Genetics

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Genetics

• Inheritance of Traits

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Gregor Mendel

• 1822 1884
• Born to peasant parents
• Ordained a priest in 1847
• Studied physics and natural science 1851-1853
• 1857(?) began pea experiments

http//www.jic.ac.uk/germplas/pisum/zgs4f1.gif
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Inheritance

• Children resemble their parents because they
  directly inherit traits from them
• Parts of DNA are expressed, and these are called
  genes (note that geneticists also refer to
  sequences not expressed as genes)
• Genes are not always identical and each is
  referred to as an allele
• One gene may have many alleles or variations of
  that genes ultimate function

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Mendels Peas

• Began with plants that only produced each of
  these only spherical or dented seeds, only
  yellow or green seeds, only purple or white
  flowers (etc.)

http//mac122.icu.ac.jp/gen-ed/mendel-gifs/03-mend
el-characters2.JPG
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Mendels Peas

• Crossed a wrinkled with a spherical seed plant
• Crossed a yellow with a green seed plant
• Results?
• Dominant and recessive genes

http//www.wwnorton.com/college/anthro/evolve4/ch/
02/2_1.jpg
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Punnett Squares

• Remember during meiosis that 1 cell replicates
  DNA, the pairs separate, then the original and
  copy of DNA separates to 4 cells
• The Punnett reflects a single mother and single
  father germ cells possibilities

http//www.biologie.uni-hamburg.de/b-online/librar
y/onlinebio/mono2.gif
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Punnett Squres

• Help to determine chance of inheriting a specific
  allele
• Genes are randomly assorted

http//courses.bio.psu.edu/fall2005/biol110/tutori
als/tutorial4_files/fig_14_8.gif
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Human Genetic Conditions

• Use of Mendelian genetics can determine the
  likelihood of inheriting or carrying a dangerous
  allele like Huntington's disease

http//www.daviddarling.info/images/autosomal_domi
nant.jpg
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Genetic Disorders Single Gene

• Cystic Fibrosis defective gene 7
• protein produced normally helps salt (sodium
  chloride) move in and out of cells
• if protein doesn't work correctly movement is
  blocked and an abnormally thick sticky mucous is
  produced on the outside of the cell
• cells most seriously affected by this are the
  lung cells
• mucous clogs the airways in the lungs, and
  increases the risk of infection by bacteria

http//www.sjsu.edu/faculty/gerstman/StatPrimer/au
torecessive.jpg
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Genetic Disorders Single Gene

• Sickle Cell Anemia single nucleotide substitution
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• prevents oxygen from reaching the spleen, liver,
  kidneys, lungs, heart, or other organs, causing a
  lot of damage
• Without oxygen, the cells that make up these
  organs will begin to die
• As a result, these patients often experience
  frequent infections
• Many others

http//library.thinkquest.org/06aug/00440/images/s
icklecell.jpg
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Genetic Disorders - Chromosomal

• Down Syndrome
• Turner Syndrome
• Klinefelter Syndrome
• Cri du chat Syndrome
• Williams Syndrome
• Many others

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Down Syndrome triploidy 21

• Distinctive features
• flat face
• small broad nose
• abnormally shaped ears
• large tongue
• upward slanting eyes with small folds of skin in
  the corners
• respiratory infections
• gastrointestinal tract obstruction (blocked
  digestive tract)
• Leukemia
• heart defects
• hearing loss
• hypothyroidism
• various eye abnormalities
• moderate to severe mental retardation

http//www.ucl.ac.uk/ucbhjow/bmsi/lec7_images/47_
xx_21.gif http//www.faqs.org/health/images/uchr_0
7_img0706.jpg
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Turner Syndrome missing X

• Distinctive features
• shorter than normal
• may fail to start puberty when they should
  because ovaries (which produce eggs, as well as
  the sex hormones estrogen and progesterone) fail
  to develop properly.
• have a stocky appearance
• arms that turn out slightly at the elbow
• receding lower jaw
• short webbed neck
• low hairline at the back of the neck
• lymphedema (swelling of hands and feet)
• heart and/or kidney defects
• high blood pressure
• infertility

https//images1.clinicaltools.com/images/gene/kary
otypes/turnersyndromexnoy.jpg http//learn.genetic
s.utah.edu/content/disorders/whataregd/turner/imag
es/turner_person.jpg
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Klinefelter Syndrome - XXY

• Distinctive features
• develop as males
• often tall
• don't develop secondary sex characteristics, such
  as facial hair or underarm and pubic hair
• extra X chromosome primarily affects the testes,
  which produce sperm and the male hormone
  testosterone

http//images2.clinicaltools.com/images/gene/triso
myxxy.jpg http//learn.genetics.utah.edu/content/d
isorders/whataregd/klinefelter/images/kleinfelter_
person.jpg
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Cri du chat Syndrome deletion 5

