Download 7.1 Chromosomes and Phenotype

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7.1 up
Chromosomes
77
Chromosomes
and Phenotype:
2.17.1
Atoms,
Ions,
and Molecules
Autosomal Genetic Disorders
1. Why is it impossible to have a “carrier”
•Topic: 7.1 Chromosomes
of an autosomal dominant disorder?
and Phenotype:
Autosomal Genetic
KEY CONCEPT
Disorders
The chromosomes on
which genes are located
•Essential Questions:
can affect the expression
1. Why is it impossible to
of traits.
have a “carrier” of an
autosomal dominant
disorder?
7.1 Chromosomes and Phenotype
KEY CONCEPT
The chromosomes on which genes are located can
affect the expression of traits.
7.1 Chromosomes and Phenotype
• Many human genetic disorders are caused by autosomal
genes, and can be predicted the same as flower color, or Pea
shape
• Autosomal genetic disorders: disorders that have no
relation to the sex of an individual
• Can be male or female in equal porportions
Ex: Albinism
7.1 Chromosomes and Phenotype
– Autosomal recessive disorder: Any offspring with two
recessive genes (cc) will have the disease/disorder
C
C
c
CC
Cc
c
Cc
cc
Disorder
Ex: Cystic
Fibrosis
7.1 Chromosomes and Phenotype
– A carrier is heterozygous (Cc) for a recessive
disorder and does not show any signs or symptoms,
but can pass on the disorder to their offspring
C
C
c
CC
c
Cc
*carrier
Cc
cc
*carrier
Disorder
Ex: Cystic
Fibrosis
7.1 Chromosomes and Phenotype
Video: Autosomal Recessive Disorders
Pg. 76
Take at least 10 bullets
(4m52s)
7.1 Chromosomes and Phenotype
– Albinism is a autosomal recessive disorder
characterized by a lack of pigment in skin, hair, and
eyes.
7.1 Chromosomes and Phenotype
7.1 Chromosomes and Phenotype
7.1 Chromosomes and Phenotype
7.1 Chromosomes and Phenotype
A
mom
a
A
dad
dad
A
a
A
a
Genotype:
Phenotype:
Carriers?:
Are either of the parents albino?
mom
a
Genotype:
Phenotype:
Carriers?:
Are either of the parents albino?
Fill out these punnett sqs. What is the probability that the
offspring will have albinism?
7.1 Chromosomes and Phenotype
A
a
A
AA
Aa
*carrier
A
AA
Aa
*carrier
Genotype: AA, Aa
Phenotype:
• O% albino
• 100% non-albino
Carrier?: 50% carrier
Parents?: Neither parent is
albino
A
a
a
Aa
*carrier
aa
*disorder
a
Aa
*carrier
aa
*disorder
Genotype: Aa
Phenotype:
• 50% albino
• 50% non-albino
Carrier?: 50% carrier
Parents: Father is albino
7.1 Chromosomes and Phenotype
Both Mom and Dad have to either have the disorder or be
carriers for offspring to be affected with an autosomal recessive
disorder!
7.1 Chromosomes and Phenotype
Video: ABC’s Special Report:
Albinism- Caught between light and dark (6m54s)
7.1 Chromosomes and Phenotype
• Autosomal DOMINANT Disorders: any offspring with a
dominant allele will have the disorder
– Dominant disorders are uncommon
– No carriers! ( Hh- would show the trait)
H
h
Hh
h
hh
Disorder
h
Hh
Disorder
hh
*anywhere
there is an
H the child
will have
the disease
7.1 Chromosomes and Phenotype
Treacher Collins Syndrome is an autosomal Dominant disorder.
It can lead to the person having no cheekbones (so the eyes droop),
and they may also have a cleft palate and under developed ears.
7.1 Chromosomes and Phenotype
T
t
t
Tt
*disorder
tt
t
Tt
*disorder
tt
Genotype:
Phenotype:
Genotype: Tt, tt
Phenotype:
• 50% will have TCS
• 50% non-TCS
If Mom or Dad have the
disorder 50/50 chance the
offspring will also have the
disorder.
7.1 Chromosomes and Phenotype
Video: Ashley’s Story- Treacher Collins Syndrome
(5m11s)
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7.1 up
Chromosomes
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Chromosomes
and Phenotype:
2.17.1
Atoms,
Ions,
•Topic: 7.1 Chromosomes and Molecules
Sex-linked Genes
and Phenotype: Sex1. Describe how Sex-linked genes are
expressed differently in men than women.
linked Genes
•Essential Questions:
1. Describe how Sex-linked
genes are expressed
differently in men than
women.
7.1 Chromosomes and Phenotype
Genes on sex chromosomes are called sex-linked genes.
– Y chromosome genes in mammals are responsible for
male characteristics.
– X chromosome genes in mammals affect many traits.
