Packaged Instructions for Life

Chromosomes are packages of DNA wrapped with help of proteins called histones Composed of two identical sister chromatids attached at centromere

Chromosome levels organization: dsDNA Nucleosome Coiled solenoid/nucleosome Chromatin Supercoiled (condensed) chromatin Chromosome

Each sister chromatid contains thousands of identical genes in the same locations on each Gene: segment of DNA that codes for specific proteins Ex: brown hair, green eyes, etc Gene A Gene B Gene C Gene D Gene E

Each human somatic or body cell contains two copies of each chromosome 23 sets of chromosomes x 2 = 46 total (other species differ in numbers) Combination of all 23 is TOTAL DNA genome (3 billion base pairs)

One set (23 rd ) contains sex chromosomes X and/or Y Females have XX Males have XY (Y is just shorter) Females: XX Males: XY

Two sets of chromosomes is termed diploid (somatic cells) One set of chromosomes is termed haploid (gametes) Necessary since combination of chromosomes from egg & sperm must be diploid to produce viable (able to live) offspring Fertilized egg = zygote haploiddiploid

Diploids have same gene (eye color) but may have different variations (brown vs. blue eyes) called homologous chromatids (similar info) One from mother, one from father gene for eye color (mom’s brown eyes) dad’s blue eyes

SOMATIC CELL GAMETE All body cellsOnly eggs or sperm 2 sets of chromosomes1 set of chromosomes 46 chromosomes (1-23 twice)23 chromosomes (1-23) DiploidHaploid Homologous pairsNo pairs

Map of all 23 sets of chromosomes from a body/somatic cell is called a karyotype Numbered from 1 – 23 based on length, location of centromere, and banding pattern #1-22 are called autosomes, #23 are sex chromosomes

Typical Karyotype w/ 23 Chromosome Pairs female male

Karyotypes are usually only completed for cases where there might be a chromosomal abnormality Monosomy (missing homolog) Trisomy (Extra homolog) Incorrect sex chromosome numbers

Quiz Friday 1/16/15 20 multiple choice