Lesson 1.1: The Central Dogma of Molecular Biology

Practice flashcards covering DNA structure, replication, transcription, and translation topics from the lecture notes.

What is the Central Dogma of Molecular Biology?

A framework that outlines how genetic information flows from DNA to RNA to protein through replication, transcription, and translation.

What is DNA?

Deoxyribonucleic acid; the molecule that carries genetic instructions for development, functioning, and reproduction in all living cells.

What are the main structural differences between DNA and RNA?

DNA is double-stranded with deoxyribose and thymine; RNA is usually single-stranded with ribose and uracil.

What is replication?

The process of copying DNA to produce two identical DNA molecules; semiconservative.

What enzymes are involved in DNA replication?

Helicase, single-strand binding proteins (SSBPs), gyrase/topoisomerase, primase, DNA polymerase III, DNA polymerase I, and DNA ligase.

What is the function of Helicase?

Exposes the nitrogenous bases by breaking the H-bonds between them

What is the replication fork?

The Y-shaped region where DNA unwinds and replication occurs.

What is the function of gyrase or topoisomerase?

Prevents supercoiling or the unwound DNA strands becoming overly twisted during replication

What are single-strand binding proteins or SSBPs?

Prevents the DNA strands from re-annealing

What is the function of Primase?

synthesizes short RNA primers that are around 8-12 nucleotides long at the 3’ end of the DNA

What is the function of DNA Polymerase III?

Adds nucleotides to the 3' end of the RNA primers to synthesize the new DNA strand.

What is the function of DNA Polymerase I?

Removes RNA primers and replaces them with DNA nucleotides.

What is DNA Ligase?

Catalyzes the formation of phosphodiester bonds to seal nicks between adjacent DNA fragments.

What direction does DNA replication proceed?

DNA is synthesized form 5' to 3' on the growing daughter strand, meaning DNA polymerase III always moves from the 3’ to 5’ end of the parents strand (the original strand)

What is the leading strand?

The strand synthesized continuously in the 5' to 3' direction using a single RNA primer.

What is the lagging strand?

The strand synthesized discontinuously in short fragments (Okazaki fragments) in the 5' to 3' direction with multiple RNA primers.

What are Okazaki fragments?

Short DNA fragments synthesized on the lagging strand, later joined by DNA ligase.

What are Chargaff's rules?

In DNA, the amounts of adenine equal thymine and guanine equal cytosine (A=T and G=C).

What is transcription?

The process of copying a DNA segment into an RNA transcript by RNA polymerase.

Which enzyme carries out transcription, which attaches to the template DNA strand and begins to catalyze production of complementary mRNA?

RNA polymerase

What is the Promoter region in transcription

DNA sequences that signal RNA polymerase to start transcription

What is the promoter region for DNA transcription for prokaryotes?

Pribnow box (sequence: TATAAT)

What is the promoter region for DNA transcription for eukaryotes?

Goldberg-Hogness box (sequence: TATTAA)

What is the template strand?

it is read by RNA polymerase form the 3’ to 5’ end, and acts as the template for the RNA synthesis

what is the coding strand?

it determines the sequences of the RNA strand, and is not read by RNA polymerase

What is reverse transcription?

how retroviruses synthesis complementary DNA, with viral RNA as the template

What is translation?

The process of assembling a polypeptide chain from mRNA using ribosomes and tRNA.

What are the three types of RNA important in translation?

Messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).

What is the Shine-Dalgarno sequence?

Prokaryotic ribosome binding site on mRNA (sequence: AGGAGGU)

What is the Kozak sequence?

Eukaryotic translation initiation (sequence: GCCRCCAUGG)

What are the three binding sites of the ribosome?

the A, P, and E site

What is the A (aminoacyl) site on the ribosome?

the site where tRNA is added to the growing polypeptide chain

What is the P (peptidyl) site?

where peptide bonds are made and where used tRNA is released

What is the E (exit) site?

where the peptide chain exits

What is a codon?

A three-nucleotide sequence on mRNA that codes for a specific amino acid.

What is the start codon and stop codons?

Start codon AUG codes for methionine; Stop codons UAA, UAG, UGA terminate translation.

Why is the genetic code degenerate?

More than one codon can code for the same amino acid.

What is reverse transcription in retroviruses?

Synthesis of complementary DNA (cDNA) from viral RNA using reverse transcriptase.

Where does translation occur?

In the rough endoplasmic reticulum or cytoplasm.