Ch 5: DNA and Chromosomes Flashcards
What is one of the most important things that life depends on?
The stable storage, maintenance, and inheritance of genetic information
General description of each DNA molecule
A double helix, composed of antiparallel complementary DNA strands, which are held together by hydrogen bonds between G-C and A-T base pairs
The nucleotide consists of a phosphate, a sugar, and a base
How is the genetic material of a eukaryotic cell kept?
it is contained in a set of chromosomes, each from a single long strand of DNA molecule that contains many genes
Besides genes, what must eukaryotic (linear) DNA contain?
- many replication origins
- one centromere
- two telomeres
What do the centromeres and telomeres do?
they help ensure that each chromosome is duplicated efficiently, and can be separated out to the two daughter cells
How is DNA folded?
It is tightly bound to histone and non-histone chromosomal proteins, this combination of DNA and protein is called chromatin
Histones pack the DNA into a repeating array of DNA protein particles called nucleosomes, which then associate with each other to form more compact chromatin structures
Cells can regulate their chromatin by temporarily condensing or decondensing particular regions
What are the different types of chromatin and what do they do?
Heterochromatin packs DNA so tightly that gene expression is often turned off. It can spread along a chromosome, and it can be inherited from one daughter cell to the next, estabilshing heritable gene expression from one cell to the next
Euchromatin is less compact, and allows access to proteins involved in transcription
cell cycle
the orderly sequence of events by which a cell duplicates it’s contents and divides into two
interphase: chromosomes are duplicated
mitosis: duplicated chromosomes are distributed to the daughter nuclei
centromere
specialized DNA sequence that allows duplicated chromosomes to be separated during M phase; can be seen as the constricted region of a mitotic chromosome
Chromatin
complex of DNA and proteins that makes up the chromosomes in a eukaryotic cell. The DNA carries the genetic information, the proteins package and control that information
chromosome
long, threadlike structure composed of DNA and proteins that carries the genetic information of an organism. It becomes visible as a distinct entity when a plant or animal cells prepares to divide
Epigenetic inheritance
the transmission of a heritable pattern of gene expression from one cell to it’s progeny that does not involve altering the nucleotide sequence of the DNA
Gene
Unit of heredity that directs the production of a particular protein or functional RNA molecule. Includes introns
Gene expression
The process by which a gene makes a product that is useful to the cell or organism by directing the synthesis of a protein or an RNA molecule with a characteristic activity
Genetic code
set of rules by which the information contained in teh nucleotide sequence of a gene and its corresponding RNA molecule is translated into the amino acid sequence of a protein
Genome
The total genetic information carried bya ll the chromosomes of a cell or organism.
In humans, the total number of nucleotide pairs in the 22 autosomes plus the X and Y chromosomes
Heterochromatin
Highly condensed region of an interphase chromosome; generally gene-poor and transcriptionally inactive
Histone
One small group of abundant, highly conserved proteins around which DNA wraps to form nucleosomes, structures that represent the most fundamental level of chromatin packing