Transcript Human Genetics Notes Continued Honors Bio

Non – Mendelian Genetics
*Not all traits follow Mendel’s rules!
*Not all traits follow the rules!
• Some don’t have dominance!
• Some have more than one dominant trait!
• Some are regulated by many genes, not just
one!
• Some are dependent on your gender!
– Sorry guys :(
Incomplete dominance
• Heterozygote shows a blended phenotype
– Example:
• RR = red flowers
• WW = white flowers
• RW = pink flowers
– make 50% less color
RR
RW
WW
Incomplete dominance
P
X
true-breeding
red flowers
true-breeding
white flowers
100% pink flowers
F1
100%
generation
(hybrids)
self-pollinate
25%
red
F2
generation
50%
pink
25%
white
1:2:1
Co-dominance
• 2 alleles affect the phenotype equally &
separately
– not blended phenotype
– Example: ABO blood groups
• 3 alleles
– IA, IB, i
– IA & IB alleles are co-dominant
» Both expressed
– i allele recessive to both
What is the phenotype?
A
•I i
• I Bi
• IAIA
A
B
A
A
B
•I I
AB
B
B
•I I
B
• ii
O
Sex-linked Traits
• First 22 pairs of
chromosomes are
called AUTOSOMAL
CHROMOSOMES
• Last pair is the SEX
CHROMOSOMES
– Females: XX
– Males: XY
Sex – Linked Traits
• Always 50/50 chance of having a boy or a girl
X
Y
X
XX
XY
X
XX
XY
Human X chromosome
Duchenne muscular dystrophy
Becker muscular dystrophy
• Sex-linked
– usually means
“X-linked”
– more than
60 diseases on
genes on X
chromosome
Chronic granulomatous disease
Retinitis pigmentosa-3
Norrie disease
Retinitis pigmentosa-2
Ichthyosis, X-linked
Placental steroid sulfatase deficiency
Kallmann syndrome
Chondrodysplasia punctata,
X-linked recessive
Hypophosphatemia
Aicardi syndrome
Hypomagnesemia, X-linked
Ocular albinism
Retinoschisis
Adrenal hypoplasia
Glycerol kinase deficiency
Ornithine transcarbamylase
deficiency
Incontinentia pigmenti
Wiskott-Aldrich syndrome
Menkes syndrome
Androgen insensitivity
Sideroblastic anemia
Aarskog-Scott syndrome
PGK deficiency hemolytic anemia
Anhidrotic ectodermal dysplasia
Agammaglobulinemia
Kennedy disease
Charcot-Marie-Tooth neuropathy
Choroideremia
Cleft palate, X-linked
Spastic paraplegia, X-linked,
uncomplicated
Deafness with stapes fixation
PRPS-related gout
Pelizaeus-Merzbacher disease
Alport syndrome
Fabry disease
Lowe syndrome
Immunodeficiency, X-linked,
with hyper IgM
Lymphoproliferative syndrome
Hunter syndrome
Hemophilia B
Hemophilia A
G6PD deficiency: favism
Drug-sensitive anemia
Chronic hemolytic anemia
Manic-depressive illness, X-linked
Colorblindness, (several forms)
Dyskeratosis congenita
TKCR syndrome
Adrenoleukodystrophy
Adrenomyeloneuropathy
Emery-Dreifuss muscular dystrophy
Diabetes insipidus, renal
Myotubular myopathy, X-linked
Albinism-deafness syndrome
Fragile-X syndrome
Lesch-Nyhan syndrome
HPRT-related gout
Human X-chromosome
• Women have 2 copies
– Getting one “bad” X has little/no effect
• other X will compensate
• Men have only 1 copy
– Getting one bad X chromosome gives them the
disease
• No backup X
• Ex. Colorblindness
– Hemophilia
– Balding
Hemophilia
sex-linked recessive
HY
HH
XHHh
Xh x X
XH
female / eggs
male / sperm
XH
XH
Y
XH XH
XH Y
XH Xh
Xh
XH
Xh
XH Xh
XhY
carrier
disease
XHY
Y
Pedigrees
• Like a family tree
• Tracks traits through generations by
recognizing phenotype
Pedigrees
•
represent females
•
represents males
• Shading represents “affected individual”
• Half shading (if present) represents carrier
Polygenic Inheritance
• Traits with more than one gene controlling
their expression
Environmental Effects on Traits
• Some genes are activated by the environment
– Ex: Fur color in animals
Chromosomal Abnormalities
• Problems can arise when chromosomes are
changed
–
–
–
–
Too many
Too few
Parts missing
Parts added
Changes in Chromosome Number
• Occurs during meiosis
– NONDISJUNCTION: chromosomes are not equally
pulled to new cells
Chromosomal Mutations
• DELETION – part of a chromosome deleted
• DUPLICATION – part of a chromosome copied
Chromosomal Mutations
• INVERSION - Part of a chromosome gets
reversed
• TRANSLOCATION – part of one chromosome
gets swapped with another
Karyotypes
• Used to ID chromosomal abnormalities
Normal Karyotype
•
•
•
•
2 copies of each autosomal chromosome
2 X’s in females; 1 X, 1 Y in males
No deletions or insertions
No extra copies