Nucleic Acids

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Questions and Answers

Which of the following accurately describes a gene?

A type of nucleotide found in RNA.

A set of DNA chains containing information for a complete organism. (correct)

A sequence of RNA bases.

A protein synthesizer in ribosomes.

What is Chargaff's rule concerning the base composition of DNA?

The amount of adenine is equal to the amount of thymine, and the amount of guanine equals the amount of cytosine. (correct)

The amount of cytosine equals the amount of thymine.

The amount of purine bases equals the amount of RNA bases.

The amount of adenine equals the amount of guanine.

What is the primary role of ribosomal RNA (rRNA)?

To synthesize DNA from RNA.

To act as a structural component of ribosomes. (correct)

To transport amino acids to ribosomes.

To carry messages from DNA to ribosomes.

Which structure is formed by the packaging of DNA around histone proteins?

Chromatin Signup and view all the answers

What is the main difference between DNA and RNA nucleotides?

DNA has deoxyribose sugar; RNA has ribose sugar. Signup and view all the answers

Which pairing of nitrogenous bases indicates proper base pairing properties of DNA?

Adenine - Thymine Signup and view all the answers

What percentage of the human genome is estimated to encode for proteins?

2% Signup and view all the answers

Which molecules are primarily involved in the process of protein synthesis?

mRNA, rRNA, and tRNA Signup and view all the answers

What role do non-coding DNA elements play in gene expression?

They regulate gene expression by turning genes on or off. Signup and view all the answers

What is a nucleosome composed of?

Eight histone proteins. Signup and view all the answers

Which of the following correctly describes the relationship between DNA replication and the template strands?

Only one strand acts as a template to produce another strand. Signup and view all the answers

What encodes the instructions for assembling amino acids into proteins?

Triplets called codons. Signup and view all the answers

Which statement about mutations is true?

Mutations can have no effect on the organism's health. Signup and view all the answers

What process synthesizes messenger RNA in the nucleus?

Transcription. Signup and view all the answers

What is the primary function of tRNA during translation?

To transfer amino acids to the growing polypeptide chain. Signup and view all the answers

How do methylation and acetylation influence DNA replication?

They can either activate or suppress DNA replication. Signup and view all the answers

Which part of the histone extends outwards to form a tail?

N-terminus. Signup and view all the answers

What is required for proper translation of codons into polypeptides?

The codons must be read in the correct order. Signup and view all the answers

Study Notes

Nucleic Acids - Lecture 4

Genome: A complete set of DNA strands holding all the instructions for an organism, inheritable. Formed by sequences of bases (A, T, G, C) – these sequences are GENES. Each gene codes for one protein. The central dogma is DNA -> RNA -> Protein .
DNA Structure: Double-stranded, anti-parallel helix. Bases pair specifically: A with T (2 hydrogen bonds), G with C (3 hydrogen bonds). Purines (A, G) and Pyrimidines (T, C) pair in a consistent manner. The numbers of A and T bases are equal to the numbers of G and C bases (Chargaff's rule). DNA strands have 5' and 3' ends.
RNA Structures: Nucleic acid, single-stranded but can form complex 3D shapes. Three main types:
mRNA: Copies the DNA code and carries it to ribosomes for protein synthesis.
tRNA: Carries amino acids to ribosomes during protein synthesis (translation).
rRNA: Component of ribosomes; site of protein synthesis.
Nucleotide Structure: Nucleotides consist of a phosphate group, a pentose sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base. Common nucleotides include ATP (energy), cAMP (second messenger), GTP (energy and information transfer).
DNA Packing (Chromatin):
DNA is neatly organized within cells by histones (proteins). Histones form a core around which DNA wraps (nucleosome).
Nucleosomes are like beads on a string; they coil and stack, creating chromatin fibers.
Humans have 25,000 genes, but most of the DNA is non-coding (“junk DNA”). Non-coding DNA plays important regulatory roles. Enhancers and repressors are types of regulatory elements in non-coding DNA.
Chromatin remodeling is crucial for controlling gene expression and cell differentiation.
Gene Expression & Cell Specialization:
Cells have the potential to become any cell type; however a cell becomes specialized by only expressing a subset of its genes. This means that cells only express 20% of their total genes.
DNA Replication:
Semi-conservative process: Each new DNA molecule contains one old strand and one newly synthesized strand.
DNA polymerase is the enzyme that builds new DNA strands using an existing strand as a template.
Mutations & Repair:
Mutations are changes to DNA, sometimes leading to incorrect protein production.
Mechanisms to detect and repair errors exist.
Genetic Code (Translation):
Instructions for assembling proteins are stored as codons (three-nucleotide sequences).
61 codons code for amino acids, 3 are stop signals.
The mRNA code directs tRNA to bring the appropriate amino acids to ribosomes, creating a polypeptide chain.
Transcription:
Copying DNA to mRNA.
Catalyzed by RNA polymerase.
RNA nucleotides are added following base-pairing rules (U replaces T).
Translation:
Protein synthesis using mRNA as a template.
Ribosomes synthesize protein using tRNA to deliver amino acids.

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Description

This quiz covers important concepts related to nucleic acids, focusing on the structure and function of DNA and RNA. Key topics include the genome, DNA structure and base pairing, and the types of RNA involved in protein synthesis. Test your understanding of the fundamental roles nucleic acids play in genetics.