warm-up october 9, 2014 1. how was dna analysis used during 9/11? copyright © 2013 crosscutting...

Warm-UpOctober 9, 2014

1. How was DNA analysis used during 9/11?

Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved.www.CrosscuttingConcepts.com

Objective

SWBAT describe the technological advances in DNA analysis.


Agenda

1. Mini-Mystery2. Extract Your Own DNA3. OJ Simpson Documentary4. STR5. Gel Electrophorisis6. Who Ate the Cheese7. PCR8. DNA Evidence9. OJ Simpson Documentary10. Exit Slip Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved.

www.CrosscuttingConcepts.com

Snack Shack\

T. Trimpe 2006 http://sciencespot.net/

Harborville's Beach Snack Shop had been open only an hour when Max stopped in and noticed a new poster announcing a price increase. "I put the sign up this morning," Mr. Levine told him. "I had to raise my prices 10% because I have so many new expenses. Like now I need a new window for my back room. Somebody broke it, trying to get into my store last night."

"Have you called the police?" Max asked. Mr. Levine replied, "No. Nothing was stolen." He led Max to a small storeroom in the back and said, “I use this space as an office. Sat here and made my price change poster last night. Soon as I was done, I left it on that old desk. I locked the door to the main part of my store when I left, so whoever got in was stuck in this little storeroom. There’s nothing here to steal."

Source: http://kids.mysterynet.com/quicksolve/

When Max left he wandered down to the break wall, where Nathan and Trevor were fishing. "Did you hear that somebody broke a window at the Shack?" he asked. "Nope," Nathan said. "We've been here since dawn and haven't talked to anybody." Trevor gestured to the bucket. "We've caught some big ones." Nathan stood. "But now I'm starving. I've got a dollar left from my allowance. If Mr. Levine is there now, I'm going up to the Shack to get a Big Beach Bun."

"Better get another dime from somewhere," Trevor told him. "A dollar's not enough any more. As for me, I'm going home to get a couple sandwiches for myself."

"You both stay right here," Max said. "I know which one of you broke that window. You'd better think of a way to pay for it, because I'm telling Mr. Levine."

How did Max figure it out?

Mr. Levine had just put up his poster about the priceincrease that morning. Nathan and Trevor said they had

been fishing since dawn and had spoken to no one. SinceTrevor knew that a dollar bun was now a dollar and ten

cents, he must have been the one who broke the windowand got inside the back room, where he read the poster

lying on the old desk.

Extract Your Own DNA Lab


Microsatellites - Short Tandem Repeats

The portion of human DNA that forms genes which code for proteins or RNA molecules is very small – over 98% of human

DNA is considered to be non-coding DNA.

For a long time, the function of this DNA was unknown, leading to the term junk DNA becoming popular. Scientists now believe that

much of this non-coding DNA may have important biological functions – we simply haven’t discovered what they are yet.



Inside these sections of non-coding DNA are sequences of 2-6 base pairs called microsatellites.

The microsatellites we’re interested in for this lesson are called Short Tandem Repeats (STRs) which:

• Are usually 2-5 bp and co-dominant

• Have a high degree of polymorphism (variation in DNA sequence between individuals) due to the different number of times the sequence is repeated in individuals

• Are used in forensic cases and paternity testing Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved.



But what does all that mean?

To illustrate, let’s go back to our inheritance example from earlier.



These are STR sequences from two separate people, each block on the ‘string’ represents one repeat of an STR sequence on a chromosome – for this

example, we’ll say the sequence is GATA.

Notice that the mother has two repeats of the GATA sequence on one chromosome and three on the other, while the father has three repeats on one chromosome and five on the other – even if they were both the same color in

this representation, there would still be a visible difference between them.

It is this measurable difference that makes STRs so valuable in forensic science.



Now we see what might happen if those two people had children

We know that STRs are in regions of non-coding DNA on chromosomes and that each person gets one half of their chromosomes from their mother and the other half from their father – tables like this one show the different possible combinations of STR lengths of the offspring of these two individuals

It is this inheritance of STR lengths that makes it so useful in studies of genetics and also in paternity testing. Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved.



Now we see what might happen if those two people had children.

We know that STRs are in regions of non-coding DNA on chromosomes and that each person gets one half of their chromosomes from their mother and the other half from their father – tables like this one show the different possible combinations of STR lengths of the offspring of these two individuals.

It is this inheritance of STR lengths that makes it so useful in studies of genetics and also in paternity testing. Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved.



Y Chromosome STRsThere are certain short tandem repeats that occur only on the Y chromosome. If DNA analysis is performed and there is a result for any of these STRs, then a

Y chromosome must be present.

Since the Y chromosome only occurs in the XY pairing, any sample which contains these STRs must be genetically male.

The STRs on the Y chromosome are highly conserved in each generation. A man inherits his Y-STRs from his father and will pass them on to his sons.

Often this will not point to a single suspect, as with autosomal STRs, but their use can potentially narrow the field to one family.

Gel electrophoresis separatesmolecules on the basis of their charge and size. The charged macromolecules migrate across a span of gel because they are placed in an electrical field. The gel acts as a sieve to retard the passage of molecules according to their size and shape.

What is Gel Electrophoresis?

http://learn.genetics.utah.edu/content/labs/gel/

Restriction Enzymes

The ability to cut and paste DNA predictably is due to the use of restriction enzymes.

They were first identified in and isolated from the bacteria that use them as a natural defense mechanism to cut up the invading DNA of bacteriophages – viruses that infect bacteria.

How does electrophoresis work?

• The gel is made from agar• DNA is negatively charged

• Do opposite charges attract or repel each other?

• Molecules sort based on• Charge• Size• shape

Stages of DNA Profiling

DNA is negatively charged so it is attracted to the positive end of the gel.

The shorter DNA fragments move faster than the longer fragments.

DNA is separated on basis of size.

The chances of two people having exactly the same DNA profile is 30,000 million to 1 (except for identical twins).

DNA Profiling can solve crimes The pattern of the DNA profile is then

compared with those of the victim and the suspect.

If the profile matches the suspect it provides strong evidence that the suspect was present at the crime scene (NB:it does not prove they committed the crime).

If the profile doesn’t match the suspect then that suspect may be eliminated from the enquiry.

Example

A violent murder occurred. The forensics team retrieved a blood

sample from the crime scene. They prepared DNA profiles of the blood

sample, the victim and a suspect as follows:

Was the suspect at the crime scene?

Suspects Profile

Blood sample from crime scene

Victims profile

Information & image from http://www.teachersdomain.org/resource/tdc02.sci.life.gen.lp_dnamysteries/

B. Whose your daddy?Which sample is most likely to be the father?

F1 or F2

C. Identical or not?

Which sets of twins are identical twins?

A. Who done it?

Which suspect matches the bloodstain?

Famous Cases

Colin Pitchfork was the first criminal caught based on DNA fingerprinting evidence.

He was arrested in 1986 for the rape and murder of two girls and was sentenced in 1988.

NOW LET’S SOLVE A MYSTERY USING DNA CLUES!

Who ate the Queen’s Cheese?

Homework

Chapter 9 Review, #12 - 19


Exit SlipOctober 9, 2014

1. Get out a mobile device or use one of the computers and go to m.socrative.com. You can also use one of the iPads that has the Socrative app. 2. When prompted, enter 417101 for the room number.QUESTION: How is DNA evidence analyzed?


warm-up october 9, 2014 1. how was dna analysis used during 9/11? copyright © 2013 crosscutting...

Documents

dna analysis

dna labcopyright

crosscutting concepts

noncoding dna

term junk dna

comquicksolvewhen max

max figure

new poster