• Distinctive features
• small head (microcephaly)
• an unusually round face
• a small chin
• widely set eyes
• folds of skin over their eyes
• a small bridge of the nose.
• heart defects
• muscular or skeletal problems
• hearing or sight problems

http//www.biology.iupui.edu/biocourses/N100/2K2hu
mancsomaldisorders.html http//www.findhealer.com/
glossary/images/criduchat.gif
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Williams Syndrome missing part 7

• Distinctive features
• mental retardation
• heart defects
• unusual facial features (small upturned nose,
  wide mouth, full lips, small chin, widely spaced
  teeth)
• low birth weight
• failure to gain weight appropriately
• kidney abnormalities, and low muscle tone
• behaviors, such as hypersensitivity to loud
  noises and an overly outgoing personality.

http//medgen.genetics.utah.edu/photographs/diseas
es/high/williams_syndrome_original1.gif
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Multifactoral Genetic Disorders

• Alzheimers Disease
• People who have the disorder slowly lose their
  ability to think clearly. At first, they may
  forget words or names, or have trouble finding
  things. As the disorder worsens, they may forget
  how to do simple tasks (such as walking to a
  friend's house or brushing their hair). Some
  people with Alzheimer's also feel nervous or sad

http//2.bp.blogspot.com/_kQrramY7bs4/RvB6HmEZFCI/
AAAAAAAACQU/b6sysujyPKU/S420/alzheimer.normal.brai
n.jpg
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More Mendel

• Besides dominance/recessive, there is
• incomplete dominance
• co-dominance
• multiple alleles
• polygenic inheritance
• pleiotrophy

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Definitions

• Phenotype the expression of the genes what
  the organism looks like and how it functions
• Genotype genes inherited the alleles of the
  genes whether expressed or not
• For example, if an organism inherits both the
  dominant and recessive alleles, it would have the
  phenotype of the dominant allele, but the
  genotype would be both dominant and recessive

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Incomplete Dominance

• Organism receives both alleles, in this case, red
  flower and white flower. The phenotype is
  intermediate to red and white - pink

http//dwb4.unl.edu/Chem/CHEM869N/CHEM869NLinks/ww
w.rrz.uni-hamburg.de/biologie/b_online/ge08/01.gif
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Co-dominance

• When alleles share fully in the expression of the
  gene. For example, our blood types A, B, AB and
  O.

http//www.agen.ufl.edu/chyn/age2062/lect/lect_10
/bloodtyp.gif
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Multiple Alleles

• Follows same rules as other inheritance
• Frequency of the allele can change with the
  population

http//static.icr.org/i/articles/imp/imp-3647-Alle
le20freq.jpg http//1.bp.blogspot.com/_DZH2cmCooi
s/Rdyly-4z72I/AAAAAAAABAg/Z8LaotoW8s4/s400/ABO_ant
igens.jpg
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Polygenic Inheritance

• But we dont inherit one gene
• Estimates range from 20,000 to 40,000 coding genes

http//porpax.bio.miami.edu/cmallery/150/mendel/c
8.14x13.polygenic.jpg http//www.diversitycourses.
co.uk/diversity3.jpg
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Pleiotrophy

• Hemophilia single gene influence multiple
  phenotypic traits
• Lacking protein in blood
• Excessive bruising
• Pain and swelling in the joints
• Vision loss
• Anemia
• Fatigue
• Neurological problems if bleeding occurs in brain

http//www.friesian.com/history/impfamil.jpg http
//upload.wikimedia.org/wikipedia/commons/a/a3/Xlin
kRecessive.jpg
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Gender

• Is it a boy or girl?
• Mom always has XX
• Dad has XY
• Dads sperm cells two X and two Y (remember,
  DNA replicates first)
• Moms egg cells four X cells

http//www.csupomona.edu/biology/bio110/inherit/f
ig10.gif
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Not true for all species

• Some species, the female has different
  chromosomes and the male has the identical
  chromosomes. In this system, the chromosomes are
  referred to as W and Z
• Some species gender is determined by temperature
• Some species can change from male to female or
  vice versa
• Some species, only queens and drones reproduce
• Some species are both male and female
  hermaphrodite
• The term "hermaphrodite" derives from
  Hermaphroditus, the son of Hermes and Aphrodite,
  who fused with the nymph Salmacis, and thus
  possessing physical traits of both sexes.

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Questions?
BJ Shaw Panochthus frenzelianus American Museum
of Natural History 2004