Transcript Genetics and Pedigrees Bio I

Genetics &
Pedigrees
Gregor Mendel
Vocabulary
 Genetics-the study of inheritance or
heredity
 Inheritance- the passing on of traits
from one generation to the next
 Trait/Characteristic- any factor used
to describe or distinguish
Vocabulary
 Acquired trait- a trait that
appears in your lifetime. You
were not born with it. It cannot
be passed onto offspring
 Inherited trait- a trait that you
were born with. You can pass it
onto offspring
 Gene- a segment of DNA that
controls/influences our physical/
psychological/ intellectual/
emotional traits
 a segment of DNA that codes for the
production of a protein
 Allele- a specific expression of a
gene.
 You inherit one allele from each
parent for a specific trait.
You have 2 alleles for
each gene
1 from your Mom
1 from your Dad
 Homozygous- both alleles for a
specific trait are identical (purebred)
 -Homozygous dominant (Ex. BB)
 -Homozygous recessive (Ex. bb)
 Heterozygous- both alleles for a
specific trait are different (hybrid)
 Ex. Bb
 Genotype- Combination of
alleles; genetic make-up
 Homozygous BB, Heterozygous Bb
 Phenotype- Physical appearance;
what that combination of alleles
looks like
 Blue or Brown
Dominant vs.
Recessive
Traits/Disorders
Dominant
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Oval face shape
Widow’s peak
Separated eyebrows
Dimples
Free earlobe
Almond eye shape
Freckles
Tongue roller
Recessive
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Square face shape
Straight hairline
Unibrow
No dimples
Attached earlobe
Round eye shape
No freckles
Non-roller
Dominant
 Inability of tongue
folding
 Mid-digit finger hair
 Straight thumb
 Dark skin
 Near-sidedness
 Far-sidedness
 Bent pinky finger
Recessive
 Ability of tongue
folding
 No hair
 Hitch-hiker thumb
 Fair skin
 Normal vision
 Normal vision
 Straight pinky finger
Dominant trait/disorder
 If B= brown hair
 And b= blonde hair
 Then:
 BB= brown hair
 Bb= brown hair
 bb= blonde hair
 The heterozygous individual
shows the trait
 Dominance- in the heterozygous
genotype, the allele expressed in the
phenotype is dominant; the allele that
is not expressed is recessive.
 Dominance is NOT determined by how
often the trait appears (frequency of
occurrence) in the population!
Recessive trait/disorder
 A carrier is heterozygous (Bb)
 But now, that recessive trait is
“hidden” by the dominant allele
 Therefore, the heterozygous individual
does not show that recessive trait
 They carry it and can pass that
recessive allele on to children
Pedigree
a family tree that traces a
trait through generations
Recessive trait/disorder
 With recessive traits, carriers
are represented in a pedigree as
a ½-shaded circle/square…
When drawing a pedigree,
you must always know if
the trait is dominant or
recessive before shading
individuals and
determining genotypes and
phenotypes