Genetics Week 9 Resource

March 15-19

Hi Everyone! As we begin Week 8 of Genetics, many students begin to have some trouble with the material being covered. Take comfort in this: genetics is an EFFORT class!!!If you put in the work, study smart, and push yourself to do your best, I am confident you can finish the course with the grade you want. Keep in mind that the Tutoring Center offers many services that you can take advantage of!

Also, make sure you come to Genetics group tutoring, every Tuesday at 6:30-7:30 You can check the Baylor tutoring website (baylor.edu/tutoring) for more information or to schedule a free, private, one-on-one tutoring appointment!

Keywords: Mutations, Restriction Enzymes, CRISPR-Cas9, PCR, Southern Blots, Plasmids

Chapter 18:

Benjamin A Pierce Genetics a Conceptional approach 6th edition

What is a base substitution? A base (ATCG) turns into another base. This DOES NOT change the reading frame. Substitutions only change one codon max, but insertions and deletions can ruin the entire protein.

Are insertions/deletions considered base substitutions? No! They are adding/getting rid of ONE base. A base substitution simply exchanges one base for another base. The total base count stays the same!

What are the types of base substitutions? No mutation, missense, nonsense, and silent. (see picture above)

Practice! If a sequence goes from ATCG to UAGC what has most likely occurred?

All figures, diagrams, and information are sourced from Pierce Genetics 7ed, unless otherwise stated.

Transcription! (tricky) Please note the use of “most likely”. All professors, even outside of genetics, will use similar terminology. Thus, there might be two technically correct choices, but you have to choose the best fit! In this case, the DNA sequence (ATCG) is correctly transcribed into its RNA sequence (UAGC), so has occurred.

What is the difference between transitions and transformations? Transitions: purine → purine pyrimidine → pyrimidine Transformations: purine → pyrimidine pyrimidine → purine

Do you remember which nucleotides are purines and which are pyrimidines? Purines: adenine and guanosine Pyrimidines: thymine, uracil, cytosine

How are in frame insertions/deletions different from silent mutations? Insertions and deletions of bases in sets of three so they add/remove an amino acid but do not change the reading frame. Remember three bases make a codon and 1 codon makes 1 amino acid!

What do I mean when I say that an in-frame insertion/deletion will not change the reading frame? The code surrounding the in-frame insertion/deletion is not affected! While we will lose an entire amino acid, the ones around it will not be affected because we went in a set of three.

Will all insertions/deletions of three be ineffective in changing the reading frame? No! If an insertion/deletion occurs in a set of three in the middle of an amino acid it will affect the reading frame (if codon AUG had insertion GUA right after the A to become AGUAUG).

Other types of mutations:

Neutral mutation • Mutation that changes the amino acid but does not alter protein function. NOT THE SAME AS SILENT MUTATION Loss of function mutation • Mutation that negatively changes protein function Gain of function mutation • Mutation that positively changes protein function Conditional mutation • Alter protein function if there is an environmental cue (i.e. if it’s warm) Lethal mutation

All figures, diagrams, and information are sourced from Pierce Genetics 7ed, unless otherwise stated.

• Mutation that kills the organism Suppressor mutation • Mutation that hides the effects of another mutation

As you know, professors love to mix up definitions, but you are all smart, determined students! Professors will NOT say “a mutation that negatively changes protein function” they will say “a mutation has occurred, and the organism can no longer …” You must APPLY what you know! The first step is memorizing and learning the material, the second step is to apply it!

Chapter 19:

Restriction enzymes recognizes specific DNA strands and makes double stranded cuts at that site. This. allows us to remove and insert DNA wherever we want.

Cohesive vs blunt ends: • Cohesive ends can connect to other strands (also known as sticky ends) • Blunt ends cannot connect to other strands

https://bitesizebio.com/31136/introduction-restriction-enzyme-cloning/

What are the different types of blots?

Southern • DNA blotting to determine the presence of different sized DNA strands Northern Blot • RNA blotting (same as Southern but with RNA) • Protein blotting to semi-quantitatively analyze the amount of protein

Quiz! 1. If we want to analyze RNA what type of blot will we use?

2. If the DNA sequence of a protein has changed but the amino acid sequence remains the same, what type of mutation has occurred? a. Nonsense b. Frameshift All figures, diagrams, and information are sourced from Pierce Genetics 7ed, unless otherwise stated.

c. Silent d. No mutation

3. A scientist is hoping to insert a DNA sequence of his choosing into a plasmid. In order to do this, what type of ends should the scientist produce in the cut plasmid with restriction enzymes?

4. Esm-1 is a protein responsible for binding to LFA-1 (another protein). If a mutation renders Esm-1 unable to bind to LFA-1, what type of mutation has occurred?

Answers: 1. Northern blot 2. C 3. Cohesive ends (also known as sticky ends) 4. Loss of function mutation

That’s it for this week! I hope this is useful for you all and please do not hesitate to reach out if you have any questions. Also, remember that past resources can be found and downloaded from the tutoring center website: https://www.baylor.edu/support_programs/index.php?id=967950

All figures, diagrams, and information are sourced from Pierce Genetics 7ed, unless otherwise stated.