Chromosomes Colored Bodies Chromosomes carry genetic information Chromosomes

Chromosomes “Colored Bodies”

Chromosomes carry genetic information • Chromosomes are wound up DNA

Diploid – Every body cell has 2 sets of chromosomes • n = number of chromosomes • Normal body cells have 2 n (2 x n) chromosomes • Humans have 23 pairs = 46 chromosomes • 2 n = Diploid (double)

Cell cycle chromosome numbers • G 1 – normal growing cell = • S – DNA duplicates = • G 2 – cell grows = • M – Mitosis, cell divides • 2 n 4 n • 4 n 2 n

Haploid - Sex Cells • Sexual reproduction Produces sperm and egg with only one set of chromosomes (1 n) • 1 n = haploid (half) • Sperm = 1 n Egg = 1 n • Fertilized zygote = 2 n

Sex determination • What causes Male and female? • Female = XX • Male = XY Autosome vs sex chromosomes

Karyotype • Sorting chromosomes photo to check for chromosome abnormalities • What is the sex of this patient? • Male = XY

Chromosomes are only visible during mitosis • Chromosomes must be photographed and sorted

Non – Disjunction • When chromosomes do not separate during meiosis • This forms an abnormal number of chromosomes in sex cells • Trisomy – 3 • Monosomy – 1

Down’s syndrome - Trisomy 21 • extra 21 st chromosome • Characteristic facial flattening • Decreased mental ability

Edward’s Syndrome - Trisomy 18 • Extra 18 th chromosome • Organ and body deformation • Early death.

Patua Syndrome or Trisomy 13 • Extra chromosome 13 • Early Death. • External symptoms are similar to Edward's. • Cleft palate

Turner syndrome = XO female • Only one X chromosome • short stature • Broad / thick • lack of secondary sex characteristics

Klinefelter Syndrome - XXY male • Male with Slight female characteristics • lower IQ and mild mental handicap

Trisomy X - XXX female • lowered intelligence. • lack of secondary sex characteristics. • Sterile • Can be “normal”

Cri du Chat (cat cry) Syndrome • Deletion of a small arm of chromosome 5 • cat-like cry • round face, heart disease • mental handicap.

Wolf-Hirschhorn Syndrome • Deletion of a segment of chromosome 4's short arm. • Affects scalp, nose, lips, palate

13 q -Syndrome • Deletion of the long arm of chromosome 13. • Severe malformations of face