A strand of DNA contains the following bases. ATT CCG GGA TTT
a) what amino acids are coded for?
First of all, would the mRNA strand be UAA GGC CCU AAA?
mRNA is short for "messenger ribonucleic acid", and is the transcription copy of the DNA sequence you provided. When transcripting from DNA to mRNA, the bases are matched up like this:
A-->U (uracil; only found in RNA, which lacks T)
T-->A
C-->G
G-->C
To translate your sequence:
DNA ATT CCG GGA TTT
mRNA UAA GGC CCU AAA
Yes, you are correct! When transcription occurs, DNA is converted into mRNA using the base pairing rules. Adenine (A) in DNA pairs with uracil (U) in RNA, thymine (T) in DNA pairs with adenine (A) in RNA, guanine (G) pairs with cytosine (C) in both DNA and RNA, and cytosine (C) pairs with guanine (G) in both DNA and RNA. So, the mRNA strand corresponding to the given DNA sequence "ATT CCG GGA TTT" would indeed be "UAA GGC CCU AAA".
Now, to determine the amino acids that are coded for, we need to refer to the genetic code. The genetic code is a set of rules that pairs specific sequences of three RNA nucleotides (called codons) with specific amino acids.
Let's break down the mRNA sequence into codons: UAA GGC CCU AAA. Each codon consists of three nucleotides. Starting from the beginning, the codons are UAA, GGC, CCU, and AAA.
To find the amino acids coded for, we can consult a genetic code table. One such commonly used table is known as the standard genetic code table. Here is an example of the genetic code table:
Codon | Amino Acid
----------------------
UAA | Stop
GGC | Glycine
CCU | Proline
AAA | Lysine
Based on the genetic code table, the codons UAA and AAA both code for a "Stop" signal, indicating the end of the protein synthesis. The codon GGC codes for the amino acid glycine, and the codon CCU codes for the amino acid proline.
Therefore, the amino acids coded for by the given DNA sequence "ATT CCG GGA TTT" are glycine and proline.