Pgx Basic Concepts I Flashcards
DNA
Deoxyribonucleic acid
Structure Features:
- thin (2 nm in diameter)
- linear
- double stranded helix
4 Nucleobases of DNA
Adenine (A) –> Thymine (T)
- contains 2 hydrogen bonds
Guanine (G) –> Cytosine (C)
- contains 3 hydrogen bonds
- much have a higher temperature to break
Genome
organisms complete set of DNA, including all of its genes, that is require to build and maintain and organism
How many base pairs in a human?
3 billion DNA base pairs
How many chromosomes in a human?
23 pairs or 46 chromosomes
How many genes in a human?
21,000
- only 5-10% of the entire genome
- very low as this is similar to mice
Gene
sequence of DNA or RNA which codes for a molecule that has a function
Classification of Genes
- Protein Coding Genes
- genes expressed to be a protein
- only 1-3% of the human genome are protein-coding sequences - Noncoding Genes
- genes expressed to be RNA
- tRNA, rRNA, miRNA
Cytochrome P450 Nomenclature
CYP3A4:
- Cytochrome P450 gene family
- 3 subfamily
- A gene
- #4
Structure of a Gene
Promoter Region –> 5’UTR –> Exons & Introns –> 3’UTR
Promoter: determines which tissue it will be expressed in –> not present in RNA
5’UTR: regulatory information –> present in RNA
Exon: present in RNA
Intron: cleaved from DNA –> not present in RNA
3’UTR: present in RNA
Average amount of introns/exons in a gene?
8.8 exons/gene
7.8 introns/gene
Chromatin vs Chromosomes
Chromatin:
- unwounded DNA with protein
- interphase
- DNA is accessible
Chromsome:
- tightly packed DNA
- metaphase
- DNA Is not used
Chromosomes
46 total chromosomes (23 pairs)
- 22 pairs of autosomes
- 1 pair of sex chromosomes
XX: female
XY: male
Karyotype: complete picture of genome in a cell
Why do we have 23 pairs of chromosomes?
- the mother donates 23 chromosomes (haploid) and the father donates 23 chromosomes (haploid) to form a human with 46 chromosomes (diploid)
- this works to increase the genetic diversity of the population
Central Dogma
DNA –> DNA replication –> transcription –> RNA –> RNA replication –> translation –> protein
DNA transcription can be reversible through reverse transcription
RNA replication is what causes mutations and different forms of viruses that cause a new vaccine to be established each year
DNA Transcription
- DNA strand is cleaved of its introns in the nucleus to form a matured mRNA strand in the cytoplasm
Matured mRNA
- introns are cleaved
- contains 5’UTR, exons, 3’UTR, and Poly-A tail
- switches the base pair Thymine (T) to Uracil (U)
Translation
- matured mRNA is used to form a protein
- begins with start codon (AUG/ATG)
- stops with stop codons (UAG, UAA, UGA)
Open Reading Frame
- coding DNA sequence from the start codon (AUG) to the codon right before the stop codon
How many codons are there to formulate a protein?
64 codons
- 3 stop codons
- 1 start codon
How many amino acids?
20 amino acids
Sequence Variations
- occurs within any given genome, between different individuals, in different populations
- influences diversity and adaptability of humans to a changing environment
- whether a variation has a functional consequence depends on its location and nature (if the SNP is located in the intron, it will have no effect)
Nature of a Polymorphism
- sequence variation at the same position of homologous chromosomes (diploid)
- there are NO polymorphisms in the genome of a single germ cell (haploid)
