7. Nucleic Acids Flashcards
(37 cards)
7.1 What is a nucleosome?
The structured unit of chromatin fiber
The fiber is wrapped around 8 histone protiens, the ends are linked to an additional H1 protien
Linker DNA connects to next nucleosome
7.1 Nucleosome preperation for nuclear division
To prepare for division, the coiled structure coils again to form a supercoiled chromosome
7.1 What is the order of strands during replication?
Leading strand: Synthesized 5’ to 3’
contineous
Lagging strand 3’ to 5’, in pieces
7.1 What does helicase do?
This enzyme breaks hydrogen bonds between bases and unwinds helix
7.1 What does gyrase do?
Relieves tension stress on DNA when unwinding
7.1 What are single strand binding protiens?
Prevent DNA strands reconnecting
7.1 What does primase do?
Synthesizes RNA primers required by lagging strand
7.1 What does DNA polymerase III do?
Builds complementary strand by adding nucleotides, moves 5’ to 3’
7.1 What does DNA polymerase I do?
Replaces RNA primers with nucleotides
7.1 What does ligase do?
Binds backbones of adjacent okazaki fragments, lagging strand
7.1 What are tandem repeats?
Do not code for protien but repeat over and over again
7.1 Function of tandem repeats
1) Telomere @ end of chromosome to protect
2) Regulates where, when and how protiens are made
3) Provides code to make RNA
4) Might be leftover from viral infections
5) “junk” DNA
7.1 What is VNTRS
Variable Number Tandem Repeat Sequences
number of repeats
Use: DNA profilling
7.1 What are dideoxynucleotides
Lack the ‘3 Hydroxyl group so they can’t form bond with next nucleotide
They also have a florecent marker on the base
7.1 Sanger sequencing
1) 4 PCR mixes are made that contain normal nucleotides (+ replication materials) and one type of dideoxynucluotide (ddA, ddT, ddC or ddG)
2) Within each mix, DNA polymerase III replicates stopping by change when it adds dideoxynucleotide (many strands of DNA with different lengths)
3) The replicated DNA is run through electrophoresis where the shorter pieces make it farther
7.1 What did the Hersey and Chase experiment prove?
Was DNA or protien the genetic material?
Vriuses with radioactive protiens (radiactive sulfur) and viruses with radioactive DNA (radiactive phosphorus) were tested as they infected bacteria
The bacteria and viruses were put into a centerifuge, the viruses beign later remained in supernatant while the bacteria formed a pellet
It was found that the supernatant was radiactive for protien, and the pellet radioactive for DNA
7.2 What is gene expression?
The appearebce in a phenotype attributed to a particular gene
7.2 Why is gene expression regulated?
- To save energy and space
- Response to changing environment
7.2 Types of sequences associated with gene regulation
Promoter-Proximal Sequences: any regulatory sequence in DNA
- Enhancers: DNA codes that increase gene expression
- Silencers: decrease
7.2 What is the role of histone tails?
Histone tails are typically positively charged so they wrap tightly around the negative DNA
7.2 Methylation of Histone Tails
A methyl group is added to the tail which maintains positive chrage, makes DNA more coiled, reduces transcription
Supercoild DNA = heterochromatin
7.2 Acetylation of histone tails
A acetyl group is added to tail which nuetralises charge making DNA less ciled, more transcription
Loosley packed = euchromatin
7.2 How do DNA methylation patterns change?
DNA (rather than histones) can alos be methylated
Nature: influenced by heritability, not genetically pre-determined. DIfferent cell types have different patterns
Nurture: Environmental factors, diet pathogen exposure, may influence level of DNA methylation
7.2 What is a gene?
A sequence of DNA which is transcribed into RNA
