The "Ifs" of NGS QC and Trimming

1. Ensures Data Integrity
   If you want to minimize errors in downstream analyses, QC and trimming remove low-quality reads and bases, ensuring high-confidence data. This step is essential for reliable variant calling, assembly, and other applications.

2. Removes Contaminants
   If adapter sequences or contaminants are present in the raw reads, trimming can eliminate them. This prevents issues like misalignment or incorrect biological interpretations, ensuring cleaner data for analysis.

3. Improves Mapping and Assembly
   If your goal is better alignment to a reference genome or improved de novo assembly, trimming low-quality bases and adapters is critical. High-quality reads map more efficiently and generate more accurate assemblies.

4. Reduces Computational Load
   If you want to save computational resources, trimming reduces the dataset size, which speeds up processing and analysis. Clean datasets mean less computational time spent on processing low-quality data.

5. Prepares for Standardized Analyses
   If your project involves multiple datasets, QC and trimming ensure uniformity across them. This standardization makes comparisons valid and reproducible, particularly in large collaborative studies.

The "Buts" of NGS QC and Trimming

1. Risk of Over-Trimming
   But excessive trimming can lead to the loss of informative sequences, reducing read depth and potentially discarding biologically relevant data. This is especially critical in studies with limited sequencing depth.

2. Bias Introduction
   But trimming algorithms might introduce biases, especially if they inadvertently remove sequences with specific biological patterns. This can skew results and compromise biological insights.

3. Loss of Context in Paired-End Reads
   But trimming one read in a pair more than the other can lead to loss of pairing information. This complicates downstream analyses that rely on paired-end data, such as structural variant detection.

4. Time and Resource Intensive
   But running QC and trimming for large datasets can be computationally expensive and time-consuming. As sequencing depth increases, preprocessing becomes a bottleneck in the analysis pipeline.

5. Variable Standards
   But the criteria for trimming (e.g., quality threshold, minimum read length) can vary between tools and datasets. This variability may affect reproducibility and comparability of results across studies.

Balancing the "Ifs" and "Buts"

To maximize the benefits of QC and trimming while mitigating the challenges, consider the following best practices:

• Use QC Tools Wisely: Start with tools like FastQC to identify quality issues in your raw data. Visualizing quality metrics helps tailor your trimming parameters.

• Choose Reliable Trimming Tools: Tools like Trimmomatic, Cutadapt, and BBduk offer adaptive and customizable trimming options. Select one that aligns with your dataset and project goals.

• Set Reasonable Parameters: Avoid over-trimming by setting quality thresholds and minimum read lengths that balance data retention and quality improvement.

• Test Downstream Effects: Validate the impact of QC and trimming on downstream analyses, such as alignment efficiency, variant calling accuracy, or assembly quality.

• Document Your Workflow: Maintain detailed records of the parameters and tools used for QC and trimming. This ensures reproducibility and enables better troubleshooting.

Conclusion

NGS quality control and trimming are essential steps to ensure reliable and accurate data for analysis. While the "ifs" highlight the clear benefits of these steps, the "buts" remind us of the potential pitfalls. By adopting best practices and carefully balancing these considerations, you can optimize your preprocessing workflow and unlock the full potential of your sequencing data.

'du' – Check the size of a directory

$ du
This command ( du) gives you a list of directories that exist in the current working directory along with their sizes in kilobytes (default). The last line of the output gives you the total size of the current directory including its subdirectories.

$ du /home/jin1
The above command would give you the directory size of the directory /home/david

$ du -h
The same “du”command with some flag gives you a better output than the default one. The option '-h' stands for human readable format. Therefore, in order to print the sizes of the files / directories in your desire notation use this time suffixed with a 'k' if its kilobytes and 'M' if its Megabytes and 'G' if its Gigabytes.

$ du -ah
If you are interested in checking everything present in a folder use above mentioned command. It gives us not only the directories but also all the files that are present in the current directory. The “-a” flag displays the filenames along with the directory names in the output.

$ du -c
This gives you a grand total as the last line of the output. So if your directory occupies 30MB the last 2 lines of the output would be 30M.

