Transcript Fundamentals of Genetics Gregor Mendel

Fundamentals of
Genetics
Gregor Mendel
 The father of modern genetics
– the study of heredity
 Experimented with garden
peas in the 1800s
 He produced a hybrid pea
plant – an organism that
receives different genetic
information from each parent in his experiments
 He looked at only a few
different traits, they were –
seed shape, color, pod shape,
pod color, flower position and
height.
Gregor Mendel


He took 2 pure bred plants – the parent contains only one gene for each
genetic trait – and crossed them.
After performing his experiment he found
 Dominant trait - the trait that is expressed – was always expressed.
Usually shown as a capital letter.
 Recessive trait – the trait that is only when there is two of them- usually
shown as a lower case letter.
Vocabulary Words
 Before beginning, a vocabulary word.
 Alleles - different versions for
the same trait.
Example: T (tall) and t (short) are alleles for the
gene that controls height of the pea plant.
 Homozygous – having two (2) of the same
alleles for the same trait.
Example – TT – homozygous dominant
– tt – homozygous recessive
 Heterozygous – having two (2) different
alleles for the same trait.
Example – Tt
More Vocabulary Words
 Genotype – the genes that an organism
possesses
 Phenotype – the way the genes are
expressed (how the organism looks)
 Can you answer this question?
How does your genotype control your
phenotype.
Mendel’s Laws
 1. Law of Segregation each pair of alleles
segregates, or separates
during meiosis.
 2. Law of Dominance –
An allele that always
controls a trait is called the
dominant allele. An allele
that is hidden when paired
with a dominant allele is
called a recessive gene
Mendel’s Laws
 3. Law of
Independent
Assortment – the
association of traits
in a parent does not
seem to matter.
Mendel concluded
that traits, or factors,
are inherited
independently.
More with the
Fundamentals of
Genetics
Since Mendels’ time, Biologists
have discovered other more
complex patterns of inheritance and
expressions. Because of these new
discoveries the scientific community
has extended his laws.
Incomplete dominance
 Incomplete dominance ocures when a
heterozygote shows the phenotype that is
intermediate between the two homozygous
phenotypes. ( Neither homozygous dominant
nor homozygous recessive is fully expressed)
Codominance
• Another form of
intermediate
inheritance is
codominance.
• Codominance is when
both alleles in the
heterozygote express
themselves fully.
Polygenic Traits
 When a trait is
controlled by two or
more gene pairs it is
called polygenetic
traits.
 Human eye color and
hair color are
examples of
polygenic traits
Multiple Alleles
 When there are
three or more
alleles for a trait
in the population.
 Human blood
type genes exist
as multiple
alleles.
Pedigree Charts
The family tree of genetics
What is a Pedigree?
 A pedigree is a chart of the genetic history
of family over several generations.
 Scientists or a genetic counselor would find
out about your family history and make this
chart to analyze.
Constructing a Pedigree
 Female
 Male
Connecting Pedigree
Symbols
Examples of connected symbols:
 Fraternal twins
 Identical twins
Connecting Pedigree
Symbols
Examples of connected symbols:
 Married Couple
 Siblings
Example
 What does a pedigree chart look like?
Summary
 Pedigrees are family trees that explain
your genetic history.
 Pedigrees are used to find out the
probability of a child having a disorder in
a particular family.
 To begin to interpret a pedigree,
determine if the disease or condition is
autosomal or X-linked and dominant or
recessive.
Human Genetic Disorders
Sickle Cell Anemia
Sickle Cell anemia is an inherited red blood cell
disorder. Normal red blood cells are round like
doughnuts, and they move through small blood tubes
in the body to deliver oxygen.
Sickle red blood cells become hard, sticky and shaped
like sickles used to cut wheat. When these hard and
pointed red cells go through the small blood tube, they
clog the flow and break apart. This can cause pain,
damage and a low blood count, or anemia.
Hemophilia
• Hemophilia is a hereditary
(X-linked, recessive) blood
disorder that affects the
proper clotting of blood.
• It is a disease that affects
males much more
frequently (1 in 10,000)
than females (1 in
100,000,000).
• This occurs because a
critical blood-clotting gene
is carried on the X
chromosome.
Albinism
• a disorder that occurs
when a person inherits
various genes that are
defective in their ability to
make the pigment melanin
• Melanin is the main
substance that determines
a person's skin, hair, and
eye color.
• In the United States,
albinism affects
approximately 1 in 17,000
http://www.humanillnesses.com/original/Apeople.
As/Albinism.html
Cystic Fibrosis
Tay Sachs Disease
• caused by a missing
enzyme that results in
the accumulation of a
fatty substance in the
nervous system
• causes disability and
death
• common among
Jewish people of
Eastern European and
Russian (Ashkenazi) Section of brain tissue from patient with TaySachs disease. (© 1992 IMS Creative. Custom
origin
Medical Stock Photo, Inc.)
Colorblindness
 non-fatal health condition
which is characterized by
difficulty in identifying and
recognizing different colors
and shades
 may either be caused due to
genetic reasons or may be
acquired during the later
stages of life due to diseases
effecting the optic nerve or
retina.
 Inherited color vision problem
http://www.scumdoctor.com/diseaseis usually linked to the X- prevention/eye-diseases/Symtoms-Of-Colorchromosome and is passedBlindness.html
from a mother to her son.
Adrenoleukodystrophy
(Lorenzo’s Oil)
•
•
The condition results in the
buildup of very-long-chain fatty
acids in the nervous system,
adrenal gland, and testes, which
disrupts normal activity
There are three major categories
of disease:
– Childhood cerebral form -- appears
in mid-childhood (at ages 4 - 8)
– Adrenomyelopathy --occurs in men
in their 20s or later in life
– Impaired adrenal gland function
(called Addison disease or
Addison-like phenotype) -- adrenal
gland does not produce enough
steroid hormones
Hereditary Deafness
 hearing loss that is
inherited or passed
down from parents to
their children
 may be inherited
from one or both
parents who may or
may not have a loss
of hearing
themselves
http://www.medhelp.org
http://www.boystownhospital.org/Images/Hearing/info/xlinkrec.gif
Coffin-Lowry Syndrome
 a condition that affects
many parts of the body
 Males typically have
severe to profound
intellectual disability and
delayed development
 women may be
cognitively normal, or
they may have
intellectual disability
ranging from mild to
profound
http://ghr.nlm.nih.gov/condition=coffinlowrysyndrome
http://jmg.bmj.com/content/vol39/issue10/images/large/mg02984.f3.jpeg
Achondroplasia (dwarfism)
 characterized by
abnormal bone
growth that results in
short stature with
disproportionately
short arms and legs,
a large head, and
characteristic facial
features with frontal
bossing and mid-face
hypoplasia
http://www.geneclinics.org/profiles/achondroplasia/details.html
http://www.mun.ca/biology/scarr/Achondroplasia_in_humans.htm
Fragile X Syndrome
 Fragile X syndrome
is the most common
inherited cause of
mental impairment.
 The syndrome
occurs in
approximately 1 in
3600 males and 1 in
4000 to 6000
females.
http://www.fragilex.org/html/summary.htm
 Leading causes of
http://geneticsmodules.duhs.duke.edu/Design/images/fragileX.jpg
Huntington’s Disease
 results from genetically
programmed degeneration of
brain cells, called neurons, in
certain areas of the brain
 This degeneration causes
uncontrolled movements, loss
of intellectual faculties, and
emotional disturbance.
 HD is a familial disease,
passed from parent to child
through a mutation in the
normal gene
http://pet.radiology.uiowa.edu/webpage/Research/CaseStudies/BrainHuntingtonsDisease.html
Marfan Syndrome (Alton
Giant)
 disorder of connective tissue
which causes skeletal defects
typically recognized in a tall,
lanky person
 may exhibit long limbs and
spider-like fingers, chest
abnormalities, curvature of
the spine and a particular set
of facial features including a
highly arched palate, and
crowded teeth
 the most significant of the http://www.nytimes.com/imagepages/2007/08/01/health/adam/9611Marfansyndrome.html
defects in the syndrome are
cardiovascular abnormalities,
which may include
Trisomy 13 (Edward’s
Syndrome)



