MCB 121 - Lecture 2

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

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
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
Image of page 1

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

View Full Document Right Arrow Icon
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
Image of page 2
- this is the probability that two regions of genome are going to interact.
Image of page 3

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

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern