3.03, 3.04 notes.pptx - svbiologymazz4

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14 Δεκ 2012 (πριν από 4 χρόνια και 6 μήνες)

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3.03: PEDIGREES

Pedigrees


The risks of passing on a genetic disorder to
offspring can be assessed by
genetic counseling
,
prenatal testing
, and by analyzing a
pedigree
.


A
pedigree

is a family history diagram that shows
how a
trait

is inherited over several
generations
.


A pedigree can be mapped out to determine if
individuals are
carriers

or if their children might
inherit

the disorder.


Carriers are individuals who are
heterozygous

for
an inherited disorder but do not show
symptoms
.
Carriers can then pass the
allele

for the disorder
on to their
children
.


Pedigrees


In a pedigree,
females

are indicated by
circles, males are indicated by
squares.


Shaded

figures represent individuals
with the
trait
, a
carrier

could be 1/2
shaded (but not always!).


Generations

are numbered with roman
numerals (
I, II, III, IV
) from top to
bottom.


People

within generations are
numbered (1, 2, 3) from left to right.


People that are
married

(or just having
children together) are connected by a
horizontal

(left to right) line.
Offspring

of
individuals are connected to their
parents by a
vertical

(up and down) line.


Pedigrees


By analyzing a pedigree you can tell if a trait is
dominant or recessive and if it is
autosomal

or
sex
-
linked.


One parent has the disease, and none of
the three children inherited it. We can
tell that this is a
recessive

trait because
not many people in the family have it. If
it were a
dominant

trait, many more
would have inherited it.

Both males and females show the trait, so
we know this is not sex
-
linked but is an
autosomal

trait.

Pedigrees


We can also analyze a pedigree to
figure out people’s
genotypes
. If we
know this is an
autosomal

recessive
trait, then anyone shaded in must
have the genotype (
nn
). Anyone not
shaded must have either (
NN
or
Nn
).


What is the genotype of person
I
1?



nn



Person
IV
2?



Nn

or NN



Who in this pedigree must be
heterozygous?



III
1 and
III
2



Only
women

are
carriers, and only
men

show the trait.
Therefore, this must
be a
sex
-
linked

trait.


We can also tell this is a
recessive

trait, because
not many people have it. In order for a trait to
have carriers, it must be recessive. If a trait is
dominant
, people either have it or they don’t.


Since this is a sex
-
linked recessive trait, what is
the genotype of Alice?



X
H
X
h




What is the genotype of Fred?



X
h
Y


3.04:
KARYOTYPING

AND GENETIC
DISORDERS

Karyotypes


Genetic disorders may be detected by
using prenatal testing and pedigrees.
They can also be detected using
karyotypes
.



A
karyotype

is a photograph of an
individual’s
chromosomes

in a dividing
cell during mitosis. The chromosomes
are arranged by
size

and numbered.


Karyotypes


A
karyotype

can show you two things:


1.
Chromosome
abnormalities
:
missing

chromosomes,
extra

chromosomes, or if
chromosomes are malformed

2.
The
sex

of the person


Karyotypes











Normal
Karyotype











Down’s Syndrome

Genetic Disorders

Down’s Syndrome
:

o
A chromosomal disorder caused by an extra
chromosome 21
. For this reason it is also known
as
Trisomy

21

(which means 3 chromosome 21’s).

o
Caused by
nondisjunction
, which means that during
meiosis a gamete is produced with an extra copy of
chromosome 21. This is not an inherited trait, it
happens in the egg or the sperm before fertilization.

o
Symptoms: learning disabilities, developmental
disabilities, and impaired physical growth.

o
Occurrence: about 1 of every 9,000 births.


Genetic Disorders

Genetic Disorders

Cystic Fibrosis
:

o
Symptoms: causes thick
mucus

to coat the
lungs

leading
to severe breathing problems. It also causes the
pancreas to not secrete enzymes as efficiently as it
should, causing poor growth, diarrhea, and vitamin
deficiency.

o
Inheritance:
autosomal

recessive

disease caused by a
mutation in a gene.

o
Occurrence: 1 in 3,900 children are born with this
disease, and there is no cure.



Genetic Disorders

Genetic Disorders

Huntington’s Disease
:

o
Symptoms: a genetic neurological disorder
characterized after onset by uncoordinated,
jerky

body
movements and a decline in some mental abilities.
People with Huntington’s Disease have too many CAG’s
in a gene on their DNA and so form a
mutant

protein
from too many glutamines.

o
Occurrence: Up to 7 people in 100,000 have this
disorder.

o
Inheritance: This is an
autosomal

dominant

trait, so an
affected individual needs just one copy of the gene to
show the disease.


Genetic Disorders

Genetic Disorders

Sickle Cell Anemia
:

o
A blood disorder in which the
red blood cells

are not flexible
and round but are rigid and sickle
-
shaped (like a crescent
moon). This restricts the blood cells’ movement throughout
the blood stream and decreases the amount of
oxygen

the
cells can carry through the body.

o
Inheritance: a
recessive

trait.

o
Symptoms: misshapen blood cells cause the blood to not
carry enough oxygen throughout the body. Individuals most
often feel fine, but their lives are interrupted by periodic painful
attacks. The only treatment is pain medication during these
attacks.

o
Occurrence: 1 out of every 10 African
-
Americans has this trait.


