* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Human karyotype
Gel electrophoresis of nucleic acids wikipedia , lookup
Human genome wikipedia , lookup
United Kingdom National DNA Database wikipedia , lookup
Epigenetics in stem-cell differentiation wikipedia , lookup
Genome (book) wikipedia , lookup
No-SCAR (Scarless Cas9 Assisted Recombineering) Genome Editing wikipedia , lookup
Comparative genomic hybridization wikipedia , lookup
DNA damage theory of aging wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Cancer epigenetics wikipedia , lookup
Non-coding DNA wikipedia , lookup
DNA vaccination wikipedia , lookup
Primary transcript wikipedia , lookup
Molecular cloning wikipedia , lookup
Genealogical DNA test wikipedia , lookup
Cell-free fetal DNA wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Genomic library wikipedia , lookup
Nucleic acid double helix wikipedia , lookup
Point mutation wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Y chromosome wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
DNA supercoil wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Designer baby wikipedia , lookup
Epigenomics wikipedia , lookup
Helitron (biology) wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
History of genetic engineering wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Microevolution wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
X-inactivation wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Chromosomes and gene regulation • DNA is just information - a “blueprint” • No use unless you know the rules for using the information • DNA is organised (in chromosomes) • The expression of genes is regulated • These 2 lectures cover these 2 issues Giant chromosome from Drosophila (From course textbook) Human chromosomes • Human body cells have 46 chromosomes in pairs: – 22 pairs of autosomes (numbered 1 to 22) – 2 X chromosomes (female) or X and Y (male) • Germ cells (sperm and egg) have 23 chromosomes – 22 autosomes and a Y or an X • Body cells are diploid and germ cells are haploid Human karyotype (picture of chromosomes) drawn from a photograph of chromosomes taken through a highpower microscope. Routine lab method. Used in hospitals. DNA is packaged into chromosomes • Each human cell contains 2 metres of DNA (3,000,000,000 bases in a haploid cell) • Nucleus is 5 microns (0.005 mm) diameter • DNA must be properly packaged, not just tangled up and stuffed into nucleus • Packaging involves coiling and folding the DNA in specific ways • Special proteins are associated with DNA together called chromatin Cell cycle nucleus 1 chromosomes interphase Mitotic spindle 2 3 chromosomes metaphase interphase • Cell cycle is the means by which cells divide • Stages: 1. Chromosome replication 2. Mitosis 3. Cell division • Chromosomes are extended during interphase, but condensed and visible under microscope during metaphase Features of the chromosome • Centromere is Mitotic telomere required to attach to spindle spindle at mitosis, so chromosomes segregate into new centromere cells • Telomeres protect the ends of mitosis telomere chromosomes replication 2 new cells • Replication origins are where DNA replication starts Nucleosomes & chromatin • Extended DNA under electron microscope looks like “beads on a string” • The beads are DNA coiled around a core of proteins (histones). DNA and proteins together are chromatin • Each of these structures is a nucleosome • Nucleosomes are the basic type of organisation of DNA in a chromosome Structure of nucleosomes Beads-on-string chromatin Digestion with nuclease enzyme Single nucleosomes Histone proteins (8 subunits) 146 bp DNA fragments Overall packaging of DNA 2 nm 11 nm 30 nm DNA double helix Nucleosomes Fibre of packed nucleosomes 300 nm Extended form of chromosome 700 nm Condensed form of chromosome 1400 nm (1 nm = 0.000001 mm) Entire chromosome Chromatin and gene activity • Stained chromosomes show bands • Bands are due to different forms of chromatin • Euchromatin is where the active genes are • Heterochromatin has no or few active genes, found near centromeres and telomeres Gene activity affected by position White eye gene inversion euchromatin heterochromatin Chromosomes in nucleus • During interphase chromosomes are organised within nucleus • Individual chromosomes probably attached at points to wall of nucleus • Part of chromosomes are in a region called nucleolus