chromosomal condition
associated with severe
intellectual disability and physical
abnormalities in many parts of
the body
Individuals with trisomy 13 often
have heart defects, brain or
spinal cord abnormalities, very
small or poorly developed eyes,
extra fingers and/or toes, an
opening in the lip (a cleft lip) with
or without an opening in the roof
of the mouth (a cleft palate), and
weak muscle tone
many infants with trisomy 13 die
http://ghr.nlm.nih.gov/condition=trisomy13
within their first
days or weeks of
life.
http://www.livingwithtrisomy13.org/Trisomy-13_KailaRecent.jpg
Phenylketonuria (PKU)
 inherited disorder that
increases the levels of a
substance called
phenylalanine in the blood
 a building block of proteins
(an amino acid) that is
obtained through the diet
 found in all proteins and in
some artificial sweeteners
 If PKU is not treated,
phenylalanine can build up to
harmful levels in the body, http://www.dshs.state.tx.us/newborn/images/PKU_untreated.jpg
causing intellectual disability
http://ghr.nlm.nih.gov/condition=phenylketonuria
and other serious health
problems
Rett Syndrome
 childhood
neurodevelopmental
disorder that affects
females almost
exclusively
 Loss of muscle tone is
usually the first symptom
 Other early symptoms
may include problems
crawling or walking and
diminished eye contact.
http://www.scoliosisjournal.com/content/figures/1748-7161-2-15-1-l.jpg
http://www.ninds.nih.gov/disorders/rett/rett.htm
Klinefelter Syndrome (XXY
Male)