7.1 Chromosomes and Phenotype
• Gene expression is often related to whether a gene is located
on an autosome or a sex chromosome
– Sex chromosomes: determine gender
– Autosomes: all other chromosomes- no relation to gender
• All genes that Mendel studied were autosomes
• Most traits are the result of autosomal genes
7.1 Chromosomes and Phenotype
• Because the X and Y chromosomes have different
genes, sex-linked genes have a pattern of expression
that is different from autosomal genes
7.1 Chromosomes and Phenotype
Only 1 Y, and 1 X
– because Males
have no second
copies of sexlinked genes ALL
of a male’s sexlinked genes are
expressed
– So even if all the
sex-linked genes of
a male are
recessive, they will
be expressed
7.1 Chromosomes and Phenotype
• Female mammals have an XX genotype.
– Expression of sex-linked genes is similar to autosomal
genes in females.
– X chromosome inactivation randomly “turns off” one X
chromosome
– ensures that females, like males, have one functional copy
of the X chromosome in each body cell
7.1 Chromosomes and Phenotype
• X Chromosome inactivation example:
Tortoiseshell and Calico Cats (always female)
• The female cats have white fur; and black (b) or orange fur (B)
alleles on their X Chromosomes- these will be expressed
randomly
• Males have white fur; and one sex-linked gene for either black
(b) or orange (B) fur
X
7.1 Chromosomes and Phenotype
X
b
B
X
Y
B
X
b
X X
Black
b
X-chromosome
inactivation
7.1 Chromosomes and Phenotype
X
b
B
X
Y
B
X
b
X X
Orange
b
X-chromosome
inactivation
7.1 Chromosomes and Phenotype
X
b
B
X
Y
B
X
b
X X
b
X Y
B
b
b
X X
b
X Y
7.1 Chromosomes and Phenotype
Males only have one
X chromosome so
one color will be
present (recessive
OR dominant)
Female cats have
two X
chromosomes.
• Each patch of fur
can be different
depending on
which X
chromosome
“turns off”
7.1 Chromosomes and Phenotype
X
B
B
X
b
X
b
X X
Calico
Y
B
X Y
b
b
X X
b
Black
b
X Y
7.1 Chromosomes and Phenotype
Answer the questions about your cat cross:
•
•
•
•
•
•
•
•
What are the chances of getting a black cat?
50% black cats
What are the chances of getting an orange, male cat?
25% orange male cat
What are the chances of a male cat being orange?
50% male orange cat
What are the chances of a female being calico?
50% female calico
7.1 Chromosomes and Phenotype
Color blindness is a recessive sex-linked trait.
A normal man marries a woman who is a carrier for color blindness.
Predict the heredity of their offspring. (Use “b” to show color blindness)
Phenotypes:
Male______% colorblind
______% Non-colorblind
______% Carrier
Female______% colorblind
______% Non-colorblind
______% Carrier
7.1 Chromosomes and Phenotype
Color blindness is a recessive sex-linked trait.
A normal man marries a woman who is a carrier for color blindness.
Predict the heredity of their offspring. (Use “b” to show color blindness)
B
b
Phenotypes:
Male50% Colorblind
50% Non-CB
NO CARRIERS
Female0% Colorblind
50% Non-CB
50% carrier
X
X
Y
B
B
X X
B
X
B
X Y
B
b
X X
b
X Y
7.1 Chromosomes and Phenotype
A white-eyed male fly mates with a red eyed female fly to produce: 24
white-eyed males, 27 white-eyed females, 26 red-eyed males, and 23
red-eyed females. Can this trait be sex-linked? Prove your answer by
completing 2 test crosses. (r=white eyes)
Phenotypes:
Male____% Red eyes
____%White eyes
Female____% Red eyes
____%White eyes
7.1 Chromosomes and Phenotype
A white-eyed male fly mates with a red eyed female fly to produce: 24
white-eyed males, 27 white-eyed females, 26 red-eyed males, and 23
red-eyed females. Can this trait be sex-linked? Prove your answer by
completing 2 test crosses. (r=white eyes)
White eyes is a recessive sex-linked trait.
R
R
Phenotypes:
X
Male100% Red eyes
0% White eyes
Female100% Red Eyes
0% White eyes
X
Y
r
R
X X
R
X
r
X Y
R
r
X X
R
X Y
7.1 Chromosomes and Phenotype
White eyes is a recessive sex-linked trait.
A white-eyed male mates with a red eyed female to produce: 24 whiteeyed males, 27 white-eyed females, 26 red-eyed males, and 23 red-eyed
females. Can this trait be sex-linked? Prove your answer by completing
1-2 test crosses. (r=white eyes)
R
r
Phenotypes:
X
Male50% Red eyes
50% White eyes
Female50% Red Eyes
50% White eyes
X
Y
r
R
X X
R
X
r
X Y
r
r
X X
r
X Y