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Unit 9: Biotechnology

How scientists read, cut, copy, and edit DNA -- from a police lab's gel to a CRISPR-edited genome.

6 topics · 18 questions

Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.

What Genetic Engineering Actually Does

  1. How it worksHow does a gene cut from one organism's DNA get inserted into another organism's genome?
  2. Common mistakeWhy doesn't inserting one foreign gene rewrite an organism's entire genetic identity?
  3. Going furtherWhat happens to a bacterium's traits once it takes up a plasmid carrying a human gene?
Your turn1 of 2
Scientists have inserted a jellyfish gene for a glowing protein into a mouse's genome, and the resulting mouse glows under UV light. Why can inserting one gene from a completely different species produce this effect?

Selective Breeding and Artificial Selection

  1. How it worksHow does choosing which individuals reproduce shift a population's traits generation after generation?
  2. Common mistakeWhy doesn't selective breeding create brand-new traits that weren't already present as variation?
  3. Ties togetherHow does artificial selection use the same underlying process as natural selection, just with a human choosing?
Your turn1 of 2
A chihuahua and a great dane belong to the exact same species, dogs, yet look dramatically different in size and shape. Why do these two breeds look so different despite being the same species?

Gel Electrophoresis

  1. How it worksHow does an electric current pull negatively charged DNA fragments through a gel at different speeds by size?
  2. Worked exampleFind which DNA fragment travels farthest on a gel among fragments of 200, 500, and 1000 base pairs.
  3. Common mistakeWhy doesn't a DNA fragment's charge, rather than its size, mainly determine how far it travels on the gel?
Your turn1 of 2
On an agarose gel, a DNA fragment's migration distance is approximately equal to a constant k divided by the fragment's size in base pairs. For a particular gel run, k is 293746 mm times base pairs. How far would a fragment of 1982 base pairs travel on this gel?

DNA Fingerprinting

  1. How it worksHow does comparing repeating DNA sequence patterns between two samples produce a unique genetic fingerprint?
  2. How it worksHow does gel electrophoresis turn cut-up DNA samples into a visible fingerprint pattern for comparison?
  3. Common mistakeWhy doesn't DNA fingerprinting compare a person's entire genome instead of just certain repeating regions?
Your turn1 of 2
Any two humans share about 99.9 percent of their DNA sequence, yet a DNA fingerprint from a few drops of blood can still identify one specific person out of billions. How does DNA fingerprinting achieve that precision?

Genetically Modified Organisms

  1. How it worksHow does inserting a Bt toxin gene from bacteria into a corn plant make the plant pest-resistant?
  2. Going furtherWhat happens to nearby wild plant populations when engineered genes spread through cross-pollination?
  3. Common mistakeWhy doesn't eating a genetically modified plant change a person's own DNA?
Your turn1 of 2
A corn plant engineered with a bacterial Bt toxin gene can resist certain insect pests without ever being sprayed with pesticide. Why can a single inserted bacterial gene make the plant pest-resistant on its own?

CRISPR Gene Editing

  1. How it worksHow does the CRISPR-Cas9 system use a guide RNA to find and cut one exact spot in a genome?
  2. Going furtherWhat happens to a gene's sequence after CRISPR cuts the DNA and the cell repairs the break?
  3. Common mistakeWhy isn't CRISPR gene editing the same technique as inserting a whole foreign gene through a plasmid?
Your turn1 of 2
Older genetic engineering methods mainly insert a whole new gene at a fairly random location in a genome, while CRISPR can target and change one exact existing DNA sequence. Why can scientists now edit a single gene inside a living cell instead of only inserting whole new genes?