Genetics & Molecular Biology Study Guide

This set of flashcards covers key concepts from Genetics and Molecular Biology, touching on the flow of genetic information, nucleic acid structure, processes like transcription and translation, as well as enzyme activity and regulation.

What is the flow of genetic information called?

Central Dogma: DNA \rightarrow RNA \rightarrow Protein.

What are the two families of nitrogenous bases?

Purines (A, G) and Pyrimidines (T, C).

What are the correct base pairings in DNA?

A–T and G–C.

What are the two types of nucleic acids?

DNA and RNA.

What are the two main differences between DNA and RNA?

DNA has deoxyribose sugar and thymine; RNA has ribose sugar and uracil.

What bond connects nucleotides in a chain?

Phosphodiester bond.

What are the parts of a nucleotide?

Phosphate group, 5-carbon sugar, nitrogenous base.

Describe the structure of DNA.

Double helix, antiparallel strands, complementary bases.

Describe the structure of RNA.

Single-stranded, folds into shapes, contains A, U, G, C.

What type of bonds connect DNA bases?

Hydrogen bonds — A–T has 2; G–C has 3.

What is transcription?

Copying DNA into mRNA in the nucleus.

What is the purpose of transcription?

To carry the genetic code to ribosomes for protein synthesis.

What happens during initiation of transcription?

RNA polymerase binds promoter and unwinds DNA.

What happens during elongation of transcription?

RNA polymerase adds complementary RNA nucleotides.

What happens during termination of transcription?

RNA polymerase reaches stop signal and releases mRNA.

Which strand of DNA is transcribed?

Template (non-coding) strand.

Which DNA strand matches the mRNA sequence?

Coding strand (except T \rightarrow U).

What does DNA Helicase do?

Unwinds DNA strands.

What does DNA Polymerase do?

Builds new DNA strands.

What does Primase do?

Lays RNA primers.

What does Ligase do?

Joins Okazaki fragments.

What does Topoisomerase do?

Relieves tension ahead of replication fork.

What type of DNA do prokaryotes have?

One circular DNA molecule.

What type of DNA do eukaryotes have?

Multiple linear chromosomes.

What is the origin of replication?

Site where DNA replication begins.

How many replication origins do bacteria have?

One.

How many replication origins do eukaryotes have?

Multiple.

What is semi-conservative replication?

Each new DNA molecule has one old and one new strand.

What are the main steps of DNA replication?

1) Helicase unwinds DNA, 2) SSB proteins stabilize, 3) Primase adds primers, 4) DNA Pol III adds nucleotides, 5) DNA Pol I replaces primers, 6) Ligase joins fragments.

What is the function of SSB proteins?

Keep DNA strands apart.

What does DNA Polymerase III do?

Main enzyme that adds nucleotides to the new strand.

What does DNA Polymerase I do?

Replaces RNA primers with DNA.

What is the difference between leading and lagging strands?

Leading is continuous; lagging forms Okazaki fragments.

What are the four levels of protein structure?

Primary, secondary, tertiary, quaternary.

What bonds hold primary structure?

Peptide bonds.

What bonds stabilize secondary structure?

Hydrogen bonds.

What bonds stabilize tertiary and quaternary structure?

Ionic, hydrogen, hydrophobic, disulfide bonds.

What is translation?

Process of converting mRNA code into protein at the ribosome.

In what direction are codons read?

5' \rightarrow 3'.

What is the start codon and its amino acid?

AUG (methionine).

Where does translation occur?

Cytoplasm at ribosomes.

What are the ribosome binding sites?

A (aminoacyl), P (peptidyl), E (exit).

What happens during initiation of translation?

Ribosome binds start codon and tRNA(Met) attaches.

What happens during elongation of translation?

tRNAs bring amino acids; peptide bonds form.

What happens during termination of translation?

Stop codon triggers release and ribosome disassembles.

What is the relationship between codon and anticodon?

Codon (mRNA) pairs with complementary anticodon (tRNA).

What are the three types of point mutations?

Silent, missense, nonsense.

What is the result of a mutation in translation?

May produce altered or nonfunctional proteins.

What is an operator?

Site where repressor binds to block transcription.

What is an operon?

Cluster of genes under one promoter.

What is a repressor?

Protein that blocks transcription.

What is an enhancer?

DNA region that increases transcription.

What is a regulatory gene?

Produces repressors or activators.

What is a promoter?

Site where RNA polymerase binds to start transcription.

What type of control is the lac operon?

Inducible, negative control.

What does allolactose do in the lac operon?

Inactivates the repressor, allowing transcription.

What are examples of post-transcriptional regulation?

RNA splicing, mRNA degradation, RNA interference.

What is alternative splicing?

Combines different exons to make multiple proteins.

What are exons and introns?

Exons = coding regions; introns = noncoding regions removed by spliceosome.

What is RNA interference?

siRNA or miRNA bind mRNA to block translation.

What are three types of translational regulation?

Initiation control, mRNA lifespan control, protein modification control.

What is metabolism?

All chemical reactions in a cell.

What are the two energy processes in cells?

Cellular respiration (releases energy) and photosynthesis (stores energy).

What is an example of energy use in cells?

Muscle contraction using ATP.

What are catabolic and anabolic reactions?

Catabolic = breakdown, releases energy; Anabolic = builds, requires energy.

What are exergonic and endergonic reactions?

Exergonic = energy-releasing (downhill); Endergonic = energy-requiring (uphill).

What is kinetic vs potential energy?

Kinetic = motion; Potential = stored energy.

What does the 1st law of thermodynamics state?

Energy is conserved.

What does the 2nd law of thermodynamics state?

Energy conversions increase entropy.

What does spontaneous mean in reactions?

Occurs without energy input.

What does a negative \Delta G mean?

Reaction is spontaneous/exergonic.

What does a positive \Delta G mean?

Reaction is non-spontaneous/endergonic.

What is a catalyst?

Substance that speeds up a reaction without being used.

How do enzymes affect reactions?

Lower activation energy, speeding reaction rate.

What is a reactant called in an enzyme reaction?

Substrate.

What suffix do most enzyme names end with?

-ase.

What is an enzyme’s active site?

Region where substrate binds.

What happens during induced fit?

Enzyme changes shape slightly when binding substrate.

How do enzymes lower activation energy?

Proper substrate orientation, bond strain, microenvironment, temporary covalent bonds.

What factors affect enzyme activity?

pH, temperature, substrate concentration.

What happens if temperature is too high for enzymes?

They denature.

What is allosteric regulation?

Molecule binds elsewhere on enzyme to change activity.

What is cooperativity in enzymes?

One substrate binding increases others’ binding.

What are enzyme activators and inhibitors?

Activator keeps enzyme active; inhibitor keeps enzyme inactive.