Chapter 6: Nucleic Acids And Protein Synthesis Flashcards
What are the components of a nucleotide?
Nucleotides consist of three components:
Sugar: Deoxyribose (in DNA) or ribose (in RNA).
Phosphate Group: A phosphate group bonded to the sugar.
Nitrogenous Base: Either a purine (adenine, guanine) or pyrimidine (cytosine, thymine, uracil).
What are purines and pyrimidines?
Purines: Adenine (A) and Guanine (G), characterized by a double-ring structure.
Pyrimidines: Cytosine (C), Thymine (T), and Uracil (U), characterized by a single-ring structure.
Describe the structure of a DNA molecule.
Double Helix: DNA is structured as a double helix.
Antiparallel Strands: The strands run in opposite directions (5′ to 3′ and 3′ to 5′).
Complementary Base Pairing: A pairs with T (two hydrogen bonds) and C pairs with G (three hydrogen bonds).
Phosphodiester Bonds: Nucleotides are linked by phosphodiester bonds between the sugar of one nucleotide and the phosphate of another.
What is semi-conservative replication of DNA?
Occurs During the S phase of the cell cycle:
- DNA double Helix Unwinds
- Helicase breaks H bonds between bases and the 2 strands are separated, both the strands are used as templates
- Free activated DNA nucleotides are activated with 2 additional phosphates - 3 total groups free in nucleus
- bases of activated nucleotides form H bonds with bases according to complementary base pairing
- DNA polymerase attaches each of the two separated strands and it catalyzes the formation of the new strand of DNA
Describe the structure of an RNA molecule using mRNA as an example.
Single Strand: RNA is usually single-stranded.
Ribose Sugar: Contains ribose instead of deoxyribose.
Nitrogenous Bases: Contains A, U (instead of T), C, and G.
What is a polypeptide and how is it related to genes?
A polypeptide is a chain of amino acids coded for by a gene, which is a sequence of nucleotides in DNA.
What is the universal genetic code?
The genetic code consists of triplets of DNA bases (codons) that correspond to specific amino acids, including start (AUG) and stop codons (UAA, UAG, & UGA).
Leading & Lagging Strands
Leading Strand: Continuously synthesized in the direction of the replication fork.
Lagging Strand: Synthesized discontinuously in Okazaki fragments due to the antiparallel nature.
These fragments are joined by an enzyme called DNA Ligase
Result of Semi Conservative DNA Replication
2 DNA Molecules, Each contains 1 original strand, 1 newly synthesized strand. This is why its called semi conservative.
How is DNA information used during transcription and translation?
Transcription: RNA polymerase synthesizes mRNA from the template strand of DNA.
Translation: Ribosomes read codons on mRNA, and tRNA delivers the corresponding amino acids using anticodons.
What are the transcribed and non-transcribed strands of DNA?
Transcribed Strand: The strand used for transcription to form mRNA.
Non-Transcribed Strand: The complementary strand that is not used in transcription.
How is the primary transcript modified in eukaryotes?
Non-coding sequences (introns) are removed, and coding sequences (exons) are spliced together to form mature mRNA.
What is a gene mutation?
A gene mutation is a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide.
What are the types of gene mutations and their effects?
Substitution: One nucleotide is replaced by another; may or may not affect the polypeptide.
Deletion: A nucleotide is removed; can cause a frameshift, altering the entire amino acid sequence.
Insertion: An extra nucleotide is added; can also cause a frameshift.
What are the three main stages of protein synthesis?
- Transcription
- RNA Processing
- Translation
