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CENG | CMB | MI > Chapter 5 CMB DNA Replication > Flashcards

Chapter 5 CMB DNA Replication Flashcards

1
Q

What is DNA?

A
  • A double-stranded nucleic acid that contains the genetic information for cell growth, division and function.
  • Made up of alphabets called bases (A,T,G,C*)
  • These bases (arranged in triplets) code for amino acids which make up the proteins
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2
Q

Where are chromosomes located?

A

Located in the nucleus of eukaryotic cells

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3
Q

What are chromosomes composed of?

A

Composed of DNA wrapped around proteins called histones

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4
Q

What are chromosomes?

A

Physical carriers of genes

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5
Q

State the structural difference between chromatin and chromosome

A

Chromatin (decondensed or thread-like) vs chromosome (X-shaped: condensed chromatin)

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6
Q

What is a chromatin?

A

A complex of DNA and proteins in the nucleus, that condense to form chromosomes, in eukaryotic cell division

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7
Q

What are genes?

A
  1. Genes are basic physical and functional units of heredity.
  2. Genes are a set of instructions that determine what the organism is like, its appearance, how it survives, and how it behaves in its environment.
  3. Genes codes for a protein
  4. Genes codes for genetic traits that are inheritable
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8
Q

Are DNA and Genes same or different?

A

Functionally they are same, structurally they are different

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9
Q

What are Alleles and where are they located?

A

Alleles are 2 copies of a gene: One derived from the Mother and the other from the Father.
Located on homologous chromosomes

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10
Q

What is a locus? (Position)

A

Position of the allele on a chromosome

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11
Q

What are homologous chromosomes?

A

A pair of chromosomes, one inherited from each parent, that have corresponding gene sequences and that pair during meiosis.

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12
Q

What is a genome?

A

The complete set of genes in an organism

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13
Q

What is the structure of a DNA?

A

Double helix (twisted ladder)
Anti-parallel orientation

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14
Q

What is the structure of a right handed double helix?

A

Sugar phosphate backbone (upright) with bases attached to sugar and lie perpendicular to backbone

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15
Q

What is anti-parallel orientation of DNA?

A
  • each sugar-phosphate chain runs in opposite direction
  • A = T
  • C = G
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16
Q

What are the 3 components of DNA?

A
  1. Bases (ATCG)
  2. Sugar
  3. Phosphate
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17
Q

How does DNA serve as the genetic basis for living things? RSVE

A
  1. Replication of information
  2. Storage of information
  3. Variation by Mutation
  4. Expression of information
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18
Q

What is storage of information?

A

Each somatic cell contains a complete set of chromosomes but expresses only part of the genetic information
(eg digestive cells only produce enzymes but not melanin)

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19
Q

What is variation of mutation?

A

Mutation: change in the A, T, G, C sequence of DNA
Beneficial (advantage passed on) vs Bad mutations (disorder & death)

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20
Q

What is expression of information?

A

DNA > transcription > mRNA -> translation > protein

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21
Q

What is the structure of a nitrogenous base?

A

Complex ring structures composed of Carbon and Nitrogen atoms

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22
Q

Name the 5 types of bases

A

Adenine, Thymine, Cytosine, Guanine & Uracil

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23
Q

What bases do DNA contain?

A

Adenine, Thymine, Cytosine & Guanine

24
Q

What bases do RNA contain?

A

Adenine, Uracil, Cytosine & Guanine

25
Q

What are purines composed of?

A

Adenine & Guanine

26
Q

What are pyrimidines composed of? (Remember CUT)

A

Thymine, Uracil & Cytosine

27
Q

How does A pair with T?

A

2 Hydrogen bonds
A === T

28
Q

How does G pair with C?

A

3 Hydrogen bonds
G===_C

29
Q

What is the ratio of purines and pyrimidines?

A

1 (same number of adenine and thymine molecules
same number of guanine and cytosine molecules)

30
Q

State whether RNA & DNA is oxygenated

A

RNA: ribose (Oxygenated)
DNA: deoxyribose (Not oxygenated)

31
Q

What is the function of phosphoric acid?

