetic marker may be a short DNA sequence, such as a sequence surrounding a single base-pair change (single nucleotide polymorphism, SNP), or a long one, like mini & microsatellites.
Serum zinc, copper and iron in children with chronic liver diseasesNoha Lotfy Ibrahim
Trace elements play a major role as both oxidants and antioxidants, promoting and protecting from tissue damage. The liver plays a pivotal role in the metabolism of trace elements and consequently their bioavailability. Therefore, we aimed to measure serum levels of essential trace elements in children with chronic liver diseases (CLDs) and to study their correlation with liver function tests.
Serum zinc, copper and iron in children with chronic liver diseasesNoha Lotfy Ibrahim
Trace elements play a major role as both oxidants and antioxidants, promoting and protecting from tissue damage. The liver plays a pivotal role in the metabolism of trace elements and consequently their bioavailability. Therefore, we aimed to measure serum levels of essential trace elements in children with chronic liver diseases (CLDs) and to study their correlation with liver function tests.
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
New Drug Discovery and Development .....NEHA GUPTA
The "New Drug Discovery and Development" process involves the identification, design, testing, and manufacturing of novel pharmaceutical compounds with the aim of introducing new and improved treatments for various medical conditions. This comprehensive endeavor encompasses various stages, including target identification, preclinical studies, clinical trials, regulatory approval, and post-market surveillance. It involves multidisciplinary collaboration among scientists, researchers, clinicians, regulatory experts, and pharmaceutical companies to bring innovative therapies to market and address unmet medical needs.
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
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Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
2. Introduction
All organisms are subject to mutations as •
a result of normal cellular operations or
interactions with the environment, leading
to genetic variation (polymorphism).
For this variation to be useful, it must be •
(1) heritable and (2) discernable.
3. Introduction
Types of genetic variation include: •
base substitutions, commonly referred to as
single nucleotide polymorphisms (SNPs).
insertions or deletions of nucleotide sequences
(indels) within a locus.
inversion of a segment of DNA within a locus.
rearrangement of DNA segments around a locus
of interest
4. DNA-based genetic markers
In the past, allozyme and mtDNA markers. •
More recent marker types include: •
restriction fragment length polymorphism (RFLP) (1)
randomly amplified polymorphic DNA (RAPD)
amplified fragment length polymorphism (AFLP)
expressed sequence tag (EST) markers
single nucleotide polymorphism (SNP)
microsatellite
5. Type I (coding) vs. type II (non coding)
markers
Molecular markers are classified into two •
categories:
type I are markers associated with genes
of known function.
type II markers are associated with
anonymous genomic segments
6. Type I vs. type II markers
Most RFLP markers are type I markers because •
they were identified during analysis of known
genes.
Allozyme markers are type I markers because the •
protein they encode has known function.
RAPD markers are type II markers because RAPD •
bands are amplified from anonymous genomic
regions via the polymerase chain reaction (PCR).
7. Type I vs. type II markers
• AFLP markers are type II because they are also
amplified from anonymous genomic regions.
• EST markers are type I markers because they
represent transcripts of genes, it is more common in
animals and plants research.
• SNP markers are mostly type II markers unless they
are developed from expressed sequences (eSNP or
cSNP) (type l).
• Microsatellite markers are type II markers unless
they are associated with genes of known function
(type l).
8. polymorphic
information content (PIC)
• The usefulness of molecular markers can be
measured based on their PIC.
• PIC refers to the value of a marker for detecting
polymorphism in a population.
• PIC depends on the number of detectable alleles
and the distribution of their frequencies.
• The greater the number of alleles, the greater the
PIC
9. Allozyme markers
• Allozymes are allelic variants of proteins produced
by a single gene locus, and are of interest as
markers because polymorphism exists and
because they represent protein products of genes.
• Amino acid differences in the polypeptide chains of
the different allelic forms of an enzyme reflect
changes in the underlying DNA sequence.
