Download Unit 8 PowerPoint

Unit 8 – Human Genetics
Human Chromosomes
●Karyotype = picture of chromosomes
arranged in pairs & organized by size
●Humans have 46 chromosomes
●2 of these are sex chromosomes
XX = female XY = male
●The other 44 chromosomes are known as
autosomes
NONDISJUNCTION
Failure of chromosomes to separate in
meiosis – results in an egg (sperm) with too
many or too few
●Down Syndrome (extra #21)
●Klinefelter Syndrome (XXY)
●Turner Syndrome (XO)
●Supermale (XYY)
Down Syndrome
- caused by an extra chromosome 21
(trisomy 21)
Edward Syndrome
- caused by an extra chromosome 18
(trisomy 18)
Median life
expectancy is
4 days.
However,
about 5-10%
survive
beyond one
year
Trisomy – 3 chromosomes
Monosomy – 1 chromosome
Checking in 1:
1. A picture of a person's chromosomes is called a _____.
2. In this pictures, chromosomes are arranged in
pairs according to their ___________.
3. Humans have ______ pairs of chromosomes.
4. The last set of chromosomes is the _____ chromosomes.
5. Males have what sex chromosomes? ______
6. A person who has an extra chromosome #21 has what
disorder? __________
7. If a person has XXY for sex chromosomes, he has what
disorder? _________________
8. As a woman gets _______, her risk for having a child with down
syndrome increases.
9. A human has 2 sex chromosomes, the other 44 chromosomes
are called ______________.
10. When chromosomes fail to separate during
meiosis, ___________ has occurred.
Human Traits
●To study inheritance, biologists use
pedigree charts
oShows relationships within a family
Not all Human Traits can be traced back to
a single gene
Many traits are strongly influenced by
environmental factors
(ex: height, weight, personality)
Human Genome
●Our complete set
of genetic info
●Includes thousands
of genes
●Base sequences of
many genes
identified
BLOOD TYPES
Genes controlling blood types were 1st
genes to be identified
ABO & Rh blood groups ( + and - )
ABO Blood Group
Multiple Allele Trait
●Controlled by 3 alleles: A, B, O
●A and B are codominant
●O is recessive to both A and B
●The blood type is the phenotype
Genotype
Blood Type
AA, AO
Type A
BB, BO
Type B
AB codominant
Type AB
(universal recipient)
OO recessive
Type O
(universal donor)
Blood Types Practice
Mom has type A blood (genotype AO), dad
has type AB blood. What blood types are
possible among their children?
Mom has type B blood (genotype BO), dad
has type O blood. What blood types are
possible among their children?
Human Genetic Disorders
Phenylketonuria (PKU)
Tay – Sachs disease
Albinism
* all recessive
Other animals can be albino too..
Sickle-Cell Disease
codominant (AA, Aa, aa )
heterozygous is resistant to malaria
Achondroplasia
(dwarfism)
Huntington’s disease
* Both dominant
Checking in 2:
1. Achondroplasia is another name for ____________
2. What are the four possible blood types? _______
3. Is albinism dominant or recessive? _________
4. If two people are both heterozygous for sickle cell trait, what
is the chance they they will have a child with sickle cell disease?
5. If a person with type A blood is married to person with type O
blood, what blood types are possible in their children?
6. The human _______ describes all the genes found in
humans.
7. What type of chart is used to study a trait in a family? __
Genes located on sex
chromosomes follow
different patterns of
heredity. Males are
more likely to be
affected by these
genes.
ALL GENES ARE LOCATED ON
CHROMOSOMES
Some genes are located on the SEX
CHROMOSOMES ( X and Y)
Genes on the X chromosome may
affect boys different from girls
These are called SEX-LINKED GENES
EXAMPLES: SEX LINKED GENES
Coat color in cats: Black, Orange, Calico
X B X B = black, female
X O X O = orange, female
X B X O = calico, female
X B Y = black, male
X O Y = orange, male
REMEMBER: THE
Y IS WIMPY! No
letters (genes) are
attached to it.
CROSSES
X B X B (black female)
x
This explains why all calico
cats are female!
ALSO: in any given cell,
one of the X's becomes
inactive, which randomizes
the pattern or orange and
black
X OY
(orange male)
COLORBLINDNESS IS ALSO SEX LINKED
Look what happens when a woman who is a CARRIER
(b) marries a normal man (B)
X BX b
x
XBY
What happens when a colorblind man marries a normal
woman?
X BX B
x
XbY
COLORBLIND TEST
Young children are given pictures
instead of numbers
HEMOPHILIA - "bleeder's disease"
Blood will not clot normally, small
injuries can be life threatening
Females can be carriers:
What happens if Mom is a carrier?
DUCHENNE MUSCULAR DYSTROPHY
- causes progressive
weakening and loss of muscle
tissue
Females can be carriers:
X DX d
Checking in 3:
1. Sex-linked genetic traits are on the _______ chromosome.
2. Are females or males more likely to be affected by a sexlinked traits? _______
3. _________ can be carriers of sex-linked traits.
4. What are two examples of sex-linked traits?