Key Concepts - DNA & Mutations Flashcards
(23 cards)
Importance of DNA
It is actually information, encoded into (almost) every one of our cells!
DNA
Double-helix structure: two strands paired, and a slight curve
Made of nucleotides
Codes for every trait
What does DNA stand for
Deoxyribonucleic Acid
Hammerling experiment
Joachim Hammerling discovered that the nucleus of a cell controls the development of organisms.
Hershey-Chase experiment
1952: Alfred Hershey & Martha Chase used bacterial viruses to confirm that DNA was, in fact, the material which contains the hereditary information and was stored in the nucleus
Chemical components of DNA (nucleotides)
Deoxyribose (sugar)
Phosphate
Nitrogen Base
Base pairs
C & G
A & T
Two rings
Giant
G and A
One ring
Teency
T and C
Watson & Crick
In 1953, James Watson and Francis Crick used what they knew about the chemical structure of DNA, Watson and Crick built a model of DNA. Watson and Crick’s model showed the molecular structure of DNA to be a double helix.
Adenine
A
thymine
T
cytosine
C
guanine
G
Chemical structure of DNA
Phosphate is the backbone
Ribosome is in the middle
Base pairs are the base
Hydrogen bonds connect the bases
Point mutations
Substitution: replacing a gene with another gene
Insertion: adding another gene to a strand
Deletion: Taking a gene away from a strand
Chromosomal mutations
An error that involves a whole chromosome or part of a chromosome
Trisomy 21(an extra copy of chromosome 21) causes Down’s Syndrome
Control of mutations
DNA has a protein called polymerase that can “proofread” DNA and check for mutations
Some types of bacteria can reduce the effect of the proofreader, allowing for more mutations when stressed. More mutations = more chance for beneficial mutation
Cystic fibrosis (caused by inherited mutations)
-one three-nucleotide deletion
- mucus buildup in lungs and GI tract
Huntington’s disease (caused by inherited mutations)
- Affects adults starting in their 30s
- Repeating section of gene is duplicated
- Seizures, muscular spasms, dementia
- Dominant trait in families
Sickle cell anemia (caused by inherited mutations)
Red blood cells are “sickle-shaped”
Single point mutation affects function of hemoglobin
Causes anemia, swelling. Death usually arise from complications involving blood flowing through organs
Recessive trait. Heterozygous carriers are protected against Plasmodium, the cause of malaria
Transposons
Barbara McClintock’s work led her to suggest the idea of “jumping genes” called transposons
These sections of DNA can move all around the genome, even between chromosomes
If a transposon lands in the middle of another gene, then that gene no longer functions. Ex: Blood clotting
Mutagens
result of exposure to a physical or chemical agent that causes mutations