10. Allozyme markers
• Depending on the nature of the amino acid
changes, the resulting protein products may migrate
at different rates (due to charge and size
differences) when run through a starch gel
subjected to an electrical field.
• Differences in the presence/absence and relative
frequencies of alleles are used to quantify genetic
variation and distinguish among genetic units at the
levels of populations, species, and higher taxonomic
designations.
11. Allozyme markers
• Disadvantages:
heterozygote deficiencies due to null (enzymatically
inactive) alleles and the amount and quality of tissue
samples required.
some changes in DNA sequence are masked at the
protein level, reducing the level of detectable variation.
some changes in nucleotide sequence do not change
the encoded polypeptide (silent substitutions).
some polypeptide changes do not alter the mobility of
the protein in an electrophoretic gel (synonymous
substitutions).
12. Mitochondrial DNA markers
• Sequence divergence accumulates more rapidly in
mitochondrial than in nuclear DNA due to a faster
mutation rate result from a lack of repair
mechanisms during replication.
• Due to its non-Mendelian mode of inheritance, the
mtDNA molecule must be considered a single
locus in genetic investigations.
• Disadvantage: mtDNA data may not reflect those of
the nuclear genome.
13. Restriction fragment length
polymorphism (RFLP)
• Restriction endonucleases are bacterial enzymes that
recognize specific 4, 5, 6, or 8 bp nucleotide sequences
and cut DNA wherever these sequences are
encountered, so that changes in the DNA sequence due
to indels, base substitutions, or rearrangements
involving the restriction sites can result in the gain, loss,
or relocation of a restriction site.
• Digestion of DNA with restriction enzymes results in
fragments whose number and size can vary among
individuals, populations, and species.
14. Restriction fragment length
polymorphism (RFLP)
• Traditionally, fragments were separated using Southern
blot analysis, Most recent analyses replace it with PCR.
• If flanking sequences are known for a locus, the
segment containing the RFLP region is amplified via
PCR.
• If the length polymorphism is caused by a relatively
large (> approx. 100 bp depending on the size of the
undigested PCR product) deletion or insertion, gel
electrophoresis of the PCR products should reveal the
size difference.
15. Restriction fragment length
polymorphism (RFLP)
• By using a ‘universal’ primers on a target DNA, PCR
products can be digested with restriction enzymes and
visualized by simple staining with ethidium bromide due to
the increased amount of DNA produced by the PCR
method.
• Advantage: they are codominant markers, because the
size difference is often large, scoring is relatively easy.
• Disadvantage: the relatively low level of polymorphism. In
addition, either sequence information (for PCR analysis)
or probes (for Southern blot analysis) are required,
making it difficult and time-consuming
16.
17. Random amplified polymorphic
DNA (RAPD)
• RAPD procedures were using PCR to randomly
amplify anonymous segments of nuclear DNA with
an identical pair of primers 8 – 10 bp in length.
• Because the primers are short and relatively low
annealing temperatures (often 36– 40 C) are used,
the likelihood of amplifying multiple products is
great, with each product representing a different
locus.
18. Random amplified polymorphic
DNA (RAPD)
• The potential power is relatively high for detection of
polymorphism; typically, 5 –20 bands can be
produced using a given primer pair, and multiple sets
of random primers can be used to scan the entire
genome for differential RAPD bands.
• Because each band is considered a bi-allelic locus
(presence or absence of an amplified product), PIC
values for RAPDs fall below those for microsatellites
and SNPs, and RAPDs may not be as informative as
AFLPs because fewer loci are generated
simultaneously.
19.
20.
21.
22. Amplified fragment length
polymorphism (AFLP)
• AFLP is a PCR-based, multi-locus fingerprinting
technique that combines the strengths and
overcomes the weaknesses of the RFLP and RAPD
methods.
