Explore
For Enterprise
Join for Free
Log In

Artes e Humanas
Negócios
Ciência da Computação
Ciência de Dados
Tecnologia da informação
da saúdesaúde
Matemática e Lógica
Desenvolvimento Pessoal
Ciência e Engenharia Física
Ciências Sociais
Línguas
Notas
Certificados

Explore todo o Coursera

Navegar
Pesquisar
For Enterprise
Entrar
Inscreva-se gratuitamente

Lecture: Sequencers give pieces to genomic puzzles

Loading...

Algoritmos Aplicado ao Sequenciamento de DNA

Universidade Johns Hopkins

4.8 (415 classificações) | 16K alunos inscritos

Curso 4 de 8 no Análise de Dados GenômicosAnálise Genômica Programa de cursos integrados

We will learn computational methods -- algorithms and data structures -- for analyzing DNA sequencing data. We will learn a little about DNA, genomics, and how DNA sequencing is used. We will use Python to implement key algorithms and data structures and to analyze real genomes and DNA sequencing datasets.

Visualizar o programa do curso

Habilidades que você aprenderá

Bioinformatics Algorithms, Algorithms, Python Programming, Algorithms On Strings

Avaliações

4.8 (415 classificações)

5 stars
337 ratings
4 stars
62 ratings
3 stars
14 ratings
2 stars
1 ratings
1 star
1 ratings

MD

Nov 10, 2016

This was really fun. Really enjoyed the a-ha of the algorithms and the fun of solving the alignment and assembly problems. Feel mildly powerful after assembling a virus genome.

LK

Mar 12, 2016

Excellent intro to the computational challenges in analyzing genomic sequences.\n\nLectures and programming exercises explain algorithms very clearly even for beginners.

Na lição

DNA sequencing, strings and matching

This module we begin our exploration of algorithms for analyzing DNA sequencing data. We'll discuss DNA sequencing technology, its past and present, and how it works.

Module 1 Introduction1:32

Lecture: Why study this?4:29

Lecture: DNA sequencing past and present3:08

Lecture: Genomes as strings, reads as substrings5:02

Lecture: String definitions and Python examples3:33

Practical: String basics 7:14

Practical: Manipulating DNA strings 7:00

Practical: Downloading and parsing a genome 6:29

Lecture: How DNA gets copied3:37

Optional lecture: How second-generation sequencers work 7:10

Optional lecture: Sequencing errors and base qualities 6:37

Lecture: Sequencing reads in FASTQ format4:39

Practical: Working with sequencing reads 11:11

Practical: Analyzing reads by position 6:58

Lecture: Sequencers give pieces to genomic puzzles5:41

Lecture: Read alignment and why it's hard3:09

Lecture: Naive exact matching10:18

Practical: Matching artificial reads 6:53

Practical: Matching real reads 7:24

Ministrado por

Ben Langmead, PhD
Assistant Professor
Jacob Pritt

Transcrição

So now that we know what a sequencer does, and what kind of data it produces,

the next question for us is, how do we analyze this data?

How do we analyze the sequencing data?

We want to answer questions like, how is my genome different from your genome?

Or what does my genome tell me about my predisposition to disease, and

questions like this.

So, unfortunately we can't answer these questions just by looking at the reads.

The reads themselves are far too short.

A single read isn't even long enough to cover a single gene in its entirety.

Human genes are on the order of something like thousands of bases long.

But like we said, one of these second generation sequencing reads is only

on the order of hundreds of bases long.

So to use an analogy if I tore a few words, a few words out of the middle of

a newspaper article, and I showed them to you, you probably wouldn't be able to

tell me very much about that article or what it says, or what newspaper its from.

So, we just can't infer that much

meaningful information from snippets that are this short.

So to answer our scientific questions,

the first problem we have to tackle is we have to take these reads,

these short snippets of DNA, and glue them back together somehow.

We have to have to stitch them back together, so

that we can infer the sequence of the input DNA.

This is analogous to putting together a puzzle.

So, say you want to put together a puzzle.

How do you do this?

Well, you can start by spreading out all the pieces on the table, and then

besides the puzzle pieces, you actually have something else that's very useful.

