Sample Genetics review for Gateway Writing Test

1. Genetics
DNA
Mitosis and Meiosis

2. What is DNA?
DNA  RNA  Proteins
• DNA: stored in nucleus; holds
information on making everything
• Does not leave nucleus!
• RNA: carries information from DNA in
nucleus to other areas
• Proteins: Help with cell processes
(making energy, breaking down waste)
gives traits to organism (hair color, skin
texture, etc.)

3. DNA  RNA
• Transcription: makes mRNA from DNA
• Occurs in the nucleus of eukaryotic cells
• Why? DNA can’t leave nucleus!
• mRNA is complementary to the DNA
Thymine(Uracil) = Adenine
Cytosine = Guanine
DNA: TAC GAT TAC CGG GTA ACT ATA TCA
mRNA: AUG CUA AUG GCC CAU UGA UAU AGU

4. RNA  Proteins
• Translation: Makes proteins from mRNA
• Ribosomes read instructions on mRNA;
find correct amino acids to build protein
mRNA: AUG CUA
AA: Methionine
Leucine

5. How is DNA organized?
• DNA is coiled into chromosomes before
mitosis and meiosis
• A normal human has 23 pairs or 46 total
chromosomes
• Each chromosome contains different
genes with information on how to create
every protein needed to make a human

6. What is Mitosis?
• Mitosis: Cell Division to create identical
copies of cells
• Occurs to replace dead cells or grow
existing tissues
• Result: Two identical cells
• Four main phases: Prophase,
Metaphase, Anaphase, Telophase
• Remember: PMAT

7. • FIRST: DNA Replicates
• Prophase: Prepare by
condensing chromosomes,
breaking down nucleus
• Metaphase: Chromosomes
line up in the middle of
the cell
• Anaphase: Chromosomes
move apart
• Telophase: Two identical
cells form
What is Mitosis?

8. What is Meiosis?
• Meiosis: Creates gametes used for
reproduction (eggs/sperm)
• Cells have half the number of
chromosomes as beginning cell
• Result: Four gamete cells
• Same phases as mitosis but they occur
twice

9. What is Meiosis?
• First: DNA Replicates
• PMAT I phases
• DNA replication
does not occur again
• PMAT II phases
• Result: Four
different gametes
with half normal
number of
chromosomes
• Why is this necessary?

10. Practice
• Fill in the chart with the necessary
information.
Mitosis Meiosis
Definition
Resulting Number
Genetically
Number of phases
List Phases

11. How are traits inherited?
• Traits in DNA are passed from parent to
offspring
• The offspring has a combination of traits
from both parents
• Offspring traits can be predicted using
parent traits in a punnett square

12. What information do you need?
• Each person’s genotype is written with
two letters
• Uppercase = dominant
• if there is a dominant trait, it will always
show!
• Lowercase = recessive
• if there is a recessive trait, it will only show if
there is no dominant!
• AA = Dominant aa = recessive
• Aa = Dominant

13. How do you complete a
punnett square?
1. Add each parents genotype
2. Carry letters across
3. Carry letters down
A
A
a
a
A A
a a
A
A
a
a

14. What does the punnett square
tell you?
• The boxes represent potential genotypes
of offspring if the two parents have
offspring
• Can find ratios/percentages of the chance
an offspring will have the dominant or
recessive trait
Percent dominant trait?
75%
Ratio of dominant:recessive?
3:1

15. Practice
• Brown eyes are dominant to blue. The
father’s genotype is Bb. The mother has
blue eyes.
1. Create a punnett square for the two
parents.
2. What is the percent chance they will
have a child with blue eyes?
3. What is the ratio of children with brown
eyes versus blue eyes?