larger flower size - West Branch Schools

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14 Δεκ 2012 (πριν από 4 χρόνια και 10 μήνες)

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Chapters 13 & 14

Genetic Engineering

&

Human Genetics

Genetic Engineering Intro:


Genetic Engineering


the process
of making changes in the DNA code
of living organisms


What are ways that humans have
affected the DNA of bacteria?
Plants? Animals? HUMANS?????


Are these ethical issues? Why or
why not?

Selective Breeding


Organisms are selected for breeding based on
desireable traits.


These desired variations are sought out in the
offspring, then bred over generations to
enhance those particular traits


Traits are not chosen by nature for survival of
the organism, but chosen by man to ‘enjoy




Examples: Modern corn originated from
small
-
grained grasses, large
-
fruiting plants,
dog breeds, etc

Examples of Selective Breeding:

Examples of Selective Breeding:

Hybrids


Hybrids


offspring of crosses
between parents with different traits.


Used by scientists to try to get the
“best” traits from each organism


Hybrids can be formed between
closely related species


Ex: Horse 62 chromosomes x


donkey 64 chromosomes


= mule 63 chromosomes


Many hybrids are infertile and cannot
reproduce

Examples of Hybrids

Inbreeding


Inbreeding


the continued
breeding of individuals with
similar characteristics


Positives


helps maintain
“breeds” of organisms


Negatives


reduces the genetic
variation and increases the
likelihood that two recessive
genes for a disease or defect can
come together

Inbreeding

Polyploidy


Scientists introduce chemicals that stop chromosomal
separation during meiosis


Result: Organisms with double or triple (or more) the
number of chromosomes


Common in plants, usually fatal in animals

Examples of Polyploidy:


A pair of
Pelargonium xhortorum

(4X, 2X) flowers is on the left.


A
pair of

P. peltatum

(4X, 2X) flowers is on the right.


Within each
pair, the flower on the left is the tetraploid, while the flower on
the right is the diploid.


One of the classic "advantages" that
polyploids exhibit is that they may have a
larger flower size
.


The
Pel flowers above are typical

---

in each pair of flowers, the
tetraploid

on the left

is visibly larger.

garden genetics.com

Genetic Engineering


Genetic engineering


scientists make changes in the
DNA of a living organism


Includes: Includes cutting, copying, and pasting DNA
to create transgenic bacteria, plants, and animals


Recombinant DNA


DNA produced by combining
DNA from different sources


Examples: Human insulin made by bacteria,
genetically modified foods that resist pests, goats that
produce spider silk in their milk, and pGlo gene from
jellyfish inserted into other organisms



A bacterial
plasmid (circular
piece of DNA,
shown in red)
has new DNA
(blue) inserted,
creating a
recombinant
plasmid

Transgenic plants and animals:


Plants with gene for
increased salt
tolerance inserted


pGlo gene inserted in
bacteria and mice

Cloning


Cloning


the process by which
one organism’s DNA is removed
from ONE cell and placed into an
ennucleated (nucleus removed)
egg cell from a donor


This egg cell is grown in “foster”
mother


The offspring is genetically
identical to the original organism

Cloning

Ethical Issues in Genetic
Engineering:


Gene therapy


using new genes
injected into humans to cure
diseases


Stem cells


from the body or
fetuses


can develop into any
body cell


Transgenic organisms


GM
foods, creating new organisms


Cloning


failure rates, humans??

Chapter 14

The Human Genome

Human Chromosomes


Humans have
46

total
chromosomes


23

from each parent come
together to form
homologous

pairs


44 Autosomes


2 sex chromosomes, XX or XY


If
non
-
disjunction

occurs in
meiosis, humans can have less or
more chromosomes

Normal Karyotype


Abnormal Karyotype


What can a karyotype reveal?
Aneuploidy


Trisomy



one extra
chromosome: Down syndrome
(47, XX, +21),, Kleinfelter’s
syndrome 47, XXY, etc.


Monosomy



missing one
chromosome Turner’s
syndrome(45, X) etc.


Translocations



pieces of
chromosomes moved to other
chromosomes
Link

Pedigrees


Hemophilia pedigree



alternate hemophilia pedigree


Other factors that affect gene
expression:


Polygenic traits



many human
traits are controlled by more than
one gene


How does the environment affect
your phenotype (what you are
physically)?
“Nature vs. Nurture”


Twin Studies


Are identical twins
always “identical”? Separated
twins?
The Jim Twins


Nutrition and treatment by
parents?

Genetic Diseases


Scientists have identified over
4,000 diseases

caused by
“genetic variants”


On average, individuals carry
between 5 and 10 variant or
disease causing genes in their
genome (kidshealth.org)


Why don’t we all exhibit disease
symptoms then?

Human Genetic Diseases caused by
recessive traits:


Albinism



lack of
melanin


Cystic fibrosis



problems transporting
chloride ions = lung,
digestive problems


Phenylketonuria (PKU)



metabolic disorder


Tay
-
Sachs disease



Jewish descent, early
death



Individuals can be
asymptomatic carriers

because they have one
normal gene


Individuals with the
disease must get one
“bad” gene from each
parent

Human Genetic Diseases caused by
dominant traits:


Achondroplasia



form
of dwarfism “LPs”


Huntington’s Chorea



causes mental
deterioration in middle
age and later. Leads to
complete debilitation
and death


Marfan Syndrome



connective tissue
disorder, tall stature



Individuals only need
one copy

of the
defective gene to cause
the disease


If married to a “normal”
person, there is a
50%

chance of passing the
disease on to your
children

Human Genetic Diseases that are

sex
-
linked:


Colorblindness



cannot distinguish
between red and
green


Hemophilia



blood clotting
disorder


Duchenne
muscular
dystrophy



severe
muscle weakness



Defective gene is found on
the
X chromosome


If the gene is dominant,
males and females can get
it equally


If gene is
recessive

(examples on left), males
get it more frequently,
because females have XX,
one “normal X, and one X
with the defective gene