Genetic Disorders

3.04: Biotechnology

3.04: Genetic Engineering


Genetic engineering

means making
changes

to an organism’s
DNA

code.



In a genetic engineering experiment,
scientists use the following techniques:


Genetic Engineering

1.
Cutting

DNA using
restriction enzymes
.
Restriction enzymes are bacterial enzymes
that bind to short sequences of DNA, then cut
the DNA between specific
nucleotides
.


Ex: the enzyme
Eco
R
I

recognizes the
nucleotide sequence GAATTC and cuts
between the G and A

ATTCACGA
GAATTC
TACCG



ATTCACGA
G

AATC
TACCG


Genetic Engineering

2. The DNA fragments are separated using
gel
eletrophoresis
. This creates a pattern of
bands made out of those DNA fragments.
These fragments can be put on a piece of
paper and made into a DNA fingerprint.


In gel electrophoresis, an electric
current

is run
through a gel containing the DNA.
Larger

sections of DNA move more
slowly
, and
smaller

sections move more
quickly
. In this
way, we get a banding pattern that is unique to
each person, since every person’s DNA is
different.


3.04: DNA Fingerprinting


A
DNA fingerprint

is the pattern of dark
bands that is made when a person’s DNA
restriction fragments

are separated by gel
electrophoresis.




Because restriction enzymes cut different
DNA sequences in different places, each
individual has a
unique

pattern of
banding
.


DNA Fingerprinting


Uses of DNA fingerprinting:


Can be
compared

to establish whether
people are related, such as in a
paternity

case.


Useful in
forensics

because it can use
DNA found in blood, semen, bone, or hair.


Useful in identifying the
genes

that cause
genetic disorders, such as Huntington’s
and Sickle Cell Anemia.


DNA Fingerprinting


DNA Fingerprinting


3.04: Cloning


Another type of genetic engineering that
you may have heard of is
cloning
.
Cloning means to create a population of
genetically
identical

cells from a single
cell.


In 1997, a Scottish scientist Ian
Wilmut

cloned a sheep by nuclear transfer. How
did he do it?


Cloning

1.
An
egg cell

was removed from a sheep
and the
nucleus

of the egg cell was
removed.

2.
The cell, now with no nucleus, was
inserted into a
donor cell

taken from a
different adult sheep.

3.
The fused cell began dividing and the
embryo

was placed into a foster mother
sheep where it developed normally.


Cloning


From this foster mother,
the cloned sheep
named
Dolly

was born.
She looked and acted
like a normal sheep and
even had a baby of her
own, but she died at an
early age. This
suggests that clones
may not have as long a
life expectancy

as the
organisms they come
from.


Cloning


Since then, scientists have cloned cows,
pigs, mice, and other
mammals
. They
have been cloning
bacteria

and other
microorganisms for much longer.



The use of cloning technology in
humans

is scientifically possible, but raises serious
moral and
ethical

issues.


3.04: Recombinant DNA


Genetic engineering very often involves
using
recombinant DNA

DNA made from
two

or more different
organisms
.


A great example of this is the making of
human
insulin

for diabetics. Insulin is a
protein hormone that controls sugar
metabolism. Diabetics don’t make enough
insulin and so must inject it. We used to
take insulin from the pancreases of
slaughtered cows and pigs, but now we
genetically engineer it.


Recombinant DNA

1.
The human
gene

for insulin is
cut

out of
the DNA using
restriction enzymes

and
transferred into bacterial DNA.

2.
The bacteria, now made of
recombinant

DNA since they contain human DNA along
with their normal bacterial DNA, then
transcribe and translate the human insulin
gene using the same code a human cell
would use in order to make human insulin.


Recombinant DNA


This is very
efficient
: since bacteria
reproduce

much more quickly than
animals do, they can produce much more
insulin.



This is also how we make other drugs,
like Factor VII to help hemophiliacs’ blood
to clot, and vaccines for viruses like
smallpox and polio.


Recombinant DNA


When scientists use recombinant DNA
technology they create
transgenic

organisms
. This is a plant, animal, or
bacteria that contains another organism’s
DNA. The bacteria that takes on the
human insulin gene becomes a transgenic
organism.

Recombinant DNA


Transgenic Organisms

3.04: Human Genome Project


The
Human Genome Project

was a research
project that was completed in 2003.
Scientists from 6 different countries identified
all of the
base pairs

that compose the DNA of
a human. They identified all
3.2 billion

base
pairs of DNA that make up the human
genome.


The goal of this project was to better
understand human DNA to find
causes

and
cures

for common diseases.



Human Genome


Here is what they found:


Only 1 to 1.5 percent of the human genome is
genes

DNA

that codes for
proteins
. Each
human cell contains about
6 feet

of DNA, but
less that
1 inch

is made of genes. These
genes are scattered about the genome in
clumps.


Human cells only contain about 30,000 to
40,000 genes. This is only
double

the amount
that a fruit fly has.