Transcript Chromosomes - cloudfront.net

Packaged Instructions for Life
 Chromosomes are packages of DNA wrapped with
help of proteins called histones
 Composed of two identical sister chromatids
attached at centromere
 Each sister chromatid contains thousands of
identical genes in the same locations on each
 Gene: segment of DNA that codes for specific
proteins
 Ex: hair color, eye color, lip shape, etc
Gene A
Gene B
Gene C
Gene D
Gene E
 Each human somatic or body cell contains two
copies of each chromosome
 23 sets of chromosomes x 2 = 46 total (other
species differ in numbers)
 Combination of all 23 is TOTAL DNA
genome (3 billion base pairs)
 One set (23rd)
contains sex
chromosomes X
and/or Y
 Females have XX
 Males have XY (Y
is just shorter)
Females: XX
Males: XY
 Two sets of chromosomes = diploid (somatic
cells)
 One set of chromosomes = haploid (gametes)
 Necessary since combination of chromosomes
from egg & sperm must be diploid to produce
viable (able to live) offspring
 Fertilized egg = zygote
=
=
 Diploids have same gene (eye color) but may
have different variations (brown vs. blue eyes)
 called homologous chromatids (similar info)
 One from mother, one from father
gene for eye
color (mom’s
brown eyes)
dad’s blue
eyes
 Map of all 23 sets of chromosomes from a body/somatic
cell is called a karyotype
 Numbered from 1 – 23 based on length, location of
centromere, and banding pattern
Typical Karyotype w/ 23 Chromosome Pairs
female
male
 Karyotypes are usually only completed for cases
where there might be a chromosomal abnormality
 Monosomy (missing homolog)
 Trisomy (Extra homolog)
 Incorrect sex chromosome numbers
 Result of mistakes in gamete production
(meiosis)
 Each gamete (sperm & egg) is haploid
 Duplication of gamete can result in
accidents causing 2 or more sets of specific
chromosome (rather than necessary 1 set)
 Down
Syndrome
 Trisomy
21 (3 #21
chromosomes)
resulting in mental
retardation
 1 in 1,300 at age 25
 1 in 1,000 at age 30
 1 in 400 at age 35
 1 in 100 at age 40
 1 in 35 at age 45
He was born with an extra #21
 Edward Syndrome
 Trisomy 18 (3 #18
chromosomes)
resulting in medical
complications that
usually result in
50% stillbirths &
high mortality rate
in general
 1 in 5,000 births
 Patau Syndrome
 Trisomy 13 (3 #13
chromosomes)
resulting in cleft lip
or palate, close-set
eyes, severe mental
retardation
 1 in 16,000 births
 Turner Syndrome
 Females with monosomy
(missing) X (also shown as XO)
 1 in 2,500 girls
 Triple-X
Syndrome
 Females with XXX
(or XXXX or XXXXX)
 No physical defects, some have learning
disabilities, tall stature
 1 in 1,000 girls
 Klinefelter
Syndrome
 Males with XXY or
XXXY
 1 in 1,000 boys
 Low levels of
testosterone,
female-like
features, infertile
 Jacobs or Super Male Syndrome
 Males with XYY
 1 in 2000
 Mostly average, but excess acne, very tall,
slightly increased aggression
 Breakage of entire chromosome,
and sometimes reattachment can
lead to four types of drastic
mutations that may involve
A A
MANY genes:
B B
1. Deletion
C C
2. Duplication
D D
3. Inversion
E E
4. Translocation
 Effects depend on number of
genes involved and on which
chromosome
F F
G G
H H
 Segment of
chromosome gets
deleted (missing genes)
A
B
C
D
E
A
B
E
F
G
H
F
G
H
before
after
 Cri-du-chat (cat cry)
syndrome
 deletion on chromosome
5
 children have a cat-like,
high-pitched cry during
infancy
 mental retardation and
physical abnormalities
 About 1 in 20,000 to
50,000 babies is born
with this disorder
Allie Wallace, left, who is 5, and Katie
Castillo, who is 20, both have "cri du
chat" or cat cry syndrome, a rare genetic
disorder that causes an array of mental
and physical impairments.
 Prader-Willi syndrome
 deletion on chromosome
15
 mental retardation or
learning disabilities,
behavioral problems and
short stature
 may develop extreme
obesity
 About 1 in 10,000 to
25,000 babies is affected.
 22q11 deletion syndrome
 Specific deletions on chromosome 22
 About 1 in 4,000 babies born
 deletions cause a variety of problems that can
include heart defects, cleft lip/palate,
immune system abnormalities, characteristic
facial features and learning disabilities
 Certain combinations of these features are
sometimes called DiGeorge or
velocardiofacial syndrome.
 Individuals with this disorder have a 50percent chance of passing the chromosomal
abnormality on to their offspring with each
pregnancy.
 Wolf-Hirschhorn syndrome
 deletion on
chromosome 4
 characterized by mental
retardation, heart
defects, poor muscle
tone, seizures and other
problems
 affects about 1 in 50,000
babies
 Segment of chromosome
gets attached to normal
chromosome, duplicating
certain genes
A
B
C
D
E
F
G
H
before
A
B
C
D
C
D
E
F
G
H
after
 Charcot-Marie-Tooth disease
 Duplication on chromosome
17
 destroys muscle tissue and
hinders the sense of touch
 breaks down strong tissue
and cripples the hands & feet
 one of the most common
inherited neurological
disorders, with 36 in 100,000
affected
The lack of muscle, high arch,
and hammer toes are signs of
the genetic disease.
 Segment of
chromosome gets
broken off, then
reattached upside down
A
B
C
D
E
A
B
D
C
E
F
G
H
F
G
H
before
after
 Norrie Disease
 Causes blindness and
oftentimes hearing loss
 Some mental
retardation
 On X chromosome
 All males affected
 Females affected only
if occurs on both X
(otherwise are
carriers)
 Segments of gene from one
chromosome get broken off
and reattached to a different
chromosome
A
B
C
D
E
A
B
C
D
X
Y
E
F
G
H
F
G
H
before
after
 Many common disorders
 Infertility (13 to14)
 Schizophrenia (1 to 11)
 Certain leukemias (1 to
12; 17 to 15)
 Certain sarcomas (11 to
22)
 Certain lymphomas (11
to 14; 5 to 1; 8 to 14)