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

23 homologous pairs 46 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 (21st pair)

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

When Meiosis Fails

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

An uneven splitting of the chromosomes during meiosis Nondisjunction An uneven splitting of the chromosomes during meiosis

Nondisjuction Animation

Down Syndrome Karyotype 3 chromosomes (21st pair)

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

Nondisjunction in Sex Chromosomes

Turner Syndrome: Missing X

Turner Syndrome Symptoms short stature sterile webbed neck skeletal disorders

XYY Syndrome 5-10 born each day in USA 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