Organisation of the human genome Flashcards
1
Q
Describe the structure of DNA
A
- Double helix
- 2 antiparallel complimentary strands
- Sugar, base and phosphate group
2
Q
What are the 4 bases
A
Adenine, thymine, guanine, cytosine
3
Q
Describe the mitochondrial genome
A
- Closed, circular DNA, densely packed
- 16 569 bp, 37 genes, 13 genes involved in respiratory chain
- 2 rRNAs, 22 tRNAs
- 13 polypeptides
- Genes do not have introns
4
Q
What is the human karyotype?
A
Characteristic number and size of chromosomes
5
Q
How is DNA packaged?
A
Using histones (nuclear-encoded genes)
6
Q
Describe the nuclear genome
A
- 2x10^9 bp, >30 000 genes
- 23 pairs of chromosomes
- Genes spaced irregularly and code for proteins
- > 2m of linear DNA per cell
7
Q
What is a LINE?
A
Long interspersed nuclear element
8
Q
Describe LINEs
A
- 6 to 8 kn sequence
- Can copy themselves to other parts of the genome
- Encode proteins which are required for their integration into the genome
9
Q
What are the 3 LINE families?
A
LINE1, LINE2, LINE3
10
Q
What is a SINE?
A
Short interspersed nuclear element
11
Q
Describe SINEs
A
Use LINE proteins to integrate into genome
12
Q
What are the 2 SINE families
A
ALUs (active) and MIRs (not active)
13
Q
Describe ALUs
A
- Occur only in primates ~ 1 every 3kb
- Classified into subfamilies based on sequence
- > 80M years old (molecular clocks)`
14
Q
What are retrotransposons
A
- Sequences related to retroviruses
- Pol produces a reverse transcriptase which allows DNA to be incorporated into the genome
- Many truncated retroviral sequences 9lack env, or LTRs)
15
Q
What are microsatellites?
A
- Short sequences (1-15bp) repeated in tandem many times
- Result in low complexity sequence
- Prone to expansion and contraction during replication due to polymerase slippage
- Not often found in coding sequences
