Template for Lectures

1
This lesson will increase your knowledge of
concepts covered in the following TEKS for
biology
3.c Evaluate impact of research on scientific
thought, society, and the environment
3.e Evaluate models according to their adequacy
in representing biological objects or events
6.c Identify and illustrate how changes in DNA
cause mutations and evaluate the significance of
these changes 6.e Compare the processes of mito
sis and meiosis and their significance to sexual
and asexual reproduction
2
Previous LessonIndividuality and Cloning
3
Question What is the difference between mitosis
and meiosis?
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Mitosis is a process producing body cells whereas
meiosis is a process producing gametesDaughter
cells produced by mitosis are 2n (diploid)
whereas daughter cells produced by meiosis are n
(haploid)
5
Question From a scientific standpoint, what is
the significance of Dolly?
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Dolly showed cloning of mammals was possible

• Scientists can take DNA from an
• adult cell and re-start the reading of
• the DNA, as if it was DNA in a
• fertilized egg
• DNA can then direct the synthesis of
• proteins to produce an embryo and
• eventually a clone of the adult

7
Question From a chromosomal standpoint, what is
wrong with the idea of using a sperm and an egg
from super athletes to try to have a super
athlete child?
8
Fig. 23.6
Random assortment of chromosomes causes the sperm
and egg to have different chromosome combinations
Meiosis I
Meiosis II
Based on Mader, S., Inquiry Into Life,
McGraw-Hill
9
The child may not get the athletic chromosomes
The chromosomes can line up 223 or 10 million
different ways in meiosis I Each person can pro
duce 10 million different types of gametes

10
Question Why not try to clone the super athlete?
11
Cloning of Humans

• Cloning results in higher rates of miscarriage
  and deathusing todays technology
  
• Although the clone would be genetically
  identical, the environment that produced the
  super athlete would be differentsame nature,
  different nurture

12
Todays LessonGenetic Disorders and Gene
Therapy
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Overview of Lesson

• Genetic diseases
• Chromosomal
• Single gene
• Genetic Testing
• Gene Therapy

14
Chromosomal Diseases

• Gametes have abnormal chromosome numbers and
  mutations
  
• Offspring inherit extra chromosome or are missing
  a chromosome
  
• Caused by problems with meiosis

15
Nondisjunction of chromosomes during meiosis
Based on Brooks/Cole Thomson Learning
16
Characteristics of a child with Down Syndrome
-wide, rounded face -equal length fingers -m
entally retarded -webbed neck
-enlarged tongue
Normal female karyotype with 46 chromosomes
Down syndrome karyotype with an extra chromosome
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Based on Mader, S., Inquiry Into Life,
McGraw-Hill
17
Amniocentesis

• Used on pregnant women over 35 years of age
• Performed during weeks 15-17 of pregnancy
• A needle is inserted into the amniotic sac
• Amniotic fluid with fetal cells is removed
• A karyotype of the fetal chromosomes is prepared

18
Risk of Having Child with Down Syndrome versus
Risk of Miscarriage due to Amniocentesis
Risk of Down Syndrome
Risk of Miscarriage
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Overview of Lesson

• Genetic diseases
• Chromosomal
• Single gene
• Genetic Testing
• Gene Therapy

20
Important Points about Inheritance

• Genes have different forms, called
• alleles
• Each trait is controlled by effects of
• two alleles
• Some alleles are dominant/recessive
• and other alleles are co-dominant

21

• Allele for Straight Hairline
• is recessive
• A person with ww will have
• a Straight Hairline

• Allele for Widows Peak
• is dominant
• A person with WW or Ww
• will have Widows Peak

22
Genotype vs. Phenotype

• Genotype refers to the alleles
• Phenotype refers to the appearance

Example Genotype - Phenotype
WW - person has a widows peak
Ww - person has a widows peak
ww - person has a straight hair line
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Genetics Problem

• A woman (Ww) with a widows peak has children
  with a man (ww) with a straight hairline
  
• What is the chance that the child will have a
  widows peak?
  

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Alleles W Widows peak w Straight
Genotypes-Phenotypes WW - Widows peak Ww - Wido
ws peak
ww - Straight
Female Ww
eggs
w
W
sperm
w
ww
Ww
Each child would have a 50 chance of having a
widows peak
Male ww
Offspring
Ww
ww
w
25
Question Why would a person with a genotype of
Ww, produce gametes with W and gametes with w?
Gametes
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Huntington Disease Person gradually loses psych
omotor control in adulthood Caused by dominant
allele
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Genetics Problem

• A woman (hh) with normal nerve physiology has a
  child with a man (Hh) who will develop Huntington
  Disease
  
• What is the chance that the child will have
  Huntington Disease?
  

