Biology 111: Unit 2                                                    February 2000

If you picked up this review on Wednesday 3/28/01 it must be completed by Saturday 3/31/01 at 9:30am. If you picked up the review on Friday 3/29/01 it must be completed by Monday 4/2/01 at 9:30am. All reviews must be turned in in class at 9:30am Monday 4/2/01.

This is a closed book, closed-note review. Once you have read any question your review period has begun. There is no time limit for taking the review. It was designed to be completed in 2 hours.

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Dogs are thought to be one of the first domesticated animals. It appears that as soon as dogs began living with humans, humans began breeding dogs so that they would have 'advantageous'characteristics.

The following characteristics will be used within this review. For the purposes of this review assume that a different genetic locus is responsible for each of the three polymorphic characteristics described.

Dog Breed: Beagle

A breeder mates a female true breeding for howling and digging with a non-digging, yipping male

A)   Using Morgan notation what are all of the possible genotypes for the dogs that were mated? (4pt)

B)   What phenotypes are possible for their puppies? (3pt)

The same breeder is interested in establishing a line of Beagles that are 25inches tall and donít dig up his flowerbeds.  Dog breeding is very competitive. He wants to know as much as he can about the traits so that he can plan an effective breeding scheme. He read that if genes are linked they 'violate' Mendel's Law of Independent Assortment, but he has no idea what this means.

C)   Briefly explain the Law of Independent Assortment (4pt)

Armed with this new knowledge he mates a number of female Beagles that are heterozygous for tall and digging with a single (lucky) short non-digging male. The phenotypes of all of the puppies are seen in the table below.

If the genes are linked a cross like this is predicted to result in a phenotypic ratio of 1:1. The height gene and the earth moving tendencies gene are linked yet the phenotypic ratio seen is not 1:1.

D)   Explain what happened to produce the phenotypic ratio seen. (5pt)

You happen to be an expert on the dog genome and know that chromosome 3 contains not only the height gene but also 3 well-characterized RFLPs named Spot1, Fido2 and Ralph3.

E)    What is a chromosome? (3pt)

F)    What is a RFLP? (State what the letters stand for and define what it is) (5pt)

G)   Previous work has shown that Fido2 is closest to the 'top' of Chromosome 3. Draw a map of the chromosome containing the relative locations and distances (in map units) of all 3 RFLPs. (6pt)

After further research you conclude that the gene controlling earth moving tendencies (digging) is 3.21kb 3' of RFLP Fido2 and is flanked by sequences recognized by the restriction enzyme BamHI.

H)   Place a star on the chromosome map you drew for question H to indicate the approximate position of the digging gene. (2pt)

I)     How many nucleotides are in 3.21kb? (2pt)

J)     BamHI breaks what type of bond? (3pt)

Bonus: Assuming that the chromosome contains the statistically predicted number of BamHI sites, what is the least number of molecules of BamHI required to completely digest a 4Mb chromosome fragment. 2pt

Understanding Beagle digging behavior has become close to an obsession and you focus your entire research lab on it. You find that the digging gene spans 70kb of DNA. mRNA transcribed from the gene is 2947 nucleotides and is only found in those cells responsible for toenail growth and in foreleg muscles.

K)   What are the basic components of a eukaryotic gene? (Include a well-labeled diagram) (5pt)

L)    Providing only one sentence for each step, describe the main steps in transcription. (3pt)

M) How is it a 70kb gene is transcribed into an mRNA that is only 2947 nucleotides? Be sure to discuss all of the differences between a gene and an mRNA that would result in changes in length. (8pt)

N)   You identified the digging gene by chromosome walking. Your breeder friend has never heard of this process. Explain it to him (in less than 100 words/preferably one or 2 sentences). (4pt)

You have identified and sequenced the digging gene from a wildtype Beagle. Now you turn to understanding the function of the digging gene product. To begin this quest you isolate the 'digging protein'from Wildtype Beagles and determine that it is 927amino acids long.

O)   Describe the complex that is responsible for making proteins. Include where it is found (2pt), its components (4pt) and the part of the complex that is responsible for catalyzing the bonds between amino acids (3pt). (9pt total)

Bonus: Draw 2 amino acids that have been joined. (2pt) In the diagram you may use the general symbol for side chain or (for 1pt more) include the structure of ërealí side chains.

Since the digging allele is dominant you hypothesize that the mutant gene (causing non-digging) encodes a non-functional protein. You also have a hunch that the Wildtype protein and mutant protein are the same size. You perform an experiment that supports this hunch.

P)    What experiment did you perform? (Be sure to describe the experimental approach and tell how the results would show that the 2 proteins are the same size.) (4pt)

Even more work shows that the mutation causing ënon-diggingí changes a single nucleotide in the digging gene.

Q)   Define the three types of point mutations. (One sentence each) (3pt)

R)   Hypothesize which type of point mutation is responsible for the non-digging allele. (Be sure to mention all 3 types when you explain you answer) (7pt)

You decide that you are spending too much time in lab and need to see a real Beagle in action. However, your scientific tendencies catch up with you and you find yourself forming a hypothesis that the dogs dig because of something in the dirt around them. To quench your curiosity you take samples from under the toenails of digging and non-digging dogs. Back in the lab you examine the samples by phase contrast microscopy using a microscope that is outfitted with a CCD camera, has two 10x oculars, one 40x and one 60x objective.

S)    You examine a wet mount slide at the highest magnification. What is the total magnification possible using this microscope? (Show any calculations) (3pt)

You determine that all of the samples contain an oval shaped green algae that has two flagella and a red dot. It reminds you of the algae that you studied back at Davidson College in that intro Biology course that made you decide to devote your life to research. You spend a moment reminiscing about the afternoon spent in the Watson Life Science Building studying ëthe Central Dogmaí by calculating flagella regeneration rates.

T)   What was the scientific name of the algae you studied in Bio111 lab? (Genus and species) (3pt)

U)   What was the red spot on the algae and for what is it used? (3pt)

V)   What is the basic building block of the cytoskeletal polymer inside the growing flagella? (2pt)

You are jolted from your daydream by the telephone. It is that breeder again and this time he sounds distraught. His neighbor is suing him for 'puppy support'. The neighbor's poodle, Billy Jean, just had puppies and they look a lot like the breeder's champion male Beagle, Rex. Rex has been known to wander the neighborhood but the breeder is certain that Rex is not responsible.

To help him out you obtain blood samples from Billy Jean, Rex and one of the puppies (King). You perform RFLP analysis and get the following results.

 

W)  What is Southern blot analysis? (3pt)

X)   Did Rex sire King? (2pt) (Note: to sire = to father)

Choose from:

1)    She's having his baby. (yes he did)

2)    Billy Jean's not his love. (no he did not)

3)    Torn between two lovers, feeling like a fool. (The data is inconclusive)

Y)   Explain the reasoning behind your answer in X. (4pt)

Bonus: For 0.5pt name the singer/group that sang any one of the 'classic hits' listed in 'X' OR how the dogs in this question relate to tennis.