exam 4 bio

Griffith's experiment

Demonstrated that genetic material can be transferred between bacteria through transformation.

Avery, MacLeod, and McCarty's conclusion

DNA is the transforming material responsible for heredity.

Hershey and Chase’s experiment

Showed that DNA, not protein, is the genetic material injected by viruses into bacteria.

Components of a DNA nucleotide

A phosphate group, deoxyribose sugar, and a nitrogenous base.

Purines vs Pyrimidines

Purines (A, G) have two rings; pyrimidines (C, T) have one ring.

Difference between DNA and RNA nucleotides

RNA has ribose instead of deoxyribose and uracil instead of thymine.

Bond connecting nucleotides in DNA strand

Phosphodiester bonds between the phosphate of one and the 3' OH of another.

Bonds holding two strands of DNA together

Hydrogen bonds between complementary bases.

Chargaff’s rule

A = T and G = C in any DNA molecule.

Rosalind Franklin’s X-ray crystallography

Revealed DNA is a helical structure with a consistent diameter.

Watson and Crick model of DNA

A double helix with antiparallel strands and complementary base pairing.

Antiparallel in DNA structure

The two strands run in opposite 5' to 3' directions.

Semiconservative replication

Each new DNA molecule consists of one old and one new strand.

Semidiscontinuous replication

Leading strand synthesized continuously; lagging strand in Okazaki fragments.

What DNA polymerase requires to begin synthesis

An RNA primer.

Enzymes involved in DNA replication

DNA polymerase, primase, DNA ligase, DNA gyrase, helicase.

Three main types of RNA

mRNA (messenger), rRNA (ribosomal), tRNA (transfer).

Relationship between genes and chromosomes

Genes are segments of DNA located on chromosomes.

Definition of a gene

A DNA sequence that encodes a functional product, usually a protein.

Structural parts of a gene

Promoter, regulatory sequences, start site, introns, exons, termination sequence.

Genetic code

A set of triplet codons in DNA or mRNA that specify amino acids.

Transcription

The process of synthesizing RNA from a DNA template.

End products of transcription

A strand of RNA (usually mRNA in protein-coding genes).

Transcribing DNA to mRNA

Replace A with U, T with A, C with G, and G with C.

Modifications to eukaryotic pre-mRNA

Addition of 5' cap, 3' poly-A tail, and splicing of introns.

Role of tRNA

Carries amino acids to the ribosome during translation.

Role of ribosomes

Facilitate decoding mRNA and forming peptide bonds during translation.

Genetic code chart

Used for translating mRNA codons into amino acids.

Translation

The process of synthesizing proteins using mRNA as a template.

Protein synthesis

The entire process from DNA transcription to protein translation.

Relation between transcription and translation

Transcription creates mRNA, which is translated into a protein.

Difference between prokaryotic and eukaryotic protein synthesis

Prokaryotes couple transcription and translation; eukaryotes separate them and process mRNA.

Role of splicing in protein diversity

Allows multiple proteins to be produced from one gene by removing different introns.

Necessity of gene control for cell survival

Allows cells to respond to environmental changes and maintain homeostasis.

How regulatory proteins control gene expression

They bind to DNA and either block or promote RNA polymerase binding to promoters.

Transcriptional control

Regulation of whether and how much a gene is transcribed into RNA.

Post-transcriptional control

Regulation after RNA is made, affecting RNA stability, translation, or processing.

Inducible operon

An operon activated by the presence of a substrate, e.g., lac operon with lactose.

Repressible operon

An operon turned off by the presence of a product, e.g., trp operon with tryptophan.

Lac operon when lactose is absent

Lac repressor binds to operator, blocking transcription.

Lac operon when lactose is present

Lactose (allolactose) binds the repressor, allowing transcription.

Glucose repression

Cells preferentially use glucose, inhibiting the use of other sugars like lactose.

Role of CAP (catabolite activator protein)

Activates transcription when glucose is low by binding with cAMP.

Difference between eukaryotic and prokaryotic gene regulation

Eukaryotic regulation is more complex due to chromatin structure and separated transcription/translation.

General transcription factors

Proteins necessary to form the basic transcription initiation complex at all promoters recognized by RNA polymerase II.

Specific transcription factors

Proteins that regulate transcription in a tissue-specific or time-specific manner.

Transcription complex

A large assembly of proteins that regulate transcription.

Effect of chromatin structure on gene expression

DNA wrapped around histones can restrict access; chromatin must be remodeled for transcription.

Regulation of translation initiation

By translation repressor proteins that block ribosome binding to mRNA.

mRNA stability influence on gene expression

mRNAs with short half-lives are degraded faster, reducing protein production.

Importance of plasmids and viruses in genetic engineering

Used as vectors to carry foreign DNA into host cells.

Function of restriction endonucleases

Cut foreign DNA to protect bacteria from viruses.

Bacterial protection against restriction enzymes

By methylating their DNA at recognition sites.

Sticky ends definition

Single-stranded overhangs created by restriction enzymes allowing easy joining of DNA fragments.

Four steps of genetic engineering

Cut DNA, Insert into a vector, Introduce into host cell, Screen for clones.

Blue-white screens for recombinant clones

White colonies contain the desired insert; blue colonies do not.

PCR (polymerase chain reaction) use

Amplifying specific DNA sequences rapidly.

Basic steps in a PCR cycle

Denaturation, annealing, and extension.

Crucial enzyme for PCR

Taq polymerase due to its heat resistance.

Function of gel electrophoresis

Separates DNA fragments based on size.

DNA library definition

Collection of cloned DNA fragments for research.

STRs usage

Short tandem repeats used for DNA fingerprinting.

Ti plasmid use in genetic engineering

A plasmid from Agrobacterium used to genetically engineer plants.

Biofuels and microalgae

Renewable fuels from biomass; microalgae produce lipids for biofuels.

Insulin production using biotechnology

Human insulin genes inserted into E. coli to produce insulin.

FISH (Fluorescent In Situ Hybridization)

Technique to detect specific DNA sequences using fluorescent probes.

New vaccine technologies

Use nucleic acid (DNA or mRNA) or viral vectors instead of weakened viruses.

Stem cells definition

Pluripotent cells that can differentiate into any cell type; used for tissue repair.

Glyphosate resistance in crops

Genetic modification making crops resistant to the herbicide glyphosate.

Bt crops

Crops engineered to produce Bt toxin, resistant to insect pests.

Stacked crop technology

Crops engineered with multiple traits, like herbicide and pest resistance.

Golden Rice significance

Genetically modified rice that produces beta-carotene to prevent vitamin A deficiency.