Packaged Instructions for Life Chromosomes

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

Each sister chromatid contains thousands of identical genes in the same locations on each Gene: segment of DNA that codes for specific proteins Ex: hair color, eye color, lip shape, 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 (23rd) contains sex chromosomes X and/or Y Females have XX Males have XY (Y is just shorter) Males: XY Females: XX

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

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

Typical Karyotype w/ 23 Chromosome Pairs female male

Karyotypes are usually only completed for cases where there might be a chromosomal abnormality Missing homologue Extra homologue Incorrect sex chromosome numbers

Chromosomal abnormalities Result of mistakes in gamete production (meiosis) Each gamete (sperm & egg) is haploid Duplication of gamete can result in accidents causing 2 or more sets of specific chromosome (rather than necessary 1 set)

Down Syndrome Trisomy 21 (3 #21 chromosomes) resulting in mental retardation 1 in 700 births (higher for women over 40)

He was born with an extra #21

Edward Syndrome Trisomy 18 (3 #18 chromosomes) resulting in medical complications that usually result in 50% stillbirths & high mortality rate in general 1 in 3,000 births

Patau Syndrome Trisomy 13 (3 #13 chromosomes) resulting in cleft lip or palate, close-set eyes, severe mental retardation 1 in 10,000 births

Turner Syndrome Females missing X (XO) 1 in 5,000

Triple-X Syndrome Females with XXX (or XXXX or XXXXX) Infertility (most), learning disabilities, tall stature 1 in 700 - 1,000

Klinefelter Syndrome Males with XXY or XXXY 1 in 1,000 Low levels of testosterone, female-like features, infertile

Jacobs or Super Male Syndrome Males with XYY 1 in 2000 Mostly average, but excess acne, very tall, slightly increased aggression

translocation