Genetic Engineering & Evolution: Key Concepts in Molecular Biology and Darwinian Theory

What is recombinant DNA technology?

Combining DNA from different sources to create new genetic combinations for research, medicine, and agriculture.

Why was cadaver-derived human growth hormone discontinued?

It was discontinued in 1985 due to contamination with prions causing Creutzfeldt-Jakob disease. Recombinant DNA technology solved this by producing safe synthetic hGH in bacteria.

What does reverse transcriptase do?

It converts mRNA into complementary DNA (cDNA), enabling cloning of eukaryotic genes without introns.

What is a plasmid and its role in genetic engineering?

A plasmid is a circular DNA molecule in bacteria used as a cloning vector to carry foreign genes.

What are restriction endonucleases?

Enzymes that cut DNA at specific palindromic sequences, creating sticky ends for ligation.

What is a sticky end?

An overhanging single-stranded end produced by restriction enzyme cuts, allowing complementary base pairing for insertion.

What does DNA ligase do?

It joins DNA fragments by forming phosphodiester bonds, sealing nicks in the sugar-phosphate backbone.

What is bacterial transformation?

The process by which bacteria take up foreign DNA, such as recombinant plasmids, from their environment.

What is a DNA probe and its role in screening a library?

A labeled DNA or RNA fragment that binds to complementary sequences to identify target genes in a DNA library.

What is the difference between a genomic library and a cDNA library?

Genomic library contains all DNA sequences including introns; cDNA library contains only expressed genes derived from mRNA.

What is PCR and its purpose?

Polymerase Chain Reaction amplifies specific DNA sequences rapidly and efficiently.

What are the steps of PCR?

Denaturation (separate strands), Annealing (bind primers), Extension (DNA synthesis by Taq polymerase).

Why is Taq polymerase used in PCR?

It is heat-stable and can withstand high temperatures during denaturation.

What is dideoxy sequencing?

A DNA sequencing method using ddNTPs to terminate synthesis, producing fragments that reveal the sequence when separated by electrophoresis.

What is a genetic map vs a physical map?

Genetic map shows relative positions based on recombination frequency; physical map shows absolute positions based on DNA sequence.

What are genetic markers and why are they important?

Polymorphic sequences like SNPs or restriction sites used to track inheritance and locate disease genes.

What is gene therapy?

Treatment of genetic disorders by introducing functional genes, e.g., SCID treated with retrovirus carrying normal gene.

What are transgenic organisms?

Organisms genetically modified to carry foreign genes, e.g., golden rice enriched with beta-carotene.

What is the Ti plasmid and its role in plant engineering?

A plasmid from Agrobacterium used to transfer T-DNA into plant genomes for genetic modification.

Define genome.

The complete set of DNA in an organism, including all genes and noncoding sequences.

What is genomics?

The study of entire genomes, including their structure, function, and evolution.

What is functional genomics?

The study of gene functions and interactions using large-scale data.

What is bioinformatics?

Computational analysis of biological data, such as DNA sequences and protein structures.

What is shotgun sequencing?

A sequencing method that breaks DNA into fragments, sequences them, and assembles overlaps to reconstruct the genome.

What was the first prokaryotic genome sequenced?

Haemophilus influenzae.

What was the first eukaryotic genome sequenced?

Saccharomyces cerevisiae (yeast).

What is an open reading frame (ORF)?

A stretch of codons without stop codons, indicating a potential protein-coding gene.

What is lateral gene transfer?

Movement of genes between species via plasmids, viruses, or transformation.

What is genome annotation?

Identifying coding regions and functional elements in a genome.

What is metagenomics?

Sequencing DNA from environmental samples to study microbial communities.

Why is there no linear relationship between genome size and gene number in eukaryotes?

Due to noncoding DNA and repeated sequences.

What are transposable elements?

DNA sequences that can move within the genome, e.g., LINEs.

What are microsatellites and why are they important?

Short tandem repeats used in DNA fingerprinting.

What is a pseudogene?

A nonfunctional copy of a gene created by duplication and mutation.

What is alternative splicing?

Process where one gene produces multiple proteins by varying exon combinations.

What is a DNA microarray used for?

Measuring expression levels of thousands of genes simultaneously.

What is proteomics?

Study of all proteins expressed by a genome.

What is systems biology?

Study of complex interactions in biological systems using computational models.

What is typological thinking?

The idea that species are unchanging and variations are imperfections.

How did Lamarck’s theory differ from Darwin’s?

Lamarck proposed inheritance of acquired traits; Darwin proposed natural selection.

What are Darwin’s four postulates?

Variation exists, traits are heritable, differential survival/reproduction, traits linked to fitness.

Define fitness.

Ability to survive and reproduce in a given environment.

Define adaptation.

A trait that increases fitness in a given environment.

What are transitional fossils?

Fossils showing intermediate traits between ancestral and modern species.

What are vestigial traits?

Reduced or nonfunctional structures inherited from ancestors.

What are the three types of homology?

Genetic, developmental, structural.

What is population thinking?

Emphasizing variation among individuals as key to evolution.

What is acclimatization and why is it not adaptation?

Short-term physiological change; does not alter genetic makeup.

What is a fitness trade-off?

A compromise between traits that increase fitness in one context but reduce it in another.

What does Hardy-Weinberg equilibrium indicate?

No evolution is occurring; allele frequencies remain constant.

What is the Hardy-Weinberg equation for allele frequencies?

p + q = 1.

What is the Hardy-Weinberg equation for genotype frequencies?

p² + 2pq + q² = 1.

What are the five assumptions of Hardy-Weinberg?

Random mating, no selection, no drift, no migration, no mutation.

What happens to heterozygosity under inbreeding?

It decreases, increasing homozygosity.

What is inbreeding depression?

Reduced fitness due to increased homozygosity of harmful alleles.

What is directional selection?

Favors one extreme phenotype, shifting the average.

What is stabilizing selection?

Favors intermediate phenotypes, reducing variation.

What is disruptive selection?

Favors extreme phenotypes, increasing variation.

What is balancing selection?

Maintains multiple alleles in a population.

How does sexual selection differ from natural selection?

Sexual selection acts on traits that improve mating success, often stronger in males.

What is the difference between intersexual and intrasexual selection?

Intersexual = mate choice; intrasexual = competition among same sex.

What is genetic drift?

Random change in allele frequencies, strong in small populations.

What is the founder effect?

Genetic drift when a new population is started by a few individuals.

What is a genetic bottleneck?

Sharp reduction in population size â†' loss of genetic diversity.

What is gene flow?

Movement of alleles between populations.

Why is mutation alone a weak evolutionary force?

It occurs slowly and needs other forces to change allele frequencies significantly.