Transcript Sex Linked Traits

Genetic Tools
The Human Genome:
A genome is all the DNA in an organism.
Human Karyotype
• A karyotype is an organized profile of a person's chromosomes
• Extra, missing, or abnormal positions of chromosome pieces can cause
problems with a person's growth, development, and body functions.
Girl
Boy
Autosomal
Chromosomes
(Pairs 1-22)
Sex Chromosomes
(23rd pair)
Chromosomal disorders are caused by nondisjunction
What is the sex of the child?
Is there a chromosomal disorder?
On which chromosome pair is the
disorder located?
Down Syndrome
Mothers in early 20s
1 in 1,500 births
Mothers over 35
1 in 70 births
Mothers over 45
1 in 25 births
Turners (45, XO)
• 1 in 3,000 female births
• Sterile females
Klinefelters (XXY)
• 2 in 1000 male births
• Sterile males
Geneticists Wanted
• WANTED: Very intelligent scientists to help figure out
what is wrong with these children?
Background:
• Mr. and Mrs. Raider are deeply worried about their child who seems
to be developing at a slower rate. They are concerned for the child’s
health just like any other parent and have come to you for help.
Jaxton's Story - Trisomy 18
What to hand in:
• You will identify the disorder that the child has based on the given
karyotype and then research information about that disorder.
• You will create a poster that describes aspects of the genetic disorder
you have diagnosed.
• Information to be included on the poster
-What is the disorder (name and chromosome location)?
-Is it an autosomal or sex linked disorder?
-How often does this genetic disorder happen?
-What are the symptoms?
-What is the life expectancy?
-Is there any help/treatment/therapy?
-Any additional information you find interesting
Child A
Child B
Child C
Child D
Child E
Child F
Child G
Sex-Linkage
• Genes that are carried on the X chromosome are
called Sex-linked genes.
• Traits determined by sex-linked genes are called sexlinked traits.
• Because of this, sex-linked traits are most often seen
in males who only have one copy of the X
chromosome.
Sex-linked traits
Since traits are sex-linked, there is usually a distinct pattern.
For example, color blindness is a sex-linked trait whose
allele is recessive and located on the X chromosome.
Conditions caused by sex-linked genes
-Hemophilia
-Colorblindness
-Duchene Muscular Dystrophy
-Male patterned baldness
Amoeba Sisters - Sex Linked Traits
Sex-Linkage
• Female- (XX) She must have two recessive alleles to express the
recessive phenotype.
• Male- (XY) He only needs one recessive allele to express the
recessive phenotype.
• Example:
C C
• X X - Woman w/ normal vision.
• X C X c - Woman w/normal vision;
Carrier for colorblindness.
• X c X c - Colorblind woman.
• X C Y - Man w/normal vision.
• X c Y - Colorblind man.
• Carrier - Heterozygous for a recessive
trait.
Colorblind mother
Normal Father
C
Y
X
X
X
c
C
c
C
c
X X
c
X X
Results:
c
X Y
c
X Y
Colorblind mother
Normal Father
Y
X
X
X
c
C
c
C
c
X X
c
Results:
X X
c
X Y
c
X Y
Female Carriers/ Male colorblind
DNA fingerprinting
• DNA Fingerprinting is a procedure whereby the genetic
information, called DNA, in a person's cells is analysed and
identified.
DNA Fingerprinting
• Crime labs can use any cell from a person’s
body left behind at a crime scene to match
them with DNA samples.
What form of DNA might be left behind and how?
DNA can also be used to determine paternity.
DNA fingerprint of 5 people
Lt. Russ is investigating a murder scene. The felon was scratched by his
victim & some of his skin cells were found under the victim’s fingernails. A
DNA test was performed.
Which of the suspects is the murderer?
Case #1
• A woman claims that a famous athlete is the father of her
child. All three gave dna samples. Use #1 to see if she is telling
the truth
• M-mother
• C- child
• F- father
Case #2
• Mrs. B went home one day and found Mr. B. dead in his
recliner with the TV on. The room looked as if there had been a
struggle and he was placed back in his chair. DNA evidence was
taken from under his fingernails left behind in a struggle.
• Who killed him?
DNA-matching results for autoradiographs 1-4
#1
#2
#3
#4
child
A/C
E/G
I/K
M/O
mother
A/D
G/G
I/J
M/N
alleged father
B/C
E/F
H/K
L/O