DNA Replication, Gene Expression, and Biotechnology

Flashcards covering DNA structure, replication, gene expression, mutations, and biotechnology protocols and regulations.

How are nitrogen bases paired in the DNA double helix and what bonds hold them together?

$A=T$ with 2 H-bonds and $G \equiv C$ with 3 H-bonds.

Which scientists are credited with discovering the structure of DNA and whose work assisted them?

Watson & Crick figured it out using Rosalind Franklin’s X-ray pictures.

What is the nucleoid in prokaryotic cells?

The single circular DNA coil found in bacteria.

Describe the four levels of DNA packaging in eukaryotes.

1. Nucleosomes (DNA wrapped around 8 histones); 2. 30 nm chromatin fibers; 3. Looped domains on a protein scaffold ($~300\,nm$); 4. Chromosomes during cell division ($~700\,nm$).

What are Okazaki fragments?

Chunks of DNA synthesized on the lagging strand that are later glued together.

What are the three steps of the Nucleotide Excision Repair process?

1. Nuclease cuts out the damaged section; 2. DNA Polymerase fills the gap; 3. DNA Ligase seals the gap with a phosphodiester bond.

What is the specific location of a gene on a chromosome called?

Locus.

Identify the start codon and the three stop codons used in genetic translation.

Start codon: AUG (codes for methionine); Stop codons: UAA, UAG, and UGA.

What modifications occur during eukaryotic pre-mRNA processing?

Splicing to remove introns, and the addition of a 5' cap and a 3' poly-A tail.

In which direction does RNA polymerase add ribonucleotides during transcription?

In the $5' \rightarrow 3'$ direction.

What are polysomes?

Multiple ribosomes working simultaneously on one mRNA for fast protein synthesis.

Define the difference between monosomy and trisomy in aneuploidy.

Monosomy is the condition of having one missing chromosome ($2n-1$), and trisomy is having one extra chromosome ($2n+1$).

What mutation causes Sickle Cell Anemia?

A mutation in the $\beta$-globin gene leading to sickled red blood cells.

Compare the chromosomal configurations of Turner Syndrome and Klinefelter Syndrome.

Turner Syndrome is $XO$ (sterile females with one X chromosome), while Klinefelter Syndrome is $XXY$ (sterile males with an extra X chromosome).

What are the five steps of DNA Isolation?

1. Cell Lysis; 2. Block DNAse; 3. Remove Proteins; 4. Purify DNA; 5. Precipitate with cold ethanol.

Match the following enzymes to their functions: Restriction enzymes, DNA Ligase, and Reverse Transcriptase.

Restriction enzymes cut DNA at specific sites (e.g., EcoRI); DNA Ligase joins DNA fragments (e.g., T4 ligase); Reverse Transcriptase makes cDNA from mRNA.

What is the function of Gel Electrophoresis?

It sorts DNA fragments by moving them through an electric field in a gel; smaller fragments move faster.

What vectors are typically used for large genes, plant modification, and human gene therapy?

Large genes: YAC or BAC; Plants: Ti plasmid; Human gene therapy: Viral vectors.

What is the purpose of the Cartagena Protocol on Biosafety (2000)?

To protect biodiversity and human health from Living Modified Organisms (LMOs) based on the precautionary principle.

What framework did the Ministry of Environment in Sri Lanka create in 2005?

National Biosafety Framework (NBFSL).