Guided Notes: Chromosomes

The Structure of DNA

What type of macromolecule is DNA? ___________________ ___________________

DNA stands for:

DNA is made up of repeating ______________________________ (the monomer of nucleic

acids!)

1) Where is it found (use figures 1 and 2 to help!) Figure 1

DNA is in the c______________ of

prokaryotes and the

n_________________ of eukaryotes

The nucleus of a human cell contains

30,000 or more g_________ in the form

of DNA, called a c_________________.

2) Function of DNA

The function of DNA is to s_______________ i_________________.

This is essential to life! DNA RNA Proteins (The c____________ d_________ of

molecular biology!

Figure 2: Structure of Chromosomes

These proteins play a key role in how we look and grow-“It’s in your genes!”

A given gene on a chromosome can have alternative forms called alleles. For now, just know

that different alleles of a gene encode the same protein, just slightly different versions of it.

Ex: gene that encodes hemoglobin can be normal allele, or a different allele that produces

abnormal hemoglobin (causes sickle-cell anemia).

DNA is packaged tightly into

pieces called

_____________________

that are visible ONLY during

cell division

Each chromosome includes

several thousand

________________

Most genes contain the

directions to make a

__________________

-Proteins are made up of

______________________

Chromosomes and Chromatids

Chromosomes are only visible during c_______ d______________, when they are tightly

condensed (wound up). Otherwise they are like long strings.

Figure 3: Homologous chromosomes and sister chromatids

Humans have _______ chromosomes.

These chromosomes come in pairs called

h_________________ c__________________

One member of each pair was inherited from

your m____________. The other was inherited

from your f______________.

How many chromosomes do you think the

sperm cell that helped create you had? ________

How many chromosomes did your mom’s egg cell have? _____________

When cells are getting ready to divide, they r____________ their chromosomes (another word

for copy).

MISCONCEPTION ALERT!

When a chromosome has replicated, it is still considered to be ONE chromosome! (Confusing, I

know!) The replicated chromosome is composed of two s__________ c___________. Each sister

chromatid is identical to the sister chromatid it is attached to! When the cell divides (we will discuss in

detail in mitosis unit), the sister chromatids separate and are then considered to be individual

chromosomes.

If a cell has 35 chromosomes, then replicates them as it prepares to divide, it will have

____________ chromosomes and ____________ chromatids. The two cells resulting from the

division will have ____________ chromosomes each.

What is the name of the structure where the sister chromatids are attached to each other?

________________________.

Synthesize your knowledge!

Crystal ponies have 6 chromosomes. That means they have ______ homologous pairs of

chromosomes.

Use a different color for maternal (inherited from mom) and paternal

chromosomes (inherited from dad).

Draw the two resulting cells and their chromosomes (you can depict the

Preparing to divide (Chromosomes have replicated)

chromosomes as still condensed even though in reality they begin to unwind back into long

strings as the cell is pinching in two). Assume the two new cells are NOT YET preparing to

divide so have NOT replicated their chromosomes yet!

Draw a crystal pony cell that is getting ready to divide (I have done

this for you). Imagine that it glitters and sparkles.

Newly formed cells (Chromosomes

have NOT yet replicated)

Make each pair of homologous chromosomes a different size.

Guided Notes: The Cell Cycle

The Cell Cycle

The c_____ c________ describes the life of a

cell from birth to death.

There are three main parts of the cycle:

I_____________ : Normal cell

activities; broken up into 3 parts.

M_____________ : Division of the

nucleus/Separation of the genetic

material into 2 new nuclei.

C_____________ : The division of the

cytoplasm following mitosis.

Interphase

________ phase : Period of cell growth.

Cells can remain in the G1 phase indefinitely, called ______________.

________ phase: Period when DNA replication occurs. Chromosomes replicate and each

chromosome is now composed of two s_____________ c_____________ attached at the

c_____________ (from chromosome notes!).

Once a cell copies its DNA, it prepares to divide.

________ phase: Cell growth and preparation for mitosis.

Mitosis

Mitosis is a form of a_____________ reproduction.

Means only _____ organism is required.

Occurs in response to the body’s need for growth and repair.

Refers to division of the n_____________. (The organelle in eukaryotes that contains DNA)

_____ stages of mitosis: Prophase, Metaphase, Anaphase, Telophase (will learn more about

this soon!).

Cytokinesis

The cell cycle ends with c_____________ : the division of the c____________ (refers broadly

to the stuff in the cell excluding the nucleus)

Overlaps with the latter part of mitosis.

This means one cell has divided into two cells, and those two cells () can continue with

their own independent cell cycles!

Chromosome appearance throughout the Cell cycle (Dr. Williams will fill in with everyone)

Chromosomes are decondensed (long and stringy) during Interphase (G1, S, G2) and do not

condense until mitosis begins! We have been drawing them in their condensed form for convenience

only! Let’s draw the chromosomes throughout the cell cycle using our crystal pony example (cells with

3 pairs of chromosomes).

1. Prophase

- longest phase of mitosis- chroms. become visible- spindle forms- nuclear envelope breaks down

3. Anaphase- sister chromatids move apart to opposite sides

of the cell

4. Telophase- chroms. disperse- 2 nuclear envelopes reform- nucleolus reappears

Cytokinesis- division of cytoplasm- NOT part of mitosis- animal cells: membrane pinches in half- plant cells: cell plate forms- 2 identical daughter cells form

2. Metaphase - chromosomes line up along middle of cell

Mitosis

Parts of Mitosis