DNA: Structure and Function

DNA Basics

• DNA's acronym stands for Deoxyribonucleic Acid.
• DNA constitutes chromosomes and functions as hereditary information.

Nucleic Acids

• DNA and RNA are the two types of nucleic acids.
• Both DNA and RNA are nucleotide polymers crucial for chromosomes and genetic processes.
• DNA shape is a double helix of repeating nucleotide units
• Nucleotides contain phosphoric acid (phosphate group), a 5-carbon sugar (deoxyribose), and a nitrogenous base.

Purines and Pyrimidines

• Purines and pyrimidines are nitrogenous bases, that make up DNA's nucleotide bases.
• Adenine and guanine are purines which contain a two-carbon nitrogen ring structure.
• Thymine and cytosine are pyrimidines with a one-carbon nitrogen ring.
• Paired bases form the "rungs" of the DNA ladder in a specific pattern where deoxyribose sugar and phosphates create the backbone.
• Adenine bonds to thymine with two hydrogen bonds.
• Guanine bonds to cytosine with three hydrogen bonds.
• Complementary base pairing occurs because bases can only bond in one way, so two purines cannot bond together because they cause overlapping and two pyrimidines cannot bond together due to their short lengths.
• Hydrogen bonds hold the double strand together between bases.
• The number, kind, and sequence of bases determines the type of organism
• The twisting of a DNA strand forms a double spiral called a double helix.

DNA Functions

• DNA replicates (duplicates) itself, ensuring each new cell gets a complete, identical copy.
• It controls cellular activities by producing proteins that determine an organism's traits (phenotype).
• DNA undergoes occasional mutations (replication mistakes) that account for the variety of living things.

Steps in DNA Replication

• DNA untwists with enzymes, unzipping to create two strands each acting as a template.
• Helicase breaks the hydrogen bonds between nitrogenous base pairs.
• New complementary nucleotides pair with bases on the exposed strands.
• DNA polymerase assists with complementary base pairing where A joins to T, and C joins to G.
• Ligase joins the sugar-phosphate backbone.
• The process produces two identical DNA molecules
• New DNA strands rewind into a helical shape.
• DNA replication is semiconservative because each helix has one old and one new strand.
• Enzymes assist the unwinding, joining, and rewinding processes.

Mutations in DNA Replication

• A mutation can occur when errors are made in replication.

Recombinant DNA

• Recombinant DNA contains genes from two different organisms, made in a lab by inserting foreign DNA into a bacterial plasmid.
• A vector introduces recombinant DNA using plasmids, which are small DNA rings found in bacteria.
• Restriction enzymes breaks the plasmid DNA allowing a foreign gene to be inserted.
• Ligase glues the foreign DNA to the plasmid, making it whole again.
• The bacteria produces a plasmid with the foreign gene every time it replicates.
• Viral DNA can be a vector that carries recombinant DNA into a cell
• Viral vectors allow cloning of a particular gene.

Genomic Libraries

• Viral vectors create genomic libraries
• A Genomic Library is a collection of engineered viruses carrying all the genes of a species, it takes about 10 million viruses to carry all the genes of a mouse.
• Bacteria can receive segments of DNA (genes) and produce specific chemicals (vaccines, antibodies).
• Insulin and Interferon are made using yeast cells and mass-produced with this method.

Application of Recombinant DNA

• Generate a DNA library
• Identify specific genes.
• Produce synthetic copies of genes to mass-produce chemicals like insulin.
• Insert genetic material into chromosomes to regulate cell function to make the organism genetically "better".

DNA Versus RNA

• DNA and RNA are both nucleic acids composed of nucleotide monomers.
• DNA contains deoxyribose sugar and the bases adenine, thymine, cytosine, and guanine, and is located only in the nucleus.
• RNA contains ribose sugar, the bases adenine, uracil, cytosine, and guanine, and is located in both the nucleus an cytoplasm.
• DNA carries and transfers genetic information.
• RNA carries/transfers genetic info and is involved in protein synthesis.
• DNA has a double-strand structure and RNA has a single-strand structure.

Types of RNA

• mRNA (messenger RNA).
• tRNA (transfer RNA).
• rRNA (ribosomal RNA).

DNA and RNA Activity

• A G in DNA pairs with C while A pairs with T.

DNA Replication Details

• DNA replication forms two identical daughter strands of DNA
• DNA replication is essential because without it cells could lose genetic information which leads to disease.
• DNA replication is termed semiconservative because it forms two identical double helices containing one original and one brand new strand.
• DNA replication involves unwinding, matching, and joining, and the enzymes helicase, DNA polymerase, and ligase.

