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The family tree of genetics
I
II
III
 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.
 Female
 Male
Examples of connected symbols:
 Married Couple
 Siblings
 What does a pedigree chart look like?
 Affected
 Carrier
 Deceased
or
Determine if the pedigree chart shows an
autosomal or X-linked disease.
1.

If most of the males in the pedigree are affected the
disorder is X-linked

If it is a 50/50 ratio between men and women the
disorder is autosomal.
 Is it Autosomal or X-linked?
 Autosomal
2.
Determine whether the disorder is dominant or
recessive.
 If the disorder is dominant, one of the
parents must have the disorder.
 If the disorder is recessive, neither parent
has to have the disorder because they can
be heterozygous.
 Dominant or Recessive?
 Dominant
 Dominant or Recessive?
 Recessive
 A karyotype is an ordered display of an individual’s
chromosome.
 Scientist take a picture of the chromosomes during
metaphase.
 Each chromosome is paired with its homologue.
 Is used to detect abnormalities.
 Different # for
Homologous
different species
Chromosomes
Full set =
2N=Diploid
are the sets of
 N= Haploid
pair
each
# pairs
 1 pair from mother
 1 pair from father
 Humans= 23 pairs or
 46 total
Autosomes = # 122 for all traits
except sex
Sex chromosomes=
Pair # 23 XX(female) or
XY(male)
 Nondisjunction is the failure of chromosomes to
separate correctly (in meiosis I)
Nondisjunction causes:

1.
A gamete with an extra chromosome (n+1)

Trisomy
2. A gamete missing a chromosome (n-1)
 Monosomy
More than
one type of
allele for a
trait
Example:
Blood Type
TYPES:
A
B
AB
O
IAIA, IAi
B
B
B
I I ,I i
IAIB
ii
 Cystic Fibrosis
 Caused by a recessive allele
 Missing protein causes mucus build up in places like the
lungs
 Most common among Caucasians
 Sickle Cell Anemia
 Caused by a co-dominant allele
 Altered protein changes the shape of red blood cells
 Most common among African Americans
 Heterozygous condition is resistant to malaria
 Tay-Sachs
 Caused by a recessive allele
 Missing enzyme causes lipid build up in the brain
(death by age 4)
 Most common among eastern European Jewish
population
 Huntington’s Disease
 Caused by a dominant allele
 Late-onset of symptoms (age 40) result in the
deterioration of nervous system
 Phenylketonuria (PKU)
 Caused by a recessive allele
 Missing enzyme prevents the break down of
phenylalanine (can cause brain damage)
 If caught early, an altered diet can prevent the damage
 Down Syndrome
 Trisomy 21(3 copies of chrom. 21)
 Most common serious birth defect in the US
 Syndrome includes characteristic facial features, short
stature, heart defects, and intellectual disabilities
 Kleinfelter’s Syndrome
 XXY
 Have abnormally small testes; are sterile; some feminine
secondary sex characteristics; normal intelligence
 Extra Y
 XYY
 No obvious differences, usually tall
 Metafemales
 XXX
 Limited fertility, possible intellectual disability
 Turner Syndrome
 XO
 Is the only viable monosomy
 Short stature; fail to develop secondary sex
characteristics; internal sex organs do not mature
making the sterile
 Restriction enzymes – enzymes used to cut DNA at
certain point
 Recombinant DNA – DNA that has been recombined
from different sources
 Environmental impact – traits are determined by
genes and the influence of the environment