MBB 267 Week 4: Barnes 2

Question 1

What is satellite DNA?

Answer 1

Satellite DNA = tandemly repeated sequences between 1 and 500 bp, found in many genomes. Especially important at mammalian centromeres

Question 2

What is a tandem repeat?

Answer 2

Tandemly repeated = the same sequence repeated one after another in the same orientation with no gaps

Question 3

How much satellite DNA is in humans?

Answer 3

6%

Question 4

What are the different types of satellite DNA?

Answer 4

DNA satellite

• DNA satellite
• Microsatellites
• Minisatellites

Question 5

What are Microsatellites?

Answer 5

Microsatellites: Defined as 1 – 13 bp Mostly 1 – 4 bp and less than 150 repeats For example - ATATATATATATATATATATATAT

Question 6

What are Minisatellites?

Answer 6

Minisatellites: Defined as 14 – 100 bp Tandem arrays of 1 – 5 kb around the genome.

Question 7

Why are there differences in the satellite DNA between individuals?

Answer 7

Many causes:
1.Replication slippage
1-Dissociation of the DNA polymerase during replication
2-Nascent DNA strand can rehybridise with another repeat in the array, in a misaligned way – i.e. with an identical repeat earlier or later in the array
3-Replication continues, yielding a daughter strand that is longer or shorter than the template
2. Unequal crossing over during meiosis
1-Crossover between misaligned repeats on sister chromatids
2-One gamete with more copies and one gamete with less copies of the repeat

Question 8

What is the scientific use of satellite DNA?

Answer 8

DNA fingerprinting.

Question 9

What is DNA fingerprinting?

Answer 9

DNA fingerprinting is a method used to identify an individual from a sample of DNA by looking at unique patterns in their DNA. Uses the polymorphism in minisatellite length between individuals to identify them: paternity testing, forensics, genetic mapping

Question 10

How does DNA fingerprinting work?

Answer 10

Process:
1-Extract DNA
2-Digest with a convenient restriction enzyme
3-Separate fragments on an agarose gel
4-Southern blot using minisatellite sequence as a probe
5-Observe characteristic bands for each individual (two alleles for each locus in a diploid individual)
6-Do this for a number of minisatellite sequences

Question 11

Uses of satellite SNA?

Answer 11

Find the length of tract lengths using southern blotting or PCR