Chapter 10 - Molecular structure of chromosomes Flashcards
What is the main function of genetic material?
to store information required to produce the traits of an organism
- largely accomplished via protein-encoding genes
Why are DNA sequences necessary for? (4)
- Synthesis of RNA and cellular proteins
- Replication of chromosomes
- Proper segregation of chromosomes
- Compaction of chromosomes so they can fit within living cells
Bacterial chromosomal DNA is usually
circular molecule that is a few million nucleotides in length
What are intergenic regions and where are they found?
- Has promoters
- no expression
- do not code for any protein coded genes
- in bacterial chromosomal DNA
What are the 6 key features of bacterial chromosomal DNA?
- Most, not all, prokaryotic species contain circular chromosomal DNA
- Most prokaryotic species contain a single type of chromosome but it may be present in multiple copies
- typical chromosome is a few million base pairs in length
- several thousand different genes are in the chromosome
- at least one origin of replication is required to initiate DNA replication
- Repetitive sequences may be throughout the chromosome
How many sets do eukaryotic species (humans) have?
2 sets of 23 chromosomes (46 total)
How are eukaryotic chromosomes composed?
- contains a single strand, linear molecule of DNA that is typically ten to hundreds of million of base pairs
- a few to hundred thousand genes
In simple eukaryotes like yeast genes are what?
In complex eukaryotes like mammals genes are ?
Simple - short
Complex - long and tend to have many introns
What are introns? and where are they found?
- Noncoding intervening sequences that will get removed from RNA not DNA!
- interrupt the sequence (helps catch mutations)
What 3 types of DNA sequences are required for chromosomal replication and segregation in Eukaryotic chromosomes?
- Origin of Replication
- Centromeres
- Telomeres
Describe Origin of replication
- can be multiple or just single
- necessary to initiate DNA replication
Describe centromeres
- play a role in the segregation of chromosomes
Describe Telomeres
- If maintained, can aid in aging + longevity
- specialized regions at the ends of chromosomes (two)
- important in replication and for stability
Large genomes does not mean?
complexity
- variation in size is not related to the complexity of species!
The total amount of ___ in eukaryotic species is typically __ ___ that that in bacterial cells
DNA
greater than
Describe Transposition
involves the integration of small segments of DNA into a new location in the genome
- can occur at many different locations within genome
Transposable Elements (TEs)
small mobile DNA segments termed “jumping genes”
Who and how discovered Transposable elements?
Barbara McClintock in the early 1950s
In corn
What are the two types of transposable elements?
- Simple
- Retrotransposition
What is simple transposition?
TE moves to a new target site
What is retrotransposition?
TE moves via an RNA intermediate
- The RNA transcribes back to DNA which breaks DOGMA and creates retroviruses since your body can’t tell its “bad” and just makes copies of it.
What is the DNA protein complex called in eukaryotic chromosomes?
Chromatin
What is chromatin?
protein bound to DNA that are subject to change during the life of the cell
How long is a single set of human chromosomes?
1 meter or 3.2 feet