$ du -s
Use this command to displays a summary of the directory size. It is the simplest way to know the total size of the current directory.

$ du -S
This would display the size of the current directory excluding the size of the subdirectories that exist within that directory. So it basically shows you the total size of all the files that exist in the current directory.

$ du --exculde=mp3
Several times it required to exclude some directory in our size calculation. In such cases the above command would display the size of the current directory along with all its subdirectories, but it would exclude all the files having the given pattern present in their filenames.

'df' - finding the disk free space / disk usage

$ df
Hmmm … now “df” command is really useful, and I guess you are going to use it over time. Typing the above command, outputs a table consisting of 6 columns. All the columns are very easy to understand. Remember that the 'Size', 'Used' and 'Avail' columns use kilobytes as the unit. The 'Use%' column shows the usage as a percentage which is also very useful.

$ df -h
Displays the same output as the previous command but the '-h' indicates human readable format. Hence instead of kilobytes as the unit the output would have 'M' for Megabytes and 'G' for Gigabytes.

Example: Linux installed on /dev/hda1
$ df -h | grep /dev/hda1

All right, this is not the only option to check the sizes and free spaces but there are a few more options that can be used with 'du' and 'df' . I will discuss it later.

"Robert Sapolsky is an American neuroendocrinologist, professor of biology, neuroscience, and neurosurgery at Stanford University, researcher and author" ----Wikipedia

Address of the bookmark: http://www.youtube.com/watch?v=_dRXA1_e30o

(details of experience required)
Pay Scale:
INR Rs.12000/-P.M. + HRA
Category:
Science and Research Jobs
How To Apply:
The interested candidates should report for the Interview on 31st
March, 2014 at 10:00 am in the Conference Room of Dean, School of Biotechnology, First floor, Gautam Buddha University, Greater
Noida. Interested candidates may also send their resume to undersigned by post-mail/e-mail shaktis@gbu.ac.in or shaktisahi@gmail.com. No TA and DA will be paid for appearing for the interview
Download Official Notification:

http://www.gbu.ac.in/Recruitment/JRF_advertisement_DSTProject_Shakti_24March14.pdf

https://github.com/iansealy/coursera-comparinggenomes

Address of the bookmark: https://github.com/iansealy/coursera-comparinggenomes

No. CBSH/MBGE/356

Subject: Advertisement for the award of Junior Research Fellowship.

Applications are invited for award of one Junior Research Fellowship on a consolidated fellowship of Rs. 12,000/- pm in the project “Bioinformatics Sub-DIC ”, under the Coordinatorship Dr. Anil Kumar. The fellowship is purely temporary and may continue till the duration of the project or maximum three years which ever is earlier. The appointment shall be given on six monthly review basis.

ESSENTIAL QUALIFICATION

M.Sc. Bioinformatics having research experience on In silico experimentation.

Candidates possessing the above qualifications may submit their application on
plain paper in the following format to the undersigned latest 18 April, 2014 the interviews will be held on 19 April, 2014 at 11.00 AM in the office of the undersigned. No separate letter for interview will be issued or any TA/DA will be paid for attending the interview.

Advertisement: http://www.gbpuat.ac.in/01042014_18april14_Advertisement%20for%20JRF%20Position,%20BI.pdf

https://bioconductor.org/packages/release/bioc/html/epivizr.html

https://github.com/epiviz

https://github.com/epiviz/epiviz

Address of the bookmark: https://epiviz.github.io/

Applications are invited from qualified individuals for a JRF/SRF position (sponsored by DBT/DST) at Prof. Jagan Pongubala’s laboratory, University of Hyderabad. Dr. Pongubala’s laboratory is investigating the molecular pathways that control the development of innate and adaptive immune cell types utilizing a combination of genetic, molecular and computational approaches.

JRF/SRF

Masters degree in Bioinformatics (M.Sc./M.Tech.)

