Chromosomes

DNA Nucleic Acid macromolecule DNA is long, thin molecule & stores genetic information called chromatin Cell division requires compact structures = chromosomes

Chromosomes DNA (eukaryotic cells) coil around histone proteins Histones help with maintaining shape of chromosome

Chromosome Chromatid = one side of chromosome Centromere = constricted area of chromosome in center – Holds chromatids together

Chromosomes Chromosomes (prokaryotic cells) are simpler consisting of circular DNA

Chromosome Numbers Different number of chromosomes in each cell Humans = 46 chromosomes

Chromosome Number Adder’s Tongue Fern = 1,262 chromosomes Dogs = 78 chromosomes

Chromosome Numbers Chimpanzee, Gorilla, and Orangutan = 48 chromosomes Horse = 64 chromosomes Earth worm = 36 chromosomes Carrot = 18 chromosomes

Does having more chromosomes mean being more complex? Complexity and chromosome number is not related

Chromosome Number In Animal cells, chromosomes categorized as sex chromosomes or autosomes – Sex chromosomes = X or Y chromosomes – Autosomes = the rest of chromosomes 2 copies same size and shape = homologous chromosomes

Chromosome Abnormalities Down Syndrome (trisomy 21) – 3 copies of chromosome 21

Chromosomal Abnormalities Female with only 1 X chromosome (XO) – Monosomy X

Chromosomal Abnormalities Klinefelter Syndrome – male with XXY

Chromosomal Abnormalities Patau Syndrome -3 copies of # 13

Can we detect these conditions before birth? Yes! Amniocentesis – removing amniotic fluid from around baby Chromosomes are photographed and organized on a chart (karyotype)

Karyotype Karyotype = chart of chromosomes in humans – Can check for abnormalities/disorders Normal Human Karyotype

Diploid Vs. Haploid Cells that have pairs of chromosomes (body cells) are diploid (2n) –have 2 sets of chromosomes (one from each parent). The diploid number represents how many chromosomes are in these cells.

Diploid Vs. Haploid Sex cells (a.k.a. gametes, a.k.a. sperm and egg) have only one of each chromosome. Haploid (n), which means they only have 1 set of chromosomes. –haploid number will always be half the diploid number.

Organism# of chromosomes in body cells (diploid number) # of chromosomes in sex cells (haploid number) Human46 Fruit fly4 Dog78 Sand dollar26 Cat16 Carrot18 horse64