Transcript how imprinting affects inheritance, boulder 2011

Stamped DNA
How ‘imprinting’ affects inheritance
A TIDBIT by:
Pat, Tammy, Marcie, Debbie,
Eric and Tingting
Context
Group 2: Heredity
Teachable Unit: Epigenetics
•Class: sophomore level genetics class ~ 50-150 students
• Previous concepts: Mendelian inheritance, DNA structure, intro
molecular genetics
•Reading assignment for class: Text information on epigenetics
•This is the first lesson in the unit, but it will be followed by two lessons on
mechanism and other epigenetic phenomena.
•Since this topic has more challenging content, we have chosen to use
guided active learning to help students construct a knowledge base,
followed by more challenging homework assignments.
•The unit will have 2 additional lessons or tidbits.
Misconceptions
 All inheritance is based on DNA nucleotide
sequence.
 All human genes are equally expressed from both
alleles.
 All genetic diseases are caused by a point mutation.
 The active genome of males and females is the
same.
Unit Learning Goals and Flow of Content
Students will understand:



The concepts of epigenetics.

Overview and definitions

Contrast with Mendelian Inheritance
The molecular basis of different types of epigenetic phenomena.

Imprinting: Normal and Disease states

Histone Modification

RNA interference

Prions
That epigenetics contributes to both diversity and disease.

Environmental impacts on the epigenome

Epigenetic determinants of cancer
Prader-Willi
Angelman
These two very different syndromes are
caused by the same deletion
Learning Outcomes for Today
 Students will define imprinting.
 Contrast imprinting and Mendelian
inheritance.
 Predict an outcome from a genetic cross
involving non-Mendelian inheritance.
What is Imprinting?
 Imprinted chromosomes are “marked”
 Imprinting differs in sperm and egg
 Imprinting turns off specific genes
 Imprinting does not change the nucleotide sequence
Think-Pair-Share/
review from last semester
Hypothesize some ways that the DNA is imprinted?
Formative Assessment; Bloom’s Synthesis (3/4)
DNA can be Methylated on cytosine residues
Gene expression
active
Gene expression
inactive
-CH3 (METHYL group)
Maternal
Paternal
CH3 CH3
CH3 CH3
XGene A
Mutation
Mutation
X
Gene A
Mutation
Mendelian
Imprinted
A mutation in Gene A may cause
a change in phenotype when:
Dominant
Recessive
1. The maternal copy is mutated
Yes
No
No
Yes
2. The paternal copy is mutated
Yes
No
Yes
No
3. When both copies are mutated
Yes
Yes
Yes
Yes
Maternally
imprinted
Paternally
imprinted
With your clicker, press A for “yes” and B for “no”
Formative Assessment;
Recall; Bloom’s 1
Formative Assessment;
Analyze; Bloom’s 3/4
CLICKER:
Based on the figure
below, which proteins
are normally produced?
Click A for
B for
C for
D for
protein A
protein B
BOTH
NEITHER
B
A
ANSWER = BOTH
CLICKER:
Which proteins are
produced with
maternal deletion?
Click A for
B for
C for
D for
protein A
protein B
BOTH
NEITHER
A
ANSWER = only protein A is made
CLICKER:
Which proteins
are produced with
paternal deletion?
Click A for
B for
C for
D for
protein A
protein B
BOTH
NEITHER
B
ANSWER = only protein B is made
Normal
Maternal
CH3 CH3
Gene A
Paternal
Paternal deletion
Maternal
Paternal
XGene A
CH3 CH3
Gene B
A
CH3 CH3
XGene A
B
X
Gene B
Gene B
[
B
]
Maternal deletion
Maternal
Paternal
[
Gene A
A
CH3 CH3
X
Gene B
]
Prader-Willi
Angelman
These two very different syndromes are
caused by the same deletion
Compose a 1 minute essay that explains the basis for the difference
between Prader-Willi and Angelman.
Formative assessment; Bloom’s level Analysis 3
Homework: To further assess your understanding of Mendelian
inheritance versus inheritance of imprinted genes
1. Define imprinting in your own words.
2. Look at the following pedigree and answer the questions below.
• Is this disease dominant? Why or why
not?
• Is this disease recessive? Why or why
not?
• Can the disease be inherited from the
paternal side?
• Can the disease be inherited from the
maternal side?
• Does this show Mendelian
inheritance?
Entrance Ticket: Parthenogenesis
(“Virgin Birth”)
 Parthenogenesis is the ability of some species
to produce offspring without any male
involvement
 Parthenogenesis is observed in various animal
species, but not mammals
How could imprinting prevent parthenogenesis?
Formative Assessment; Bloom’s Analyze, 4
SCIENTIFIC TEACHING
Goals

Active Learning
Clicker
Active
Learning/Assessment
Define Epigenetics and
Think/Pair/ Share
Brainstorming (think-pairImprinting
Brainstorming
share)
Group problem solving
Entrance ticket
Summative:
Homework/write in your
own words
Call-out
Bloom’s Level/Verb
Hypothesize/grapple
with/3-4
Define/1
Contrast imprinting and Worksheet activity/
Mendelian
inheritance.
individual/Peer

Assessment-all
of above formative
interaction/Group problem
Individual take-home questions
are summative
solving/call out/clicker
assessment

Diversity
Recall/1
Predict an outcome from Formative/visual/clicker
Auditory/visual
a genetic cross
questions
involving non-Mendalian
Social learning and individual
work
inheritance.
1 minute essay
Predict/ 3
Summative:Homework/
Pedigree/Parthenogenesis
Analyze/3-4
Compose/Explain/Analyze
/3
Analyze/Predict/relate/3-4