Download The Chromosomes of a Nerf: An Imaginary Animal

The Chromosomes of a Furnf: An Imaginary Animal
ANSWER QUESTIONS SHOWN IN BOLD!
Introduction
By now, you should probably know that chromosomes contain genetic information (they
are made up of (a)___________) and that every person has (b)______ pairs of
chromosomes containing exactly the same genetic information in every cell in his/her
body (except the sex cells). But have you ever seen a chromosome? Have you ever seen
mitosis or meiosis as it was happening? Probably not because chromosomes are too
small to see with the naked eye. One way that scientists try to understand processes that
are too small (or too big) to see is to build simple models and to use them to try to
understand how things work. In this lab, you will use colored paper to make models of
the chromosomes in a cell of your Furnf that has a total of 6 chromosomes per cell
(2n=6). You will use these models to help you answer questions throughout the lab.
Procedures
1. Fold the blue sheet in half lengthwise (along the solid line).
2. Keeping the sheet folded, cut on the dotted lines-Keep the 3 folded pieces of
paper that have a shape that looks like this <.
3. Repeat steps 1 and 2 with the pink sheet of paper.
4. You should end up with 6 pieces of paper that have the < shape. For now, keep
them folded.
5. Write 1 group members name on the back/bottom of each chromosome.
6. Number each of your chromosomes from 1 to 3 (make sure you write the same
number on each chromatid).
7. These are the chromosomes in a normal Furnf cell. (b.1) Please make a labeled
drawing of your chromosomes below. Be sure to consider the size, shape,
number, and colors of the chromatids.
Interphase
With your paper models folded, you are looking at a chromatid.
(c) During what part of Interphase does replication of the chromatids take place?
____________
1. Unfold all of your chromosomes so that the models looks like an X. The
unfolding represents the replication of the DNA in the chromatid. Notice the
2 sides of the X are identical and are called (d)___________ _____________.
(e) What structure holds the 2 chromatids of a chromosome together? __________
2. Put this structure onto your chromosomes by drawing a circle in the center of
each chromosome.
Modeling Mitosis
You should all be quite familiar with the process of mitosis, which is the division of the
(f)__________. You will notice as you begin to perform mitosis, that some very
important functions will be ignored like the (g)___________ ___________ whose job is
to connect to the chromosomes and pull them to opposite sides of the cell.
1. Attempt to model mitosis by moving the chromosomes around on the table to
represent each of the 4 phases, (h) _____________ _____________
____________ and _______________. You will need scissors to do the 3rd
step of mitosis.
2. Draw each of these 4 phases below as is shown by your Furnf (6 total
chromosomes). Remember to label each drawing.
The process of mitosis begins with one cell, and finishes with (j) ______ identical cells.
(k) In ONE of your new cells following mitosis, how many chromatids of each color
are there? _______________
(l) In ONE of your new cells following mitosis, how many chromatids of each size
are there? ________________
3. Use a piece of tape to rejoin your identical chromatids once again, making
chromosomes.
Modeling Meiosis
Before we can begin, let’s think about sex. (m) First of all, why do you think some of
the chromosomes are blue and some are pink?
Furnfs are animals and each Furnf has a mother and a father. When Furnf males mate
with Furnf females, a sperm cell from the father joins an egg cell from the mother. The
haploid sperm cell from the father and the haploid egg from the mother both contain
DNA in the form of chromosomes. They join together and their chromosomes mix
making an embryo cell called a zygote that is now (n) ___________, which will
eventually become a baby Furnf (after a great deal of mitosis!). The baby Furnf has to
also go through meiosis to make its own sex cells (in males, not until puberty, in females
before they’re born). In our model, the chromosomes that are blue have come from the
father Furnf, while the chromosomes that are pink have come from the mother Furnf.
1. Using a pencil or pen, draw a line on the large blue chromosome to represent a
gene and label it with the letter B. Remember these 2 chromatids are
identical!
2. Draw a line on the large pink chromosome in the same place, but label this
gene b. Again, remember these 2 chromatids are identical!
3. (o) Different variations of the same gene are called ____________.
Meiosis I (you will need scissors again for parts of Meiosis)
(p) For each phase of meiosis, draw what your chromosomes look like in the boxes
provided.
Prophase I
During this phase, homologous
chromosomes line up together.
Metaphase I:
Notice that the blue and the pink chromosomes do not
always have to be on the same side of the equator (middle line)
when the pairs move to the center.
This is called (q)____________ _____________.
Anaphase I:
Telophase I:
Meiosis II
Prophase II:
Metaphase II:
Anaphase II:
Telophase II:
(r) At the end of Telophase II, how many new cells have been formed? ___________
4. Re-tape your chromatids back together again.
5. Repeat Meiosis again, but this time switch the large chromosomes to the
opposite sides of the equator (middle line). This means, if your Large blue
chromosome was on the left side of the cell before, this time put it on the right
side of the cell in Metaphase I.
6. (s) What has this change in the placement of the large blue and pink
chromosomes during Metaphase I done to the sperm in the final result?
Additional Questions
(t) During which phase of Meiosis can crossing over occur? ________________
(u) How many chromatids are present in each cell at the end of meiosis? ________
(v) Are these final cells made at the end of meiosis haploid or diploid? ____________
(w) Can you come up with an analogy to represent the idea behind independent
assortment?
(x) What is Mendel’s Law of Random Segregation? Explain in your own words….
(y) Which stage of Meiosis (I or II) is most similar to mitosis? _______
Draw a picture of your Furnf below. We are all very curious to know what Furnfs
really look like!