TOPIC: Genetics & Heredity
Class notes: Pwpt
WHAT:
EXTRA NOTES:
WHO:
WHEN:
WHERE:
HOW:
WHY:
APPLY PART 1:
APPLY PART 2:
(SKIP SPACE BETWEEN EACH POINT)
What: What is heredity?
Genetics-study of heredity
Heredity-the passing of
genetic traits from parent
to offspring
You “inherit” traits from
your parents
Examples of Genetic Traits
Some Genetic
Characteristics:
Eye Color
Hair Color
Height
Body Structure
Facial Features
Skin Color
What genetic traits did you inherit
from your parents? Name two genetic traits“Nature vs. Nurture” is debated about some characteristics.
Who/When/Where
• Gregor Mendel-an Austrian
monk; in the mid 1800s
studied the genetics of pea
plants.
-“The Father of Genetics”
*Watch Mendel Video to
answer the who/when/where.
http://teachertube.com/viewVid
eo.php?video_id=886
How are traits passed?
Traits are determined by
one’s genes.
Genes (DNA) from both
parents are given to their
offspring during
reproduction.
DNA is the genetic material
found in a cell’s nucleus.
DNA acts like a set of
instructions for the cell.
Dominant and Recessive
Each parent has two or more forms of a gene (or letters)
for a certain trait. These letters are called alleles.
An allele is one of two or more forms of a gene.
*Capital letters represent dominant alleles.
When these alleles are present, they mask the recessive
trait. They are the “stronger” alleles.
*Lower case letters represent recessive alleles and
are the “weaker” of the alleles. They are hidden when in
the presence of a dominant allele.
Homozygous & Heterozygous
If the alleles are the same, the genotype (genetic makeup)
is called “homozygous”; also called “pure”
Ex:
HH-homozygous dominant
hh-homozygous recessive
If the alleles are different, the genotype is called
“heterozygous”; also called “hybrid”
Ex:
Hh-heterozygous
There are 3 possible genotypes and 2 possible phenotypes
in situations exhibiting complete dominance.
Genotype vs. Phenotype
Genotype=genetic makeup; what genes it has
(EX: QQ, Qq, qq)
Phenotype=physical characteristics; what it looks like
(Ex: has dimples; lacks a widow’s peak, etc…)
Let’s Apply (Part 1) the Terms
1. What do you call the
genotype… HH?
2. Hh?
3. hh?
Let’s Apply the Terms:ANSWERS
HH-homozygous dominant or pure-dominant
Hh-heterozygous or hybrid
hh-homozygous recessive or pure-recessive
Why
Punnett Squares
Reginald Punnett (1875-1967)
Using Punnett Squares
allows us to use
probability to predict
the genotypes and
phenotypes of future
offspring, if we know
the genotypes of the
parents.
Monohybrid Punnett Square
Let’s Practice a Punnett Square!
http://www.zerobio.com/drag_gr11/mono.htm
• Watch video
• Practice Punnett square problems on next slide
Apply (Part 2)
Practice Problem #1
A)An individual heterozygous for flower color is
crossed with an individual that is homozygous
dominant. (Purple is dominant to white in flower
color.) Write the genotypes crossed.
____________x____________
B)Draw the Punnett square for this cross. Use the
letters H and h to represent the alleles.
C) What percent of the offspring will be homozygous
dominant?
D) What proportion of the offspring flowers will have
white petals?
Practice Problem #1 Answer
A) (Hh x HH)
B)
H h
H HH Hh
H HH Hh
C) What percent of the offspring will be homozygous
dominant? (HH) 2/4=50%
D) What proportion of the offspring flowers will have
white petals? 0/4
Practice Problem #2
A)A hybrid pea plant is crossed with a pure yellow pea
plant. (Green is dominant to yellow in pod color.)
What color is the hybrid plant?
B) Write the genotypes crossed.
____________x____________
C) Draw the Punnett square for this cross. Use the
letters Q and q to represent the alleles.
D) What percent of the offspring will have the hybrid
genotype?
E) What proportion of the offspring flowers will be
yellow?
Practice Problem #2 Answer
A) green
B) (Qq x qq)
C)
Q q
q Qq qq
q Qq qq
D) What percent of the offspring will have the hybrid
genotype? 50%
E) What proportion of the offspring pods will be
yellow? 50%