Download Sex-Linked Traits

Sex-Linked Traits
Autosomal Traits
● Most traits and disorders are found on autosomes
○ autosome- a body chromosome (44 in humans)
● Some disorders are caused by recessive alleles
○ homozygous recessive (dd) = recessive disorder
○ homozygous dominant (DD) = healthy
○ heterozygous (Dd) = healthy, but carrier
● ex) cystic fibrosis, sickle-cell anemia
Autosomal Traits
● Some disorders are caused by dominant alleles
○ just one dominant allele = disorder
● Less common than recessive disorders
● ex) Huntington disease, Marfan syndrome
Sex Chromosomes
● Our cells have 2 sex chromosomes
○ X- contains gender info and
some autosomal traits
○ Y- contains only gender info
● XX = female
● XY = male
● Each parent donates one sex
chromosome to offspring
Sex-Linked Traits
● Some genetic information for non-gender traits are found on the
X chromosome
○ For males, X chromosome comes from their mother
■ all body traits on the X are automatically shown, even
recessive
○ For females, one X comes from mom and another from dad
■ standard hereditary rules apply
● ex) color blindness, male pattern baldness, hemophilia
Sex-Linked Traits
XB
● If XB = allele for normal vision, and
Xb = allele for colorblindness, what
are the possible phenotypes for a
woman homozygous for normal
XB
vision and a man with normal vision?
● Genotypes● dad = XBY
1 XB XB : 1 XBY
B B
● mom = X X
● Phenotypes-
XB
Y
XB XB
XBY
XB XB
XBY
1 normal female : 1 normal male
Sex-Linked Traits
XB
XB XB XB
● If XB = allele for normal vision, and
Xb = allele for colorblindness, what
are the possible phenotypes for a
B b
b
X
X
woman heterozygous for normal
X
vision and a man with normal vision?
● Genotypes● dad = XBY
1 XB XB : 1 XBY :1 XB Xb : 1 XbY
B b
● mom = X X
● Phenotypes-
Y
XBY
XbY
1 normal female : 1 normal male : carrier
female : 1 color blind male
Sex-Linked Traits
Xb
Y
XB XB Xb
● If XB = allele for normal vision, and
XBY
Xb = allele for colorblindness, what
are the possible phenotypes for a
b b
b
b
X
X
X
Y
woman heterozygous for normal
X
vision and a man with color
blindness?
● Genotypes1 XB Xb : 1 XBY :1 X b Xb : 1 XbY
b
● dad = X Y
● PhenotypesB b
● mom = X X
1 carrier female : 1 normal male : color
blind female : 1 color blind male
Brain-Melting Bonus! Sex-Linked, Codominant Traits
● In some cats, hair color is found on the X chromosome
○ Orange and black hair are codominant traits
● Calico cats have orange, black, and white hair
○ Females have an orange allele on one X, and a black
allele on the other X
■ show up as patches due to X-gene inactivation
○ Since males only have one X, they cannot be calico
■ exception- a cat with XXY
Brain-Melting Bonus! Sex-Linked, Codominant Traits
Brain-Melting Bonus! Sex-Linked, Codominant Traits
● If XO= orange fur, and
XO
XB
XB = black fur, what
XB XO XB XBXB
would be the possible
phenotypes between a
O
B
X
Y
X
Y
calico female and black
Y
male cat?
● male= XBY
● Phenotypes1 calico female: 1 black female: 1 orange
● female= XOXB
male: 1 black male