Lesson 4: Human Chromosomes and Chromosome Behavior Flashcards
the structures of chromosome can be best seen during
cell division
most common
autosomal trisomy
trisomy 21
The chromosomes with satellite are known as
sat-chromosome
it binds to DNA and wraps it into coiled loops and we get the compacted chromosome
condensin
A very long DNA molecule and associated proteins, that carry portions of the hereditary information of an organism
chromosomes
has an intellectual disability and a risk of Alzheimer’s
Trisomy 21
Overlapping fingers, low-set ears, decreased muscle tone, heart/lung abnormalities, small physical size, and clubfeet
trisomy 18
DNA-protein complex organized into nucleosomes
chromatin
Karyotype:
47, XXX
Triple X Syndrome
extra segment
duplication
When an individual has more than two chromosomes instead of a pair, the condition is called
trisomy
Chromatin further condenses with the help of protein known as
condensin
Chromosome is composed of:
DNA and histone proteins
Clinical features:
* Short stature
* Webbed neck
* Low posterior hairline
* Shield chest
* Amenorrhea
* Absence of puberty
* The early loss of ovarian function (ovarian dysgenesis)
* Infertility
* Skeletal abnormalities (i.e., cubitus valgus),
* Lymphedema
* Congenital kidney and/or heart disease (i.e., horseshoe kidney, coarctation of the aorta)
Turner Syndrome
Some cases may seem
phenotypically normal
Triple X Syndrome
Approximately 1:1000
male births
XYY Syndrome
Clinical features:
Characteristic facial appearance, flat facies, prominent epicanthic folds, weak muscle tone at birth, single transverse palmar crease (simian crease), clinodactyly, congenital digestive and cardiac defects, intellectual disability, increased risk for leukemia, Alzheimer disease and hearing an vision problems
trisomy 21
Chromatin is made up of
DNA, RNA, and proteins
Chromosome is made up of
chromatin
As with triple X syndrome, some cases may seem phenotypically normal.
XYY Syndrome
Telomeres are ____, which prevents the fusion of chromosomal segments
polar
characteristic facial features, web of skin, constriction of aorta, poor breast development, under-developed ovaries
Triple X Syndrome
happens when there is a rearrangement of a chromosome that breaks off then reattaches in the original breakpoints
inversions
Approximately 1/3000
to 1:5000 live births
trisomy 18
it is a technique to study the structure of chromosomes present in a species
karyotyping
Other term for Trisomy 18
Edward’s Syndrome
Germ cells
23 chromosomes
(one copy of each autosome plus a single sex chromosome)
Contains how many genes that can precisely code for several proteins in the cell.
hundreds and thousands
clinical features:
small head, absent eyebrows, cleft lip and/or palate, dysplastic or malformed ears, clenched hands and polydactyly, or extra fingers, undescended or abnormal testes
trisomy 13
other term for trisomy 21
Down Syndrome
types of chromosome based on the position of the centromere
- Telocentric
- Acrocentric
- Submetacentric
- Metacentric
Clinical features:
Presents with increased height and risk of learning disabilities, delayed development of speech, language, and motor skills, weak muscle tone, behavioral and emotional difficulties, seizures, kidney abnormalities
Triple X Syndrome
are the basic unit
of chromatin.
nucleosomes
identical copies of DNA
chromatids
tall stature, tendency to lose hair, poor beard growth, female pattern or fat distribution, female-type pubic hair pattern, testicular atrophy
Klinefelter Syndrome
Approximately 1:700
to 1/800 live births
trisomy 21
When an individual is missing one of the chromosomes from a pair, the condition is called
monosomy
Clinical features:
Increased height and risk of learning disabilities, delayed development of speech, language, and motor skills, weak muscle tone, hand tremors, seizures, asthma, scoliosis, behavioral and emotional difficulties
XYY Syndrome
protect chromosome ends
telomeres
second most common autosomal trisomy
trisomy 18
Karyotype:
47, XX or XY, +18
Trisomy 18
Approximately 1 in 2000 to 1 in 2500 live female births
Turner Syndrome
Karyotype:
47, XYY
XYY Syndrome
severe intellectual disability, also has heart defects
trisomy 13
links sister chromatids
centromere
Approximately 1/1000
female births
Triple X Syndrome
Normal human somatic cells
46 chromosomes (22 pairs, or homologs, of autosomes)
2 sex chromosomes
Clinical features:
Increased height, long extremities, low upper/lower segment ratio, gynecomastia, reduced facial and body hair (female hair distribution), delayed and incomplete puberty, small testes (testicular atrophy), infertility, developmental delay (learning disabilities, delayed speech and language development), increased risk for breast cancer.
Klinefelter Syndrome
Karyotype:
47, XX or XY, +21
Trisomy 21
DNA is wound around histone proteins to form a
nucleosome
segment moves to another chromosome
translocation
Passed from parent to child through the egg and the sperm
chromosomes
5 STRUCTURAL ABNORMALITIES
- Deletions
- Duplications
- Translocations
- Inversions
- Substitution
eyes slants up with palpebral fissures, enlarged tongue that sticks out of mouth, small stature & low muscle tone, gap between 1st & 2nd toe, broad hands with short fingers, epicanthic fold, low set of ears, low nasal bridge & dorsum, abnormal & excessive facial fat distribution, delayed growth of brain results in reduced mental capacity
trisomy 21
happens when the segment of a chromosome is substituted with another segment to complete the structure
substitution
1/500 to 1:1000 male
births
Klinefelter Syndrome
Clinical features:
Low birth weight, microcephaly, micrognathia, low-set, malformed ears, clenched fists with overlapping fingers, congenital heart and renal abnormalities, rocker-bottom feet, severe intellectual disability, survival about one year.
Trisomy 18
Karyotype:
Typically 47, XXY (greater than 90%).
However, other karyotypes have been described:
48, XXXY
and 49, XXXXY
and 46, XY/47, XXY (mosaicism)
Klinefelter Syndrome
third most common autosomal trisomy
Trisomy 13
chromatids are visible in
mitotic metaphase
Structures that hold all of our genes
chromosomes
Karyotype:
47, XX or XY, +13
Trisomy 13
Most common sex chromosomal abnormality in females and the most common genetic cause of primary amenorrhea
Turner Syndrome
Approximately 1 in 5000 to 1 in 16000 live births
Trisomy 13
has low birth weight and a short life span for an individual
trisomy 18
Clinical features:
small or poorly developed eyes (anophthalmia or cyclopia), cleft lip and palate, congenital heart disease, cryptorchidism, brain or spinal cord abnormalities, weak muscle tone at birth
trisomy 13
This technique is useful in finding out any chromosomal abnormalities such as extra or missing chromosomes
karyotyping
DNA packing is facilitated by proteins called
histones
Short stature, webbing of neck, low posterior hairline, broad chest and widely spaced nipples, cubitus valgus, pigmented nevi, coarctation or aorta, streak ovaries, infertility, amenorrhea, peripheral lymphedema at birth
Turner Syndrome
types of chromosome based on the number of centromere present
- Monocentric
- Holocentric
- Acentric
- Dicentric
Karyotype:
45, X accounts for 45% of cases because most zygotes cannot survive extrauterine life.
Turner Syndrome
Terminal part of a
chromosome
telomere
It is an elongated segment that is sometimes present on a chromosome at the secondary constriction
satellite
missing chromosome segment
deletion
