PCR & DNA TECH
What are the three main steps of PCR that repeat in each cycle and what do they do?
Denaturation (heating to separate strands)
Annealing (cooling so primers attach)
Extension (DNA polymerase builds complementary strands)
What percentage of the human genome actually codes for proteins (exons)?
About 2.5%
What does CRISPR technology allow scientists to do?
Edit DNA by making targeted, precise changes to specific nucleotide sequences in genes
True or False: Only animal cells can perform cellular respiration.
False - both plant and animal cells have mitochondria and perform cellular respiration to produce ATP
If you run PCR for 10 cycles starting with 1 DNA molecule, how many copies will you have?
1,024 copies (2^10 = 1,024)
What is chromatin made of?
DNA wrapped around histone proteins (DNA-protein complex)
Who won the 2020 Nobel Prize in Chemistry for inventing CRISPR technology?
Jennifer Doudna and Emmanuelle Charpentier
What is the difference between passive and active transport?
Passive transport doesn't require energy and goes with the concentration gradient whereas Active transport requires energy and goes against the concentration gradient.
Why must the primers in PCR have their 3' ends oriented toward each other?
Because DNA polymerase can only build from 5' to 3' the primers need to point toward each other for the DNA to be copied in both directions
What is a nucleosome and what does it consist of?
A nucleosome is the basic unit of DNA packaging, consisting of 8 histone proteins wrapped with about 150 base pairs of DNA
What are restriction enzymes used for, and what do they recognize?
Restriction enzymes cut DNA at specific recognition sequences (specific base pair sequences) on double-stranded DNA - used for recombinant DNA and genome editing
If you have an mRNA sequence 5'-AUGCGUUAA-3', what would be the anticodon sequence for the tRNA that brings in the second amino acid?
3'-GCA-5' (the second codon is CGU, so the anticodon is 3'-GCA-5', antiparallel to the codon)
In gel electrophoresis, do smaller or larger DNA fragments travel farther through the gel, and why?
Smaller fragments travel farther because they can move more easily through the pores in the gel matrix
What are transposons, and what percentage of the human genome do they make up?
Transposons are "jumping genes" - DNA sequences that can copy themselves and move to other locations in the genome. They make up about 45% of the human genome
What's the difference between "sticky ends" and "blunt ends" when restriction enzymes cut DNA?
Sticky ends have overhangs (uneven cuts) with unpaired bases that can base-pair with complementary sequences, while blunt ends are even cuts with no overhangs on both strands
Name three things that the cell membrane contain.
Integral & Peripheral proteins, cholesterol, Phospholipids.
What special property must the DNA polymerase used in PCR have that normal DNA polymerase doesn't need?
It must be heat-stable (thermostable) because PCR involves repeated heating to 95°C for denaturation, which would denature normal polymerase
Is there a connection between the number of genes an organism has and its biological complexity? For instance, do more complex species have more genes than simpler ones?
Gene number doesn’t always reflect biological complexity. For example, humans have about 20,000–25,000 genes, while an onion has around 40,000. This shows that gene count alone doesn’t determine complexity, how genes are regulated and expressed matters more.
Explain how recombinant DNA is made using restriction enzymes and what enzyme seals the final product.
Restriction enzymes cut both the donor DNA fragment and the vector (like a plasmid) at recognition sites, creating complementary sticky ends. The fragments are mixed and their sticky ends base-pair together, then DNA ligase seals the sugar-phosphate backbone to create the final recombinant DNA molecule
What are the four stages of Cellular Respiration?
Glycolysis, Pyruvate oxidation, Citric acid cycle and Electron Transport Chain (Oxidative Phosphorylation)