Chromosomes

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Karotypes are used to

1) Can confirm a clinical diagnosis 2) Can reveal effects of environmental toxins 3) Can clarify evolutionary relationships

A karyotype can be abnormal in what two way?

1) In chromosome number 2) In chromosome structure

Triploid is produced in what two ways?

1. fertilization of one egg by two sperm 2. fusion of haploid and diploid gametes

Which chromosomes of trisomes are seen in newborns?

21, 18, and 13

Humans have how many chromosome types?

23; autosomes numbered 1-22 and sex chromosomes: X and Y

Abnormal chromosomes account for at least how many spontaneous abortions?

50%

Karyotype

A chromosome chart Displays chromosomes arranged by size and structure

Fetal Cell Sorting

A new technique detects fetal mRNA in the bloodstream of the mother

Ideogram

A schematic chromosome map Indicates chromosome arms (p or q) and delineates major regions and subregions by numbers

XYY Syndrome

Also known as Jacobs syndrome 1 in 1,000 male births 96% are phenotypically normal Modest phenotypes may include great height, acne, speech and reading disabilities Studies suggesting increase in aggressive behaviors are not supported

mosaic

An individual with two chromosomally-distinct cell populations

Metacentric

At midpoint

Telocentric

At tip

Turner Syndrome

Called the XO syndrome 1 in 2,500 female births 99% of affected fetuses die in utero Features include short stature, webbing at back of neck, incomplete sexual development (infertile), impaired hearing Individuals who are mosaics may have children

Triplo-X

Called the XXX syndrome 1 in 1,000 female births Few modest effects on phenotype include tallness, menstrual irregularities and slight impact on intelligence X-inactivation of two X chromosomes occurs and cells have two Barr bodies May compensate for presence of extra X

Klinefelter Syndrome

Called the XXY syndrome 1 in 500 male births Phenotypes include: - Incomplete sexual development - Rudimentary testes and prostate - Long limbs, large hands and feet - Some breast tissue development Most common cause of male infertility

Acrocentric

Close to end

A chromosome consists primarily of ___ and ___

DNA; protein

What are genes associated with down syndrome?

DYRK1A, DSCR1, and NFATc

Amniocentesis

Detects about 1,000 of the more than 5,000 known chromosomal and biochemical problems

What is an example of Trisomy 21?

Down syndrome

What is trisomy 18 known as?

Edwards syndrome

FISH

Fluorescence in situ hybridization DNA probes labeled with fluorescing dye bind complementary DNA used to determine down syndrome

Submetacentric

Off-center

What is trisomy 13 known as?

Patau syndrome

Chorionic Villi Sampling

Performed during 10-12th week of pregnancy Provides earlier results than amniocentesis However, it does not detect metabolic problems - And has greater risk of spontaneous abortion

Nondisjunction

The failure of chromosomes to separate normally during meiosis Produces gamete with an extra chromosome and another with one missing chromosome

Centromeres

The largest constriction of the chromosome and where spindle fibers attach

ring chromosome

a chromosome that forms a ring due to deletions in telomeres, which cause ends to adhere

isochromosome

a chromosome with identical arms

NFATc

a transcription factor that affects expression of genes important in central nervous system development regulated by levelsof DYRK1A and DSCR1

DSCR1

alters synapses

aneuploidy

an extra or missing chromosome

What happens when nondisjunction occurs in Meiosis II?

both sister chromatids are in one gamete

triploid

cells have three sets of chromosomes

Telomeres

chromosome tips composed of many repeats of TTAGGG - Shorten with each cell division

What happens when nondisjunction occurs during Meiosis 1?

copies of both homologs are in one gamete

Heterochromatin

darkly staining - Consists mostly of repetitive DNA

Describe Edwards syndrome

due to nondisjunction in meiosis II in oocyte and do not survive

A mitotic nondisjunction event that occurs ______ can have serious effects on the health of the individual

early in development

Most autosomal aneuploids cease developing as ____ or ___

embryos; fetuses

Centromeres are replicated when?

end of S-phase

DYRK1A

expressed in brain(hippocampus, cortex, and cerebellum) and heart starts amyloid formation

polyploidy

extra chromosomes sets

T/F Excess genetic material has less effects on health than a deficit.

false, it has milder effects

How are fetal cells distinguished from maternal cells?

fluorescense-activated cell sorter and identifies cell-surface markers

What happens when aneuploidy occurs during mitosis?

groups of somatic cells are produced with extra or missing chromosomes

Describe Patau syndrome

it is very rare and generally do not survive 6 months serious mental and physicial disabilites distinctive feature is eye fusion

Euchromatin

lighter-staining - Contains most protein-encoding genes

describe down syndrome

most common trisomy among newborns they have distinctive facial and physical problems they have varying degrees of developmental disabilites individuals are more likely to develop leukemia it is linked to one form of Alzheimer disease

monosomy

one chromosome absent

trisomy

one chromosome extra

deletion

part of a chromosome missing

duplication

part of a chromosome present twice

the bases that form the centromere are_____

repeats of a 171-base DNA sequence

inversion

segment of chromosome reversed

What are the characteristics of Edwards syndrome?

serious mental and physical disabilites distinctive feature: oddly-clenched fists

How are chromosomes distinguished?

size and shape

Cytogenetics

subdiscipline within genetics Deals with chromosome variations

what are the essential parts of chromosome?

telomeres, origins of replication sites ( ORIs), and centromere

those who are born with aneuploidy either have ____ or ____

trisomy; monosomy

T/F most large-scale chromosomal abnormalities present in all cells disrupt or halt prenatal development

true

translocation

two chromosomes join long arms or exchange parts

What tool is used to perform amniocentesis?

ultrasound


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