ch 21 Nucleic Acids and Protein Synthesis Overview

Nucleic Acids

Biomolecules transferring genetic information between cells.

RNA

Ribonucleic acid, primarily found in cytoplasm.

DNA

Deoxyribonucleic acid, mainly located in cell nuclei.

Nucleotide

Monomeric unit forming polymeric nucleic acids.

Pyrimidine

Single 6-membered ring with 2 nitrogen atoms.

Purine

Fused ring system with 6 and 5-membered rings.

D-Ribose

Sugar in RNA, has a hydroxy group at 2'.

D-Deoxyribose

Sugar in DNA, lacks hydroxy group at 2'.

Phosphate Group

Derived from phosphoric acid, carries 2- charge.

Phosphodiester Bond

Links nucleotides via 5' to 3' carbon connections.

Nucleic Acid Backbone

Sugar-phosphate chain common to all nucleic acids.

Primary Structure of DNA

Order of bases in a DNA sequence.

Hydrogen Bonds

Hold complementary base pairs together in DNA.

Adenine-Thymine Pairing

Connected by 2 hydrogen bonds in DNA.

Guanine-Cytosine Pairing

Connected by 3 hydrogen bonds in DNA.

Complementary Strands

DNA strands that pair via specific base pairing.

Base Sequence

Order of nucleotides in a DNA strand.

Transcription

Process of synthesizing RNA from a DNA template.

Translation

Process of synthesizing proteins from mRNA.

Chromosome

Tightly packed DNA and protein bundle for cell division.

Histones

Small, basic proteins that package DNA.

Gene

Segment of DNA directing specific protein synthesis.

DNA Replication

Process producing an exact copy of DNA molecule.

Template Strand

Original DNA strand serving as a guide for replication.

Semiconservative Replication

New DNA has one parent and one daughter strand.

Replication Fork

Point where double helix unwinds during replication.

Helicase

Enzyme catalyzing unwinding of the double helix.

DNA Polymerase

Enzyme linking nucleotides to form daughter strands.

Nucleotides

Building blocks of DNA linked during synthesis.

Chromosomal Structure

Chromosomes contain one DNA molecule coiled tightly.

Okazaki fragments

DNA segments synthesized away from replication fork.

DNA ligase

Enzyme that closes nicks in DNA strands.

Polymerase Chain Reaction (PCR)

Technique amplifying DNA through thermal cycling.

Amplification factor

Theoretical increase of DNA copies, up to 1 billion.

Heat denaturation

Process of separating DNA strands at 94°C-96°C.

Messenger RNA (mRNA)

Carries genetic information from DNA to ribosomes.

Ribosomal RNA (rRNA)

Main component of ribosomes, 80-85% of cellular RNA.

Transfer RNA (tRNA)

Delivers amino acids for protein synthesis.

Anticodon

tRNA region that binds to mRNA during translation.

Nicks

Gaps between segments in daughter DNA strands.

Single-stranded RNA

RNA structure lacking complementary base pairing.

Ribose

Sugar in RNA, replacing deoxyribose in DNA.

Uracil (U)

RNA base that substitutes thymine (T) in DNA.

Phosphodiester bonds

Link nucleotides in RNA via 3'→5' connections.

Cytoplasm

Location of protein synthesis in eukaryotic cells.

Ester bond

Link between tRNA and amino acid at 3' end.

Ribosomes

Cellular structures where protein synthesis occurs.

Ribosomal RNA (rRNA)

80% of RNA in cells, 3 subtypes, 1700 nucleotides.

Transfer RNA (tRNA)

15% of RNA in cells, 46 subtypes, 73-93 nucleotides.

Messenger RNA (mRNA)

5% of RNA in cells, many subtypes, 75-3000 nucleotides.

Introns

Non-coding segments of DNA, do not code proteins.

Exons

Coding segments of DNA that produce proteins.

Heterogeneous nuclear RNA (hnRNA)

Pre-mRNA that includes introns and exons.

Genetic code

mRNA template for assembling amino acids.

Precise code

Specific codon represents only one amino acid.

Chain initiation

Start of protein synthesis coded by AUG.

Chain termination

End of protein synthesis coded by UAA, UAG, UGA.

Total codons

64 codons in the genetic code.

mRNA codons

64 codons correspond to 20 amino acids.

Translation process

Exact translation from mRNA to tRNA.

A site

Location on ribosome for incoming tRNA.

Translocation

Ribosome movement during protein synthesis.

Termination factor

Binds to stop codon, ending synthesis.

Mutation

Change in DNA base sequence.

Sickle-cell disease

Genetic disorder caused by mutation.

Muscular dystrophy

Genetic disorder causing muscle degeneration.

Restriction enzyme

Enzyme cleaving specific DNA sequences.