practice quiz hikhok

• Muscular Dystrophy is a heterogenous group of inherited disorders.
• This is characterized by progressive weakness and degeneration of skeletal muscles.
• This X-linked inherited disease is most common in males.

Proteins

• Proteins are composed of a long chain of amino acids (polypeptide) linked by covalent peptide bonds.
• Digestive enzymes facilitate chemical reactions including antibodies to support immune function.
• Proteins support the regulation and expression of DNA and RNA.
• Proteins also support muscle contraction and movement, provide support to the body and hormones help coordinate bodily function.
• Proteins move essential molecules around the body.

Examples of Muscular Dystrophy

• Duchenne Muscular Dystrophy (DMD) involves progressive muscle degeneration/weakness due to alterations in the dystrophin protein.
• Becker's Muscular Dystrophy (BMD) is less severe and progressive than DMD.
• Muscle weakening leads to symptoms like Gower's sign.
• Physiological changes include a curved spine, arms held back for balance, belly sticking out, and swollen calves.

Muscular Dystrophy Treatments

• Treatments include medications, physical and occupational therapy, and surgical procedures.
• Treatment is adjusted as the disease progresses, informed by ongoing assessments of walking, swallowing, breathing, and hand function.

DNA

• Deoxyribonucleic Acid (DNA) is hereditary material in humans/almost all organisms.
• DNA contains the genetic information that programs all cellular activities and characterizes each organism.
• DNA structure was discovered by James Watson and Francis Crick in 1953.
• DNA is considered the blueprint of life and was identified 9 years earlier by Swiss chemist Frederick Miescher.
• DNA illustrates the molecular structure of DNA, RNA, and proteins.

Hereditary Information

• Mendelian and Non-Mendelian Inheritance predict genotype and phenotype using laws of inheritance.
• This explains sex linkage and recombination; it describes modifications to Mendel's Classic ratios.
• Nucleic Acids are the principle information molecule in the cell.
• All the genetic codes are carried out on the nucleic acids and a linear polymer of nucleotides.

Types of Nucleic Acids

• RNA's pentose sugar is ribose, whose bases are Purines (A, G) & Pyrimidines (C, U).
• DNA nucleotides are composed of a phosphate molecule, a 5-carbon sugar (pentose), and a nitrogen-containing base.

Nucleotides

• Nucleotides are the units structure of nucleic acids.
• They are linked together by phosphodiester to form the polymer nucleic acids.
• Its 3 components are nitrogenous base (A, C, G, T or U), pentose sugar, and phosphate.
• Nitrogenous bases are classified into two types: Purines (two-ring structure, Adenine & Guanine) and Pyrimidines (single-ring structure, Cytosine & Thymine or Uracil).
• The common 5 are Adenine, Cytosine, Guanine, Thymine, Uracil

Bonds in DNA

• Nucleotides are joined together using phosphodiester bonds.
• RNA is a single-stranded polynucleotide molecule with 3 levels: primary (sequence of nucleotides), secondary (hairpin loops/base pairing), and tertiary (motifs and 3D folding).

DNA vs RNA

DNA

• DNA contains 2 strands
• It is located in the nucleus
• Uses Deoxyribose sugar
• Guanine pairs with Cytosine
• Adenine pairs with Thymine

RNA

• RNA contains 1 strand
• It is located in both the nucleus and cytoplasm
• Uses Ribose sugar
• Guanine pairs with Cytosine
• Adenine pairs with Uracil
• The Human Genome Project completed in 2003, 50 years after discovering the double helix, found approximately 3.2 billion base pairs in the human genome.

Information Content of DNA

• The information content is in the form of specific sequences of nucleotides along the DNA strands.
• DNA leads to specific traits by dictating synthesis of proteins.
• DNA directs protein synthesis through gene expression by transcription and translation.
• A ribosome is part of the cellular machinery for translation (polypeptide synthesis).

