Pgx Basic Concepts I

Question 1

DNA

Answer 1

Deoxyribonucleic acid

Structure Features:
- thin (2 nm in diameter)
- linear
- double stranded helix

Question 2

4 Nucleobases of DNA

Answer 2

Adenine (A) –> Thymine (T)
- contains 2 hydrogen bonds

Guanine (G) –> Cytosine (C)
- contains 3 hydrogen bonds
- much have a higher temperature to break

Question 3

Genome

Answer 3

organisms complete set of DNA, including all of its genes, that is require to build and maintain and organism

Question 4

How many base pairs in a human?

Answer 4

3 billion DNA base pairs

Question 5

How many chromosomes in a human?

Answer 5

23 pairs or 46 chromosomes

Question 6

How many genes in a human?

Answer 6

21,000
- only 5-10% of the entire genome
- very low as this is similar to mice

Question 7

Gene

Answer 7

sequence of DNA or RNA which codes for a molecule that has a function

Question 8

Classification of Genes

Answer 8

1. Protein Coding Genes
   - genes expressed to be a protein
   - only 1-3% of the human genome are protein-coding sequences
2. Noncoding Genes
   - genes expressed to be RNA
   - tRNA, rRNA, miRNA

Question 9

Cytochrome P450 Nomenclature

Answer 9

CYP3A4:
- Cytochrome P450 gene family
- 3 subfamily
- A gene
- #4

Question 10

Structure of a Gene

Answer 10

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

Question 11

Average amount of introns/exons in a gene?

Answer 11

8.8 exons/gene

7.8 introns/gene

Question 12

Chromatin vs Chromosomes

Answer 12

Chromatin:
- unwounded DNA with protein
- interphase
- DNA is accessible

Chromsome:
- tightly packed DNA
- metaphase
- DNA Is not used

Question 13

Chromosomes

Answer 13

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

Question 14

Why do we have 23 pairs of chromosomes?

Answer 14

• 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

Question 15

Central Dogma

Answer 15

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

Question 16

DNA Transcription

Answer 16

• DNA strand is cleaved of its introns in the nucleus to form a matured mRNA strand in the cytoplasm

Question 17

Matured mRNA

Answer 17

• introns are cleaved
• contains 5’UTR, exons, 3’UTR, and Poly-A tail
• switches the base pair Thymine (T) to Uracil (U)

Question 18

Translation

Answer 18

• 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

Question 19

How many codons are there to formulate a protein?

Answer 19

64 codons
- 3 stop codons
- 1 start codon

Question 20

How many amino acids?

Answer 20

20 amino acids

Question 21

Sequence Variations

Answer 21

• 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)

Question 22

Nature of a Polymorphism

Answer 22

• sequence variation at the same position of homologous chromosomes (diploid)
• there are NO polymorphisms in the genome of a single germ cell (haploid)