Download Genetics Notes HONORS

Warmup
• What is Down Syndrome?
• What does the word non-disjunction mean?
(break down the word)
• What is a mutation?
• What is the difference between identical and
fraternal twins?
• Why are there so many variations among
people?
Genetics Unit
Test Date: 4/12/16
Mutations
• Errors in DNA sequence (bases) that results in
wrong amino acids in the protein, thus
changing the protein
• Causes:
– Radiation
– Nuclear
– UV rays
– Certain chemicals
– Certain foods can increase chances of mutations
Mutations
Sex cell mutations
• Mutation takes place in
adult tissues, and gets
passed down to the
future offspring
• Not expressed in the
adult-in other words,
the mutation does not
affect the person it took
place in
• Give rise to genetic
disorders
Somatic cell mutations
• Mutation takes place in
adult tissues and does
NOT get passed down
to future offspring
• Usually not expressed in
the adult
• Cancer is the exception,
it is expressed in the
adult tissues, but still
does not get passed
down to offspring
Mutations
• Many types:
– Chromosomal Mutations
• Polyploidy Changes in #s of pairs of chromosomes: humans
are diploid 2n)-2 pairs of chromosomes
– If a human was triploid which is three sets of chromosomes
• Nondisjunction
– Gene Mutations
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Insertions
Deletions
Duplications
Inversions
Translocation
Duplications
Deletions
Inversions
Translocation
What do we call the movement of genetic information
between homologous chromosomes?crossing over
Nondisjunction
• When chromosomes fail to separate, so one
gamete gets both chromosomes and the other
gamete gets neither. Zygote now has 3
chromosomes instead of 2.
• Aneuploidy insertion or deletion of just ONE
chromosome
– Having 1 chromosome #1
– Down syndrome (3 chromosome #21)
• Polyploidy entire set of extra
chromosomeshuman having 69 instead of 46
chromosomes. 3n (3 pairs) instead of 2n (2 pairs)
Example of Nondisjunction
• Example of Aneuploidy
• Down syndrome
– trisomy 21 (3 of chromosome #21)
Name the type of mutation do not
use your notes
• ABCDEFGH
– ABCDPFGH
• ABCDEFGH
– ABCFGH
• ABCDEFGH
– ABCDGFEH
Sex chromosomes
Males
• XY chromosomes
• Y is dominant
• Males(sperm) determines
sex of the baby
Females
• XX chromosomes
• “Almost like” X is recessive
to being female
• Females do not determine
sex, because they give an x
no matter what
Nondisjunction in sex chromosomes
• “Turner’s syndrome” woman has only one X
chromosome
– Results in a short female with low intelligence and
sterility
• Klinefelter’s syndrome male with extra X
chromosome (XXY)
– Results in male with long arms and legs, low
intelligence, and sterility
• In both situations, individuals survive
Gene Linkage
• Genes come as a “package deal” meaning that if they
are in close proximity to each other, then they are
more likely to be linked together and will not
separate
– Examples in humans include freckles for gingers, brown
eyes and brown/black hair for African Americans,
Gene linkage
Sex linkage
• Traits that are found on the 23rd
pair(sex) of chromosomes
• Ex: color blindness, hemophilia
• Usually are passed from mother
to son, and father to daughter.
How to determine if a trait in a
pedigree is autosomal or sex-linked
• Always assume sex-linked first, and try to
show evidence that it is not sex linked
• Evidence:
– If the trait is sex linked, then all affected females
must also have a father that is affected (mother
also has to be a carrier)
– Males can come from a carrier female and a
normal male. If a mother is affected, all of her
sons must be affected
• If these criteria are not met, then the trait is
autosomal
How to determine if the trait is
autosomal dominant or recessive
• Start off by trying to prove it cannot be recessive, if you
can it is dominant, if you can’t, its probably dominant
• DominantTrait will not skip generations. An affected
person married to a normal person should have about
50% of the offspring affected
• RecessiveTrait may skip generations. If both of the
parents are affected, all of the children must be affected.
