Comprehensive Nucleic Acids: DNA, RNA, Replication, Mutations & Protein Synthesis

Nucleic Acids

One of the four macromolecules that make up living things.

Monomer

Nucleotide.

Deoxyribonucleic acid (DNA)

One of the two main types of nucleic acids.

Ribonucleic acid (RNA)

One of the two main types of nucleic acids.

Rosalind Franklin

Provided the X-ray photo of DNA.

Watson & Crick

Described the DNA molecule from Franklin's X-ray as a twisted ladder (3D double helix shape).

The Zipper Theory

Proposed by Watson & Crick regarding the structure of DNA.

Nucleotide Structure

Each DNA nucleotide consists of a phosphate group, deoxyribose, and one of four nitrogenous bases.

Nitrogenous Bases

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

DNA Function

Genetic Code (stores the information in genes for making proteins) and Replication (makes copies of itself).

Interphase

The stage of the cell cycle when DNA replication occurs.

Purines

Double ring of carbon and nitrogen; includes Adenine (A) and Guanine (G).

Pyrimidine

Single ring of carbon and nitrogen; includes Thymine (T) and Cytosine (C).

Base Pair Rule

A (adenine) binds to T (thymine) forming a double hydrogen bond; C (cytosine) binds to G (guanine) forming a triple hydrogen bond.

Antiparallel

The orientation of DNA strands running in opposite directions.

Chargaff Rule

In DNA, there is always equality in quantity between the bases A and T and between the bases G and C.

RNA

Ribonucleic Acid; monomer is nucleotide composed of phosphate group, ribose, and one of four nitrogenous bases.

Codons

Sequence of three nucleotides.

mRNA

Messenger RNA; a copy of a specific gene on a DNA molecule that carries the message for making a specific protein to the site of protein synthesis.

tRNA

Transfer RNA; carries the amino acid that the mRNA codes for and has an anticodon that is complementary to the mRNA codon.

rRNA

Ribosomal RNA; makes up the ribosome and is involved in protein synthesis.

DNA Replication

Occurs during S phase of interphase, starting with one strand of DNA and producing two identical strands.

Semiconservative

After DNA replication, it consists of one original strand and one new strand of DNA.

5' and 3'

Indicate the carbon numbers in the DNA's sugar backbone; the 5' carbon has a phosphate group and the 3' carbon has a hydroxyl (-OH) group.

Leading strand

5' → 3'

Lagging strand

3' → 5'

Replication fork

Develops at the 'Origin of replication'

Helicase

Opens the DNA strand by breaking the hydrogen bonds between the nitrogenous bases

Topoisomerase

Functions at the replication fork to prevent DNA from coiling too tight

Single Stranded binding proteins (SSB's)

Bind to the newly split single stranded DNA and prevent it from coming back together

DNA polymerase

Adds DNA nucleotides to the leading and lagging strand following the complementary base pair rules

Leading strand addition

Bases can be added continuously [5'-3']

Lagging strand addition

Can only be made in fragments [3'-5']

Okazaki Fragments

RNA primer is added to allow for the fragments to be made

Ligase

Fills any gaps in the DNA lagging strand

Semi-conservative replication

Each new DNA molecule contains one original (parent) strand and one new strand

Genetic code

Universal; all living cells store hereditary information in double-stranded DNA

Building blocks of DNA

A, T, C, G

Genetic engineering

Theoretically, DNA from one organism can be placed into another organism

Central Dogma

DNA ⇒ RNA ⇒ Protein

Protein structure

Proteins are made up of amino acids connected by peptide bonds

Polypeptide chain

Many amino acids connected together

Functional protein

Formed when a polypeptide chain folds

Gene expression

Gene → Protein → Trait

Transcription

Process of making a copy of a gene on DNA [DNA → mRNA]

Translation

Process of converting RNA into Protein

RNA polymerase

Binds to DNA at a specific gene location and breaks the hydrogen bonds between DNA nucleotides

Transcription steps

1. Initiation 2. Elongation 3. Termination

Transcription vs Replication

Transcription copies a gene; replication copies all the DNA

Replication

Uses helicase & DNA polymerase.

Amino Acids

Building blocks of proteins.

Peptide Bonds

Amino acids connect via peptide bonds to form a polypeptide chain.

Codon

A sequence found on mRNA that determines the amino acid.

Codon Combinations

There are 64 possible 3-letter codon combinations.

Ribosome

Takes place in ribosome for both prokaryotic and eukaryotic cells.

Anticodon

A set of three nucleotides that is complementary to the mRNA codon, carried by tRNA.

Initiation

tRNA binds to a start codon on mRNA and signals the ribosome to assemble.

Start Codon

AUG, which codes for the amino acid Methionine (Met).

Elongation

tRNA molecules will continue to come into the ribosome and the amino acid from the first tRNA will be transferred to the second tRNA.

Termination

A stop codon will be reached, the ribosome will release the protein and will disassemble.

Stop Codons

UAG, UAA, UGA.

Mutation

Any change in an organism's DNA.

Somatic Mutations

Mutations in somatic (body) cells only impact the individual.

Germline Mutations

Mutations in gametes (sex cells) may impact offspring.

Gene Mutations

Typically involves one nucleotide and affects one single gene.

Chromosomal Mutations

Involves pieces of or even entire chromosomes.

Point Mutation

One nucleotide is substituted for another.

Missense Mutation

If the substitution changes the amino acid.

Silent Mutation

If the substitution does not change the amino acid.

Nonsense Mutation

If the substitution changes the amino acid to a 'stop' codon.

Frameshift Mutation

One nucleotide is inserted/deleted from sequence, changing the entire amino acid sequence after the point of mutation.

Insertion Mutation

Addition of base to the DNA sequence.

Deletion Mutation

Loss of base in the DNA sequence.

Translocation

When a segment of genetic material breaks from one chromosome and reattaches to another chromosome.

Nondisjunction

Chromatids fail to separate during meiosis.

Monosomy

Losing 1 chromosome.

Trisomy

Gaining an extra chromosome.

Polyploid

More than the correct number of chromosome sets.