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Alleles H Huntington h Normal
Genotypes-Phenotypes HH - Huntington Hh - Huntin
gton
hh - normal
Female hh
eggs
sperm
Each child would have a __ chance of having
Huntington Disease
Male Hh
Offspring
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Alleles H Huntington h Normal
Genotypes-Phenotypes HH - Huntington Hh - Huntin
gton
hh - normal
Female hh
eggs
h
h
sperm
Each child would have a 50 chance of having
Huntington Disease
H
Hh
Hh
Male Hh
Offspring
hh
hh
h
30
Cystic Fibrosis Mucus in bronchi is thick, inte
rfering with lung function Caused by a recessiv
e allele
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Genetics Problem

• A woman (Nn) with normal lung physiology has a
  child with a man (Nn) who has normal lung
  physiology
  
• (both are carriers of allele)
• What is the chance that the child will have
  Cystic Fibrosis?
  

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Alleles N Normal n Cystic Fibrosis
Genotypes-Phenotypes NN - Normal Nn - Normal nn
- Cystic Fibrosis
Female Nn
eggs
sperm
Each child would have a __ chance of having
Cystic Fibrosis
Male Nn
Offspring
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Alleles N Normal n Cystic Fibrosis
Genotypes-Phenotypes NN - Normal Nn - Normal nn
- Cystic Fibrosis
Female Nn
eggs
n
N
sperm
N
Nn
NN
Each child would have a 25 chance of having
Cystic Fibrosis
Male Nn
Offspring
Nn
nn
n
34

• Sickle Cell Disease
• Red blood cells are sickle shaped,
• interfering with circulatory system
• and causing anemia and pain
• Caused by a recessive allele

Based on Harvard Family Health Guide, 1999
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Genetics Problem

• A woman (Nn) with sickle cell trait has a child
  with a man (NN) who has normal red cells.
  
• What is the chance that the child will have
  Sickle Cell Trait?
  

36
Alleles N Normal n Sickle Cell
Genotypes-Phenotypes NN - Normal Nn - Sickle Cel
l Trait
nn - Sickle Cell Anemia
Female Nn
eggs
sperm
Each child would have a __ chance of having
Sickle Cell Trait
Male NN
Offspring
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Alleles N Normal n Sickle Cell
Genotypes-Phenotypes NN - Normal Nn - Sickle Cel
l Trait
nn - Sickle Cell Anemia
Female Nn
eggs
n
N
sperm
N
Nn
NN
Each child would have a 50 chance of having
Sickle Cell trait
Male NN
Offspring
NN
Nn
N
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Overview of Lesson

• Genetic diseases
• Chromosomal
• Single gene
• Genetic Testing
• Gene Therapy

39
Genetics Human Diseases

• About 4,000 human diseases are thought to be
  inherited
  
• Scientists are making good progress figuring out
  where genes are located on chromosomes and in
  understanding how the mutations in genes cause
  disease

40
Genetic map of chromosome 17
Based on Mader, S., Inquiry Into Life,
McGraw-Hill
41
Genetic Testing

• Now have DNA tests for 30 - 40 diseases
• Cystic fibrosis, some forms of breast cancer,
  fragile X syndrome, Huntington disease, Duchenne
  muscular dystrophy
  
• Tests are up to 99 accurate
• Tests can be run on embryos created by in-vitro
  fertilization prior to implantation

42
Future of Genetic Testing

• When will we have tests for 1000s of genetic
  diseases in human or what project must be
  completed for scientists to understand the
  DNA-protein relationships that cause many human
  diseases?

Answer
43
Issues about Genetic Testing

• What if the news is bad? Should the fetus be
  aborted or allowed to live with a cruel
  disease?
  
• Should insurance coverage provide care for a
  child having a genetic disease that was diagnosed
  before birth?
  
• Should blood relatives be warned?
• Should our genetics be part of our records?
• Should employers be allowed to consider
  genetically based diseases in hiring employees?
  
• Will eugenics (manipulation of the hereditary
  qualities of a race) be practiced?

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Overview of Lesson

• Genetic diseases
• Chromosomal
• Single gene
• Genetic Testing
• Gene Therapy

45
Gene Therapy

• Gene therapy is lagging behind genetic testing
• For example, gene for cystic fibrosis was
  identified in 1989
  
• Scientists have been testing ways to insert
  copies of the normal gene into cells of the
  respiratory tract
  
• It is difficult to get the gene inserted into the
  tissue so that it can take over control of
  protein synthesis

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Steps in Gene Therapy In Utero
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Number of approved gene-therapy trials as of 2004
Gene therapy trials are now underway around the
world. When will the results be considered part
of world knowledge?
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Next Class
Exam I (Lessons Labs)
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Genetic tests for 1000s of genetic diseases will
be available after the Proteome Project is
completedor after scientists figure out which
proteins go with which genesprobably in 10-20
years.
Back
50
Scientific Methodology
World knowledge in scientific
journals Publication
Rejection Peer review
Submission of paper to scientific journal
Observation Hypotheses Tests of hypothes
es
Results
Back
51
Meiosis - formation of gametes in gonads
Back
Based on Mader, S., Inquiry Into Life,
McGraw-Hill