A

Connects adjacent sugars by a phosphodiester bond

32
Q

What is DNA replication?

A

The process by which DNA makes a copy of itself

33
Q

When does DNA replication occur?

A

Occurs during interphase, prior to cell division

34
Q

What are involved in DNA replication?
dEET

A
  1. deoxyriboNucleosideTriPhosphate (dNTP)
  2. Energy source (ATP)
  3. Enzyme & proteins
  4. Template DNA
35
Q

What does dNTP serve as?

A

Building blocks for DNA

36
Q

State enzymes & proteins involved in DNA replication

A

1.DNA polymerases
2.Helicase
3.SSBP (Single-stranded DNA binding proteins)
4.Gyrase/Topoisomerase
5.Primase
6.Ligase.

37
Q

What is template DNA for in DNA replication?

A

Parent base sequence that specifies the complementary sequence of the new daughter DNA

38
Q

What are the 7 steps of DNA replication?

A
  1. DNA Gyrase:- unwinds the double helix
  2. DNA Helicase:- Unzips the double helix
  3. SSBP:- Stabilise the phosphodiester bonds between the sugar and phosphate preventing its breaking
  4. Primase:- Lays down RNA primer from which nucleotide polymerization can begin
  5. DNA Pol III:- Lays down complementary nucleotides in the 5’ – 3’ direction of the growing strand
  6. DNA Pol I:- Removes the RNA primers and lays down DNA nucleotides instead, however it leaves phosphodiester gaps towards the 3’ end.
  7. DNA Ligase:- Seals the gap in between the sugar-phosphate backbone (Okazaki fragments)
39
Q

What is leading strand?

A

polymerase travels in the same direction as the helicase.

40
Q

What is lagging strand?

A

moving away from the helicase

41
Q

What are okazaki fragments joined together by?

A

Okazaki Fragments are joined together by DNA ligase

42
Q

State the function of Gyrase/Topoisomerase in DNA replication

A

Topoisomerase/Gyrase creates nicks in DNA ahead of the replication fork to relax the supercoiling induced in the DNA by helicase activity

43
Q

What is the junction between the unwound part and the open part in DNA replication called?

A

A replication fork.

44
Q

Function of DNA helicase

A

-Breaks the hydrogen bonds between DNA strands
-Helicase unwinds and separates the DNA strands so that replication can continue.

45
Q

Function of Topoisomerase

A

regulates over winding or under winding of DNA

46
Q

Function of Single-stranded DNA binding proteins (SSBPs)

A

keeps the parental strands apart

47
Q

Function of primase

A

synthesizes a RNA primer (beginning of new DNA strand synthesis)

48
Q

Function of DNA polymerase I & III

A

DNA Polymerase III: Lays down complementary nucleotides in the 5’ – 3’ direction of the growing strand
DNA Polymerase I: Removes the RNA primers and lays down DNA nucleotides instead, however it leaves phosphodiester gaps towards the 3’ end.

49
Q

Function of DNA ligase

A

covalently links the Okazaki fragments together. It plays a role in repairing single-strand breaks in DNA (basically fill gaps).

50
Q

How are chromatids formed?

A

Result from the chromosome undergoing DNA replication just before cell division

51
Q

Where will a chromatid be distributed in?

A

A daughter cell

52
Q

What is a centromere and state its function.

A

Region with attachment sites for microtubules (spindle apparatus) that will move the chromosome during division

53
Q

Why is RNA Primase required before DNA Polymerase is able to synthesize new strand?

A

-DNA polymerase can only add nucleotide but cannot initiate DNA replication.

-To initiate the DNA replication, the enzyme RNA Primase adds a short sequence called PRIMER to the “origin” region so that DNA replication can be started.

-DNA polymerase is now able to add nucleotide and continue the DNA replication

54
Q

What can replication errors cause?

A

can cause a genetic MUTATION

55
Q

How to prevent replication errors?

A

PROOFREADING by the polymerase prevents mismatches
DNA REPAIR ENZYMES can repair damaged DNA also

56
Q

What are DNA binding proteins for?

A

keep the DNA apart

CENG | CMB | MI (25 decks)

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