DNA vs RNA Contradictions

• DNA is found only in the nucleus while RNA is found in both the nucleus and cytoplasm.
• DNA only controls cell activities and RNA performs protein synthesis along with controlling cell activities.
• DNA has a double helix shape while RNA has a single strand shape.

DNA Replication

• DNA replication makes an identical strand of DNA in the nucleus.
• Protein synthesis uses info encoded in DNA to make proteins, through transcription, where DNA makes mRNA, and translation, where mRNA directs protein synthesis.

Protein Synthesis Introduction

• DNA replication produces an identical DNA strand.
• Protein synthesis uses DNA to produce proteins.
• DNA is the master instructions for protein production, taking part in structural and functional roles.
• Cytoplasm is where proteins are assembled, but a copy of DNA (mRNA) must be made to carry the message to ribosomes.
• Copying genes to make mRNA from a DNA template is called transcription.

Protein Synthesis

• Nitrogenous bases in DNA have the instructions for making proteins.
• Every three DNA strand bases code for one amino acid.
• Many amino acids make up a protein.
• The code for protein synthesis gets transcribed from a DNA template into messenger RNA (mRNA).
• Codons are sets of 3 bases on the mRNA strand that has been transcribed.

Genetic Code Specifics

• There are 64 possible codon combinations but only 21 amino acids, therefore most amino acids have multiple codons,.
• Duplicate codons can protect against mutations and are called degeneracy.
• Genetic code is universal where the same codons stand for the same AAs.
• The start codon is AUG (methionine).
• Stop codons are UAA and UAG.
• Long chains of adenine bases (adenine tail) at the end of mRNA detect mRNA function.
• When enough protein is created the adenine tail falls off.

Transcription Details

• Gene selection, isolation, and uncoiling by RNA polymerase occurs.
• The gene that is chosen codes the eventual protein.
• Hydrogen bonds are broken between complementary base pairs to provide the DNA template.
• Nucleotides join complementary to the gene on the DNA template assisted by RNA polymerase, and ligase joins the alternating sugar-phosphate backbone.
• Uracil joins to adenine in mRNA as thymine is only found in DNA.
• Enzymes break the hydrogen bond between the mRNA and DNA template.
• mRNA molecules are released to be modified and pass through nuclear pores into the cytoplasm while DNA rejoins to its double helix.

Translation Overview

• mRNA links to a ribosome made of ribosomal RNA (rRNA). When the mRNA encounters two ribosomal subunits, the large subunit adheres to the mRNA strand.
• The first tRNA arrives at the ribosome with a anticodon complimentary to the mRNA's start codon and binds to the met strand. Once all subunits are attached a functional complex is formed.
• Each tRNA contains a certain amino acid based on its anticodon.

Elongation Process

• The second tRNA binds complenentary to the sedond mRNA codon and adheres to the mRNA strand.
• The ribosome aids the transfer of amino acids from the first tRNA to the second and this creates a peptide bond in the process.
• The ribosome travels down that mRNA by one codon where, unless occupied, tRNA is released and recycled to pill up other amino acids.
• Simultaneously the third tRNA with a complimentary anticodon connects with the third mRNA's codon and the amino acids transfers.

Termination

• The ribosome continues to read/ translate the mRNA strand where a chain grows and a terminator/ stopping codon is reached.
• a Terminator codon causes the release of a completed polypeptide ( protein). The mRNA will be read by various ribosomes.
• There are often many ribosomes that are detected together reading the same mRNA. This unit of ribosomes is the polyribosome.

Mutations

• A gene mutation means a continuous shift inside the DNA order or in the DNA.
• Mutations affect anything from single DNA (base pair) that makes up for to a big segment of a chromosome.
• Hermeditary mutation is present from a parent.

2 types of genes:

• Hermeditary mutations form inside the parents stem cell or eggs and spirm cells which transfer DNA and the mutations through the child. Acquired somatic mutations do not transfer to the next generation.
• Gene Types of Mutation which occurs often inside germ Gametes and chromosome and somatic mutations.

Environmental Mutagens

• chemicals
• radiation

DOWN' SYNDROME

• chromosomal translocation where one part of the #21 chromosome transfers on to more chromosomes.

Sickle Anaemia Cell

• substitution of bas to grow more Amino acids which become abnormal more than hemoglobin levels.

Cancer + Hemophilia

• Cancer is somatic.
• Hemophilia germ cell.

Protein synthesis steps:

• 1. The genetic code.
• Please complete the following table. Replication has been filled out as an example.

List 3 process

• list the steps of translation and prove a brief description of each step
• Initation attaches
• Elongation a bonds
• Termination translation con.