Chromosomes “Colored Bodies”

Chromosomes carry genetic information Chromosomes are wound up DNA

Mitosis ensures identical daughter cells Each has same number of chromosomes

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

Cell cycle chromosome numbers G1 – normal growing cell = S – DNA duplicates = G2 – cell grows = M – Mitosis, cell divides 2n 2n  4n 4n 4n  2n

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

Meiosis The process of producing sperm and eggs with only half the normal number of chromosomes. Cell divides twice!

Sex determination What causes Male and female? Female = XX Male = XY

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

Chromosomes only visible in mitosis Chromosomes must be photographed and sorted

Chromosomal mutations All mutations listed in Karyotype lab

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 21st chromosome Characteristic facial flattening Decreased mental ability

Edward’s Syndrome - Trisomy 18 Extra 18th 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”

Deletion Removal of a chromosome segment

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

Other chromosome problems

Duplication Repeats a segment of DNA/ gene ABABCD Antifreeze in ice fish

Inversion Reverse a segment ACBDEF Ex. white throat/tan striped sparrows

Translocation A segment from one chromosome joins a non homologous chromosome ABCLMNDE Leukemia Infertility