Answer:
The correct option is option A
Explanation:
Restriction enzymes are endocleases that cleave DNA fragment (<u>of usually four, five or six nucleotide long</u>) at <u>specific sites to produce blunt or sticky ends</u>. They <u>recognize palindromic sequences of host DNA when cleaving the specific sites</u>. The sequences below (on complementary strands) give an example of a palindromic sequences.
5'-CCC║GGG-3'
3'-GGG║CCC-5'
As can be seen above, when read from 5' to 3', the two sequences are the same despite being on opposing strands. And when cut between the guanine (G) and cytosine (C) (as shown above), it produces a blunt end. But when cut as shown below produces a sticky end.
5'- G║AATTC -3'
3'- CTTAA║G -5'
The explanation above shows options C and D are right while option A is wrong (hence the correct option).
Also, bacteria prevent their own DNA from been digested by restriction enzymes by adding methyl group to their restriction sites <u>which prevents restriction enzymes from recognizing restriction sites of their DNA;</u> this generally makes bacterial DNA to be highly methylated. This explanation makes option B right also.
Answer:
The dominant curled wing allele is also a recessive lethal.
Explanation:
If we look at the F2 ratio we see that :
curled wings: straight wings= 160:80
=2:1
Hence, if curled wings is considered to be a dominant trait then Curled wings * straight wings
Dd x dd
Punnet square will be as follows :
d d
D | Dd | Dd
d | Dd | dd
Hence in order to get F2
Dd x dd
Punnet square will be the same as above if the F1 cross is Dd* Dd
D d
D DD Dd
d Dd dd
if DD is lethal then the ratio is
Dd:dd=2:1
that is curled wings: straight wings=2:1
Hence, The dominant curled wing allele is also a recessive lethal.
Are there options, or is it short answer?