Most affected individuals have “normal” parents. When
a normal person is married to an affected individual, all
of the children are normal( indicating that the parent is
probably homozygous dominant)
X Chromosome Inactivation
• Females have XX
• One of those is turned off “randomly”
• Results in some cells having turned off X and others having
turned on X one from mother and one from father it is
completely random which one gets turned off
• Ex: Calico cats fur cells are either turned on, or turned off.
Hairs that are orange have ben turned on and the black fur
has been turned off. White is just the absence of any color on
hair. This results in three different colors.
– Male calico cats only have one X either orange and white or black
and white… depending on which color is turned off in the X
inactivationmales cannot be all three colors.
Twins
Fraternal
• Two eggs released at same
time
• Fertilized by two separate
sperm
• No more alike than a
normal brother and sister
• Can be opposite sex
Identical
• One egg is released
• fertilized by one sperm
• Genetically identical
• Cannot be opposite sex
Twins
Fraternal
Identical
Lethal genes
• Genes that result in death
• If egg contains gene, then baby will either be
miscarried, or mother will never become
pregnant
• Average person has 7
• Lethal genes are recessive, so we have the
lethal genes, but we have the dominant, so it
does not change our phenotype
Problem causing genes
• Genetic Disorder- is a disorder that is
inherited from parents and not based on the
environment of pregnancy
• These are not caused by drugs, radiation,
alcohol, smoking.
• Can be dominant or recessive, but in all cases,
they are autosomal
• Impt note: Dominant does not mean more
common
Huntington’s disease
• Rare lethal genetic disorder inherited by
autosomal dominant trait.
• Causes jerky, uncontrolled movements of the
head and limbs- results in mental
deterioration or brain damage
• No treatment. Symptoms don’t occur until
individual is between ages 30 to 50.
– Bad thing most people who have it, already
have children and pass it on to children before
they realize they have the disease
Huntington’s disease
Polydactyly
• Having more than five
fingers or toes on any
given appendage
• Is actually a dominant
trait even though it is
not common- which
means it is recessive
to actually have five
normal digits
Sickle Cell Anemia
• Sickle-cell anemia -abnormal hemoglobin causes
deformed red blood cells
• Shaped like “sickles” instead of round (frisbee)
shaped red blood cells can treat but not successful
• Inherited as an autosomal recessive trait
• Most common in African Americans originating from
Africa, and white Americans who come from around
the Mediterranean sea.
• One out of twelve African Americans have the
heterozygous form…
• Caused by an insertion or deletion of a few alleles
Muscular Dystrophy
• Muscle weakness and loss of muscle tissue, which
get worse over time.
• Can be born with it, or it can show up later in life.
• Loss in control of muscles
• Signs:
– Drooling, drooping eyelids
– Loss in muscle size-very hard to tell, because the overall
body part will appear larger, but most of the size increase
is a buildup of fat.
– Abnormally curved spine
– Difficulty walking-possible clubbed feet
– Mental retardation in severe cases
Muscular Atrophy
• Three major types:
– Disuse atrophy-comes from the inability to use a
muscle for whatever reason, possibly from injury
– Neurological atrophy-nerve damage results in the
inability to use a particular muscle, permanent
damage.
– ALS (Amyotrophic Lateral Sclerosis) or Lou
Gehrig’s disease a degenerative disorder,
inherited from family, in which the nervous system
or brain stop communicating signals to your
muscles-eventually the chest muscles will stop
working, and breathing seizes.
Cystic Fibrosis
• An inherited genetic recessive disorder in which the
body over produces mucus throughout the entire
body.
• Mucus lines every organ in the body, so this disorder
really attacks every organ you have.
• Lungs are affected first, and eventually lungs will fill
with the sticky mucus, and breathing seizes.
• Pancreas is affected also, and digestion is always
difficult.
