Genetics Cheatsheet
DNA and RNA
Nucleotides
| Nucleotide |
DNA |
RNA |
| Adenine |
A |
A |
| Cytosine |
C |
C |
| Guanine |
G |
G |
| Thymine |
T |
|
| Uracil |
|
U |
Complementary Base Pairing
DNA Replication
- Helicase unwinds the DNA double helix
- Primase adds RNA primer to the template strand
- DNA polymerase adds nucleotides to the growing strand
- Leading strand is synthesized continuously while lagging strand is synthesized in Okazaki fragments
- DNA ligase joins the fragments on the lagging strand
Transcription
- RNA polymerase binds to the promoter region of DNA
- DNA unwinds and RNA polymerase adds nucleotides complementary to the template strand of DNA
- RNA polymerase reaches the terminator region and the newly synthesized RNA strand is released
Translation
- mRNA binds to a ribosome
- tRNA with complementary anticodon and amino acid bind to the mRNA codon
- A peptide bond is formed between the amino acids
- Ribosome moves to the next codon on mRNA and the process repeats
- The polypeptide chain is released when a stop codon is reached
Mendelian Genetics
Laws of Inheritance
- Law of Segregation - each parent has two copies of a gene, but only one is passed on to each offspring
- Law of Independent Assortment - genes for different traits are inherited independently of each other
- Law of Dominance - one allele is dominant over the other and will determine the phenotype if present
Punnett Squares
Used to predict the probability of offspring inheriting certain traits based on the genotypes of the parents.
Pedigrees
Used to track the inheritance of traits within a family.
Genetic Disorders
Autosomal Recessive Disorders
- Cystic fibrosis
- Sickle cell anemia
- Phenylketonuria (PKU)
Autosomal Dominant Disorders
- Huntington’s disease
- Marfan syndrome
X-Linked Recessive Disorders
- Hemophilia
- Color blindness
- Duchenne muscular dystrophy
Resources