Lecture Study Guide_ Microbial Genetics I

What is a Genome?

The complete set of genetic material in an organism.

Define a Gene.

A segment of DNA that contains the instructions for building a specific protein.

What is a Gene product?

The protein or RNA molecule that is produced as a result of gene expression.

What does the Central dogma describe?

The flow of genetic information from DNA to RNA to protein.

What is the structure of DNA?

A double helix formed by two strands of nucleotides held together by base pairs.

What are the base pairing rules in DNA?

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

What is the structure of RNA?

A single-stranded molecule made up of nucleotides, with ribose sugar and uracil instead of thymine.

How do RNA and DNA differ?

RNA is single-stranded, contains ribose sugar, and has uracil; DNA is double-stranded, contains deoxyribose sugar, and has thymine.

What is the purpose of DNA replication?

To create an identical copy of the DNA for cell division.

How do DNA replication and Transcription differ?

DNA replication copies the entire genome, while transcription synthesizes RNA from a specific gene.

What are the three types of RNA and their functions?

mRNA (carries genetic information), tRNA (transfers amino acids), rRNA (makes up the ribosome).

Why can transcription and translation occur simultaneously in prokaryotes?

Because prokaryotic cells lack a nuclear membrane, allowing RNA to be translated while it is still being transcribed.

Why is DNA replication considered semi-conservative?

Because each new DNA molecule consists of one original strand and one newly synthesized strand.

What is the purpose of DNA replication?

To ensure that each new cell receives an exact copy of the DNA.

What is the product of DNA replication?

Two identical DNA molecules.

What is the function of Helicase?

To unwind the DNA double helix at the replication fork.

What is the function of RNA polymerase in transcription?

To synthesize RNA from the DNA template.

What is the function of DNA polymerase I?

To remove RNA primers and replace them with DNA during replication.

What is the replication fork?

The area where the double helix is unwound and replication occurs.

What is the leading strand?

The strand of DNA that is synthesized continuously in the same direction as the replication fork.

What is the lagging strand?

The strand of DNA that is synthesized discontinuously in short sections (Okazaki fragments) opposite the direction of the replication fork.

What are Okazaki fragments?

Short sequences of DNA synthesized on the lagging strand during DNA replication.

What enzyme closes the gaps between Okazaki fragments?

DNA ligase.

In which direction does DNA replicate?

DNA replicates in the 5' to 3' direction.

What is the purpose of Transcription?

To synthesize RNA from a DNA template.

What is the product of Transcription?

mRNA, which carries the genetic information from DNA.

What components are needed for Transcription?

Promoter, RNA polymerase, and terminator.

What are the RNA base pairing rules during Transcription?

Adenine pairs with Uracil (A-U) and Cytosine pairs with Guanine (C-G).

What is the purpose of Translation?

To synthesize proteins based on the sequence of mRNA.

What is the product of Translation?

A formed polypeptide or protein.

What components are needed for Translation?

mRNA, ribosomes, tRNA, and amino acids.

Which part of the ribosome binds to mRNA first?

The small ribosomal subunit.

What does the ribosomal small subunit search for to initiate Translation?

The start codon (AUG) on the mRNA.

What part of the ribosome binds second and what is its purpose?

The large ribosomal subunit, which provides the catalytic site for peptide bond formation.

What is a codon?

A sequence of three nucleotides on mRNA that encodes a specific amino acid.

What is an anticodon?

A sequence of three nucleotides on tRNA that is complementary to a codon on mRNA.

Why is the genetic code referred to as degenerate?

Because multiple codons can code for the same amino acid, providing redundancy.

How does the degenerate code help the cell?

It offers some protection against mutations, as changes in the DNA may not affect the protein.

What are the sites on the ribosome?

A-site (acceptor), P-site (peptidyl), and E-site (exit).

Where does the first codon attach on the ribosome?

The P-site.

Where do the rest of the polypeptide attach on the ribosome?

The A-site.

What is f-Met (N-formyl methionine)?

The first amino acid incorporated into a new polypeptide in prokaryotes, coded by AUG.

What else does AUG code for?

Methionine in eukaryotes.

How are f-met and methionine different?

f-Met is modified with a formyl group, while methionine is not.

What is a stop codon?

A codon that signals the termination of translation, leading to the release of the newly synthesized protein.