1 - MOLECULAR BASIS OF GENETICS Flashcards
- Study of inherited traits, rooted in DNA, and their variations and transmission
- Started from plant breeding experiments
- Has evolved to become a major medical discipline
Genetics
Transmission of traits and biological information between generations
Heredity
- Functions as the units of heredity in that copies of genes are passed from one generation to the next
- Consists of the long molecule DNA
Genes
People performed selective breeding of good traits and characteristics of animals they herded and domesticated. What animals are these?
Horses
Important Events in Genetic History
- People performed selective breeding of good traits and characteristics of animals they herded and domesticated
- Later on was used in improving the quality of crops as well
8000-1000 BC
8000-1000 BC
Father of Medicine proposed that invisible seeds found in the male semen serve as the bearers of the hereditary traits
Hippocrates
8000-1000 BC
- Argued that the blood contained materials for building all parts of the body
- He believed that the semen was purified blood
- Further argued that some seeds from the blood would not appear until later in life
Aristotle
18th Century
believed that miniature humans were found in the head of sperm cells called homunculus
Concept of Preformation
18th Century
confirmed that all organisms were derived from cell
Cell Theory
18th Century
- Proposed the theory of natural selection
- Stated that the best adapted characteristics of parents are those that get carried over to their children
- Overtime, these new characteristics combined leading to the birth of a new species
Charles Darwin
1865
experimented with pea plants and established basic rules of heredity and made him “Father of Modern Genetics”
Gregor Mendel
1944
confirmed that it was DNA that carried the genetic information
Avery
1953
discovered the double helix structure of DNA
Watson and Crick
1956
Diploid number of chromosomes was identified as?
46 chromosomes
1956
Haploid number of chromosomes was identified as?
23 chromosomes
1959
- Showed that Down Syndrome is a chromosomal abnormality
- First identification of the genetic basis of a disease
J. Lejenne
1975
This allowed the detection of specific DNA sequences
Southern blot
1977
developed the chain termination method for sequencing DNA
Fred Sanger
1983
Localization of Huntington’s disease
chromosome 4
1985
developed the PCR which provided a rapid way to make many copies of DNA molecules
Mullis & co-workers
1989
identified as the gene causative for cystic fibrosis when mutated
Cystic fibrosis transmembrane conductance regulator gene on chromosome 7
1990
- $3 billion, 15-year project with the goal to sequence the human genome
- The endgame of the project was to determine the genres associated to diseases and predict and possible diseases in the future
Human Genome Project
Formed by linking multiple nucleotides
DNA
Basic unit of the DNA
Nucleotides
Components of nucleotides
Nitrogenous base
Sugar
Phosphate
6-membered ring containing 2 nitrogens
Pyrimidines
9-membered ring consisting of 2 rings
Purines
Types of Pyrimidines
Cytosine
Uracil
Thymine
Types of Purines
Adenine
Guanine
5 membered rings of sugar
Pentoses
2 types of sugars
Ribose
Deoxyribose
Components of nucleoside
Sugar
Nitrogenous base
- Forms the backbone of the DNA
- One chain runs in 5’ to 3’ direction while the other is 3’ to 5’
Phosphate
- Bond that holds the different nucleotides together
- Links the 3’ carbon of one sugar to the 5’ carbon of the next sugar
Phosphodiester bonds
Formation of protein from DNA
Central Dogma
- First step in gene replication
- Because the DNA is too big to exit the nucleus, a small copy of it must be created and exits to the cytoplasm
- A DNA strand molecule splits by the help of RNA polymerase enzyme
- Nucleotides complementary to the template strand are formed on the RNA
Transcription
- The mRNA is translated to synthesize proteins
- Each amino acid is formed by 3 nitrogenous bases
- In the cell cytoplasm, the ribosome reads the sequence of the RNA in groups of three bases
- An anticodon or complementary codon is matched to the RNA coding for a specific amino acid
Translation
start codon
AUG (methionine)
stop codons
UAA, UGA, UAG
The process of forming more copies of DNA
Replication
separates DNA strands
Helicase