Genetics

1
Genetics
Gregor Mendel

• _________________- Austrian Monk who studied pea
  plants from 1857-1865
• - determined ½ genes come from mother and ½
  come from father
• - _____________- gene for tall is dominant over
  gene for short ( )
• -TT is
• -Tt is
• -tt is
• -homozygous ( )- same two alleles for a trait
• -heterozygous ( )- two different alleles
  for trait

dominance
recessive
tall
tall (hybrid)
short
pure
hybrid
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Punnett Square

• ________________- way to represent genetic
  crosses
• Ex A homozygous tall pea plant is crossed with a
  homozygous short pea plant
• What is the genotype (what the genes are) of the
  offspring?
• What is the phenotype (what they look like) of
  the offspring?

T
T
t
Tt
Tt
Tt
Tt
t
100 Tt
100 tall
3

• Ex A heterozygous tall pea plant is
  self-fertilized.
• What is the genotype of the offspring?
• What is the phenotype of the offspring?

T
t
T
TT
Tt
t
Tt
tt
25 TT 50 Tt 25 tt
75 Tall 25 short
4

• Incomplete Dominance- red gene and white gene
  make a _______ flower
• RR
• Rr
• rr
• Codominance- cattle with a white gene and a red
  gene have
• RR WW RW

pink
red
pink
white
½ hairs are red ½ hairs are white
red
white
roan
5

• Human Genetics-
• 1. Polygenetic inheritance- control human
  height (for example)
• 2. Linked genes- genes on
• ex OR
• 3. ____________- chromosomes that dont determine
  the sex of an individual
• 4. ________________- chromosomes that do
  determine the sex of an individual
• - two in humans (one pair)
• - females ( ) males ( )

many different genes
the same chromosome
blonde hair and blue eyes
red hair and freckles
Autosomes
Sex Chromosomes
XX
XY
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X

• 5. sex-linked traits- genes are all on the
  chromosome (__________________, _______________,
  Duchenne muscular dystrophy, and night blindness)
• (X)- normal X (X-)- abnormal X
• ( )- normal female ( )- normal male
• ( )- abnormal female ( )- abnormal
  male
• ( )- carrier female
• http//www.toledo-bend.com/colorblind/Ishihara.htm
  l
• ex a color blind man and a normal female have
  children. What are chances his sons will be
  colorblind?
• What are chances his daughters will be
  colorblind?
• ex A carrier female and a normal male have
  children. What are the chances her sons would be
  colorblind?

color-blindness
hemophilia
XX
XY
X-Y
X-X-
X-X
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• 6. nondisjunction- the addition or loss of a
• -takes place when chromosomes that normally
  separate during meiosis
• a. ____________________- caused by
  nondisjunction of chromosome 21 (person has 3
  chromosome 21)
• -cause mental retardation and physical
  abnormalities
• b. _____________________- female with only one X
• -underdeveloped sexual characteristics
• c. _____________________- male with XXY
• - underdeveloped sex organs infertility

whole chromosome
remain together
Downs Syndrome
Turners Syndrome
Klinefelters Syndrome
8

• 7. Autosomal genetic disorders- problems with
  autosomes (not on )
• a. sickle-cell disease (anemia)- (
  )
• -red blood cells have an
• -causes the red blood cells to
• -cant carry as much
• -caused by a change in one base (out of about
  900) in the gene that controls the production of
  one polypeptide chain in the
• (mutation in DNA sequence)
• -carriers are resistant to
• -people with the disease live to early
  adulthood
• -most common in

X or Y
recessive
abnormal sickle shape
clump block blood vessels causing severe pain
oxygen
hemoglobin molecule
malaria
Africans
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• b. phenylketonuria (PKU)- (recessive)
• -causes the development of
• -body cant make necessary for the normal
  metabolism of phenylalanine (an amino acid)
• - can be controlled by
• -routine tests done at birth
• c. Tay-Sachs- (recessive)
• -deterioration of causing death in
  childhood
• -accumulation of fatty material as a result of
  the inability to synthesize a specific
• -most common in people of Central
  European descent.

mental retardation
an enzyme
diet
nervous tissue
enzyme
Jewish
10

• d. Cystic Fibrosis- (recessive)
• -glands produce a thick mucus that clogs and
  damages the
• -with treatment children can live to early
  adulthood
• -the most common fatal genetic disease in
  white Americans
• e. Huntingtons Disease- (dominant)
• -causes a progressive breakdown of leading
  to death
• - ,but symptoms dont appear until a person
  is over 30

lungs
brain cells
Fatal
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• 8. Causes of Mutations-
• a. random errors in
• (occur naturally at certain low rates in
  populations)
• b. ____________- factors in the environment that
  causes mutations.
• ex _______,_________________,________,______
  
• chloroform, mustard gas, formaldehyde, benzene

replication
mutagens
UV light
X-rays
radioactive substance
asbestos
12

• 9. Studying human heredity-
• Difficult for the following reasons
• 1.
• 2.
• 3.

time between generations is too long
number of offspring is small
no controlled experiments are possible
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Pedigree Chart

• ______________- diagram that shows the presence
  or absence of a particular trait in each member
  of each generation
• -genetic counselor can work to determine
  genetics of past generations

14

• 10. Detecting Genetic Disorders-
• a. _____________- chemical analysis of body
  fluids such as blood and urine
• b. _____________- a cell undergoing mitosis is
  photographed (photograph is enlarged) and the
  chromosomes are cut out, arranged in pairs, and
  compared with a normal human karyotype

Screening
Karyotyping
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• c. amniocentesis- a long needle is inserted into
  the ______________ of a woman who is about 16
  weeks pregnant. A sample of fluid, with shed
  cells from the fetus, is removed. Cells are grown
  and checked for abnormalities after 4 more weeks.
  Cells are checked for

amniotic sac
genetic disorders
16

• d. chorionic villus sampling- sample of chorion
  (part of the ) is removed for
  examination. The cells of the chorion are
  identical to those of the fetus. Can be done
  earlier than amniocentesis.
• e. Cordocentesis- a needle is used to remove
  blood from the umbilical cord and the
  chromosomes of the blood cells are examined
• f. _____________- uses high frequency
• sound waves to produce an image
• of the fetus. Can detect abnormalities
• of bone, muscle, heart
• g. Fetoscopy- a needle-thin tube containing a
  viewing scope is inserted into the uterus. The
  fetus can be observed, blood and cell samples
  may be taken by inserting special tools through
  the endoscope.

placenta
Ultrasound