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Human
Heredity and
Biotechnology
Chapter 11.1 & 11.3
with a scattering from
Chapter 13
RECESSIVE GENETIC DISORDERS
• may be passed on to children without knowing
– because parent can be “carrier”
• passed like any recessive trait
• heterozygous condition - “carrier”
• some recessive genetic disorders include…
Cystic Fibrosis
Albinism
Galactosemia
Tay Sachs
RECESSIVE GENETIC DISORDERS
CYSTIC FIBROSIS (CF) – affects the mucus producing glands,
digestive enzymes and sweat glands
Caused by a defective gene
Effects
• excessive mucus production
• higher risk of infection and respiratory system is compromised
• digestive and respiratory system failure
Cure/Treatement
• no cure
• daily breathing treatments
• mucus-thinning drugs
• pancreatic enzyme supplements
• life expectancy 36.8 years
RECESSIVE GENETIC DISORDERS
ALBINISM – partial or total lack of pigment (melanin)
in hair, skin and eyes
Cause – defective gene; do not produce
normal amounts of pigment (melanin)
Effects
- skin susceptible to UV damage
- higher risk of skin cancer and eye damage
- occurs in humans and other mammals
Cure/Treatment
- No cure
- Protect eyes and skin from sun
RECESSIVE GENETIC DISORDERS
GALACTOSEMIA –
an inability to digest galactose (milk sugar)
Caused by – absence of a gene that codes
for the enzyme that breaks down galactose
Effects
• enlarged liver and kidney failure
• galactose builds up in the cells and becomes toxic
• usually causes no symptoms at birth
• if not detected immediately results in liver disease, mental retardation and death
Cure/Treatment
• no cure
• children diagnosed early can have a normal, healthy life
• treatment is the restriction of galactose and lactose from the diet
RECESSIVE GENETIC DISORDERS
TAY-SACHS DISEASE – a build up of fatty deposits in the brain - only affects
people of Jewish descent
Caused by – absence of an enzyme
that breaks down fatty substances
Effects
• inability to break down fatty acids
• fatty acids build up in the brain
• brain cells deteriorate
• mental capacity is diminished
Cure/Treatment
• No cure or treatment
• Death by age 5
Dominant Genetic Disorders
• only need one dominant allele to inherit the
disorder
• no carriers
• some dominant genetic disorders include…
Huntington’s Disease
Achondroplasia
DOMINANT GENETIC DISORDERS
HUNTINGTON’S DISEASE results from the genetically
programmed degeneration of brain cells
Caused by a gene affecting neurological function
Effects
• symptoms appear between 30 and 50 years of age
• degeneration of brain cells (neurons)
• loss of intellectual faculties
• uncontrollable movements
• emotional disturbances
Cure/Treatment
none
woman with Huntington’s
Disease at age 48
DOMINANT GENETIC DISORDERS
ACHONDROPLASIA – most common form of dwarfism
Caused by a mutated gene that affects bone growth
Effects
• short arms and legs
• 75 % of individuals with achondroplasia
are born to parents of average size –
HOW CAN THIS HAPPEN?
Conclusion – occurred because of mutation
Cure/Treatment
• none
• normal life expectancy
PEDIGREE
chart which shows the
inheritance of a trait
from one generation
to the next
Allows geneticists to trace
the transmission of a trait
through a family.
square = male
circle = female
colored shape = has trait
half colored shape = carrier
slash = deceased
Alexandrina Victoria, born May 1819
British Monarch
Queen Victoria was a carrier of hemophilia.
She had nine children and passed hemophilia
on to several of them.
All of her children married into the royal
families of various countries of Europe.
In this way, all of the Royal Families of Europe
inherited the gene for hemophilia.
How many generations are represented?
How many males? afflicted males? normal males?
How many females? afflicted females? normal females?
Any carriers?
Sex-linked or autosomal trait?
Dominant or recessive trait?
Any twins? deceased individuals?
HUMAN CHROMOSOMES
Human somatic cells contain….
46 individual chromosomes
or 23 chromosome pairs
Of these 23 pairs…
SEX CHROMOSOMES (1 pair)
• determine the sex
of an individual
AUTOSOMES (22 pairs)
• do not determine the sex
of an individual
KARYOTYPE
is a photomicrograph
of the chromosomes
in a dividing cell
chromosomes are grouped
and placed into pairs
female - 46 XX
male - 46 XY
Telomeres
protective caps on ends on chromosomes
made of protein and DNA
may play a role in cancer and aging
Mutations
What is a mutation? a change
in the DNA or a
change in a gene
– it is interesting that mutations
can be helpful, harmful or
may have no effect
mutations – are a source of
genetic variation in LT
Mutations
What causes a mutation? a mutagen….
A mutagen is….anything that may cause a change
in the DNA
Some mutagens are viruses, chemicals, toxins,
UV light,….
Mutations can also happen as a result of the
DNA being copied incorrectly
Types
of
Mutations
1.
Somatic cell mutations: affect body cells
 will affect individual, but not offspring
2.
Germ cell mutations: affect germ cells – what are these?
 Will affect offspring, but not the individual
3.
Lethal mutations
 Will cause death either before or shortly after birth
Chromosome
Mutations
Deletion
– A piece of a chromosome is lost
Inversion
– A piece of a chromosome breaks off, flips over, and reattaches
Translocation
– A piece of a chromosome breaks off and attaches to another chromosome
Nondisjunction
– Homologues do not separate properly during cell division
loss of a portion of a chromosome
Inversion – a section of a chromosome breaks off,
flips over and reattaches
Translocation – a portion of a chromosome detaches and
reattaches to a nonhomologous chromosome
Let’s Practice – What type of mutation?
