Heredity
Reflection Questions……
Using your graph answer the following
using complete sentences – page 68
• Did you share a trait with another classmate?
• Did you find a trait that was unique to you?
• Why do some of the traits have such a big difference in the number of
students that have the trait and the number that do not have the trait?
• If we took a poll of the entire school would the results be similar?
Explain your answer.
Vocabulary to Know!
START YOUR FLASH CARDS NOW
• allele
• heterozygous
• chromosome
• homozygous
• codominance
• pedigree
• DNA
• phenotype
• dominant allele
• Punnett square
• gene
• recessive allele
• genotype
• trait
• heredity
Gregor Mendel
• Gregor Mendel is known as the father of
Genetics
• He was an Austrian Augustinian monk and
scientist who studied the inheritance of certain
traits in pea plants
What did Mendel do??
• Gregor Mendel had two significant discoveries in
the mid-nineteenth century:
• The first is that organisms have “factors” or what is
more commonly known as genes, that control their
physical traits
• Secondly, organisms pass on their genes to their
offspring in predictable ways
Because of Gregor
Mendel…….
• Scientist can now predict the likelihood that
children, not yet conceived may inherit certain
diseases
• Scientists are also using this knowledge of
genetics to alter the biology of plants, animals
and humans.
Heredity
• Heredity refers to the passing of traits from
parents to their offspring.
• Genes control the traits that appear in those
offspring. When organisms reproduce, they
give genes to their offspring, and those genes
cause traits to appear.
More About Heredity
• Each gene is a small piece of a long
complicated molecule called DNA. DNA is an
abbreviation for Deoxyribonucleic Acid.
• In the reproductive process, DNA arranges
itself into structures called chromosomes
found in the nucleus of the cell.
Write the term that matches each definition.
1.
A section of a DNA molecule that controls a trait is
called ___________________.
2. The passing of traits from parents to offspring is
known as ___________________.
3. _____________________ is a complicated molecule
that contains genes.
4. A characteristic in an organism
___________________.
5. The structure into which DNA arranges itself:
___________________.
Answers!
• A section of a DNA molecule that controls a trait is
called a Gene
• The passing of traits from parents to offspring is
known as Heredity
• DNA is a complicated molecule that contains
genes.
• A characteristic in an organism: Trait
• The structure into which DNA arranges itself:
Chromosomes
Phenotype and Genotype
•Phenotype – Scientists can study
traits by examining how organisms
look on the outside. The outside
expression of a gene is called a
phenotype. Example: Chris has a
widow’s peak. A scientist will say
that Chris is expressing the widow’s
peak phenotype.
Phenotype and Genotype
•Genotype – Humans have two
copies of each gene, called alleles,
one from the biological mother and
one from the biological father.
When a scientist determines which
two alleles a person has, they are
determining the person’s genotype.
Dominant vs. Recessive
• A dominant allele causes a widow’s peak in
humans. Scientists use an upper case letter
(W) to indicate a dominant allele and a
lowercase letter (w) to indicate a recessive
allele.
• The widow’s peak gene has three possible
genotypes: WW, Ww, or ww. Chris has a
widow’s peak. Therefore we know that he has
at least one dominant allele. His genotype is
either WW or Ww.
Homozygous vs.
Heterozygous
• If a person has two identical alleles, in Chris’s case,
if he has WW as his genotype, then he is
homozygous dominant for the trait.
• If a person has a dominant and a recessive allele,
in Chris’s case, if he has Ww as his genotype, then
he is heterozygous.
• Amy doesn’t have a widow’s peak. Write the letters
for her genotype. ____________
• What is Amy’s genotype: homozygous dominant or
homozygous recessive? ______________________
Heterozygous or
Homozygous??
• AA ____
• Ee ____
• Bb ____
• ff ____
• Cc ____
• GG ____
• Dd ____
• HH ____
Punnett Square
• A Punnett square shows the possible
combinations of alleles that children can
inherit when two people produce offspring.
• The Ameba Sisters help us to understand!
• https://www.youtube.com/watch?v=i0rSv6oxSY&index=14&list=PLwL0Myd7Dk1F0i
QPGrjehze3eDpco1eVz