HLTH101 Lecture Notes - Lecture 8: Cystic Fibrosis, Klinefelter Syndrome, Cervical Cancer
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1 Aug 2016
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HLTH 101 – Week Four Notes Cont’d
How do genes control the growth and division of cells?
-Cell cycle is controlled by checkpoints to ensure
-Proper replication of DNA many DNA repair mechanisms
-Each daughter cell receives proper # of chromosomes
-Proliferation = rapid reproduction
-If DNA errors cannot be repaired programmed cell death (apoptosis, figure
next slide)
What is Apoptosis?
-Apoptosis basically = voluntary suicide (not necessarily voluntary but is
best for cell in that situation)
-A damaged cell may undergo apoptosis if it is unable to repair genetic
errors
How are cancer cells formed?
-Result when cells accumulate genetic errors (approx. 60) and multiply
without control
-Normal cellular proliferation requires a balance between the activity of
genes that promote growth and those that suppress it
-Growth-promoting genes (oncogenes) become too active
-Too much proliferation a tumor
-Other mutations inactivate tumor-suppressor genes that normally put the
brakes on growth or that signal the need for apoptosis
-p53 is the most common mutated gene in human cancers
oPlays a very important role in detecting errors in DNA and triggering
response or cell death if errors are beyond repair
-Malignant keeps growing out of control and has the ability to go into blood
stream/other parts of the body to make more and more = cancerous
-Most cancer cells don’t have the proper number of chromosomes
What are some examples of body parts that are able to regenerate cells?
- Liver - has the ability to regenerate parts of itself when necessary (only parts
that need to be though)
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-Lining of digestive tract as well – replacing cells as they go (die)
What is a gene mutation and how do mutations occur?
-Gene Mutation = A permanent change in DNA sequence that
codes for a gene
oRange from single base change to whole segments of
chromosomes
-Occurrence (variations) of mutations:
oInherited: Present in germ or egg cells
oAcquired: DNA of individual somatic cells during lifetime (e.g.
mutations that lead to cancer)
Somatic Cell = diploid (containing 2 sets of chromosomes – 1
from each parent) cell that includes all cells of body except
sperm and egg cells
oPolymorphisms: normal variations in DNA (SNPs)
Single nucleotide polymorphisms
What is Point Mutation and what are the different types?
-Point Mutation = single-base-pair change
oBecause DNA is a double helix, it would really be a pair that’s been
mutated because they have to pair up with each other with 1 mutation
2
-Different types:
Silent altered codon still codes for same amino acid
Missense altered codon leads to altered amino acid
Nonsense changes codon to a stop codon
oMissense and nonsense can greatly alter function of a protein or even
stop it from functioning at all!
What 2 types of mutations cause Frameshift?
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1. Insertion
2. Deletion
-Occurs because you throw off the reading
frame (3 nucleotides at a time to code for
1 amino acid) when either occurs
What is the most commonly inherited gene
disorder that occurs as a result of
frameshift?
-Cystic Fibrosis!
oCFTR (Cystic Fibrosis
Transconductance Regulator) =
a gene that codes for a protein
that transports chloride
oSymptoms = in lungs and
digestive tract – affects mucous
viscosity (makes it very thick)
pneumonia
What disease occurs as a result of Nucleotide
Repeat Expansions?
-Huntington’s Disease!
oGene normally has approx. 15 repeats
o35-40 repeats means you actually have the disease
What
is an
Allele?
-Allele = one of two or more alternative forms of a gene that arise by mutation
and are found at the same place on a chromosome.
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