NTRES 2830 Prelim 2

Recombinant DNA

DNA molecules joined together from different sources. Produced by artificially joining DNA from different sources not found together in nature. It’s used to isolate, replicate, and analyze genes.

Restriction Enzymes

DNA-cutting enzymes originally produced by bacteria as a defense mechanism against bacteriophages. They bind to DNA at specific restriction sites and cleave both strands of DNA to produce restriction fragments.

DNA Ligase

An enzyme that joins fragments of DNA together to produce intact DNA molecules

DNA Vector

A DNA molecule used to transport foreign genetic material into another cell. Commonly used in molecular cloning to carry and replicate DNA sequences.

Must be able to replicate independently. Have several restriction enzyme sites to allow insertion of DNA fragments. Carry certain gene markers that help to distinguish between which host cells have taken them up from those that haven’t.

Plasmid

A small, circular DNA molecule found in bacteria that can replicate independently of chromosomal DNA. They often carry genes that confer advantageous traits, such as antibiotic resistance. They’re used in DNA cloning and genetic engineering to insert specific genes into host organisms.

Transformation

Plasmids are introduced into bacteria through this method.

• use calcium ions and brief heat shock to pulse DNA into cells

• electroporation: a brief but high intensity pulse of electricity to move DNA into bacterial cells

Blue white screening

-agar contains x-gal (similar to lactose) which turns blue when cleaved

-bacterial cells with functional lacZ genes are carrying non recombinant plasmids (uninterrupted gene, so no insert) = blue colonies

-bacterial cells with disrupted lacZ genes have recombinant plasmids (lacZ gene interrupted, cloned DNA inserted) = white colonies

-lacZ gene produces beta galactosidase which cleaves x-gal for blue coloration.

PCR

-DNA amplification of specific DNA sequences present in very very small quantities without the use of a host cell for cloning.

-denaturing (~94 deg C)

-primer annealing (45-65 deg C)

-extension (~72 deg C)

-template DNA + pair of primers (forward and reverse) + dNTPs (nucleotides) + Taq polymerase + buffer and co-factors for polymerase

What can we do with genome sequencing

-sequence whole genomes across the tree of life

-sequence many more individuals at greater efficiency, speed, and much lower costs per sample

-analyze the composition of mixed samples

quantitative traits

Traits that vary in degree and are often measured on a continuous scale, such as height or weight. They are often polygenic or multifactorial. If you can count in whole numbers to record the phenotype, it’s not continuous.

polygenic traits

Traits influenced by multiple genes, often exhibiting continuous variation.

multifactorial traits

Traits influenced by both genetic and environmental factors, often includes polygenic and quantitative traits.

additive alleles

Alleles that contribute to the phenotype in a cumulative manner. Each allele adds a small, approximately equal, effect to the trait, leading to a range of phenotypic possibilities. Often the basis of continuous variation.

1/(4^n) = ratio of F2 individuals expressing either extreme phenotype

formula where n is the number of gene pairs involved in a polygenic trait.

broad sense heritability

a measure of the proportion of phenotypic variance in a trait that is attributable to all genetic variance, additive, dominant, and interactive, and considers genotype by environment variance to be negligible.

narrow sense heritability

proportion of phentypic variance due to additive genotypic variance alone

hardy weinberg model assumptions

equal rate of survival and reproduction (no selection)

no new alleles arise by mutation

no migration in to/out of population

infinitely large population

random mating

hardy weinberg equillibrium

describes the genetic variation in a population that remains constant from one generation to the next in the absence of evolutionary influences.