Genetics Prelab

 
   

In living things that reproduce sexually, a set of chromosomes from each parent (or from two sources in a single parent) go into each offspring. Each set of chromosomes carries more-or-less a full set of genes, each of which is the "code" for a particular type of protein. Proteins have many, many roles in an organism, and sometimes a single protein is critical in making a certain obvious trait; however, each gene comes in a variety of code forms, or alleles, which may produce proteins with identical functions or very different functions. Each type of protein that an organism makes is a product of the alleles that it has, so the resulting traits are not only different in a group, but can be different in an individual depending upon how the two alleles are expressed. Often the resulting trait is a blend of the two alleles’ proteins’ effects, but sometimes one allele’s (a dominant allele) protein produces an effect so powerful that it can completely cover up the weaker effect of another allele’s ( a recessive allele’s) protein. It also must be noted that a huge number of traits are the product of at least two proteins working together, and so have many various ways that the alleles involved can mix effects.

This lab will look at some of the more simple properties of basic genetics, the working of genes. It requires part of your lab work to be done ahead of time. You are going to make up a chart or table to bring with you to the lab. Each column or line will be a different trait, off the trait list below; running the other way on the chart will be the people you have surveyed. People related to you are preferred but not necessary; be sure that the relationships among your subjects are noted on the table (it's more important than people's names). You need at least two other people and yourself on the table, but get as many as you can. Record your data in an easily readable form. You may not be able to determine everything, but be sure to note where data has not been available with "NA."

 

Traits List:

WIDOW'S PEAK. This is found at the top center of the forehead - it's a distinct downward point on the hairline. You either have it or you don't.

EARLOBE. Look for where the lower earlobe attaches to the head - does it hang freely, more like a "U" (unattached), or curve directly into its attachment on the face, more like a "J" (attached)?

EYE COLOR. Record eye color in as much detail as you want; in the lab, we'll be interested in basic colors.

EYELASHES. Record either long (over 1 cm.) or short.

TONGUE ROLLER. Someone who can do this can stick out their tongue so it looks like an "O" or "U" from the front. You either can do it or you can't.

DIMPLES. If present, tell where and how many. Cleft chin counts.

FRECKLES. Looking for facial freckles, enough to be obvious.

HITCHHIKER'S THUMB. When present, the thumb, held up, has almost a right angle bend on the outside and the pad is almost parallel to the ceiling.

INTERLOCK. When you fold your hand together in front of you, which hand's thumb is on top?  (May not be clearly dominant - recessive trait, but fun to test.)

HANDEDNESS.  Recent discoveries make right-handedness dominant over no pre-determination - folks with two recessives are about 50% left-handed.

LONG PALMAR MUSCLE. Make a tight fist and bend your wrist toward you, to make the tendons stand out. If three (or more) are clearly there, you are considered to have a long palmar muscle.

MIDDIGITAL HAIR. Almost everyone has hair on the bottom segment of their fingers - you're looking for a similar patch of hair on one or more of the middle segments of the fingers. A very few stray hairs aren't enough.

BENT LITTLE FINGER. Put you hands side-by-side, palms up and facing you. Do the tips of the little fingers seem to point away from each other? If so, you have bent little fingers.

 

BLOOD TYPES. Not everyone knows their blood type ( A, B, AB, or O), but gather what information you can, including Rh factor ( + or - ). One whole section of the lab is on blood type, and we will look for family-based examples from the class.


 
     

 

Original Version 1987;  Web Version 2004.  M. McDarby.

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