Lecture 2: DNA Synthesis and Replication Flashcards Preview

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Flashcards in Lecture 2: DNA Synthesis and Replication Deck (28):
1

"Beads on a String"

DNA tightly wound to histones. Must be unwound to this form to be usable for DNA replication.

2

Histones

Positively charged protein in chromatin used for condensing DNA.

3

Nucleosomes

Protect DNA from degradation. Made up of 8 histones (80bp between each histone).

4

Histone Acetylation

Acetylated histones- Have a neutral charge that does not interact with DNA. DNA is more unwound (less condensed) and able to have more gene expression.
Unacetylated histones- Have a positive charge and keep DNA condensed and tightly wound.

5

Origin Recognition Complex

Multi-subunit complex that binds to origin site and regulates the start of replication. This occurs during S phase.

6

Epigenetic Inheritance

Heritable traits that occur without changes to DNA sequence. i.e. Methylation of histones is inherited and is not in the genome.

7

Replication

Process by which DNA creates an exact copy of itself.

8

DNA Polymerase

Enzyme that copies template strand and adds complimentary base pairs on new strand. Synthesizes in 5' to 3' direction. Also has proofreading mechanisms to ensure correct base pairing.

9

Okazaki Fragments

Small fragments synthesized from the 5' to 3' direction on lagging strand. Fragments joined together by DNA Ligase.

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Leading Strand

5' to 3' direction and is synthesized continuously by the DNA Polymerase.

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Lagging Strand

3' to 5' direction and is made up of Okazaki Fragments. DNA Polymerase uses an RNA Primer

12

RNA Primer

Created by DNA Polymerase and Primase. Adds a short strand of RNA for starting point of DNA synthesis. Necessary for DNA polymerase to function (especially on lagging strand).

13

Primase

Builds RNA primers

14

DNA Ligase

Joins together Okazaki fragment and exons. Acts as a "glue".

15

DNA Helicase

Unzips double-stranded DNA at origin site to begin replication. Uses ATP as motor to slide along DNA.

16

Single-strand DNA Binding Proteins

Aid helicase in unwinding DNA. They bind to single-stranded DNA and help to prevent the DNA from creating hairpin loops.

17

Sliding Clamp

Keeps DNA Polymerase bound to strand of DNA during replication. Without it the polymerase would detach too early.

18

Clamp Loader

Loads a sliding clamp to each primer to aid DNA Polymerase.

19

Telomere

End of linear chromosomes that are composed of tandem repeats. Telomere length is maintained in germ cells by telomerase, but in somatic cells telomeres are shortened and can lead to cell senescence(cell stops dividing) or apoptosis.

20

Telomerase

Recognizes end of telomere and elongates it in 5' to 3' direction. Places a primer on lagging strand as well to extend it.

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Reverse Transcriptase

Synthesizes DNA from RNA. Telomerase has the ability to do this.

22

Telomerase

Recognizes end of telomere and elongates it in 5' to 3' direction. Places a primer on lagging strand as well to extend it. In cancer cells, cells express high levels of telomerase which make them immortal. In Progeria, cells do not express telomerase and cells senesce quickly.

23

Reverse Transcriptase

Synthesizes DNA from RNA. Telomerase has the ability to do this.

24

Topoisomerase

Relieve torsional stress in unwound DNA and prevents super coiling

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Cell Senescence

Cell stops dividing. (Cause of aging)

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Bloom's Syndrome

BLM protein is defective and helicase does not work properly. DNA cannot unwind or be repaired. Leads to developmental delays, high risk of cancer, and causes premature aging.

27

Heterochromatin

Highly condensed DNA and genes are silenced (not expressed). This occurs near the nuclear periphery.

28

Euchromatin

Highly expressed regions of DNA not wound tightly. Found in central core of nucleus and is easily accessible for replication.