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
condition that occurs in men who
have an extra X chromosome in
most of their cells.
The syndrome can affect
different stages of physical,
language and social
development.
The most common symptom is
infertility.
Because they often don't make
as much of the male hormone
testosterone as other boys,
teenagers with Klinefelter's
syndrome may have less facial
and body hair and may be less
http://www.healthofchildren.com/images/gech_0001_0002_0_img0156.jpg
muscular than other boys.
They may
have trouble using
http://www.nlm.nih.gov/medlineplus/klinefelterssyndrome.html
Turner Syndrome
 disorder caused by the loss of
genetic material from one of
the sex chromosomes.
 affects approximately 1 out of
every 2,500 female live births
worldwide.
 broad spectrum of features,
from major heart defects to
minor cosmetic issues.
 Almost all people with Turner
syndrome have short stature
and loss of ovarian function,
but the severity of these
http://turners.nichd.nih.gov/
problems varies considerably
amongst individuals.
Progeria (premature
aging)
 rare condition that is
remarkable because its
symptoms strongly resemble
normal human aging, but
occur in young children.
 Ninety percent of children with
progeria have a mutation on
the gene that encodes the
protein lamin A.
 Progeria usually occurs
without cause.
 It is not seen in siblings of http://images.google.com/images?gbv=2&hl=en&sa=3&q=progeria
affected children, although -in very rare circumstances -http://www.nlm.nih.gov/medlineplus/ency/article/001657.htm
more than one child in a
Xeroderma Pigmentosum
 an autosomal recessive
genetic disorder.
 characterized by
abnormal pigmentation
on the Sun exposed
areas of the skin
 extreme sensitivity of the
skin to Sunlight and
marked predisposition to
skin cancer.
 In some cases growth
and mental retardation
are also associated with
http://phobos.ramapo.edu/~pbagga/xpcs.htm
Gaucher Disease
 inherited metabolic
disorder in which
harmful quantities of
a fatty substance
called
glucocerebroside
accumulate in the
spleen, liver, lungs,
bone marrow, and
sometimes in the
brain.
http://www.ninds.nih.gov/disorders/gauchers/gauchers.htm
http://history.nih.gov/exhibits/genetics/images/sect3/3-sm.jpg
Prader-Willi Syndrome
 a problem in their
hypothalamus, a part of the
brain that normally controls
feelings of fullness or
hunger. As a result, they
never feel full and have a
constant urge to eat that they
cannot control.
 Most cases of Prader-Willi
syndrome result from a
spontaneous genetic error in
genes on chromosome 15
that occurs at conception. In
very rare cases, the mutation
is inherited.
http://www.nichd.nih.gov/health/topics/Prader_Willi_Syndrome.cfm
http://www.scotland.gov.uk/Resource/Img/54357/0009794.jpg
Duchenne Muscular
Dystrophy

a rapidly-worsening form of
muscular dystrophy
 caused by a defective gene for
dystrophin (a protein in the
muscles)
 males are more likely to develop
symptoms than are women
 The sons of females who are
carriers of the disease (women
with a defective gene but no
symptoms themselves) each
have a 50% chance of having the
disease
 The daughters each have a 50%
chance of being carriers.
 occurs in approximately 1 out of
every 3,600 male infants
http://www.nlm.nih.gov/medlineplus/ency/article/000705.htm
http://www.dinf.ne.jp/doc/english/global/david/dwe002/dwe002g/dwe00212g01.gif
Down Syndrome
 is set of mental and physical
symptoms that result from
having an extra copy of
Chromosome 21.
 Normally, a fertilized egg has
23 pairs of chromosomes.
 In most people with Down
syndrome, there is an extra
copy of Chromosome 21 (also
called trisomy 21 because
there are three copies of this
chromosome instead of two),
which changes the body’s
and brain’s normal
http://www.nichd.nih.gov/health/topics/Down_Syndrome.cfm
development.
http://www.miscarriage.com.au/images/pages/t21karyo.jpg
Unusual
Inherited Disorders
Werewolf
Syndrome
Manuel
Aceves
Hirsute Man
German, c. 1580
It is a portrait of
Petrus Gonsalvus.
Born in 1556, he came
as a child to the court
of the French King
Henry II, who had him
trained and educated.
Children of Petrus Gonsalvus.
Brachydactly
Syndactyly
Polydactyly
Fugate Family with rare blood disease called
(methemoglobinemia)
Kentucky Blue People
Fugate Family pedigree
Kentucky Blue People