Chapter 10 Flashcards
What is supercoiled DNA?
DNA that is more compact than its relaxed counterpart
Underwound DNA is (negatively or positively) supercoiled?
Negatively
Overwound DNA is (negatively or positively) supercoiled?
Positively
What is the purpose of underwound DNA?
To allow chromosomes to fit within the nucleus
Type I topisomerases do what?
Change the supercoiled state by creating a transient break in one strand of the duplex
Type II topisomerases do what?
Make a transient break in both strands of the DNA duplex, can also tie a DNA molecule into knots or untie DNA knots
Define: Transient
Lasting for a short time
Define: Denaturation
Ability to separate into its separate components
Thermal denaturation
DNA melting
How can you monitor thermal denaturation?
The increase in absorbance of UV light by dissolved DNA
Higher the GC content (higher or lower) the melting temp?
Higher
Higher AT (higher or lower) the melting temp?
Lower
Define: Renaturation
When single-stranded DNA molecules are capable of reassociating
Reannealing is also known as
Renaturation
What are the 3 broad classes of DNA sequences?
- highly repeated fraction
- moderately repeated fraction
- nonrepeated fraction
Highly repeated DNA sequences represent how much total DNA?
1-10%
What are satellite DNAs?
Short sequences that tend to evolve very rapidly
What are minisatellite DNAs?
Unstable and tend to be variable in the population; form the basis of DNA fingerprinting
What are microsatellite DNAs?
Shortest sequences and typically found in small clusters; implicated in genetic disorders
FISH stands for
Fluorescent In Situ Hybridization
What are FISH?
Fluorescent probes are generated towards a specific DNA sequence which allows determination of its location within the genome
What are FISH commonly used for?
Visualize repetitive sequences like that found in satellite DNA localized in the centromeric regions of chromosome, or determining location of single copy genes
SINEs stand for:
Short Interspersed Elements
LINEs stand for:
Long Interspersed Elements
Where are noncoding elements found in the genome?
Throughout the genome, and grouped into SINEs or LINEs
What is polyploidization?
Whole-genome duplication
What is Whole-genome duplication?
offspring that have 4 chromosome homologs rather than 2
Where are whole-genome duplication typically found?
In higher order plants
Mechanism is whole-genome duplication
2 related species can mate to form a hybrid organism with the combined chromosomes from both parents
How can duplication occur in DNA sequences?
Unequal crossing, plays role in evolution
What are pseudogenes?
Genes that resemble active genes but are inactive
Where can DNA duplication occur?
Within a portion of a single chromosome
What are transposons?
Jumping genes
Transposons require what? (3)
- transposase enzyme
- certain sequences that are transposon sequence
- target site
Transposable elements appear to have done what?
Given rise to genes and advanced eukaryotes
How many genes does a human have approximately?
20,000
What is alternative splicing?
When a single gene can encode a number of related proteins
What are microRNAs?
Noncoding RNAs that can have gene regulatory functions
Define: Intergenic
Majority of the genome lies between protein coding genes and is intergenic
What are structural variants?
Large changes range from hundreds to millions of base pairs in length
