Cornell Notes
Topic/Objective:
Name:
Human Genetics Vocabulary
part 2
Class/Period:
Science
Date:10/28/2014
Essential Question: What are some key terms for understanding human genetics?
Questions:
Notes:
Key Term
Definition
Chromosome A structure made of DNA,
found in the nucleus of a
cell.
You inherit 1/2 of your
chromosomes from Mom
and 1/2 from Dad
They come in pairs –
humans have 23 pairs of
chromosomes in each cell. It
is the location of genes
gene
occur in pairs specific
location on a chromosome
contains exact instructions
for creating a trait
allele
genotype
phenotype
complete
dominance
A form of a gene. 2 possible
alleles – dominant and
recessive. A capital letter
represents dominant allele
and a lower case letter
represents recessive allele.
two letters representing a
gene pair
physical appearance
what the trait will look like
(based on the genotype)
Dominant allele completely
masks (covers up) the
recessive allele. If even one
dominant allele is present in
a genotype, the dominant
trait will show. A recessive
trait only shows when there
are no dominant alleles
present in the genotype.
Example
F – dominant allele
f – recessive allele
GG , rr , Bb
purple flower color
green eyes
no widow’s peak
EE – dominant trait
shows
Ee – dominant trait
shows
ee – recessive trait
shows
Questions:
Notes:
incomplete
dominance
EE – dominant trait shows
dominant allele does not
completely mask (cover up) Ee – part dominant /part
recessive trait shows
the recessive allele
ee – recessive trait shows
Punnett
square
A tool used to predict the
probability of offspring having a
particular trait. The parent’s
genotypes are written on the top
and left side. The offspring
possibilities are written inside
the squares. An allele from each
parent is combined inside the
squares.
probability
Likelihood that a particular
genotype or phenotype will
occur. Can be shown as a
percentage or a ratio. In a 2x2
Punnett square, each offspring
square is equal to 25%.
prefix homo- means “same”
both alleles in a genotype are
the same – both are dominant,
or both are recessive
homozygous
synonyms
purebred
truebreeding
Heterozygous prefix hetero- means “different”
synonym:
the alleles in a genotype are
hybrid
different – one is dominant and
the other is recessive
coTwo equally dominant alleles
dominance
either (or both) will completely
mask the recessive allele. If
both dominant alleles are
present in a genotype, both
forms will show. Recessive form
only shows when neither
dominant allele is present in the
gene pair
Three alleles: A, B, and O
blood types
In the Punnett square
shown above, the
probability of
having a particular
genotype is 50% for AA,
and 50% for Aa.
EE – homozygous
dominant
ee – homozygous
recessive
Ee – heterozygous
See blood types
(below)
for an example.
Mom is type B; Dad is O
A & B are co-dominant. O is recessive Mom could be genotype
Six possible genotypes & Four basic
BB or BO; Dad
blood types (phenotypes): A, B, AB,
must be OO
and O
Summary: