Transcript Human Heredity

Human
Heredity
Karyotype
Single
Genes With Two Alleles
Single
Genes With Multiple
Alleles
Sex-Linked
Genes
X-Chromosome
Inactivation
Definitions:

Genome: the full set of genetic
information that an organisms
carries on it’s DNA

Karyotype: the complete set of
chromosomes grouped together in
pairs, arranged in order of
decreasing size

pairs 1-22 = autosomes; pair 23 =
sex chromosomes (XX = female, XY
= male) – usually…
Lab 21 – A
Chromosome Study
Human Genes controlled by one gene (letter)
with a dominant or recessive allele
Trait
Dominant
Recessive
Earlobe Attachment
free
attached
Tongue Rolling
can
cannot
Cleft Chin
cleft
smooth
Dimples
have them
do not
Handedness
right
left
Freckles
yes
no
Naturally Curly Hair
curly
straight
Hand Clasping
left thumb over right
right thumb over left
Hitch Hiker’s Thumb
thumb straight
bent thumb
Bent Little Finger
bent
straight
Hairline Shape
widow’s peak
straight hairline
PTC Tasting
taste
cannot taste
On to Multiple Alleles 
http://learn.genetics.utah.edu/content/begin/traits/
http://gslc.genetics.utah.edu
http://www.flickr.com/photos/munson/225270836/
http://www.flickr.com/photos/timengstrom/5
08402553/
http://www.nps.k12.nj.us/vailsburg/VMS%2
0Human%20Genetics/traits.htm
http://www.stratford.org/file.cfm?resourceid=2407&filename=Human Genetics.ppt
Curly
Straight
http://rds.yahoo.com/_ylt=A0WTbx.7FNRJUN4AVXSjzbkF/SIG=122hi1k2
o/EXP=1238722107/**http%3A//www.flickr.com/photos/bfish/2833346448/
http://gslc.genetics.utah.edu
http://mysite.verizon.net/vzepz6a9/biorefwe
b/phenotypeslab.html
Hitchhiker's Thumb
http://www.ncrtec.org/tl/camp/gene/thumbs.htm
Regular Thumb

Having a bent little finger is a dominant trait
http://mysite.verizon.net/vzepz6a9/biorefweb/phenotypeslab.html
http://www.grisda.org/tstandish/teachers/presentations/General%20Biology/Human%20Genetics.ppt
www.autographedtoyou.com/.../butch_patrick5.jpg
www.thetech.org/.../images/ask/widowsPeak.jpg
http://gslc.genetics.utah.edu
- Human Inheritance
Inheritance of Blood Type

Blood type is determined by a single gene with
three alleles. This chart shows which combinations
of alleles result in each blood type.
B. Multiple Alleles
(more than one letter for a trait)
(skin color & blood types)

blood type – three alleles: A, B or O

A & B are both dominant, O is recessive
Phenotype (blood type)
Genotype(s)
A
IAIA or IAi or
(AA,AO)
B
IBIB
IBi
or
or
(BB,BO)
AB
IAIB or (AB)
O
ii or (OO)
AA, BB – homo
AO, BO - hetero
the importance of blood typing:
 during transfusions, incompatible blood
types would result in clumping & death
 helpful in cases of disputed parentage
O
O
O OO OO
O OO OO
B B
A AB AB
A AB AB
B
O
A AB AO
O BO OO
A
B
O AO BO
O AO BO
A
B
A AA AB
B AB BB
100
0
0
0
0
0
0
100
25
25
25
25
0
50
50
0
0
25
25
50
- Human Inheritance
The Sex Chromosomes

The sex chromosomes carry genes that determine
whether a person is male or female. They also
carry genes that determine other traits.
the sex chromosomes
the Y chromosome
true
X-chromosome
Inactivation
In females, most of the genes in one of the
X chromosomes are inactivated (by super
coiling into a structure known as a Barr
Body) in each cell.
**Example: calico cats – color of spots on
fur is controlled by gene on X
chromosome; spots are orange or black
depending on which X chromosome is
inactivated in different patches of skin.
C. Sex-linked Traits
– traits carried on the sex chromosomes
– usually the X
** If X-linked: males pass on to daughters & not
sons; females pass to daughter or son
X-linked are usually recessive (all of your X’s must
have it to show it)
**If Y-linked (rare): males pass to sons; females
neither pass nor are affected
Females XX:
XCXC – okay
Males XY:
XCXc – carrier
XCY – okay
XcXc – has it
XcY – has it
Examples of Sex-Linked
Inheritance
1. red-green color blindness:
**more common in males since they only have one X
2. hemophilia – blood doesn’t have the ability to clot
properly – also X-linked recessive
**studied in the family of Queen Victoria
**can be treated with transfusions or injections of a
clotting agent
On To Slide 30 practice 
Color blindness test
http://www.stratford.org/file.cfm?resourceid=2407&filename=Human Genetics.ppt
- Human Inheritance
Colorblindness Punnett Square

Red-green colorblindness is a sex-linked trait. A
girl who receives only one recessive allele (written
X c ) for red-green colorblindness will not have the
trait. However, a boy who receives one recessive
allele will be colorblind.
Hemophilia
http://www.stratford.org/file.cfm?resourceid=2407&filename=Human Genetics.ppt
Queen Victoria
http://www.stratford.org/file.cfm?resourceid=2407&filename=Human Genetics.ppt
Hemophilia
http://www.stratford.org/file.cfm?resourceid=2407&filename=Human Genetics.ppt
Name: __________________________
Period #: ________ Date: ____________
Pod Name: ____________________
No Excuses
Sex-Linked Traits
1. What makes something sex-linked trait instead of just a regular trait.
Trait is carried on a sex (X) chromosome
_____________________________________________________________________________________
_____________________________________________________________________________________
2. Are males or females be more susceptible (likely to be affected) to sex-linked diseases? Explain.
Trait shown
when on all X chromosomes; males have a greater
_____________________________________________________________________________________
chances of
having on all X chromosomes since they only have one X
_____________________________________________________________________________________
3. Hemophilia is a sex-linked trait found on the X chromosome. To get this disease, a person must
have a recessive copy of the gene (h) on every X chromosome. Predict the genotypic and
phenotypic probabilities of the offspring if a woman who was a carrier for the disease had a
baby with a man who had the disease.
h
XhX
Genotype of one parent: _______
Genotype of other parent: ______
XhY
X
X
Xh XhXh
XhX
XhY
XY
Y
h h
h
h
GENOTYPE: ________________________________________________________________________
Girls ½ X X ½ X X Boys ½ X Y ½ XY
½ hemophilia ½ normal Boys ½ hemophilia ½ normal
PHENOTYPE: Girls
_______________________________________________________________________
4. Baldness is also a sex-linked trait found on the X chromosome. To become bald, a person must
have a recessive copy of the gene (b) on every X chromosome. Predict the genotypic and
phenotypic probabilities of the offspring if a woman who has no history of baldness in her
family (B) had a baby with a man who was bald.
.
Genotype of one parent: _______
XX
Genotype of other parent: ______
XbY
X
X
Xb
XbX
XbX
Y
XY
XY
Girls 100% XbX Boys 100% XY
100% normal; no bald children
PHENOTYPE: _______________________________________________________________________
GENOTYPE: ________________________________________________________________________
SpongeBob Genetics:
Blood Types & SexLinked Traits
YAY! Homework!
Human Pedigrees

A chart used to analyze the pattern of
inheritance that shows the
relationships in a family is a
pedigree. Pedigrees can be used to
determine the nature of genes and
alleles associated with inherited
human traits.
Pedigree Problems
Whale Book
My Sample Problems
Frog Book
four
the father
1
III
III
Yes
No
III-8 and III-9
four
four
The square stands for a tall male dog. It is half shaded
because the dog carries the recessive trait.
the first male in generation II
Four carry the short trait. Two are short.
The following questions refer
to the pedigree shown for
one type of deafness in
human beings. Squares
symbolize males, circles
females; filled symbols
designate deaf individuals;
open symbols individuals
with normal hearing.
1. The genotype of individual 4 in generation I is probably
a.
D/D
b. D/d
c. d/d
d. X D Y
e. X d Y
 b. D/d
2. The genotype of individual 3 in generation IV is probably
a.
D/D
b. D/d
c. d/d
d. X D Y
 b. D/d
3. This type of deafness is probably inherited as
e. X d Y
recessive
If it were dominant it could not show up in
the F3 generation unless at least one parent in the F2 generation showed the trait
dominant
The female’s parent in the F1 generation must be heterozygous
dominant, or she could not have two children with the trait
recessive
carrier
As a young woman needs two genes to be colorblind,
the mother must have carried a gene for the trait
Mistakes in
Meiosis
extra, missing or mixed
up chromosomes
Autosomal Aneuploidy

having an unusual number of
chromosomes 1-22

usually fatal

Trisomy – have three of a particular
autosome instead of just two results
from nondisjunction
(homologous
chromosomes fail to separate)
Examples:
1. trisomy 8
2. trisomy 13 (Patau syndrome)
3. trisomy 18 (Edward syndrome)
4. trisomy 21 (Down syndrome)
Trisomy 13
Patau’s Syndrome
An individual with full
trisomy 13 at age 7 years
(survival beyond the first
year is uncommon).
He is deaf and legally
blind
Edward’s Syndrome
trisomy-18
1/8000 live births
Possible Malformations:
*
*
*
*
*
*
Back part of head may be prominent
Short eyelids
Small mouth and unusually small jaw
A small head
Fold of the eyelid in the lateral corner of the eye
Low set malformed ears
Trisomy-21

Three chromosomes in the 21 st pair, and 47 total
chromsomes

Also called Down Syndrome

Leads to physical defects and mental retardation
Trisomy 21
(Down Syndrome)
Decreased muscle tone at birth
Separated sutures (joints between the bones of the skull)
Asymmetrical or odd-shaped skull
Round head with flat area at the back of the head
Small skull
Upward slanting eyes
Small mouth with protruding tongue (see tongue problems)
Broad short hands
Single crease on the palm (see below)
Retarded growth and development
Delayed mental and social skills (mental retardation)
http://www.wayzata.k12.mn.us/cms/images/stories/academics/7t
h%20Grade/7%20Blue%20Science/genetics-human_gen.ppt
sex chromosome
aneuploidy

missing or extra sex chromosome(s)
Examples:
1. Turner Syndrome - XO
 females who lack ovaries & sex characteristics; short & sterile
2. Klinefelter Syndrome - XXY
 taller, longer limbs, sterile, some exhibit mental retardation
3. XYY male – 1 in every 1000; normal, fertile,
taller than average
Two men, one taller than the other.
(c) Dorling Kindersley
How to Study
aneuploidy:
 take
sample cells from
fetus & photograph
metaphase
chromosomes – line
them up according to
length & location of
centromere = karyotype
A. Dominant
Autosomal Heredity

Huntington’s disease – a rare genetic
disorder caused by a dominant gene

 progressive degeneration of the
nervous system causes uncontrolled jerky
movements & mental deterioration

 no effective treatment exists

 passed on because symptoms don’t
occur until 30-50, after they have
children

 if you are at risk, you can find out if
you are a carrier with a biochemical test
B. Recessive
Autosomal
Heredity
most genetic disorders
caused this way; rare
except in some ethnic
groups
1. cystic fibrosis

most common lethal genetic disorder
among Americans

1 in 20 carry the recessive allele; 1 in
2000 has it

thick mucous in lungs makes breathing
difficult; frequent lung infections

thick mucous also slows the secretion of
some digestive enzymes

physical therapy, special diets, & new
drug therapies have raised average life
span
Physiotherapy for cystic fibrosis sufferer.
(c) Dorling Kindersley
2. sickle-cell anemia

a blood disorder

most common in black Americans (Africa)
or white Americans (Mediterranean Sea)

red blood cells are shaped like a sickle or
half moon – can clog blood vessels

 rbc’s have a shorter life span – people
suffer from anemia

hemoglobin protein in these cells differs
from normal by one amino acid

treatments include transfusions & drug
therapy

hetero’s can show signs if oxygen
availability is low
3. Tay-Sachs disease

affects the nervous system

missing an enzyme that normally
breaks down a lipid produced &
stored in the central

nervous system & it accumulates in
the cells

results in blindness, progressive loss
of movement & mental deterioration

symptoms occur within the first year
of life & result in death by age 5; no
treatment

allele common in PA Dutch
4. phenylketonuria

is a treatable genetic disorder (Norway, Sweden)

absence of an enzyme that converts one amino acid,
phenylalanine, to tyrosine

phenylalanine accumulates & can cause severe damage
to the central nervous system

newborns appear normal since mother ’s normal enzyme
level prevents accumulation,

but when newborn begins drinking milk (high in
phenylalanine) accumulation begins

PKU tests are now preformed on all newborns a few
days after birth to prevent retardation
Even More
Genetic
Disorders:
Achondroplasia
(dwarfism)
Symptoms
•Absent or delayed sexual development in
an adolescent
•Excessive thirst with excessive urination
•Headaches
•Increased urine volume
•Short stature -- below 5th percentile on a
standardized growth chart, an adult less
than 5 feet tall
•Slow growth before age 5
•Slowed or absent increase in height
Short person with short limbs, with large
head and prominent forehead.
(c) Dorling Kindersley
Fragile X Syndrome
Overview
Fragile X syndrome is a genetic
condition involving changes in part of
the X chromosome. It is the most
common form of inherited mental
retardation in males and a significant
cause of mental retardation in
females.
Grey haired man with prominent chin.
(c) Dorling Kindersley
Symptoms
•Mental retardation
•Large testicles (macro-orchidism)
after the beginning of puberty
•Large body size
•Tendency to avoid eye contact
•Hyperactive behavior
•Large forehead or ears with a
prominent jaw
Albinism
Albinism is a congenital absence of normal pigmentation. It is
characterized by partial or total lack of melanin pigment in the eyes,
skin and hair. People who have this condition have visual difficulties
like hypersensitivity to bright light and glare and many others.
Galactosemia
Cri-du-Chat
Symptoms
•Cry that is high-pitched and
sounds like a cat
•Downward slant to the eyes
•Low birth weight and slow growth
•Low-set or abnormally shaped
ears
•Mental retardation
•Partial webbing or fusing of
fingers or toes
•Single line in the palm of the
hand (simian crease)
•Skin tags just in front of the ear
•Slow or incomplete development
of motor skills
•Small head (microcephaly)
•Small jaw (micrognathia)
•Wide-set eyes
Williams Syndrome
Williams syndrome is a rare genetic disorder
that can lead to problems with development
•affects a child's growth, physical
appearance, and cognitive development
• missing genetic material from
chromosome 7, including the gene elastin gives blood vessels the stretchiness and
strength
•The most common symptoms of Williams
syndrome are mental retardation, heart
defects, and unusual facial features (small
upturned nose, wide mouth, full lips, small
chin, widely spaced teeth).
•People with this syndrome also exhibit
characteristic behaviors, such as
hypersensitivity to loud noises and an
overly outgoing personality.