# AS biology introns and exons

Watch
Announcements
#1
Can someone help with these questions/ check my answers are correct?

There are 3 billion bases in human DNA.
60 million bases make up the exons.

1)Calculate the percentage of human DNA which make up codons.
I got 33.3 % because i divided the 3 billion bases in human DNA by 3. ( not sure if this is right but does dividing the total number of bases in human DNA by 3 give us the number of codons?) I got 1 billion codons and then divided that by 3 billion and then multiplied by 100??

2)how many bases are there that make up the junk DNA?
2940000000 because I did 3 billion - 60 million

3)what percentage of human DNA is introns?
3 billion-60 million= 2940000000/3 billion X100= 98%
Last edited by idk__21; 1 month ago
0
1 month ago
#2
1. I don’t think this is asking about the number of codons as a percentage of total bases. I think instead you need to think about if codons include introns or just exons and use that to work out the percentage.

2 and 3 look right to me.
0
1 month ago
#3
I forgot to add codons are found on mRNA - I don’t know if this means you have to halve it (I don’t think it would but I’m tired).
0
#4
(Original post by Hellllpppp)
1. I don’t think this is asking about the number of codons as a percentage of total bases. I think instead you need to think about if codons include introns or just exons and use that to work out the percentage.

2 and 3 look right to me.
yeah so for q1 what calculation could we do sorry but im lost
0
1 month ago
#5
(Original post by Amnar_1)
yeah so for q1 what calculation could we do sorry but im lost
I think it’s 60 million/ 3 billion x 100
1
1 month ago
#6
(Original post by Amnar_1)
yeah so for q1 what calculation could we do sorry but im lost
60 million/3 billion x 100
2
#7
(Original post by Hellllpppp)
I think it’s 60 million/ 3 billion x 100
right that makes sense thank you!!
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### What factors affect your mental health the most right now?

4.93%
Uncertainty around my education (378)
14.78%
Uncertainty around my future career prospects (283)
11.06%
Lack of purpose or motivation (359)
14.03%
Lack of support system (eg. teachers, counsellors, delays in care) (119)
4.65%
Impact of lockdown on physical health (155)
6.06%
Loneliness (218)
8.52%
Financial worries (94)
3.67%
Concern about myself or my loves ones getting/having been ill (106)
4.14%
Exposure to negative news/social media (120)
4.69%
Lack of real life entertainment (135)
5.28%
Lack of confidence in making big life decisions (224)
8.76%
Worry about missed opportunities during the pandemic (241)
9.42%