Topic 5 Dna and Chromosomes

genes

hereditary information of the cell, segment of dna that contains the instructions for making a specific rna molecule

how many base pair per turn

10 bp

what holds dna together/ the nuclotides

phosphodiester bonds

genetic code

the relation between 4 letter codon and 20 amino acids

gene expression

dna to rna to protein and if you

chromatin

the complex of dna and protein

homologous chromosomes

maternal and paternal chromosomes

y and x chromosomes are nonhomologous

junk dna

noncoding dna interspersed between and within genes

can be highly conserved among related specides suggesting imprtance for the organisms

interphase chromosomes

• longer and finer than than mitotic chromosomes

nucleosomes

first and most fundamental leeel of chrolmatin packing

converts the dina into a fiber 1/3 of its intial length

chemical treatments can separate them to get a beads on a string appearancel

linker dna

exposed dna in between core particles of nucleosomes

histones

each with a long unstructured n terminal amino acid tail

postititly charged lysine and arginine bind negatively changed dna

histone h1

linker histone that changes the path dna takes as it exits the nucleosome

pulls adjacent nucleosomes together to condense the fibre

looped domain

linear chromatin fibre packed into a series of loops that extend from the centre of the chromosome

SMC Proteins

protein complex that uses atp hydrolysis to move along the dna to form a loop

cohesin

smc ring complex that organizes the structure of interphase chromsome

Clamp protein

stop or stall cohesion bind each other to draw together the dna at the base of each loop

condensins

smc ring proteins

replaced most of the cohesins

use atp hydrolysis to form loops within loops to wond the chromatin into an even tighter mass coils

atp dependent chromatin remodeling complexes

• one for every 5 nucleosomes

• use atp hydrolys to change the positions of nucleosomes on the dna

  • makes the dna more a less accessible to other proteins

histone modifying enzymes

addition and removal of acetyl phosphate and methyl groups

affects how tightly dna is packed

serve as docking sites for regulatory proteins

spreads along the dna until it reaches a barrier sequence

heterochromatin

the most highly condensed form of interphase chromatin

half remains permanently condensed gene expression turned off

euchromatin

chromatin that exists in a less condensed state

gene expression can be turned on

epigenetic inheritance

Cells can pass on patterns of gene expression without changing the DNA sequence itself.

chromatin structure and histone modifications, not through mutations in nucleotides.