NONDISJUNCTION - may arise when
chromosomes don’t separate properly during
CELL DIVISION …
CAN OCCUR IN mitosis or meiosis
nondisjunction
means
“not coming apart”
Nondisjunction in Meiosis…can lead to …
monosomy (45) – missing a chromosome of a pair (having
only 1 chromosome of the pair)
trisomy (47) – having an extra chromosome in a pair (having
3 chromosomes in the pair)
Conditions resulting from
Nondisjunction
• Down’s Syndrome
• Turner’s Syndrome
• Klinefelter’s Syndrome
DOWN SYNDROME
(also called trisomy 21)
male or female having an extra chromosome in pair #21
(3 chromosomes instead of 2)
male or female having an extra AUTOSOME
47 XX or 47 XY
Nondisjunction on #21 = Trisomy 21
(Down Syndrome)
Characteristics of Down Syndrome
•
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•
•
•
•
•
•
•
almond shaped eyes
flat nose bridge
large tongue
ears are set a bit lower on the head
shorter in stature
simean crease on the palm of the hand
possible congenital heart defects
lat feet, sandal toe (large gap between big toe and the next)
lower IQ
developmental delays
TURNER SYNDROME
female that is missing a sex chromosome - 45 XO
KLINEFELTER SYNDROME
male having an extra sex chromosome
47 XXY
Fetal (genetic)Testing
– pre-pregnancy: DNA testing & genetic counseling
– post-pregnancy: PKU testing
– during pregnancy:
• Amniocentesis
• Chorionic Villi Sampling (CVS)
• Fetal Blood Sampling
Amniocentesis - a small amount of amniotic fluid (containing
fetal tissues and cells) is extracted from the amniotic sac
surrounding the developing fetus - the DNA is examined
for genetic abnormalities
Chorionic Villi Sampling (CVS) - the removal of a small
piece of the placenta (chorionic villi) during early
pregnancy to screen for genetic defects – the placenta has
the same genetic makeup as the fetus
Fetal Blood Sampling(FBS) - the collection of fetal blood
from the umbilical cord or fetus – the blood is tested
genetic defects or other abnormalities
HUMAN GENOME PROJECT
Begun in 1990, it was
an attempt to sequence
all of the human DNA.
Genome = an organism’s DNA
Mapping of the human
genome completed in 2003.
DNA fingerprinting
or DNA profiling
• A technique for analyzing and
comparing DNA from separate
sources
• Used to identify criminal suspects,
determine paternity or the identity
of unknown persons
• DNA samples are taken from hair,
blood, semen, or other biological
materials
• No two people, except identical
twins, have exactly the same DNA
According to the DNA
fingerprint above, who are
the parents of the child?
A (A+B)
B (C+D)
C (E+F)
D (G+H)
DNA fingerprints
of 3 people created
using 7 different
DNA probes.
What do persons
1 and 2
2 and 3
1 and 3
share in common?
GENE THERAPY
process in which an absent or faulty gene is replaced by a
normal, working gene
various approaches have been taken…
– Bone marrow removed, modified in the laboratory and
placed back in the body
– Modified viruses have been used to carry replacement genes
into the body
– Inhalation of genetically engineered viruses containing
“good” genes has been attempted
up to this point, gene therapy has not been very successful
Manipulating DNA…
• Today, we have expanded our use of genetic
information and we are able to use techniques
for manipulating (modifying) DNA.
We can….
• extract DNA from cells,
• cut it into small pieces,
• identify the genes and sequences in DNA
• make copies
Cell Transformation….
process by which a cell takes in DNA from an
outside source
• the external DNA may become part
of the cell’s DNA
Recombinant DNA – taking DNA from one organism and combining it
with another organism
• we have inserted the genes for human insulin and human growth hormone
into bacteria
Transgenic Organism…
an organism containing genes from
another organism
bacterium containing
recombinant DNA
cow containing genes
for producing
human milk proteins
Cloning…
process of producing an identical copy of an organism
• we have successfully cloned frogs, salamanders, mice,
sheep and other organisms
DOLLY
What is genetic engineering?
it is simply….
genetic modification
Throughout the ages,
man has applied his knowledge
of genetics to the world around him –
especially to plants and animals.
Selective Breeding…
aka Artificial Selection
is the process of breeding animals or plants
with desired characteristics
• man has used selective breeding to develop plants and animals
with “desirable traits”
• nearly all domestic animals – dogs, cats, horses, and most crop
plants have been produced by selective breeding
Selective Breeding…of plants
Selective Breeding…of animals
Selective Breeding…
Can involve…
• Hybridization
• Inbreeding
Hybridization…
crossing dissimilar individuals to bring together the best
traits of both organisms
hybrids (produced by
such crosses) are
often healthier and
hardier than either
of the parents
Hybridization …
ZEDONK – cross between a zebra and a donkey
Hybridization
LIGER – cross between a male lion and a female tiger
Hybridization
Tigon – cross between a female lion and a male tiger
Hybridization …
male DONKEY
and
female HORSE
=
MULE
Offspring (mules) are almost always sterile. The mule has
greater endurance, is stronger and less excitable than a horse.
Inbreeding…continued breeding of individuals
with similar characteristics - used to maintain
characteristics in a breed
Inbreeding…
Selective breeding often limits variation…..is this good?
Scientists are also interested in preserving the genetic
diversity in organisms.
WHY is it important to maintain diversity/variation ?
How can genetic diversity/variation occur…
1. by inducing mutations (using chemicals or radiation)
mutation = a change in the DNA
2. polyploidy – having extra sets of chromosomes – often
results in more vigor or increased size
3.
genetic recombination as a result of …
* crossing over during prophase I of meiosis
* sexual reproduction - union of 2 haploid gametes