Transcript 1 Heredity Notes

Heredity
S7L3. Students will recognize how biological traits
are passed on to successive generations.
S7L3.a Explain the role of genes and chromosomes
in the process of inheriting a specific trait.
S7L3.b Compare and contrast that organisms
reproduce asexually and sexually (bacteria, protists,
fungi, plants & animals).
S7L3.c Recognize that selective breeding can produce
plants or animals with desired traits.
Important Vocabulary
• Genetics- the study of heredity
• Heredity- Passing of traits from parent to
offspring.
• Trait- physical characteristic
– Ex: brown hair, red hair
Offspring
• Organism that is the result of reproduction
How do you inherit traits?
• Meiosis
• Occurs in gametes (sex cells): sperm in
males & egg in females
• results in 4 cells with ½ as many
chromosomes
• New cells are genetically different
Who was Gregor Mendel?
How Mendel's pea plants
helped us understand
genetics
Who was Gregor Mendel?
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Father of Genetics
Austrian monk
born in 1822
known for research and teaching
after his death (1884) acknowledgment of his
discoveries in 1900
• Discovered the principles of heredity
• Performed experiments with pea plants
• Realized that offspring
inherit traits from their
parents
What decides what traits get
passed down?
Dominant trait
• Trait that masks or
covers the other form of
the trait
• Represented with a
capitol letter
– Examples
• Round seed –R
• Tall plant--T
• purple flower—F
Recessive trait
• Trait that is masked or
covered by a dominant
trait
• Represented with a lower
case letter
• Examples
– Wrinkled seed—r
– Short plant—t
– White flower--f
genes
• Your traits are determined by your
genes.
• Instructions for an inherited trait
• Each parent gives
one set of genes to the
offspring
• Offspring has 2 forms
of the same gene
for every characteristic
allele
• Different forms of a gene are called alleles.
• Can be dominant alleles or recessive alleles
• Example
–Tt
– Dominant allele
recessive allele
Practice
• Monster # 1 has Rr or 1 dominant and 1
recessive allele
• How many eyes will this monster have???
• Monster # 2 has RR or 2 dominant alleles
• How many eyes will this monster have???
• Monster #3 has rr or 2 recessive alleles
• How many eyes will this monster have?
Baby Boom Genetics Activity
• http://www2.edc.org/weblabs/BabyBoom/BabyB
oomLabMenu.html
• Choose 2 aliens that will mate to create an
offspring
• Flip the coin to choose the alleles that will
combine to create traits
• Use the “screen clipping” option in Microsoft
word to create a 1 page document of the
parents and their offspring
• After your teacher has checked your document
you may print.
Exceptions to the rules
• Incomplete dominance- there is a blending
of traits expressed; neither trait is fully
expressed
• Codominance- both alleles are shown
Genotype
• Combination of genes for a specific trait
• Example:
– TT, Tt, tt
** expressed
in letters
Phenotype
• Physical appearance of
the trait
• Examples: purple
flowers, white flowers,
yellow seeds, white
seeds
Answer the following questions
on the back of your
Alien Offspring Print out
1. What is the difference between genotype and
phenotype?
2. Give an example of when dominant allele
masked a recessive allele in your offspring.
3. What recessive traits did your offspring inherit
from their parents?
Punnett Squares
• Tool used to
organize all
possible
combinations of
offspring from
particular parents
Homozygous genotype
• Two same alleles for a trait
• aka—Purebred
• Examples: TT, tt
Heterozygous genotype
• 2 different alleles for the same trait
• aka hybrid
• Example: Tt