LINES AND SINES

Question 1

What are the two types of repetitive DNA?

Answer 1

Tandem repeats: short repeated sequences that are present in clusters

Interspersed repeats: repeated sequences with gaps in between, so you have the repeat, then some normal DNA, then another repeat

Question 2

What are the 4 main classes of interspersed repeat sequences in the genome.

Answer 2

Long Interspersed Nuclear Elements (LINES)
Short Interspersed Nuclear Elements (SINES)
Endogenous Retroviruses
DNA transposing

Question 3

Which interspersed genetic elements replicate via a copy and paste mechanism?

Answer 3

Remember this used an RNA intermediate so:
LINES
SINES
Endogenous retroviruses

Question 4

Which interspersed genetic elements replicate via a cut and paste mechanism?

Answer 4

DNA transposons

Question 5

DNA transposons make up how much of the human genome?

Answer 5

DNA transposons make up 3% of the human genome

Question 6

Endogenous retroviruses make up how much of the human genome?

Answer 6

Endogenous retroviruses comprise 8% of the human genome

Question 7

Which types of interspersed repeat are believed to be transpositionally active?

Answer 7

Only the LINES and SINES are believed to be transpositionally active. Endogenous retroviruses and DNA transposons are believed to be transpositionally inactive.

Question 8

How much of the human genome is comprised of LINE elements? (All 3 families)

Answer 8

21%

Question 9

How much of the human genome is comprised of LINE1 elements?

Answer 9

17%

Question 10

How much of the genome is comprised of SINES?

Answer 10

13%

Question 11

Describe the ways in which LINEs and SINEs can disrupt genome function?

Answer 11

1) Transposition of LINEs and SINEs into a gene can disrupt gene function
2) Germline insertions of LINEs and SINES can be the cause of many genetic disorders. (Mechanisms of silencing, methylation, histone modification, piwi interacting RNAs in operation in germline)
3) In somatic cells, transposition into a tumour suppressor gene can result in cancer
4) unequal crossing over involving LINEs and SINEs can result in gene duplication or deletion

Question 12

Which one, LINEs or SINEs could be referred to as an autonomous retrotransposable element

Answer 12

LINEs because they contain two open reading frames encoding a RNA binding protein and a endonuclease/reverse transcriptase that are required for insertion into a distant site in the genome

Question 13

Describe the structure of a LINE1 element

Answer 13

Promoter is in the line 1 element as opposed to outside, has two open reading frames, a polyA site and is flanked by direct repeats