Karyotyping Karyotyping is when a scientist cracks open

Karyotyping

• Karyotyping is when a scientist cracks open a nucleus, removes all the chromosomes. • The scientist then lays out all the individuals chromosomes and pairs the homologous pairs in order to learn something about the individuals genetics • So lets first discuss what a chromosome is and what we can learn from them

CHROMOSOMES ARE IN NUCLEUS

CHROMSOMES ARE TIGHTLY WRAPPED DNA

A GENE IS A SEGMENT OF DNA THAT CODES FOR A PARTICULAR TRAIT

REMOVED FROM NUCLEUS

STAINING

• CHROMOSOMES LOOK LIKE Xs if you find them in when the DNA is duplicated (Interphase S phase-Metaphase)

• The rest of the time the chromosomes are singular poles • This is how they will be shown the majority of the time

Human Chromosomes • Humans have 46 chromosomes normally. • 22 autosomes (2 of each) and 2 “sex” chromosomes “Sex Assigned At Birth”- male or female designation made by hospital either by karyotyping or by physical anatomy at birth Female: X___ Male: X__

Human Chromosomes • Humans have 46 chromosomes normally. • 22 autosomes (2 of each) and 2 “sex” chromosomes “Sex Assigned At Birth”- male or female designation made by hospital either by karyotyping or by physical anatomy at birth Female: XX Male: XY

Karyotype • Karyotype- when scientists look at chromosomes and arrange them, and analyze them.

Karyotype • Arranged by size • Arranged by position of centromere • First arrange normal chromosomes • Try to arrange anything irregular

Staining chromosomes • Stain Giemsa Staining stains the A and T rich portion of DNA dark. • Banding patterns depend on genetic code • Banding patterns unique to certain chromosomes

Normal Karyotype 23 homologous pairs 46 chromosomes

• What are the sex chromosomes ?

X and Y

What is determined by sex chromosomes? • SOME TRAITS: sex chromosomes do not carry an identical complement of genetic information. The X chromosome, being larger, carries many more genes than does the Y. Traits controlled by genes found only on the X chromosome are said to be sex-linked. Recessive sex-linked traits, such as hemophilia and red–green color blindness, occur far more frequently in men than in women. This is because the male who inherits the recessive allele on his X chromosome has no allele on his Y chromosome to counteract its effects. • Controls Hormone Production

Chromosomal notation: • 46, XY(chromosomally normal female) • 46, XX(chromosomally normal male) • 47, XX, +21 ABNORMAL EXTRA 21 what’s the disease?

Down Syndrome 3 chromosomes (21 st pair)

Down Syndrome Traits • mental retardation • epicanthal folds over eyes • flattened bridge of the nose

When Meiosis Fails

Normal Meiosis: produces 4 genetically different sex cells but same chromosome number

Nondisjunction An uneven splitting of the chromosomes during meiosis

Nondisjuction Animation

Down Syndrome Karyotype 3 chromosome s st (21 pair)

Down Syndrome Traits • mental retardation • epicanthal folds over eyes • flattened bridge of the nose

Nondisjunction in Sex Chromosomes

Turner Syndrom e: Missing X

Turner Syndrome Symptoms • short stature • sterile • webbed neck • skeletal disorders

XYY Syndrome • Falsely called “superman” or “criminal” syndrome. • 5 -10 born each day in USA

XYY Symptoms • taller • more hairy • heavy facial features • delays in learning & language • violent tendencies ? ?

Klinefelter Syndrome: XXY

Klinefelter Symptoms • underdeveloped male traits • mammary development • learning disabilities • language delays • infertility