What the 3 components of a nucleotide?
Describe the DNA molecule formed form the model
3. What is a codon?
Describe the backbone of a DNA molecule
Explain the base-pair rule among DNA nucleotides.
Explain the base-pair rule during transcription of DNA to form an RNA molecule. (5 points)
Allow the DNA strand to be transcribed to an mRNA
The Correct Answer and Explanation is :
1. The 3 components of a nucleotide:
A nucleotide, which is the basic building block of DNA and RNA, consists of three components:
- A phosphate group: This is a phosphorus atom bonded to four oxygen atoms. It connects nucleotides together in the chain by forming phosphodiester bonds.
- A sugar molecule: In DNA, this is deoxyribose, and in RNA, it is ribose. The sugar has five carbon atoms, with one oxygen atom attached to each carbon. The sugar provides the structural framework for the nucleotide.
- A nitrogenous base: This can be one of four bases: adenine (A), thymine (T), cytosine (C), or guanine (G) in DNA; in RNA, thymine is replaced by uracil (U).
2. DNA Molecule and Its Structure:
DNA, or deoxyribonucleic acid, is a double-stranded molecule composed of two long chains (polynucleotide strands) that coil around each other to form a double helix. Each strand consists of a backbone of sugar and phosphate groups, with nitrogenous bases extending toward the inside. The two strands are held together by hydrogen bonds between complementary base pairs, which are crucial for maintaining the structure of the double helix. The strands are anti-parallel, meaning they run in opposite directions. The structure was famously elucidated by James Watson and Francis Crick.
3. What is a codon?
A codon is a sequence of three nucleotides in mRNA that encodes for a specific amino acid or a stop signal during protein synthesis. For example, the codon “AUG” codes for the amino acid methionine, which is the start codon for translation.
4. The Backbone of a DNA Molecule:
The backbone of a DNA molecule is made up of alternating sugar (deoxyribose) and phosphate groups. This structure forms the “sides” of the ladder-like structure of the DNA, with the nitrogenous bases extending inwards, forming the “rungs.”
5. Base-Pair Rule in DNA:
The base-pair rule is fundamental for DNA structure and replication. Adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). These pairs are held together by hydrogen bonds, which ensure the two DNA strands remain stable but can separate during processes like replication.
6. Base-Pair Rule during Transcription:
During transcription, a DNA sequence is used to synthesize an RNA molecule. The base-pair rule is similar, but with one key difference: uracil (U) replaces thymine (T) in RNA. So, during transcription:
- Adenine (A) pairs with uracil (U),
- Thymine (T) pairs with adenine (A),
- Cytosine (C) pairs with guanine (G),
- Guanine (G) pairs with cytosine (C).
7. Transcription of DNA to mRNA:
Let’s say we have the following DNA strand:
DNA strand (template):
5′ – ATCGGCTA – 3′
During transcription, the RNA polymerase reads the template DNA strand and synthesizes a complementary mRNA strand. The resulting mRNA will be complementary to the DNA template, with uracil (U) replacing thymine (T). Here’s how it works:
- The DNA sequence “A” pairs with “U” in RNA,
- “T” pairs with “A”,
- “C” pairs with “G”,
- “G” pairs with “C”.
Thus, the transcribed mRNA would be:
mRNA (after transcription):
5′ – UAGCCGAU – 3′
This mRNA will later be used during translation to synthesize proteins. The process ensures the genetic information is faithfully copied and used to create proteins necessary for cell function.