• Like RFLPs, the molecular basis of AFLP
polymorphisms includes indels between restriction
sites and base substitutions at restriction sites; like
RAPDs, it also includes base substitutions at PCR
primer binding sites.
23. Amplified fragment length
polymorphism (AFLP)
• The unique feature of the technique is the addition
of adaptors of known sequence to DNA fragments
generated by digestion of whole genomic DNA.
• This allows for the subsequent PCR amplification of
a subset of the total fragments for ease of
separation by gel electrophoresis.
• It is the same as RFLP, but instead of analyzing
one locus at a time, it allows for the analysis of
many loci simultaneously.
24.
25. Single nucleotide polymorphism
(SNP)
• It describes polymorphisms caused by point
mutations that give rise to different alleles
containing alternative bases at a given nucleotide
position within a locus. lt is used for DNA
sequencing.
• SNP markers are inherited as co-dominant
markers.
• Its PIC is not as high as multi-allele microsatellites.
• Random shotgun sequencing, amplicon
sequencing using PCR, and comparative EST
analysis are among the most popular sequencing
methods for SNP discovery.
26. Expressed sequence tags (ESTs)
• ESTs are single-pass sequences generated from
random sequencing of cDNA clones used for gene
profiling and genomic mapping.
• It offers a rapid and valuable first look at genes
expressed in specific tissue types, under specific
physiological conditions, or during specific
developmental stages.
• ESTs are useful for the development of cDNA
microarrays that allow analysis of differentially
expressed genes.
27. What is microsatellites & SSRs?
• Microsatellites or simple sequence repeats (SSRs),
represent codominant molecular genetic markers, i.e., both
allele in an individual are present in the analysis.
• Microsatellites are stretches of DNA consisting of tandemly
repeated short units of 1–6 base pairs (bp) in length. SSRs
typically span between twenty and a few hundred bases
• Due to their high level of polymorphism, relatively small size,
multiallelic nature, codominant inheritance and rapid
detection protocols, easily amplified with the PCR using two
unique oligonucleotide primers that flank the microsatellite
and hence define the microsatellite locus, these markers are
widely used in a variety of fundamental and applied fields of
life and medical sciences.
28. Microsatellites &SSRs
• Application in biology and medicine including:
forensics, molecular epidemiology, parasitology,
population and conservation genetics, genetic
mapping and genetic dissection of complex traits.
• Microsatellites are considered selectively neutral
markers, found anywhere in the genome, both in
protein-encoding (9-15%) and noncoding DNA.
• SSRs contribute to DNA structure, chromatin
organization, regulation of DNA recombination,
transcription and translation, gene expression and
cell cycle dynamics.
29. Microsatellites &SSRs
• The majority of microsatellites (30–67%) found are
dinucleotides, mostly represented by poly (A/T)
tracts, which are the most frequent classes of
SSRs, where (tri-, tetra-, penta-and
hexanucluotides) are about 1.5-fold less common in
genomic DNA.
• In the human genome, one microsatellite was found
every 6 kb and one CA repeat (the most common
type of tandem repeat) occurred every 30 kb of
DNA.
30. Microsatellites &SSRs
• Di- and tetranucleotide motifs are mostly clustered
in noncoding regions. In vertebrates, they are
distributed 42- and 30-fold less frequently in exons
than in intronic sequences and intergenic regions,
respectively.
• Long dimeric motifs are highly unstable within
expressed sequences, while in noncoding regions
most dinucleotide repeats can have surprisingly
long stretches, probably due to the high tolerance of
noncoding DNA to mutations.
31. Microsatellites &SSRs
• In contrast, triplets are found in both coding and
non-coding genomic regions with a high frequency.
• In humans, the expansion of trinucleotides,
encoding polyproline (CCG)n, polyarginine
(CGG)n, polyalanine [(GCC)n and (GCG)n] and
polyglutamine (CAG)n tracts within exons has been
described.