Metabolic Studies

• Archibald Garrod, a British Physician in 1909, first suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cell.
• Beadle and Tatum caused bread mold to mutate with X-rays in Nutritional Mutants in Neurospora: Scientific Inquiry which creates mutants that could not survive on minimal medium.
• Genetic Crosses determine that their mutants fell into three classes, each mutated in a different gene.
• Beadle and Tatum developed the "One Gene-One Enzyme Hypothesis" which states the function of a gene is to dictate the production of a specific enzyme.

Transcription and Translation

• Transcription is the synthesis of RNA under the direction of DNA, which produces messenger RNA (mRNA).
• Translation is the actual synthesis of a polypeptide under the direction of mRNA (occurs on ribosomes).
• Translation and transcription occur together in prokaryotes.
• RNA transcripts are modified before becoming true mRNA in eukaryotes.
• Cells are governed by a cellular chain of command: DNA » RNA » PROTEIN.

Genetic Code

• Genetic information is encoded as a sequence of nonoverlapping base triplets or codons.
• During transcription, the gene determines the sequence of bases along the length of an mRNA molecule.
• A codon in messenger RNA is either translated into an amino acid or serves as a translational stop signal.
• Codons must be read in the correct reading frame to produce specified polypeptide.
• The Evolution of the Genetic Code is nearly universal and shared by organisms from the simplest bacteria to complex animals.

Molecular Components of Transcription

• RNA Synthesis is catalyzed by RNA polymerase, which pries the DNA strands apart and hooks together the RNA nucleotides.
• RNA synthesis follows the same base-pairing rules as DNA, except uracil substitutes for thymine.
• The stages of transcription are initiation, elongation, and termination.
• Promoters signal the initiation of RNA synthesis using transcription factors.
• Transcription factors help eukaryotic RNA polymerase recognize promoter sequences.

Elongation of the RNA Strand

• As RNA polymerase moves along the DNA, it continues to untwist the double helix therefore exposing about 10 to 20 DNA bases at a time for pairing with RNA nucleotides.
• Eukaryotic cells modify RNA after transcription via enzymes in the eukaryotic nucleus.
• pre-mRNA is modified in specific ways before the genetic messages are dispatched to the cytoplasm.
• The 5' end receives a modified nucleotide cap and the 3' end gets a poly-A tail in the alteration of mRNA ends.

RNA Splicing

• RNA Splicing removes introns and joins exons (carried out by spliceosomes in some cases).
• Ribozymes are catalytic RNA molecules that function as enzymes and can splice RNA.
• The presence of introns allows for alternative RNA Splicing.
• A cell translates an mRNA message into protein, with the help of transfer RNA (tRNA).
• RNA is a single strand of about 80 nucleotides and is roughly L-shaped.
• Molecules of tRNA are not all identical, but each carries a specific amino acid on one end and each has an anticodon on the other end.

Ribosomes in Protein Synthesis

• Ribosomes facilitate specific coupling of tRNA anticodons with mRNA codons during protein synthesis.
• There are 3 binding sites for tRNA: the P site, the A site, and the E site.
• Translation can be divided into three stages: initiation, elongation, and termination.

Protein Synthesis

• Ribosome Association and Initiation of Translation occurs in the Initiation Stage of Translation, which brings together mRNA, tRNA bearing the first amino acid of the polypeptide, and two subunits of a ribosome.
• In the Elongation Stage of Translation, amino acids are added one by one to the preceding amino acid.
• The final stage of translation involves termination.
• Termination occurs when the ribosome reaches a stop codon in the mRNA.
• A number of ribosomes can translate a single mRNA molecule simultaneously which forms a polyribosome.
• Polypeptide chains undergo modifications after the translation process during completing and targeting the functional protein.

Protein Folding

• After translation, proteins may be modified in ways that affect their three-dimensional shape.
• Two populations of ribosomes are evident in cells which involves free and bound ribosomes. Free ribosomes in the cytosol initiate the synthesis of all proteins.
• Proteins destined for the endomembrane system for secretion must be transported into the ER.
• These have signal peptides to which a signal-recognition particle (SRP) binds therefore enabling the translation ribosome to bind to the ER.
• Mutations are changes in the genetic material of a cell.
• Point mutations are changes in just one base pair of a gene which leads to the production of an abnormal protein.

