UNIT 4
DNA / Genetics
TEST DATE:____________
Essential Concepts and Skills for LS 12 &13
1. Understand the history of DNA.
a) Understand the contributions of all scientists that led to the development of
the Double Helix structure by Watson, Crick, Franklin and Chargaff.
2. Explain how the genetic code is contained in DNA
a) DNA is a macromolecule (polymer) made up of repeating subunits called
nucleotides (monomers).
a) There are 4 DNA nucleotides:adenine (A), guanine (G), thymine (T), cytosine (C).
b) The genetic code is the sequence of DNA nucleotides.
c) DNA is a double-stranded molecule. The strands are connected by complementary
base pairs: A-T and C-G, like rungs on a ladder.
d) DNA directs the cell through protein production.
The ladder twists to form a double helix.
3. Describe how cells pass on the genetic code by replicating
(copying) their DNA.
a) Enzymes unwind and unzip the double helix.
b) Each strand serves as a template for building a new DNA molecule.
c) Free nucleotides bond to the template (A-T and C-G), forming a complementary
strand.
d) The final product is two identical DNA molecules
4. Understand the Heredity and the scientist behind the science….
a. Gregor Mendel- Known as the father of genetics. Studied the hereditary
patterns in pea plants.
a. 1st Experiment – Specifically he observed the following traits in pea
plants:
i. Height, seed color, flower color, pod color, pod shape, seed
shape, flower position
ii. He crossed a homozygous dominant pea plant (TT) with a
homozygous recessive (tt) pea plant. In each experiment the
recessive trait disappeared in the first generation created.
b. 2nd Experiment—Working with the same traits he used the offspring
(children) of the 1st cross
i. This time he crossed two (Tt xTt) of the f1(first generation).
ii. His results showed not only the dominant trait but also the
recessive reappear!!
b. Reginald Punnett - invented the Punnett Square to determine
the probability of an offspring having a particular genotype.
Mercer Middle
Loudoun County Public Schools
Aldie, VA
Reading
p.129
p. 128
p. 131
p. 106-113
5. You should be able to define and utilize the following important
terminology of genetics
a) gene- section of DNA that carries a trait
b) allele- as a form of a gene.
c)dominant- a trait, that when present will be seen
d) recessive- a trait that will only be seen when it is the only one present
e) genotype the genes that an organism has.
f) phenotype the appearance of a trait in an organism.
g) homozygous having two of the same alleles : a purebred: RR
h) heterozygous as having two different alleles: hybrid : Rr
i) Punnett square tool used to predict inheritance of traits through generations.
k) monohybrid crossing of one trait in a punnett
m) probability the chances of inheriting a particular trait
q) autosomes the 22 pairs of body chromosomes in our bodies
r) sex chromosomes –the 23rd pair of chromosomes that determines the sex.
6. Using Tools of inheritance such as a Punnett square and pedigree chart
you will be able to predict the probability of inheriting a trait
a) using a monohybrid cross / dihybrid cross
c) using a test cross - this is used to determine the genotype of
the parental generation when the genotype of the offspring are known.
d) Using a pedigree chart you will be able to plot the path of a traits in families.
7. You will be able to predict inheritance from patterns other than pure
dominant/ recessive.
a) Codominance - where traits of the P1 are expressed equally in all of the offspring: a
speckled chicken and human blood types
b) Incomplete dominance- where the traits of the parents are blended to create a
new expression. Red + white = pink flower
c) Sex linked where traits are inherited on the sex chromosome,
most often the X chromosome; color blindness, and hemophilia
d) polygenic inheritance- inheritance that depends on more that
one gene : examples- hair, skin, eye colors and height
8. Describe mutation and the effects of mutations in humans
a) A mutation is a change in the base sequence of a gene.
b) Since the base sequence of the gene is changed, the amino acid sequence
of the protein is changed.
c) An amino acid change in a protein could affect its information, resulting in
a change in the protein’s function. (Diabetes)
d) The CHROMOSOMAL mutations are insertion, deletion, and substitution.
Define and understand all.
p. 106-113
supplement
class notes
p.111-112
p.140-141
class notes
class notes
pg. 134
pg. 119
p.138-139
Assessment:
 There will be quizzes
 There will be various labs.
 There will be a Test that will cover all the essential concepts.
EXTRA CREDIT
 This is worth a lab or test grade…which ever assists you the most!!!
 You will create a genetic disorder pamphlet.
 If planning to do this project you must see me to pick a disorder and get the grading criteria.
o First come first serve! Limited Choices….
Mercer Middle
Loudoun County Public Schools
Aldie, VA