Download Mutations

Mutations
A change in the DNA structure
There are two categories of mutations
Gene Mutation
1.
2.
3.
A change in the DNA
A change in the sequence of nitrogenous bases
Mutagens can cause the change
What’s Happened to the DNA?
Both had one base
substituted for another.
How was the DNA changed in these examples?
Comparing Gene Mutations
Additional Ways DNA Mutated
What can a changed protein do
to an organism?
Changes the reading of the DNA
2. Results in the formations of new mRNA
codons leading to a change in the
polypeptide structure
3. Types are: insertion or deletion
1.
Mutation: Frameshift
Identify the category and
type of mutation affecting
this strand of DNA
1.
AUGCCGUACCUUAUGGCUG
Mutated Strand reads:
1. AUGCACGUACCU…
A
2.
AUGC_GUACCUUAUGGCUG
2. AUGCGUACCUUA…
Notice that the reading of the DNA will be shifted.
Hence, these are frameshift mutations. The mRNA
when translated will produce a different amino acid
sequence.
Human Red Blood Cells
Contain the protein, hemoglobin (Hb)
2. O2 binds to Hb = oxygenated blood
3. Red Blood Cells are doughnut shaped
cells
1.
Sickle Cell Anemia
1.
2.
3.
4.
RBC’s are “sickled shape”
Hemoglobin protein has been altered -shape
has changed
Cells stick to each other; Oxygen binding
capacity has been altered.
Circulatory problems arise
Why?
Normal Hemoglobin:
Valine-Histidine-Leucine-Threonine-Proline-Glutamic Acid-Glutamic Acid
Abnormal Hemoglobin:
Valine-Histidine-LeucineThreonine-Proline-Valine-Glutamic Acid
Sickle Cell Anemia had change in the polypeptide chain:
Glutamic acid is changed to Valine
Why??????? How can this be??????????????
Normal Hb
Sickle Hb
DNA:
CTT
mRNA: GAA
Amino Acid: Glutamic acid
DNA:
CAT
mRNA: GUA
Amino Acid: Valine
…Proline-Glutamic AcidGlutamic Acid…
…Proline-Valine-Glutamic
Acid…
What type of mutation caused the altered hemoglobin?
A Point Mutation – base substitution
Change Affects Codon
This is normal structure
Codon Change Affects Protein
Structure
Chromosomal Mutation
Alterations in chromosome number and/or structure
Structural Chromosomal
Mutations
Deletion
Duplication
Homologous
chromosomes
Inversion
Reciprocal
translocation
Nonhomologous
chromosomes
Read 8.22, 8.23, 8.24
Figure 8.23A, B
Chromosome Number for a Species
Species
# of
chromosomes
Species
# of
chromosomes
Fruit fly
8
Human
46
Rye
14
Ape
48
Guinea Pig 16
Sheep
54
Dove
16
Horse
64
Snail
24
Chicken
78
Earthworm 32
Carp
104
Pig
40
Butterflies
~380
Wheat
42
Fern
~1200
Does the embryo have the correct
number of chromosomes?
Egg
cell
Sperm
cell
zygote
Does the zygote have the correct number of
chromosomes?
Chromosome Number Mutation
LE 13-10
Key
Maternal set of
chromosomes
Possibility 2
Possibility 1
Paternal set of
chromosomes
Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Daughter
cells
Combination 1
Combination 2
Combination 3
Combination 4
Interphase
Homologous pair
of chromosomes
in diploid parent cell
Chromosomes
replicate
Homologous pair of replicated chromosomes
Sister
chromatids
Diploid cell with
replicated
chromosomes
Meiosis I
Homologous
chromosomes
separate
Haploid cells with
replicated chromosomes
Meiosis II
Sister chromatids
separate
LE 13-7
Haploid cells with unreplicated chromosomes
A karyotype:
a photographic inventory of an
individual’s chromosomes

To study human chromosomes
microscopically, researchers stain and
display them as a karyotype
◦ A karyotype usually shows 22 pairs of
autosomes and one pair of sex chromosomes
Additional information 8.19-20
Preparation of a karyotype
Blood
culture
Packed red
And white
blood cells
Hypotonic solution
Fixative
Stain
White
Blood
cells
Centrifuge
3
2
Fluid
1
Centromere
Sister
chromatids
Pair of homologous
chromosomes
4
5
Figure 8.19
Let’s look at this Karyotype
This karyotype shows three number 21
chromosomes
 An extra copy of chromosome 21 causes
Down syndrome

Figure 8.20A, B

The chance of having a Down syndrome
child goes up with maternal age…why?
Figure 8.20C
Beginning the Karyotype
1.
2.
3.
You will simulate the karyotyping task.
You will create a karyotype and determine the
gender and developmental status of the baby.
You must carefully cut out all chromosomes
and correctly match them up by:
a. Size of chromosome
b. Location of centromere
c. Banding pattern on chromosome
Karyotype Lab
Finished Karyotype
Another Karyotype
Male or Female?