• Such expansions can lead to various
neurodegenerative and neuromuscular disorders,
including myotonic distrophy, fragile X syndrome,
Huntington's disease and spinocerebellar ataxia.
32. Function of microsatellites
1. DNA & chromosome structure
• Microsatellites are involved in forming a wide variety of
unusual DNA structures with simple and complex loop-folding
patterns.
• Telomeric and centromeric chromosome regions have
been shown to be rich in long arrays of a variety of
mono-, di-, tri-, tetra-and hexanucleotide motifs.
• The (TTAGGG)n hexamer sequence is recognized by
ribonucleoprotein polymerase, a telomerase, which
synthesizes telomere repeats onto the chromosome
ends to overcome the loss of sequences during DNA
replication, whereas other proteins prevent nucleolytic
degradation and confer stability of chromosomes.
33. Function of microsatellites
2. DNA recombination
• Dinucleotide motifs are preferential sites for
recombination events due to their high affinity for
recombination enzymes.
• Some SSR sequences, such as GT, CA, CT, GA
and others, may influence recombination through
their effects on DNA structure.
• SSRs were shown to be associated with the
assignment of some Rh phenotypes, and to be
involved in the molecular evolution of the human Rh
gene family and its orthologs in other eukaryotes
via replication slippage and recombination (gene
conversion) mechanisms.
34. Function of microsatellites
3. DNA replication
• Human genes encoding important cell fidelity and
growth factors, such as the B-cell
leukemia/lymphoma 2 (BCL2)-associated X protein,
insulin-like growth factor 2 receptor (IGF2R), breast
cancer early onset protein 2 (BRCA2) and
transforming growth factor beta 2 (TGF-β2), contain
short repeated sequences.
• Frame-shift mutations, resulting in both insertions
and deletions of repeat units within these
sequences that affect these genes and could
therefore initiate tumorigenes and can affect
enzymes controlling mutation rate and cell cycles.
35. Function of microsatellites
4. Gene expression
• SSRs located in promoter regions can influence drastic
or quantitative variations in gene expression and
change the level of promoter activity. The human insulin
minisatellite is highly polymorphic, and some of its
alleles were shown to regulate the expression of the
insulin gene.
• Intronic SSRs also can affect gene transcription affect
mRNA stability, representing binding sites for
translation factors. For example, such an effect was
measured for the tetrameric microsatellite located in
intron 1 of the human tyrosine hydroxylase gene and
the (CA)n dinucleotide repeat in the first intron of the
human epidermal growth factor receptor gene.
36. Development of type I (coding) and type II
(non-coding) microsatellite markers
• Type I markers are more difficult to develop. While non-gene
sequences are free to mutate, causing higher levels
of polymorphism, sequences within protein-coding regions
generally show lower levels of polymorphism because of
functional selection pressure.
• The most effective and rapid way for producing type I
microsatellites is the sequencing of clones from cDNA
libraries. Both 5′- and 3′-ends of a cDNA clone can be
sequenced to produce expressed sequence tags (ESTs).
• An EST represents a short, usually 200–600 bp-long
nucleotide sequence, which represents a uniquely
expressed region of the genome.
37. Development of type I (coding) and type II
(non-coding) microsattellite markers
• EST sequences are archived in a special branch of the
GenBank nucleotide database (dbEST). In Nov. 2005, the
EST database contained more than 31.3 million sequence
entries from around 500 species.
• A typical strategy for the development of ESTderived
microsatellite markers (data mining) includes preliminary
analysis of EST sequences from the DNA database to
remove poly(A) and poly(T) stretches which are common in
ESTs developed from the 3′-ends of cDNA clones and
correspond to the poly(A)-tails in eukaryotic mRNA.
• Sequences are further screened for putative SSRs (all
SSR-containing EST sequences). Following the
identification of ESTs, flanking primers should be designed
to amplify a microsatellite.
