Test 4: Genetic Engineering, Population Genetics, Quantitative, Micro and Macroevolution Flashcards
Recombinant DNA technology
- Recombining DNA segments from different species in the test tube
- Reintroducing it back into a living organism
2 Discoveries that made Recombinant DNA technology possible
1) plasmids
2) restriction endonucleases
Plasmids
- bacterial extrachromosomal DNA
- small circular DNA molecules w/ around 2700 bps
Restriction endonucleases
- naturally-occuring enzymes in bactera
- a defense mechanism against invading virus DNA
- bacteria with these enzymes were able to restrict infection
Difference between Endonuclease & Exonuclease
Endonuclease: breaks an internal phosphodiester linkage, fragmentation of the DNA molecule
Exonuclease: breaks the terminal phosphodiester linkage again and again
E.Coli RNA polymerase
- recognizes and binds the promoter to initiate transcription
- does not recognize or initiate transcription at the promoter from another species
Type I diabetes (juvenile onset)
cause: lack of insulin (a protein hormone)
original treatment: bovine or porcine insulin
problem: allergies, side-effects to animal protein
recombinant source: engineered bacterial cells harboring the human insulin gene grown in bioreactors
Dwarfism
cause: lack of growth hormone (a protein)
original treatment: human GH isolated from pituitary glands of cadavers
problem: possible co-isolation of infectious agent
recombinant source: engineered bacterial cells harboring the human GH gene grown in bioreactors
Hemophilia
cause: lack of clotting factor VIII (a protein
original treatment: human factor VIII isolated from donated blood
problem: possible co-isolation of HIV
recombinant source: engineered mammalian cells harboring the human GH gene grown in tissue culture
Genetic Engineering in Plants
- does not usually involve the simple modification of a zygote
- scientists employed the help of bacteria that practice recombinant DNA technology
CRISPR-Cas9 components
- dCas9
- sgRNA 1
- sgRNA 2
- donor DNA
HDR
- homology directed repair (HDR)
- if ligase repairs before HDR, paired nickases will act again
BT toxin
-protein that kills lepidopterans
-extremely species specific: onlu Lepidopterans (moths, caterpillars, butterflies)
-create genetically modified crop plants that harbor
the BT-toxin gene
Why was SCIDS chosen?
1) single gene trait
2) no complex regulation
3) human gene had been isolated and cloned
4) affected organ system easily accessible to genetic modification
Population
- A group of interbreeding individuals
- same species, same range = matings produce fertile offspring
Hardy-Weinberg Equilibrium
- p2 + 2pq +q2= 1
- if =1, in Hardy-Weinberg Equilibrium and allele frequencies will stay the same generation to generation
Polymorphisms
-Many forms (of a trait) in the population
2 Ways for a restriction fragment to differ in length between two chromosomes
1) missing or extra RE recognition site
2) more or less DNA between RE recognition sites
VNTRs
(1/2)n(n+1)
n= number of alleles in the population
Quantitative trait inheritance
-continuous variation between extremes in phenotype
Quantitative traits
-are polygenic (controlled by two or more genes)
number of phenotypic classes = 2n+1 (n = number of genes)
Sample mean
X = sigma(Xi)/n
Xi = each value n = number of values in sample
Sample variance
s^2 = sigma(Xi - X)^2/(n-1)
-need to know X first (sample mean)
establish purebreeding line with smallest value…
… homozygous noncontributing alleles at all genes
establish purebreeding line with largest value…
… homozygous contributing alleles at all genes
Heritability
[S^2(F2) - S^2(parental)]/(S^2(F2)
F1
X = 65 s^2 = 4 s = 2
F2
X = 65 s^2 = 25 s = 5
Determine environmental s^2, genotypic s^2, and total s^2, then determine heritability
environmental s^2 = 4
total s^2 = 25
genotypic s^2 = 21
21/25 = 0.84 heritability
Darwin’s Postulates
1) Individuals within species are variable (VARIABLE)
2) Some of these variations are passed on to offspring (HEREDITY)
3) In every generation, more offspring are produced than can survive
4) Survival and reproduction are not random: The individuals that survive and go on to reproduce, or who reproduce the most, are those with variations that fir the environment best. They are naturally selected. (SELECTION)
Microevolution
-Allele frequency changes in populations (small incremental changes)
Macroevolution
- speciation
- large differences as a result of accumulated microevolutionary changes over time