You have the picture of the completed puzzle that's printed on

top of the puzzle box.

And this picture gives you a useful shortcut.

It's sort of a guide.

So, for example, if you discover that a particular puzzle piece, like, let's say

this puzzle piece up here, which has a lot of bright red on it, we might say,

oh, well, there's only one flower in the picture that looks so bright red.

I guess that puzzle piece probably comes from somewhere around here.

All right so in fact, it turns out we can use pretty much the same kind of strategy

when we're putting together reads from a DNA sequencer.

An important fact about human genomes is that if you take two unrelated human

beings and compare their genome sequences, they're actually very, very similar.

They're about 99.8 to 99.9% similar, depending on exactly how you count.

So that's only about one or two differences every one 1,000 bases or so.

So even though my genome is not exactly the same as yours,

we can still use my genome, or someone else's genome, as a kind of template or

a guide, in the same way that you can use the picture of the completed

puzzle to help you put together the puzzle.

So, let's say that these purple sequences on the left are some sequencing reads.

And they're from your genome.

And then this long string on the right, this black string is my genome,

or someone else's genome, or let's say that it's the human reference genome.

In other words, that's the genome that was put together by the Human Genome Project,

back when the Human Genome Project finished around 2001.

So we can take one of your sequencing reads, one of the sequencing reads from

your genome, and essentially hold it up to the reference sequence.

And look for the spot where that read matches most closely, and

the spot where it matches most closely is our best guess as to where it originated,

as to where it belongs with respect to that genome.

A key point is that we have reference genomes like this.

We have them for many different species, not just for the human genome, but

also for the fruit fly, and the mouse, and

the honey bee, and the cow, chicken, rat, corn, the list goes on.

We have many, many hundreds, thousands of these referenced genomes that are just

available for download in public databases.

So for the first half or so of this course, we'll be discussing some very

useful algorithms and data structures for solving this problem.

We can call this the read alignment problem.

Given a read, a sequencing read, and given a reference genome, how do we find where

the read best matches, where it aligns most closely to the reference genome?

The topic that we'll discuss in the second half

is about the case where we don't have a reference genome.

So maybe we're studying some exotic plant, whose genome no one has ever sequenced

before, or were otherwise working without the benefit of a reference genome.

So in this case, since we don't have a reference, there's no guide to help us put

the puzzle together, in which case we have no choice but to do something analogous to

what you would do, if you wanted to put together a puzzle.

But without the picture of the completed puzzle,

you would just have to hold the puzzle pieces up to each other and

then look for pieces that look like they have patterns that overlap.

So like, for example, in this picture, in this jumble of puzzle pieces here,

we might see this puzzle piece which has bright red on it, and

this other puzzle piece that has bright red on it, and we might say okay,

well maybe they go close to each other.

And then try every possible way of putting them together.

So, there's an analogous way,

there's still a way that we can put together the puzzle,

even if we don't have the picture of the completed puzzle to help us.

And that is the kind of problem that we'll examine in the second half of the course.

But speaking more broadly now, when there is no guide, when we do have to solve this

assembly problem rather than the read alignment problem, this is going to lead

us to a very different set of algorithms and data structures.

And it's actually a very difficult problem, an inherently difficult one.

But it's also a very interesting one.

So that's what we'll discuss in the second half.

Explore nosso catálogo

Registre-se gratuitamente e obtenha recomendações, atualizações e ofertas personalizadas.

O Coursera proporciona acesso universal à melhor educação do mundo fazendo parcerias com as melhores universidades e organizações para oferecer cursos on-line.

© 2019 Coursera Inc. Todos os direitos reservados.

Baixar na App Store

Baixar no Google Play

Coursera
Sobre
Liderança
Carreiras
Lista de cursos
Certificados
Certificados MasterTrack™
Notas
For Enterprise
For Government

Comunidade
Learners
Partners
Developers
Beta Testers
Translators

Conectar
Blog
Facebook
LinkedIn
Twitter
Instagram
YouTube
Tech Blog

Mais
Termos
Privacidade
Ajuda
Acessibilidade
Imprensa
Contato
Diretório
Afiliados