Storing and using genetics information mw %% + Flashcards Preview

ME2308 Principles of Disease > Storing and using genetics information mw %% + > Flashcards

Flashcards in Storing and using genetics information mw %% + Deck (21)
Loading flashcards...

Phenotype and Genotype

Phenotype = Outward, physical manifestation of organism

Genotype = Full hereditary information of organism (even if not expressed)



Each nucleotide contains

  • Sugar
  • Base
  • Phosphate group


Difference between Deoxyribose and Ribose

  • Carbon 2
  • Ribose, OH
  • Deoxy, H


Complementary Base-Pairing

  • Adenine – Thymine (Uracil in RNA)
  • Cytosine - Guanine


Structure of Nucleus

  • Usually the largest organelle in the cell
  • Contains most of the cell’s genetic material (DNA)
  • Replication of DNA and the first steps in decoding it for protein production take place in the nucleus


Chromosomes (Only visible when cell dividing)

  • In the nucleus the DNA molecule is packaged into thread-like structures called chromosomes.
  • Chromosomes are a single piece of DNA containing many genes, regulatory elements and other nucleotide sequences.


Chromosome wrapping stages pic



  • The DNA double helix in the cell nucleus is packaged by special proteins termed histones. The formed protein/DNA complex is called chromatin. The basic structural unit of chromatin is the nucleosome.
  • It is divided between heterochromatin (condensed) and euchromatic (extended) forms.


Transcription & Replication

  • Both require the two strands of DNA to separate temporarily to allow enzymes access to the DNA template
  • Nucleosomes and folding of chromatin pose barriers to enzymes
  • Cells must have means of opening up chromatin fibers and/or removing histones


Two major mechanisms by which chromatin is made more accessible

  1. Histones can be enzymatically modified
  2. Histones can be displaced by chromatin remodeling complexes

These processes are reversible


DNA Replication is Semi-Conservative & Bi-Directional

  • Semi-conservative: one-half of each new molecule of DNA is old; one-half new.
  • Special proteins ‘unzip’ the double helix by breaking the hydrogen bonds.
  • New nucleotide molecules are then paired with the two DNA strands.
  • Replicated in 5’ to 3’ direction.


Protein-coding Genes

  • <2% of the genome codes for proteins.
  • The functions are unknown for over 50% of discovered genes.

  • Repeated sequences that do not code for proteins ("junk DNA") make up at least 50% of the human genome.


Exons and Introns

  • Generally Exons = Coding Regions
  • Introns = Non-coding Regions


Genetic Code

  • Each set of 3 bases is called a codon
  • Each codon specifies a particular amino acid
  • However only 20 amino acids found in proteins



With the exception of methionine and tryptophan they are all encoded by more than one codon.  This is referred to as degeneracy or the redundancy of the genetic code.


Role of RNA

The major role of RNA is to participate in protein synthesis



Transcribed from DNA.

Carries information for protein synthesis. 


Alternative Splicing

  •   a regulated process during gene expression that results in a single gene coding for multiple proteins. In this process, particular exons of a gene may be included within or excluded from the final, processed messenger RNA (mRNA) produced from that gene
  • In a genome of 3.12 billion base pairs, It's estimated that humans use at least 100,000 different proteins, maybe a lot more


Overall picture



  • Major role is to translate mRNA sequence into amino acid sequence. 
  • Acts as an adapter molecule between the coded amino acid and the mRNA



  • Component of ribosomes.
  • rRNA molecules are produced in the nucleus
  • Transported to cytoplasm, where they combine with proteins to form a ribosome