38. Applications of microsatellites
1. Genetic mapping
2. Individual DNA identification and
parentage assignment
3. Phylogeny, population and conservation
genetics
4. Molecular epidemiology and pathology
5. Quantitative trait loci mapping
6. Marker-assisted selection
39. 1. Genetic mapping
• SSRs remain the markers of choice for the
construction of linkage maps, because they are
highly polymorphic (and highly informative) and
require a small amount of DNA for each test.
• However, type II (noncoding) microsatellites are
very helpful for building a dense linkage map
framework into which type I (coding) markers can
then be incorporated (type I markers directly shows
the location of genes within the linkage map).
40. 1. Genetic mapping
• Linkage map is known as recombination maps and define
the order and distance of loci along a chromosome on the
basis of inheritance in families or populations.
• During meiosis, one random copy of each chromosome
pair is passed on to the gamete. Only genes located next
to each other are tightly linked.
• Crossingover results from physical exchange of
chromosome segments between two homologous
chromosomes of meiosis.
• Recombination results in the exchange of grandparental
alleles of genes further apart on that chromosome
41. 1. Genetic mapping
• Genetic distance is usually measured in
centimorgans (cM), where 1 cM is equivalent to
1% recombination between markers.
• Linkage map length differs between sexes. In
species with the XY sex determination system,
the female map is usually longer than the male
map because of higher recombination rates in
females compared to males.
42. 2. Individual DNA identification and
parentage assignment
• Microsatellites represent codominant single-locus DNA
markers. For each SSR, a progeny inherits one allele from
the father and another allele from the mother.
• Appropriate mathematical tools are available to evaluate
genetic relatedness and inheritance in these systems.
• A suitable methodology should be chosen for accurate and
correct analysis of genotyping data to reconstruct parentage
and pedigree structure.
• Due to the small size of SSRs, they are relatively stable in
degraded DNA. This is one reason why polymorphic SSRs
are widely used in forensic science, as microsatellite loci
remain relatively stable in bone remnants and dental tissue,
providing the basis for the successful application of ancient
DNA.
43. 3. Phylogeny, population and
conservation genetics
• By using variability within stretches of tandem
repeats, which evolve significantly more rapidly
than flanking regions.
• Flanking regions of microsatellites have proven
their value in establishing phylogenetic
relationships between species and families,
because they evolve much more slowly than
numbers of tandem repeats.
• Phylogeographical applications of micro-satellites
are eminently suitable, where population structure
is observed over a large geographical scale.
44. 4. Molecular epidemiology and
pathology
• Genomic instability of microsatellites has been extensively
evaluated in the field of carcinogenesis, where chromosomal
rearrangements (e.g., translocations, insertions and
deletions of genomic regions) occur.
• Carcinogenic events often happen within a genomic region
harboring a tumour suppressor gene and hence inactivate
the gene.
• Carcinogenic rearrangements are associated with loss of
heterozygosity (LOH) in microsatellites located within the
affected chromosome region.
• Thus, detecting microsatellite LOH in tumour tissues
contributes not only to molecular diagnosis of cancer, but
also points the possible location of a tumour suppressor
gene.
45. 5. Quantitative trait loci mapping
• A quantitative trait is one that has measurable
phenotypic variation owing to genetic and/or
environmental influences.
• The variation can be measured numerically (for
example, height, size or blood pressure) and
quantified.
• Generally, quantitative traits are complex
(multifactorial) and influenced by several
polymorphic genes and by environmental
conditions.
46. 6. Marker-assisted selection
• Marker-assisted selection is based on the concept that it
is possible to infer the presence of a gene from the
presence of a marker tightly linked to that gene.
• So, it is important to have high-density and high-resolution
genetic maps, which are saturated by markers in the
vicinity of a target locus (gene) that will be selected.
• The degree of saturation is the proportion of the genome
that will be covered by markers at the density such that
the maximum separation between markers is no greater
than a few centimorgans (usually 1–2 cM), within which
linkage of markers can be detected.