MCB 121 - Lecture 2

MCB 121 - Lecture 2 - MCB 121 - Lecture 2 Outline: I....

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: MCB 121 - Lecture 2 Outline: I. Chromosome structure (DNA) II. Chromatin structure (proteins) III. Heterochromatin/ Euchromatin IV. Methods of Chromosome Biology Chromosome : nucleic acids and associated proteins required to replicate and segregate genetic material Karyotype of human cell:- cell is at metaphase (most compact stage) * at interphase (the chromsomes are more diffuses)- 22 pairs of autosomes and 1 pair of sex chromsome (X = female, Y= male)- for each pair; one comes from dad, another comes from mom Homologous Chromosomes: are chromosomes in a biological cell that pair during cell division during the creation of gametes- one from mom, another from dad - contains the sequence required for proper segregation: centromeres, telomeres (maintance), origins of replications => note these are not coding region of the genome There are two copies of each chromosome = sister chromatids; each chromatid is one molecule DNA = one continuous strain without interruption along the length Cell cycle: After division, we have G1 (diploid = 2n) -> S phase (DNA replication) -> G2 (4n= 4 copies of genome) - > M phase (mitosis occurs, chromosome segregate from each other) -> create two G1 cells Conversion of diploid genome to haploid gamete: Gametes (1n, egg and sperm) fuse -> 2n zygote -> mitosis -> G1 (2n) G1 (2n) -> meiosis -> gametes (1n) When cells are not in mitosis => interphase => G1, S, G2 When cells are in mitosis => mitotic chromosomes are in most compacted phase => M Interphase of nucleus = several levels of packages First level: beads on the string = 10nm fiber DNA wraps twice around the histone proteins (nucleosome) * nucleosome is about 145bp followed by 60 bp linker * this about 10X level of compaction compared to B-form DNA Second level: solenoid (loop) = 30 nm fiber * neuclosomes pack with each other * about 6 nucleosome per loop * this is about 30X level of compaction Third level: loop/scaffold * each of the loop is 30nm fiber, each loop is about 40-80kb * this is about 1000X level of compaction * this is the level where chromosomes start to condense Forth level: coiled loops * metaphase chromosomes * 10000X level of compaction * most compact form During meiosis, which are the divisions that form haploid germ cells from a diploid parent, chromosome structure is spatially and temporally dynamic. The progression of chromosome forms through meiosis can be appreciated through this figure of meiosis in Petunia. Chromosomes are stained with a DNA intercalating dye 4',6-diamidino-2-phenylindole (DAPI) which appear blue when excited with UV light. - DAPI binds to the bases of the chromosomes - they emit light under UV light and can be observed under fluoresce microscope - Different chromosomes are individually labeled (painted with different color) using DNA probe (using nucleotide that have different fluoresce labels on it.) - Homologous chromosomes are not necessary in proximity with one another - Each chromosome seems to occupy it's own territory in the nucleus...
View Full Document

This note was uploaded on 05/09/2010 for the course MCB 121 taught by Professor Gasser during the Winter '09 term at UC Davis.

Page1 / 11

MCB 121 - Lecture 2 - MCB 121 - Lecture 2 Outline: I....

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online