Biology Reference
In-Depth Information
as a result of the duplication of an ancestral
-luteinizing hormone-like (
LHB
;
19q13.3) gene. A single base deletion (A1540) altered the translational reading
frame of the ancestral gene allowing read-through into what was originally 3
untranslated region (UTR). An insertion of a CG dinucleotide also occurred at
nucleotide 1612 within the ancestral 3
UTR region and served to extend the
chorionic gonadotropin
-subunit protein by a further 8 amino acids. The
CGB
gene therefore evolved from its
LHB
-like ancestor by acquiring 8 amino acids
through translation in a new reading frame and incorporating 24 novel amino
acids from the 3
UTR into its coding sequence.
8.4. Insertion of transposable elements in evolution
Transposable elements in the human genome are essentially of two kinds, those
Table 8.1.
Retroelements in the human genome
Retroelement type
Retroelement
Copy number
% of genome
family
C-type-related HERVs
HERV-ER1
0.07%
superfamily
HERV-E (4-1,
35-50
ERVA, MP-2)
HERV-E LTR
500-600
51-1
35-50
ERV1
10-15
HERV-R (ERV3)
10
RRHERV-1
20
S71
15-20
S71 LTR
50-100
ERV-FRD
5-7
ERV9
30-40
0.2%
ERV9 LTR
3000-4000
HERV-P (HuERS-P1,
50-90
0.01%
HuERS- P2, HuERS-
P3/HuERS-P)
HERV-I (RTV
L
-I)
25-50
0.01%
ERV-FTD
5-7
C-type and HTLV-
HERV-H (RTVL-H,
900-1000
0.2%
related HERVs
RGH)
HERV-H-LTR
1000
HRES1
2
A-B- and D-type-
HML families 1-6
50
0.5%
related HERVs
HERV-K (HM,
HLM, HML-1)
HERV-K LTR
10000-25000
ERV-MLN (HML-4)
20-25
THE-1 elements
THE 1
10000
1%
TTHE-1 LTR
30000
Nonviral retroposons
LINE-1
100000
5%
Alu
500000
5%
SINE-R
5000
0.1%
