Ch. 27 Applied Genetics - TeacherWeb

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Dec 14, 2012 (4 years and 8 months ago)

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Ch. 27

Applied Genetics

Mutations

Gene Mutation


A change in the sequence of
bases of DNA



Could be caused by toxic
chemicals (metals, pesticides,
fertilizers, PCB’s) or radiation
(
Xrays
, UV rays)

A Pretend DNA Sequence

THE FAT MAN WAS TOO BIG






FOR HIS BED

DNA Sequence

THE FAT MAN WAS TOO BIG






FOR HIS BED

Substitution
-

Switching one letter

THE FA
R

MAN WAS TOO BIG






FOR HIS BED

May cause no change at all, it may be totally lethal, or
anywhere in between.


DNA Sequence

THE
FAT

MAN WAS TOO BIG







FOR HIS BED


Inversion
-

Turn around three letters

THE
TAF

MAN WAS TOO BIG







FOR HIS BED

May cause no change at all, it may be totally lethal, or
anywhere in between..

DNA Sequence

THE
F
AT MAN WAS TOO BIG







FOR HIS BED


Deletion
-

Delete one letter

THE ATM ANW AST OOB IGF







ORH ISB ED

May be totally lethal, usually causes major change in
protein structure and function.

DNA Sequence

THE
F
AT MAN WAS TOO BIG








FOR HIS BED


Addition
-

Add one letter

THE
F
FA TMA NWA STO OBI GFO








RHI SBE D

May be totally lethal, usually causes major change in
protein structure and function.


Results of mutation


Proteins are not formed correctly, and
often will not do their jobs.



Can result in disease or death



Mutation may have no effect



Mutation may be beneficial to an organism



HUMAN GENETIC
DISORDERS


SEX
-
LINKED
: colorblindness, hemophilia,
Duchenne

Muscular Dystrophy



AUTOSOMAL

(not sex chromosome): Sickle
-
Cell
Disease,
Phenylketonuria
,
Tay
-
Sachs Disease,
Cystic Fibrosis, Huntington Disease



CHROMOSOMAL
: Down’s Syndrome, Turner
Syndrome,
Klinefelter

Syndrome

A SMIDGEN MORE ABOUT
CHROMOSOMAL MUTATIONS:

Translocation
-

transfer of part of a
chromosome to a
nonhomologous

chromosome (not like crossing
-
over)

Inversion
-

a piece of a chromosome is rotated

Addition
-

a piece of a chromosome is added to
an existing chromosome, so gene(s) get
repeated

Deletion
-

a piece of a chromosome is broken
off, so gene(s) are missing.


NONDISJUNCTION
-

the addition or loss of an
entire chromosome

PEDIGREE CHARTS

= Male

= Male with the trait

= Male carrier of the trait

= Male without the trait

= Female

= Female with the trait

= Female carrier of the trait

= Female without the trait

Married

Children

First,
learn the
symbols!

Remember
: A child
gets one allele from
each parent!

Now, Look at one all put together:

The Roman
Numerals
identify the
generations

= BB or Bb

= bb

I



II



III



IV

1 2


1 2 3 4 5 6


1 2 3 4

1

These
numbers
identify the
individuals
(III
-
2)

GENOTYPES FROM PEDIGREES

= BB or Bb

= bb

I



II



III



IV

1 2


1 2 3 4 5 6


1 2 3 4

1

Start by
giving all
shaded
individuals
bb…

Next, work backward to figure out the
unshaded

individuals. Start with
parents of shaded offspring…they
have one B at least.

= BB or Bb

= bb

I



II



III



IV

1
bb

2


1 2
bb

3 4
bb

5 6


1 2 3 4
bb

1
bb

Since
II
-
4

is
bb

and he
got one b from his
mother
(I
-
1)
, the other b
must have come from his
father
(I
-
2)

The Complete Pedigree with
Genotypes

= BB or Bb

= bb

I



II



III



IV


1
bb

2
Bb

1
Bb

2
bb

3
Bb

4
bb

5
Bb

6
Bb

1
Bb

2
Bb

3
B
-

4
bb

1
bb

Note:

III
-
3 is B?

