C HAPTER 6: G ENETIC DISEASES. I NTRODUCTION Cystic fibrosis: .
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Transcript of C HAPTER 6: G ENETIC DISEASES. I NTRODUCTION Cystic fibrosis: .
CHAPTER 6:GENETIC DISEASES
INTRODUCTION
Cystic fibrosis:
http://www.youtube.com/watch?v=Twjg7v-pTO4
WHAT ARE GENETIC DISEASES/DISORDERS?
A genetic disorder is an illness caused by abnormalities in genes or chromosomes
What are chromosomes?
CHROMOSOMES
A normal human being has 46 of these chromosomes in each cell (excepting reproductive cells) Of these 46 chromosomes, 44 are ‘autosomal’ 2 chromosomes are ‘sex chromosomes’
X and Y
GENETIC DISORDERS Sometimes genetic disorders are caused by a
whole chromosome:: Down syndrome Klinefelter syndrome
Down syndrome is caused by a trisomy: Instead of a pair of chromosomes, you have 3
In this case 21 Down syndrome is also called ‘trisomy 23’.
Other trisomies can occur, but often result in a miscarriage For example: trisomy 16
TRISOMIES The most common types of autosomal
trisomy that survive to birth in humans are: Trisomy 21 (Down syndrome) Trisomy 18 (Edwards syndrome) Trisomy 13 (Patau syndrome) Trisomy 9 Trisomy 8 (Warkany syndrome 2) Trisomy 22
Sometimes, there is an extra copy of a sex chromosome present: XXX, XXY or XYY (XYY is not really a disorder) Klinefelter syndrome is an example: XXY
GENETIC DISORDERS
Other genetic disorders are not caused by a whole chromosome, but by a fault in one or more genes
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and
RNA that code for a polypeptide or for an RNA chain that has a function in the organism.
GENES
http://www.youtube.com/watch?v=8s4he3wLgkM
Cystic fibrosis is an example of a disorder caused by only 1 faulty gene You can only get it when this faulty gene is
present on both chromosomes of chromosome 7
If only one chromosome 7 has the faulty gene you are a carrier You don’t get ill because the normal gene is
dominant over the faulty gene
CYSTIC FIBROSIS
HUNTINGTON’S DISEASE
Cystic fibrosis is caused by a recessive (non-dominant) gene
Some genetic disorders are caused by faulty genes that are dominant Huntington’s disease In this case you will get the disease, even if only
one copy of your chromosome 4 has the gene
http://www.youtube.com/watch?v=4HgFUvVyHYQ
WORK
Read pages 76 – 78 Answer questions 1 - 6