DNA and Genes Flashcards
Epigenetics
Interaction of many genes or of the genotype with the environment.
3 genetic rules
- Genotype and phenotype are distinct
- Phenotype a from some alleles can mask others
- Organisms have two copies of each gene.
Replicon
Length of DNA that is replicated following one initiation event at a single origin.
What removes primers and fills in gaps
DNA polymerase ll
Critical requirements for replication
Template
Primer
3’OH end
What synthesizes RNA primer
Primase
Enzymes needed at replication fork
DNA polymerase lll SSBP DNA gyrase DNA helicase Primase
Why deoxyribose sugar in DNA?
Additional OH affect helix structure/packing
DNA must remain stable (DNA needed for life, RNA less so)
Mutation in splice site causes
Splicing at alternative sites (cryptic sites)
Point of genetic exchange between synapses chromosomes
Chiasmata
Complete linkage
Only parental gametes produced (no crossing over)
Degree of crossing over between two loci is proportional to..
Interlocus distance.
G rich regions looped back on themselves..
G-quartets.
Genotype
The alleles present at one or more specific loci
Genome
The total genetic information in an organism
Phenotype
The observable characteristics of an organism distinct of its genotype.
Pure breeding
When a certain trait is seen regardless of generation.
Chromatin
Complex of DNA, histones and nonhistone proteins within nucleus of eukaryotic cell
Chromatic
One of the two copies of a replicated chromosome that is joined at the centromere to the other copy
Centromere
Chromosomal region that holds sister chromatids together
Nucleosome structure
Histones octamer
- 2 copies of each core histone
- long N terminus amino acid tail from each histone
Transposon
DNA sequence that can change its position within the genome and alter the genome size
Satellite DNA
Large arrays of tandemly repeating, non-coding DNA
- main component of centromeres
Why is DNA replication regulated?
- to ensure all chromosomes replicate once per cycle
- to ensure that replication of the genome is error-free
Replisome
Replicates DNA bidirectionally from origins
Modes of DNA replication
- conservative
- semi conservative
- dispersive
Sequences that enhance ORC recognition
- AT-rich sequences
- dinucleotide repeats
- asymmetrical purine-pyrimidine sequences
- matrix attachment region sequences
Topoisomerase
Initiates unwinding by cutting one of the strands
Helicase
- assists unwinding
SSBP
Stabilizes separated strands and prevents them from recombining
DNA polymerase
- links together nucleotides monomers as they hydrogen bond to complementary bases
- can check for errors and make corrections
Ligase
Unites small unattached DNA segments on a strand
Key issues in DNA replication
- unwinding of helix
- reducing increased coiling generated during unwinding
- synthesis of primer for initiation
- discontinuous synthesis of second strand
- removal of RNA primers
- joining of gap-filling DNA to adjacent strand
- proofreading
Role of S checkpoint
- stabilizes stalled replication forks
- inhibition of initiation at unfired origins
- inhibition of entry into G2 or M
- slowing of ongoing fork progression
Implications for low DNA replication
Wound healing
Development of embryo
Functions of telomeres
- protect chromosomes from improper fusion
- protect from degradation
How can dsDNA be damaged
- chemicals
- spontaneous hydrolysis of nucleosides
- spontaneous hydrolysis of cytosine to uracil
- oxidation or methylation
- UV light
Uses of isolated genomic DNA
PCR template Cloning DNA sequencing DNA fingerprinting Crime investigation