Because we
cannot tell his
complete
genotype

If III
-
3 has a child
with bb, then you
will know III
-
3 is Bb


Human
Chromosomes

Isolated from

a cell

A Normal
Karyotype

Male or
Female?

22 pairs of
autosomes

and
1 pair of sex
chromosomes

Karyotype
-

Used to detect chromosomal
abnormalities
-

extra or missing
whole chromosomes

Abnormal
Karyotype

What is
different?

Trisomy

21 (Down’s Syndrome)

Other Techniques to Detect
Genetic Problems

Amniocentesis
-

a sample of
amniotic fluid is taken from a
pregnant woman and enzyme
tests are conducted, as well
as a
karyotype

in some cases

Chorionic
Villus

Sampling
-

a
sample of the
chorion

(part of
the placenta) is examined since
it has the same genetic make
-
up as the fetus.

Ultrasound
-

sound waves are
used to check for physical
indicators of genetic problems

Chapter 27

Section 3

HISTORICAL BACKGROUND

SELECTIVE BREEDING
:

Choosing organisms with the most
desirable traits for mating


Example
-

mating only the cows
who have produced large
quantities of milk.

Example
-

mating the fastest race
horses.

HISTORICAL BACKGROUND

HYBRIDIZATION:

When individuals from different , but closely
related species are mated to introduce
new, beneficial alleles into a population.


Example
-

the mule… a cross between a
donkey and a horse. Is superior in
strength, endurance, and resistance to
disease.

Usually are sterile (incapable of
reproducing).

HISTORICAL BACKGROUND

CLONING:

Producing an organism from a single parent.


Example
-

plants… buds of spider plants may be cut
from the original parent plant and allowed to grow
roots. It will develop into its own organism and
obviously be a genetic duplicate of its parent.


RECENT GENETIC ADVANCES
-

GENETIC ENGINEERING

Biologists can cut, separate, and splice
together DNA sequences in any
order.


Gene Splicing
-

Inserting a human gene
into a bacterial plasmid. The bacteria
will then produce whatever protein
the human gene coded for.


example
-

human insulin

RECENT GENETIC ADVANCES

GENETIC ENGINEERING

CLONING ANIMALS



RECENT GENETIC ADVANCES

GENETIC ENGINEERING

GENE THERAPY
-



AKA Gene Replacement


Correcting genetic defects through
transferring normal (correct) genes into
cells that lack them.


Example
-

cystic fibrosis

RECENT GENETIC ADVANCES

GENETIC ENGINEERING

GENETICALLY ENGINEERED FOODS

AKA GENETICALLY MODIFIED FOODS (GMO)


Inserting a desirable gene from one organism into
a food product for corporate benefit.


example
-

flounder gene inserted into tomatoes

Or if you are a fan of the
Simpsons…

RECENT GENETIC ADVANCES IN GENETIC
ENGINEERING

THE HUMAN GENOME PROJECT
-


International group of scientists (and private
companies).


Goal is to map the entire human genome.


This goal was met in 2003.


The sequence of bases on each of the 23
chromosomes was mapped.


Results of this project have identified genes
associated with genetic disorders.

RECENT GENETIC ADVANCES

GENETIC ENGINEERING

Gel Electrophoresis/ DNA Fingerprinting


Used to diagnose disease


Used for criminal identification


Used to identify unknown bodies


Involves separating DNA sequences on
a charged gel according to their relative
sizes and making a ‘picture’ of these
sequences.

GEL ELECTROPHORESIS

Loading DNA into the Gel

See an Animation of the process

This is
a virtual gel
electrophoresis lab



POSITIVE ASPECTS OF
GENETIC ENGINERRING

NEGATIVE ASPECTS OF
GENETIC ENGINEERING

Prevention of disease and
death in humans

If people continue to live
longer, we complicated the
overpopulation issue

Improved crop/ food
production
-

less starvation

Long term negative
consequences of genetically
altered foods are unknown/
lack genetic variation

Production of medicines/
reduction in the number of
genetic disorders

Are we overstepping our
bounds and playing ‘God?’