Rs. 12,000+HRA
Rs. 16,000+HRA

Initial appointment is for one year and subjected to renewal up to 2 years

Candidates selected for the above position would have a choice to work on computational biology or experimental biology. Candidates interested to work on computational biology are expected to perform high-throughput sequencing (NGS) data analysis and should have a strong background in Bioinformatics & Computational Biology, good programming skills particularly Perl, Python, R and work experience in Linux environment.

Candidates interested to work on experimental biology should have work experience in techniques that are routinely used in molecular biology and mammalian cell culture. A basic knowledge of bioinformatics is also desired.

Applicants for the above positions should have a Masters degree (M.Tech/M.Sc) with an aggregate marks greater than 70% or a 7.5 CGPA. Candidates having JRF-fellowship through CSIR/UGC/ICMR/DBT will be encouraged to enroll into Ph.D. program. The interested candidates having excellent organizational skills and the ability to work in a team environment with an aspiration to learn new techniques and explore new scientific areas are requested to generate their resume using the link https://cvmkr.com/CV/new#0 and forward to pongubalajagan@gmail.com

Review of applications will begin immediately and continue until the position is filled. Eligible candidates will be called for an interview. No TA/ DA will be paid for attending the interview or at the time of joining the post. Applicants should note that the appointment is purely temporary and subjected to renewal up to three years and there is no Right to Claim for any regular appointment with the University.

Corresponding address: Jagan Pongubala, Ph.D.
Department of Animal Sciences
School of Life Sciences, Room:S44
University of Hyderabad
Gachibowli, Hyderabad 500046

Advertisement: https://www.uohyd.ac.in/images/recruitment/jrf-srf_130414.pdf

Bose Institute, Kolkata, invites applications from Indian Citizens for ONE (01) temporary position of Junior Research Fellow in the DBT sponsored project entitled, “Centre of Excellance (CoE) in Bioinformatics at Bose Institute”, running under Prof. Pinakpani Chakrabarti, Project Co-ordinatior, Bioinformatics Centre. The project is tenable upto 31.03.2017, but duration of the fellowship is one year only. The JRF will work with one of the faculty members of the center based on his / her motivation in any specific area on Bioinformatics.

Essential Qualification: 1st class M.Sc. / M.Tech degree in any stream of Chemical/ Biological Sciences with CSIR-UGC-NET-JRF / ICMR-JRF / DBT-JRF or CSIR-UGCNET- LS / GATE qualification.

Desirable qualification:

(i) Specialized knowledge in Organic / Physical chemistry.
(ii) Any exposure to research involving the small molecules (like drug) and / or protein structure determination or prediction.
(iii) Basic knowledge in computer programming, e.g. using FORTRAN, C, shell, perl etc.
(iv) Hands-on-experience on any of the following software : CHARMM/AMBER/NAMD/GROMACS,Gaussian/Gamess, Haddock/Autodock, Schrodinger etc. (or any other software serving similar purposes in molecular modeling)

Fellowship :

(i) Rs. 16,000/- p.m., plus admissible HRA & Medical Benefit for M.Sc. with CSIRUGC NET-JRF/ICMR-JRF/DBT-JRF or M.Tech. with CSIR-UGC NETJRF/
ICMR-JRF/DBT-JRF/CSIR-UGC NET-LS/GATE
(ii) Rs. 12,000/- p.m., plus admissible HRA & Medical Benefit for M.Sc. with CSIRUGC NET-LS/GATE

Age : Below 28 years as on the day on which the application is made (relaxable in case of SC/ST/OBC/WOMEN candidates only as per rule).

Interested and eligible candidates should apply on plain paper duly signed by them clearly mentioning the area of interest in research, possession of any desirable qualification (s) as mentioned above and quoting Advertisement No. on the envelop as well as application with complete Bio-data giving e-mail ID, Phone No. and details of qualification i.e. examination passed, year, division, percentage of marks, from Secondary onwards with attested copies of testimonials, addressed to the Registrar, Bose Institute, P-1/12, CIT Scheme VII-M, Kankurgachi, Kolkata-700054 on or before April 25, 2014.

The shortlisted candidates will be called for an interview. Applicants are advised to check our website for future updates.

Advertisement: www.boseinst.ernet.in/ADVT/14/p_2.pdf