Loci and the Human
Karyotype
Honors Biology
Unit 5
2012-2013
Chromosomes
—  Karyotype:
◦  ordered display of an individual’s
chromosomes.
◦  Collection of chromosomes from mitotic
cells.
◦  Staining can reveal visible band patterns, gross
anomalies.
Karyotyping
Meiosis KM
3
—  Karyotypes
arrange
chromosomes
in order by
size: Largest to
smallest
Chromosomes
—  Some large like
#1
—  Some small like
#22
Homologous pairs
—  Same
Length
—  Centromere in
same location
—  Same bands
(genes)
Centromere Position
—  The
centromere is not
exactly in the center of the
chromosome
—  “p” arm: (p=petite) the
shorter arm of the
chromosome
—  “q” arm: the longer arm of
the chromosome
Locus (plural=loci)
—  The
position that a given gene
occupies on a chromosome. (Its
like an address for your genes)
—  Written like this: 15p23
Example: 15p23=Chrom 15 small arm, 23rd
band from the centromere
Chrom
#
2
Gene
Description
Skin Color
Polygenic
Locus
2p18
2q21
Allele
S = Dark
s= Light
My
My
Geno. Pheno
Lt
Ssss Olive
SSSS= Dark
SSSs= Fairly Dark
S
s
s
s
SSss= Olive
Ssss = Light Olive
ssss = Lightest White
Chrom
#
4
Gene
Description
Acne
Polygenic
Incomplete
Dominance
Locus
4p20
Allele
A=Acne
a=No Acne
AA=Lots
Aa=some
aa= none
My
My
Geno. Pheno
Aa
A
Some
Acne
a
Chrom
#
4
Gene
Description
Cleft Chin
Regular
Dominance
Locus
4p19
Allele
N = Cleft
n= no cleft
My
My
Geno. Pheno
nn
n
No
Cleft
n
Chrom
#
7&
(15)
Gene
Description
Eye color
polygenetic
Incomplete
Dominance
Locus
7p15
Allele
B=Brown
b=Blue
My
My
Geno. Pheno
Bb green
BB=Brown
Bb=Light Brown,
Hazel, Green
bb=blue
B
b
Chrom
#
7
Gene
Description
Hair Color
Incomplete
Dominance
Locus
7p11
Allele
My
My
Geno. Pheno
H=Brown/Black
Hh
h=blonde
Light
Brown
HH=Brown/Black
Hh=Light Brown
hh=Blonde
H
h
Chrom
#
7
Gene
Description
Cystic Fibrosis
Autosomal
recessive
Locus
7q25
Allele
F = No CF
f = CF
My
My
Geno. Pheno
FF
F
No
CF
F
Chrom
#
7
Gene
Description
Acne
Polygenic
Incomplete
Dominance
Locus
Allele
My
My
Geno. Pheno
7q11
A= Acne
Some
acne
a = no Acne
Aa
A
a
Chrom
#
9
Gene
Description
Blood Type
A & B Codom.
O=Recessive
Locus
9q34
Allele
My
My
Geno. Pheno
IA=A
ii
IB=B
o
i=O
i
i
Chrom
#
9
Gene
Description
Rh Factor
Normal
Dominance
Locus
9q30
Allele
My
My
Geno. Pheno
R = +Rh
Rr
r = - Rh
R
Rh+
r
Chrom
#
12
Gene
Description
Freckles
Normal
Dominance
Locus
12p5
Allele
F = Freckles
f= no freckles
My
My
Geno. Pheno
Freckles
Ff
F
f
Chrom
#
12
Gene
Description
Hair Type
Incomplete
Dominance
Locus
12q24
Allele
CC= Curly
cc = Straight
My
My
Geno. Pheno
Cc
wavy
Cc=Wavy
C
C
Chrom
#
15
Gene
Description
Tay-Sachs
Autosomal
recessive
Locus
15q23
Allele
T = No TS
t = TS
My
My
Geno. Pheno
Tt
T
No
TS
t
Chrom
#
16
Gene
Description
Dimples
Normal
Dominance
Locus
16p10
Allele
D=Dimples
My
My
Geno. Pheno
dd
No
Dimples
d = No Dimples
D
d
Chrom
#
Gene
Description
Locus
Allele
B= Not Colorblind
23
Color Blind
b = Colorblind
A= No Hemophilia
Hemophilia
My
My
Geno. Pheno
XBXB
XAXa
Not
colorblind
No
hemophilia
(but a
carrier)
a = Hemophilia
B
B
A
a