• 1 in 25 people are heterozygous for the disorder
• Caused by a single allele mutation
Cri Du Chat syndrome
• The syndrome gets its name from the characteristic
cry of affected infants, which is similar to that of a
meowing kitten
• feeding problems because of difficulty swallowing
and sucking, low birth weight and poor growth,
severe cognitive, speech, and motor delays,
behavioral problems such as hyperactivity,
aggression, tantrums, and repetitive movements,
unusual facial features which may change over time,
excessive drooling, constipation, small head and jaw,
wide eyes, skin tags in front of eyes
• Deletion of one gene on chromosome number 5
Charcot-Marie-Tooth syndrome
• progressive loss of muscle tissue and touch sensation
across various parts of the body. Currently incurable,
this disease is one of the most common inherited
neurological disorders affecting approximately 1 in
2,500 people
• Signs:
– Loss of sensation in lower limbs
– Highly arched foot
– “stork leg”
• Unknown mutation, but we do know it is inherited
Angelman syndrome
• is a neuro-genetic disorder characterized by
severe intellectual and developmental
disability, sleep disturbance, seizures, jerky
movements (especially hand-flapping),
frequent laughter or smiling, and usually a
happy demeanor.
• On chromosome number 15, the person
inherits a normal copy of fathers genes, but
the mothers gene may be mutated, and the
mother’s overpowers the father’s.
Prader-Willi syndrome
• low muscle tone, short stature, incomplete
sexual development, cognitive disabilities,
problem behaviors, and a chronic feeling of
hunger that can lead to excessive eating and
life-threatening obesity.
• The incidence of PWS is between 1 in 25,000
and 1 in 10,000 live births.
• Similar situation as Angelmans syndrome. It is
inherited the exact same way, but this time,
the fathers mutation overpowers the mothers
normal genes on chromosome 15.
Galactosemia
• Missing enzyme that breaks down galactose
type of sugar; nervous system damage
• Cannot break down any form of milk at all,
human or animal
• Shows up within the first few days of life
• Brain malfunction, lower intelligence
• Weak motor and sensory skills
Phenylketonuria-recessive disorder
• PKU-missing enzyme that breaks down certain
chemicals that are in foodsphenylalanine into
tyrosine amino acids
• Babies born with PKU are normal at first, but once on
milk (high in Phenylalanine) is consumed, baby
develops abnormal brain function and mental
retardation.
• Now doctors perform tests right after birth, and if
baby shows signs, then they give special milk, low in
phenylalanine until brain develops treatable
• More common in whites who’s descendants are from
Norway or Sweden
Tay Sachs Disease
• Tay-sachs disease-recessive disease, where body is
missing enzyme that breaks down fat-lipid
• Fat accumulates in body resulting in blindness,
muscle deterioration, and mental retardation of the
central nervous system-brain, nerves
• Symptoms occur within a year of birth, and death
occurs before age 5.
• No treatment for disease
• More common in Pennsylvania Dutch and Jews
Diabetes in young children (juvenile
diabetes Type I diabetes)
• Diabetes-body cannot produce enough insulin
to control blood sugar
• Insulin does not reach inside the cell, nor does
glucose, so your cells are starving for sugar or
glucose.
• Signs are extreme hunger-body never feels
full, extreme thirst, and rapid weight loss
• Purposefully inject insulin inside cells
Diabetes in middle aged people
Type II diabetes
• They have higher than normal levels of insulin
and sugar in their blood. This is the form
where the body has become resistant to
insulin. So insulin does not break down sugar.
• Diabetes does not come from
overconsumption of sugar products. This is a
myth.
• Video
Prenatal studies
• Amniocentesis process of sampling amniotic
fluid to test for many things, including genetic
problems
• Ultrasound formation of a picture done
inside the womb to view the baby.
• Fetoscopy the use of an endoscope to view
internally
Chromosome Theory of Inheritance
• genes are located on chromosomes and that the
behavior of chromosomes during meiosis
accounts for inheritance patterns, which closely
parallels predicted Mendelian patterns.
– Explains those things Mendel did not understand
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Independent assortment
Segregation
Gene linkage
Crossing Over
Incomplete Dominance
Codominance