CHROMOSOME STRUCTURE page 12 EUKARYOTIC – DNA wrapped around histone proteins. Banding pattern – dark – heterochromatin – non-coding Light – euchromatin – DNA that codes for proteins

Prokaryotic chromosomes DNA wrapped around DNA binding proteins forming a single circular chromosome

Eukaryotic chromosome

Map of chromosome #4

Chromosomes- sex determination

karyotype a way to show chromosomes in a cell Usually taken at the metaphase stage Arranged according to size, centromere position and banding patterns Can detect unusual chromosome numbers, sizes and banding patterns

fluorescence in situ hybridization A modification on karyotyping

Fish for cml – 9-22 translocation

Examples of diseases that are diagnosed using FISH include: Prader-Willi syndrome, Angelman syndrome, 22q13 deletion syndrome, chronic myelogenous leukemia, acute lymphoblastic leukemia, Cri-du-chat, Velocardiofacial syndrome, and Down syndrome.

Sky karyotyping Provides a color code to identify particular chromosomes

The Cell Cycle page 10

Mitosis

Meiosis Occurs in sexually reproducing organisms Produces haploid gametes from diploid cells Occurs in two stages Meiosis I – homologous pairs separate Meiosis II – chromatids separate Four haploid gametes are produced ( for sperm cells / three polar bodies and one ovum)

Stages of Meiosis

L. CHROMO SOMAL DISORDERS IN NUMBER AND THEIR CONSEQUENCES MUTATION page 21 L. CHROMO SOMAL DISORDERS IN NUMBER AND THEIR CONSEQUENCES

1.NONDISJUNCTION VS. MOSAICISM VS. CHIMERA NONDISJUNCTION - FAILURE OF HOMOLOGOUS CHROMOSOMES TO SEPARATE IN MEIOSIS

MOSAICISM - RESULTS WHEN HOMOLOGOUS CHROMOSOMES FAIL TO SEPARATE IN MITOSIS. FROM ONE FERTILIZED EGG

CHIMERA - RESULTS FROM THE FUSION OF TWO CELL LINES - EITHER FROM A DOUBLE FERTILIZATION OR FROM THE FUSION OF TWO ZYGOTES. THE GENOTYPE XX/XY IS FORMED EITHER FROM THE EGG BEING FERTILIZED BY AN X SPERM & A Y SPERM, OR FROM THE FERTILIZED EGG & FERTILIZED POLAR BODY FUSING

2. PLOIDY AN EXTRA COMPLETE SET OF CHROMOSOMES; 3N- TRIPLOID; 4N - TETRAPLOID; USUALLY LETHAL, BUT MAY OCCUR IN HUMAN LIVER CELLS Induced in plants (using colchicine) to produce Seedless varieties

3. SOMY INVOLVES NONDISJUNCTION IN A PAIR OF CHROMOSOMES, EX. MONOSOMY & TRISOMY

a. AUTOSOMAL TRISOMIES TRISOMY 21 - DOWN’S SYNDROME, occurs in all population subgroups and in chimpanzees TRISOMY 18 - EDWARD’S SYNDROME few survive, then only a few weeks, occurs 4:1 in females:males TRISOMY 13 - PATAU’S SYNDROME most die before the age of three months

b. GONOSOMAL ABNORMALITIES IN NUMBER Turner’s Syndrome - XO a.k.a. gonadal dysgenesis Klinefelter’s Syndrome - XXY, XXXY… a.k.a. seminiferous tubule dysgenesis Polysomal X - Triple 47 XXX, Tetra 48 XXXX, Penta 49 XXXXX… a.k.a. “Super Female” tetra, penta - mental retardation

XYY - due to a nondisjunction in male germ cell, or a mitotic nondisjunction in zygote male tall with severe acne, was once believed to be correlated with criminal behavior, those advocating a eugenic philosophy proposed testing for and isolating the “genetic criminals” before they do society harm.

M. CHROMOSOME TYPES METACENTRIC SUBMETACENTRIC ACROCENTRIC

CHROMOSOME TYPES (CONT.) TERMINOLOGY OF THE ARMS p - short arm q - long arm

N. CHROMOSOMAL DISORDERS IN STRUCTURE 1. INVERSIONS - USUALLY DO NOT AFFECT THE GENOTYPE OF THE ORGANISM, THEY DO HOWEVER AFFECT LINKAGE GROUPS.

2. TRANSLOCATIONS A. RECIPROCAL - AN EXCHANGE BETWEEN NON HOMOLOGOUS CHROMOSOMES

(1) ANEUCENTRIC- PRODUCES DICENTRIC AND ACENTRIC CHROMOSOMES, ALMOST NEVER SURVIVE THE NEXT DIVISION

(2) EUCENTRIC - EACH RESULTING CHROMOSOME HAS ONE CENTROMERE (2) EUCENTRIC - EACH RESULTING CHROMOSOME HAS ONE CENTROMERE. MOST COMMON TYPE OF TRANSLOCATION.

PHILADELPHIA CHROMOSOME FOUND IN PATIENTS WITH CHRONIC GRANULOCYTIC LEUKEMIA - A TRANSLOCATION BETWEEN 22 & 9. THE LONG ARM PORTION OF 22 (22q) IS LOST AND THE LONG ARM OF 9 (9q) GAINS.

ROBERTSONIAN TRANSLOCATION/ FUSION TRANSLOCATIONS OF UNEQUAL INTERCHANGES BETWEEN ACROCENTRIC CHROMOSOMES (14 & 21)

SAME GENETIC MATERIAL, BUT A DECREASE IN # OF CHROMOSOMES

3. DELETIONS a) partial monosomy

ex. Wolf Hirschhorn Syndrome 4p- deletion of the short arm of chromosome #4 defect of midline fusion

Cats Cry Syndrome - Cri-du-chat 5p- mental and motor disorder growth retardation simian fold in the hands microcephaly

Refractory Anemia Syndrome 5q- increased platelet count

Wilms Tumor 11p- aniridia ambiguous genitalia mental retardation kidney malignancy

Retinoblastoma 13q- DELETION OF TUMOR SUPPRESSOR GENE RESULTS IN TUMORS IN THE EYE