Question

How many amino acids could be specified if codons consisted of two nucleotides instead of three? What problem would this present for an organism making proteins using all 20 amino acids?

Answer 1

So have you seen this chart before?

Answer 2

err table*

Answer 3

yes in my notes

Answer 4

its in*

Answer 5

So how many nucleotides are there normally?

We have adenosine, thymine, cytosine, and guanine

Do you agree

Answer 6

agreed

Answer 7

so in a codon, how many nucleotides do we usually have?

Look at the table

It can be CAG or TCG

how many of the letters do we need?

Answer 8

normally 20 but up to 64 possible codes right

Answer 9

so you have 20 different amino acids from the 64 possible codes, yes

Answer 10

but how many letters are in a codon?

Answer 11

three

Answer 12

Good

so we had 64 possible codes because

we have 4 nucleotides (our letters A, T, C, and G)

and since a codon is made up of 3 letters
4 * 4 * 4 = 64

Answer 13

so for your question, we're saying that we only have 2 nucleotides, so we only have 2 letters

Answer 14

but what about amino acids?

Answer 15

Yeah, so about that, I don't know how they expect you to give a precise answer because there's no way to know

Answer 16

We could give a range?

Answer 17

oh wait

Answer 18

yeah thats what i dont understand

Answer 19

`codons consisted of two nucleotides instead of three`

so we still have 4 nucleotides or letters

but instead of using 3 letters we will only use 2 letters

Answer 20

Let's just try to see mhmm

Answer 21

So if you compare it with this table

Answer 22

16?

Answer 23

t's possible that each box in the table that I just drew for you has an amino acid

So I guess we could say that's the maximum number of amino acids that could be specified
But in reality if it codons were really 2 nucleotides and not 3, there would probably be more amino acids (just like we see in the main table since we do have a start codon and a stop codon and multiple codes are for the same protein)

Answer 24

Does that make sense?

Like our big table has 16 boxes too but there's 20 amino acids
But that's because of wobble pairing where the third letter of the codon might not necessarily change what amino acid it is coding for

so similarly for our table, it's possible to have 16 or maybe more. It could even be less if a group of them were just a stop codon and start codon
But it would be somewhere around 16

Answer 25

Alright that's what i thought, but for the second part "What problem would this present for organisms making proteins using all 20 amino acids?" if they only have 16 will they become unnourished and overworked?

Answer 26

no no, these are just the building blocks for proteins so it's like trying to say that sugar would get worked out if something in it has been changed

think about mutations
if there's only 2 letters to make a codon, what happens if one of the letters gets changed?

When we have 3 letters, you can see that if we change the last letter, most likely nothing will change
But what would happen if it's only 2 letters aka nucleotides?

Answer 27

So everything would stay the sam and they would still be able to get the necessary proteins

Answer 28

Well maybe organism would be able to make the necessary proteins in this new world where it exists

But think about what would happen in a mutation?

Answer 29

mutations happen all the time and the organisms have processes to try to correct it

but some mutations can cause diseases and all because proteins don't function properly

Answer 30

That would happen in this case? If only 16 amino acids could be specified, how could an organism use all 20 amino acids to make proteins.

Answer 31

oh you're right mhmm, I guess 16 really is the max number of amino acids that could be specified

Answer 32

so yeah that would be a problem, it would be able to use all 20 amino acids

Answer 33

So then it would cause the organism to be overworked and undernourished, or still incorrect?

Answer 34

that could work but you could also say that the organism wouldn't be able to function properly since it's not able to produce the amino acids it needs to make certain proteins

Answer 35

Yes that makes since, thank you so much for helping me

Answer 36

No problem!