1.2 DNA Replication - Transcription - Translation

What is the genome of an organism?

The sum total of genetic material of an organism.

Where do most genomes exist?

In the form of chromosomes.

What additional forms can genomes take in eukaryotes?

Plasmids or in certain organelles like mitochondria and chloroplasts.

What is the composition of the genome of cells?

Exclusively made up of DNA.

What can the genome of viruses contain?

Either DNA or RNA.

What defines a chromosome?

A distinct cellular structure composed of a neatly packaged DNA molecule.

What structure is DNA wound around in eukaryotic chromosomes?

Histone proteins.

Where are eukaryotic chromosomes located?

In the nucleus.

What are the two types of chromosome sets in cells?

Diploid (in pairs) or haploid (single).

How does bacterial chromosome structure differ from eukaryotic?

Bacterial chromosomes are condensed into a packet by histone-like proteins.

What are the three categories of genes?

Structural genes, regulatory genes, and genes coding for RNA machinery.

What is meant by genotype?

The sum of all gene types; an organism’s distinctive genetic makeup.

What is meant by phenotype?

The expression of the genotype that creates traits.

What is a nucleotide?

The basic unit of DNA structure including phosphate, deoxyribose, and a nitrogenous base.

How do nucleotides bond in DNA?

Covalently bond to each other in a sugar-phosphate linkage.

What nitrogenous bases pair together in DNA?

Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).

What is the arrangement of DNA strands in a double helix?

Antiparallel arrangement.

Which direction does one side of the DNA double helix run?

From 5' to 3'.

What is the overall DNA replication process termed?

Semiconservative replication.

What is the function of helicase in DNA replication?

Unzipping the DNA helix.

What does DNA polymerase III do?

Adds bases to the new DNA chain and proofreads for mistakes.

What is the role of ligase in DNA replication?

Final binding of nicks in DNA during synthesis and repair.

During DNA replication, what keeps the strands apart?

Single-strand binding proteins.

What distinguishes the leading strand from the lagging strand during DNA synthesis?

The leading strand is synthesized continuously, while the lagging strand is synthesized in segments.

What are Okazaki fragments?

Short DNA fragments synthesized on the lagging strand.

What is a gene?

A segment of DNA that holds the code for one polypeptide.

How is the code for protein synthesis determined?

By the specific order of nitrogen bases in the gene.

What is transcription?

The process of transferring code from DNA to complementary base sequence of mRNA.

What is the role of mRNA?

Carries the genetic code from DNA to the ribosome for protein synthesis.

What is the role of tRNA?

Carries amino acids to the ribosome and matches them with the corresponding mRNA codon.

What is the start codon?

The first codon of an mRNA molecule that signals the start of translation, usually AUG.

What happens during termination of translation?

The polypeptide chain is released when a stop codon is reached.

How do mutations affect the genetic code?

Mutations can lead to changes in genotype and phenotype, affecting protein function.

What is a point mutation?

A mutation affecting a single base in the DNA sequence.

What is a missense mutation?

A change that results in the placement of a different amino acid in a protein.

What is a silent mutation?

Alters a base but does not change the amino acid.

What is a nonsense mutation?

Changes a normal codon into a stop codon, truncating the protein.

What is a frameshift mutation?

Insertion or deletion of bases that alters the reading frame of mRNA.

What role does DNA polymerase I play during DNA replication?

Removes RNA primers and replaces them with DNA.

What is the function of helicase in DNA replication?

Unzips the DNA strands to allow for replication.

What is meant by 'redundancy' in the genetic code?

Some amino acids are represented by more than one codon, providing a safeguard against errors.

What is the primary role of the rough ER in protein synthesis?

Processing and modifying newly synthesized proteins before they are sent to the Golgi apparatus.

What are spliceosomes responsible for?

Removing introns from pre-mRNA during mRNA processing.

What molecule links mRNA to ribosomes?

Ribosomal RNA (rRNA).

What is the role of amino acids in proteins?

They are the building blocks that form polypeptides and ultimately proteins.

How are amino acids linked together?

By peptide bonds.

What happens to an mRNA after translation?

It is often degraded after the polypeptide is synthesized.

What do anticodons on tRNA do?

Base-pair with codons on mRNA during translation.