Mutations

• Gene Mutations change the nucleotide sequence of a gene with only a single nucleotide may being involved and may be due to copying errors, chemicals, viruses, etc.
• Types of mutations are point mutations, substitutions, insertions, deletions, frameshift.

Point Mutations

• Point Mutations change a single nucleotide includes the deletion, insertion, or substitution of ONE nucleotide in a gene.
• Sickle Cell Disease is the result of one nucleotide substitution and occurs in the hemoglobin gene.
• Point Mutations within a gene can be divided into two general categories: base-pair substitutions and base-pair insertions or deletions.

Substitutions

• Substitutions involve a base-pair substitution (no change in amino acid sequence) and the replacement of one nucleotide/its partner with another pair of nucleotides.
• Substitutions can cause missense (change in amino acid sequence) or nonsense (stops early in the amini acid sequence).

Insertions and Deletions

• Insertions and Deletions are additions or losses of nucleotide pairs in a gene that may produce frameshift mutations.
• Frameshift causing immediate nonsense (early stop).
• Frameshift causing extensive missense (change in amino acid sequence).
• Insertion/Deletion of 3 nucleotides: no frameshift but extra or missing amino acid.
• Frameshift Mutation involves inserting/deleting one or more nucleotides and changes the reading frame.
• Frameshift mutations therefore leads to a changed amino acid sequence and a protein built incorrectly.

Genes

• A Gene is a region of DNA whose final product is either a polypeptide or an RNA molecule.
• Mutations are changes in the nucleotide sequence of DNA that may occur in somatic cells (aren't passed to offspring) or in gametes.
• Mutations happen regularly and almost all mutations are neutral.

Mutagens

• Chemicals & UV radiation cause mutations and many mutations are repaired by enzymes.
• Some types of skin cancers and Leukemia result from somatic mutations. Some mutations may improve an organism's survival (beneficial).

Types of Mutations

• Chromosome mutations change the structure of a chromosome.

Chromosome structure changes

• Deletion is the loss or gain of part of a chromosome that is due to breakage and a lost piece of chromosome.
• Inversion: chromosome segment breaks off and segments flips around backwards.
• Translocation involves two chromosomes that aren't homologous, where part of one chromosome is transferred to another chromosomes.
• Nondisjunction refers to the failure of chromosomes to separate during meiosis and the causes gamete to have too many or too few chromosomes.
• Duplication occurs when a gene sequence is repeated.
• Molecular Genetics Analysis focuses on the structure and function of genes at a molecular level.
• It involves the study of DNA, RNA, and Proteins.

Molecular Genetic Analysis

• Molecular Genetics Analysis understands genetic variation.
• It leads to biomedical research and the development of biotech products and environmental impact assessment.

Genetic Testing

• Genomics is the study of genomes.
• Genomes are the complete set of DNA in an organism.
• Proteomics is the study of proteins (the building blocks of cells and tissues).
• Gel Electrophoresis separates DNA fragments based on size.
• Large fragments take longer than small fragments migrate through an agarose gel.
• Agarose is a polysaccharide derived from red algae and purified from agar.
• Fragments of DNA move in an electric field and are separated according to size.
• This can be used to separate large molecules (including nucleic acids and proteins) based on the size, electric charge, and other physical properties.

DNA Profiling

• DNA PROFILING (fingerprinting) is a technique where it identifies the variations found in the DNA of every individual for forensic purposes.
• DNA » RNA » AMINO ACID; DNA: A to T if T is present.
• T to A, G to C, C to G ,RNA: A to U if U is present, G to C, C to G, T to A.
• Wild Type: standard non-mutated sequence - no difference from reference.
• Mutated: Any change in the sequence - difference detected.