Download Name: Date: Period:___ Midterm Review: Study Guide # 3 TOPICS

Name:_______________________________
Date:_________________
Period:___
Midterm Review: Study Guide # 3
TOPICS: DNA/Chromosomes, Cancer, & Meiosis
Please read before studying:
1. First, take time to review your Study Guide #1 & #2 Worksheet before beginning Study Guide #3.
1. After you are done, locate your guided notes and any other associated sheets for ALL the topics
listed above.
2. Next, scan the objectives for the topic you are about to study in order to get a sense of what
you should be focusing your time and energy on.
3. Start mastering each objective by answering the associated review questions right on this sheet.
4. After you have finished, use this sheet as a study tool to quiz yourself. Quiz yourself by trying to
answer all the questions aloud. This will probably take you a few times to feel comfortable. You are
finished studying when and only when you can answer 100% of the objectives correctly without
having to look back at your notes for help.
Topic # 6 – DNA/Chromosomes
 I am able to describe the structure of a DNA molecule:
 What part of the DNA molecule is in
the shape of a pentagon? sugar
 What part of the DNA molecule is
labeled “P”? phosphate

What does A, T, G, & C stand for?
Adenine, thymine, guanine,
cytosine

How do the nitrogen bases pair
together? A-T and G-C

Where is DNA found in the cell?
Nucleus

Which bases are considered purines?
Adenine and guanine

Which bases are considered pyrimidines? Cytosine and thymine
Appendix_Science7H
Name:_______________________________
Date:_________________
Period:___
 I am able to describe how DNA makes us who we are:
 How do the four letters that compose DNA make us who we are?
The cell reads the order of the nitrogen bases (letters). The order
tells the cell what proteins to make and this gives rise to traits.
 What would happen if one of the nitrogen bases in DNA was changed? Mutation
 I am able to describe when, where and how DNA replication occurs:
 When does DNA replication occur?
Interphase
 Where does DNA replication occur?
Nucleus
 How does DNA replication occur? Make sure to describe the specific enzymes involved.
1. Unzipping
2. Base pairing
(by DNA helicase)
(by DNA polymerase)
 I am able to define the following terms:
 Karyotype – picture of an organism’s chromosomes
 Trisomy – 3 chromosomes in a pair (extra!)
 Monosomy – 1 chromosome in a pair (missing 1!)
 Autosomes – chromosome pairs 1-22
 Sex Chromosomes – chromosome pair 23
 Down Syndrome – extra chromosome 21 (Trisomy 21)
 Klinefelter’s Syndrome - extra sex chromosome XXY
 I am able to analyze a karyotype for a chromosome disorder:
 What does a normal human karyotype look like? 23 pairs of chromosomes (46 total)
 What would an abnormal one look like?
Extra one, missing one, missing bands (genes), extra bands (genes)
 How can you tell if the patient is a male or female? XX = female
XY = male
Topic # 7 – Cancer
 I am able to describe what cancer is and how it begins:
 What is cancer? A disease in which cells grow and divide uncontrollably
 What can cause cancer? Smoking, unhealthy diet, chemicals, radiation
Appendix_Science7H
Name:_______________________________
 How does cancer start?
 What is a tumor?
Date:_________________
Period:___
With a mutation
A large mass of abnormal cells that divide uncontrollably
One of the cells breaks off from the tumor and
travels in bloodstream to a new location
 How can cancer spread?
 I am able to describe at least 3 cancer treatments:
 Chemotherapy - the use of drugs to kill cancerous cells

Surgery - removal of a tumor
 Radiation - the use of high energy electron beams to kill cancer cells
 Angiogenesis Inhibitors - “starving” the tumor by blocking blood flow
Topic # 8 – Meiosis
 I am able to describe the main goal of meiosis:
 What is the main goal of meiosis?
To produce 4 unique sex cells each with ½ the # of chromosomes
 How many chromosomes are in the sex cells of a human egg or sperm? 23
 Why is the process of meiosis important to organisms? So that when sperm and egg
unite the original chromosome number is restored
 I am able to state the main events of meiosis I and meiosis II:
 Meiosis I – chromosome pairs split
 Meiosis II – duplicated chromosomes split
 I am able to explain what crossing over is and how it occurs:
 What is crossing over? When 2 chromosomes swap DNA, this ends up shuffling
the genes
 During which phase of meiosis does it occur?
Prophase I
 I am able to identify the different stages of meiosis:
 Look at your hand drawn notes for the stages of meiosis. Are you able to correctly
identify each stage? Circle one: Yes or No
 If you can not find your notes make sure to copy one from a friend.
Appendix_Science7H
Name:_______________________________
Date:_________________
Period:___
 CRITICALLY THINK! – Try making connections between the topics you have learned about so far. A
good student doesn’t just learn the facts and memorize, but can APPLY their knowledge and make
connections between topics. Try some of these questions to jump start your critical thinking
abilities. Be on the lookout because many questions on the exam will test how your critical thinking is
progressing, especially the essays!

A mule is the offspring of a horse and a donkey. A donkey sperm contains 31 chromosomes
and a horse egg has 32 chromosomes. The new cell then has a total of 63 chromosomes.
This new cell develops normally into a mule. The combined set of chromosomes is not a
problem in mitosis, and the mule combines some of the best characteristics of horses and
donkeys. However, a mule is sterile; meiosis cannot occur normally in the testes or ovaries.
Explain why mitosis is normal but a mixed set of chromosomes interferes with meiosis.
 Mitosis works because the duplicated chromosomes individually line up in the
center of the cell. When anaphase occurs, 63 chromosomes will move to one
side and 63 will move to the other. However, meiosis does not work because
during meiosis I chromosome pairs need to line up in the center of the cell.
Due to an ODD number of chromosomes, one chromosome can not find its pair
and the process in unable to occur.

DNA replication happens in a cell each time a cell wishes to divide. However, scientists
have figured out a way to make DNA replicate in a test tube without the cell. This
process is commonly used in the pharmaceutical industry and is known as PCR (polymerase
chain reaction). This is helpful to scientists because now researchers can make a large
number of DNA copies. Use your knowledge of DNA replication and describe at least 3
things that would need to be present in the test tube for replication to occur and explain
why these things would be needed.
 For DNA replication to occur in a test tube you would need:
 Something to unzip the DNA ladder (HEAT is used in PCR)
 A protein to add in nitrogen bases
 A pool of nucleotides (A, T, G, C)
Appendix_Science7H