Chapter 5 Flashcards
What is DNA? A gene? A genome? A chromosome?
DNA- material in cells that contains gentic information
gene- a region of DNA that contains instructions for making a particular protein or RNA
genome- complete set of information contained within an organism’s DNA
chromosome- long threadlike structures that are composed of DNA and associated proteins that carries genes which are part of the genome
What is the structure of DNA?
- 2 strands or polynucleoide chains
- made up of one phosphate group, 5 carbon sugar, and nirogen containing base
- chains made up of phophodiester covalent bond (h bond between bases)
- sugars and phosphates are the backbone on outside
- each strand has polarity with the 5’ end the phosphate group and 3’ end the OH group
Characteristics of the complementary base pairings
purines= double ring A&G
pyrimidines= single ring c&T
A&T bonds- 2 hbonds
C&G bonds- 3hbonds
How many bases per helical turn? What are with the grooves?
10
major groove= indentation running the entire length of the helix (bigger and allow for proteins to bind)
minor groove= smaller
As one increases the temperature what type of strand would fall apart 1st?
The strand with less G and Cs because there would be less H bonds holding the strands together
What is gene expression?
the process by which the linear sequence of nucleotides by a gene is converted into a.a sequence (through transcription, mRNA processing, translation)
What are some characteristics of the eukaryotic chromosomes?
- total length of DNA in a human cell is 2m or Nucleus is 5-6 micrometer
- DNA is packaged into an organized manner into chromosomes and so they could easily be replicated and split into daughter cells
- genes are interspersed with linker DNA (function not clear)
What is chromatin?
complex of DNA and protein (histones) that makes up chromosome
What are characteristics of prokaryotic chromosomes?
- bacteria have a singular circular chromosome
- bacterial DNA is associate with proteins
- replication different
What are the 3 things that a functional chromosome must do?
- carry genes
- have the ability to replicate
- have its 2 copies separated and partitioned into 2 daughter cells during cell division
What are the 3 DNA elements important for replication and segregation?
- replication origins= location where DNA replication begins, open DNA and make copies, many per chromosome
- Centromere- important for separation of 2 copies of a duplicated chromosome during mitosis; 1 per chromosome, constricted region of a mitotic chromosome, holds together 2 sister chromatids
- Telomeres- 2 per chromosome, repeated DNA sequences @ ends of chromosomes, important for full replication of the ends of chromosomes
What are centromeres?
site of chromosome where kinetochore forms which is protein complex that attaches the sister chromatids to mitotic spindle (microtubles), allows for the 2 sisters to be pulled apart with one copy going to each daughter cell
What are chromosomes like during the interphase and mitotic phases?
interphase- chromosomes are less folded so that the chromosomes can be replicated or repaired or for genes to be expressed
mitotic- tightly folded chromosomes
1st level of chromatin packaging: beads on a string
- involves nucleosomes
- nucleosome core particles= piece of double stranded DNA wrapped 2 times around a protein complex of eight histones molecules (histone octamer)
- beads (histone octamer) connected and wrapped by linker DNA
- histones are basic (positively charged) so they’re attracted to negatively charged DNA
- each of the core histones has a tail which can be chemicaly modified by the addition of various chemical groups
2nd level of chromatin packaging: 30nm fiber
- folding of beads on a string in a zig-zag function
- requires a fifth histone
- H1 helps to pull nucleosomes together into 30 nm fiber
