Download File

Name_________________________________________ Date ___________________ Period _______
Make a Face: A genetic simulation of
making a baby!
Background:
We have previously learned that inherited traits vary from acquired traits
in that they must be passed from parents to offspring through the molecule
known as DNA. DNA can take two forms, chromatin (loosely coiled and easy to
read for cell activities) and chromosomes (tightly coiled and easy to move for cell
division and reproduction). On each piece of DNA are thousands and thousands
of genes which are sections of DNA that code for traits.
Before a child is born, father and mother create sex cells (sperm cells or
egg cells respectively) that will eventually combine to become the child’s DNA. In
the sperm or egg cell there are 23 singular chromosomes rather than 23 pairs of
chromosomes. That is because only one out of each pair of chromosomes will be
passed to your child (to prevent the child from having double the genes it needs!).
23 singular chromosomes in the sperm cell will combine with 23 singular
chromosomes in the egg cell to give the child exactly 23 pairs of chromosomesjust like each parent! However, which singular chromosome within each pair will
be present in the sperm or egg cell is completely random/up to chance.
The interaction between the combination of genes (genotype) on the
chromosomes within each pair (one chromosome from dad + one chromosome
from mom = 1 pair of chromosomes for the baby) will determine the phenotypes
for each trait or the physical features that we can actually see. Of the 23
chromosome pairs, 22 of them are known as autosomes because they contain
genes for traits that are not specific to a gender (ex. Having ten fingers and ten
toes regardless of being male or female). The last pair of chromosomes, pair #23
is known as your sex chromosomes. This is either XY genotype for males or XX
genotype for females.
1
Name_________________________________________ Date ___________________ Period _______
Since females have XX genotype for sex chromosomes, an X will always be
present in each female’s sex cell (egg cell). Males have XY genotype for sex
chromosomes, and therefore there is a 50% chance a sperm cell receives an X
and a 50% chance a sperm cell receives a Y. Male sperm cells thus technically
determine the gender of the child, even though it’s still a 50/50 chance of having
a boy or girl.
In this lab you will:
-Simulate the creation of sex cells (sperm and egg) that have half of the DNA
compared to the rest of the cells in the human body
-Simulate fertilization of egg by sperm and combination of DNA
-Investigate the genotypes and phenotypes of the child to determine its
inherited traits
Procedure:
-Cut chromosomes, fold in half lengthwise and tape or glue (this simulates the
50% chance of any given copy of a chromosome pair to be passed to the offspring
via sperm or egg
-Place chromosomes randomly on desk and arrange in size/number order
-Line up your chromosomes with your partners (be sure to discuss which sex
chromosomes to use- pair #23)
-Record the genotypes that correspond to each trait in the data table
-Look up the phenotypes that each genotype would produce in the lab booklet
-Complete the drawing of the child assuming he/she has grown up to age 15
2
Name_________________________________________ Date ___________________ Period _______
Data table
Trait
Genotype Phenotype
Gender
Face Shape
Chin Shape (round or square)
Skin Color*
Hair Color*
Eye Color*
Hair type (curly wavy or straight)
Widow’s Peak
Eyebrow thickness
Eye Shape (almond or round)
Eyelashes
Dimples
Nose size
Ear lobes (attached or lobed)
Freckles on cheeks
*May require more than 1 gene
3
Name_________________________________________ Date ___________________ Period _______
Drawing of child 15 years after birth
4
Name_________________________________________ Date ___________________ Period _______
Analysis Questions:
1. How many chromosome pairs does each human parent have?
2. How many individual chromosomes does each parent give to the next generation via sperm or egg?
3. Are some genes and characteristics expressed over others or do all genes have an equal chance of
being expressed? Give evidence from your experience in lab.
4. How is there so much variation in the way children look even if they come from the same parents?
5
Name_________________________________________ Date ___________________ Period _______
Make a Face: Prelab
Directions:
Write 1 paragraph describing the features your ideal baby would
have. Include as many inherited traits as possible. We will compare
your ideal baby to the baby you produce during the lab this week.
6