Week 6 - the genetic material Flashcards Preview

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Flashcards in Week 6 - the genetic material Deck (20)
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1

DNA - structure

nucleic acid composed of NUCLEOTIDES
- 5 carbon sugar (DEOXYRIBOSE)
- phosphate group (PO4)
- nitrogenous base → adenine, thymine, cytosine, guanine
- free hydroxyl group (-OH) →attached at the 3' carbon of sugars

2

phosphodiester bond

- bond between ADJACENT nucleotides
- formed between phosphate group of one nucleotide & the 3' -OH of next nucleotide

3

nitrogenous bases

PYRIMIDE - SINGLE RINGED STRUCTURE → thymine & cytosine
PURINE- DOUBLE RING STRUCTURE → adenine & guanine

4

chargaff rules

- amount of adenine = amount of thymine
- amount of cytosne= amount of guanine
- always equal proportion of purines & pyrimidines

5

DNA helix

- 2 strands are polymers of nucleotides
- phosphodiester backbone- repeating sugar & phosphate units joined by phosphodiester bonds
- consists of two polynucleotide strans wrapped aorund eachother in a double helix

6

DNA genes & inheritance

- nucleic acids STORE & TRANSMIT hereditary info
- sequence of bases along a nucleotide polymer →unique for each gene
- genes:
→ units of inheritance
- program the amino acid sequence of polypeptides and functional RNA species

7

DNA replication

EVERYTIME A SOMATIC CELL DIVIDES, CHROMOSOMAL DNA IS REPLICATED
- DNa replication in cells must be V accurate
- since the two strands of DNA are:
→complimentary , each strand acts as a template for building a new strand during DNA replication

8

DNA replication requirements

- something to copy: PARENT DNA MOLECULE
- something to do the copying: REPLICATION MACHINERY & REPLICATION ENZYMES
- building blokes to make copy: NUCLEOTIDE TRIPHOSPHATES

9

DNA replication - polymerase

DNA polymerase (SYNTHESISES a polymer of nucleotides; in this case - DNA strand)
- matches existing DNA bases w/ complementary nucleotides & links via PHOSPHODIESTER BOND
→ adds new bases to 3' end of strands
→ SYNTHESISE IN 5' TP 3' DIRECTION

RNA primers are removed and replaced w/ DNA later in process

10

Helicase

unwinds parental helix at replication forks

11

single-strand binding protein

binds & spabilises SS DNA until it can be used as a template

12

Topoisomerase

relieves ' overwinding' strain ahead of replication forks by breaking, swivelling & rejoining strands

13

primase

synthesise RNA primer at 5' end

14

DNA pol III

synthesises new strand, add NT to 3' of strand

15

DNA pol I

remove RNA NT of primer @ 5', replace w/ DNA NT

16

DNA ligase

joins 3' end of DNA that replaces primer to rest of leading strand & joins okazaki fragments

17

lagging strand synthesis

- discontinuous synthesis (Done by DNA Pol III)
- RNA primer made by primase for each okazaki fragmnet
- all RNA primers removed & replaced by DNA (DNA pol I)
- backbone sealed (by DNA ligase)

18

replication - prokaryotic

- E.coli model
- single circular molecule of DNA
- replication begins at one origin of replication
- proceeds in both directions around the chromosome

19

replication eukaryotic

complicated by:
- larger amount of DNa in multiple chromosomes
- linear structure of chromosomes

basinc enzymology is similar to bacterial replication
- reg. new enzymatic activirt for ealing w/ ends only (telomeres)

unable to rep. last sec.. of lagging strands → gradual shortening

20

telomeres

- composed of short repeated sequences of DNA at the ends of chromosomes
- telomerase - enzyme makes telomere of lagging strands useing internal RNA template
- leading strand can be replicated to tghe end
- telomerase developmentally regulated
- relationship between senescence & telomere length
- cancer cells generally show activation of telomeres