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MTM > WEEK 4 > Flashcards

WEEK 4 Flashcards

1
Q

Detail the ‘Central dogma’ of molecular biology

A

DNA⇌DNA⇌RNA→Protein
dna to dna via replication, dna to rna via transcription, rna to dna via reverse transcription (reverse transcriptase in retrovirus), rna to protein via translation

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2
Q

What is DNA?

A

Deoxyribonucleic acid, double-stranded molecule that forms a helix

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3
Q

What is RNA?

A

Ribonucleic acid. single-stranded molecule with intra-molecular base pairing

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4
Q

What are the differences between DNA and RNA?

A

RNA has an OH group at ribose C2, DNA doesn’t

RNA uses uracil (U), DNA uses thymine (T)

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5
Q

Bases of DNA/RNA

A 
Adenine
Guanine
Cytosine
Thymine (DNA)
Uracil (RNA)
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6
Q

What effect does RNA having an OH group at ribose C2 but DNA not having one have?

A

Causes RNA to be unstable in aqueous environments where DNA is more stable

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7
Q

Which are the purine bases?

A

Adenine and Guanine

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8
Q

Which are the pyrimidine bases?

A

Cytosine, Thymine and Uracil

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9
Q

How many H bonds between the respective purine and pyrimidine base pairs?

A

A-T=2 H bonds

G-C=3 H bonds

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10
Q

How do H bonds between base pairs aid DNA replication?

A

Allows easy replication as H bonds easily broken, so strands separate and complementary bases pair to form two molecules

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11
Q

What is a gene?

A

Sequence of DNA nucleotides

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12
Q

What is the genome?

A

An organism’s complete set of genetic information

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13
Q

Excluding genes, what are the other elements of the genome?

A

regulatory elements→’promoter’ and ‘enhancer’ regions
non-coding DNA→introns, removed from primary RNA transcript via splicing (exons=coding DNA)
repeat elements→regions that don’t endode a protein that occur commonly in tandem arrays

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14
Q

What is the method of DNA replication?

A

Semi-conservative

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15
Q

How is the DNA helix arranged?

A

contains two strands that run anti-parallel (5′ and 3′ ends at opposite ends of DNA molecule)

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16
Q

LOOK AT DNA STRUCTURE AND BONDING OF DNA MOLECULES

A

5′ end=triphosphate

3′ end=hydroxyl

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17
Q

What is the basic DNA building block?

A

deoxynucleotide triphosphate (dNTPs)

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18
Q

What are the enzymes for DNA synthesis?

A 
DNA helicase-causes separation of DNA helix to form 2 strands
DNA polymerase (1, 2 or 3)
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19
Q

Process of DNA synthesis

A

DNA helicase separates the two strands, H bond formed between complementary bases, a second dNTP comes in which is complementary to the next base so forms a H bond, then forms a covalent bond with the dNTP adjacent via DNA polymerase causing two phosphates to be lost

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20
Q

Characteristics of DNA polymerase

A

Proceeds in 5′ to 3′ direction
Adds 1000 bases/second to the chain
Requires dNTPs
Must have a template and an RNA primer→provides free 3′ end which receives incoming dNTP’s

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21
Q

What is the replication fork?

A

Contains leading and lagging strands on which DNA polymerase acts, DNA polymerase synthesis from 3′ end of the leading strand to the 5′ end, forming the 5′ to 3′ new strand-complementary to the leading strand, on the lagging strand, Okazaki fragments are formed in a 5′ to 3′ manner but from the 5′ end to the 3′ end via multiple DNA polymerase, ligation of strands via DNA ligase forms one big new strand complementary to the lagging strand

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22
Q

What initiates whole chromosome replication?

A

Origin proteins which form a replication ‘bubble’

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23
Q

How does DNA polymerase prevent errors in DNA replication?

A

It adds a base, moves back to check it and excises it if it’s wrong and moves on

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24
Q

What is the process of DNA forming RNA?

A

Transcription

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25
Q

What enzyme is needed for RNA synthesis?

A

RNA polymerase

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26
Q

What are the building blocks of RNA?

A

Adenine/Guanine/Cytosine/Uracil Triphosphate (ATP/GTP/CTP/UTP)

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27
Q

What is the directionality of RNA synthesis?

A

5′ to 3′

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28
Q

What is different from DNA replication and RNA synthesis?

A

Only one strand is copied in RNA synthesis (template/non-coding strand)

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29
Q

Process of transcription

A

Local DNA melting produces roughly 30bp bubble which moves along the DNA and extends the RNA chain, proteins involved in RNA processing bound to primary RNA transcript (spliceosome-removes introns from pre-mRNA)

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30
Q

What occurs between transcription and translation?

A

mRNA moves out the nucleus into the cytoplasm via nuclear pores

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31
Q

What is tRNA?

A

An adaptor molecule with 3 ‘hairpin’ stem-loop structures formed from intramolecular base pairing

32
Q

What are the two distinct functional regions on tRNA?

A

Amino acid binding site (specific to anticodon) and anticodon site (complementary to specific codon)

33
Q

What is an anticodon?

A

Trinucleotide sequence which is complementary to a codon found on mRNA-relates to DNA sequence

34
Q

What is a codon?

A

Trinucleotide sequence found on mRNA which is complementary to DNA sequence

35
Q

What is a polyribosome?

A

Multiple ribosomes found along the mRNA strand

36
Q

What are the two sub-units of a ribosome?

A

40S and 60S

37
Q

What is the function of ribosomes?

A

They are complexes that assemble strings of amino acids as introduced by the mRNA sequence

38
Q

What are the two binding sites on ribosomes?

A

A-site→aminoacyl-tRNA binding site

P-site→peptidyl-tRNA binding site

39
Q

What bonds are formed between AAs to form the polypeptide?

A

Covalent peptide bond on the C-terminus of the AA

40
Q

What defines the start of the coding region?

A

Methionine (MET) AA initiates protein synthesis universally

41
Q

Characteristics of the genetic code

A

read in groups of 3 bases
read in 5′ to 3′ direction
each AA is coded for by a codon
some AA coded for by more than one codon (degenerate)
3 codons don’t encode AAs (UAA, UGA and UAG are stop codons)

42
Q

What does it mean for the genetic code to be non-overlapping?

A

Each base is read only once

43
Q

What makes up the human genome?

A

DNA sequence on 1 chromosome from each of the 22 autosomal pairs and both X + Y (sex) chromosomes

44
Q

Define the transcriptome

A

The complete set of RNA transcripts

45
Q

Define the proteome

A

The complete set of proteins produced

46
Q

What is the major difference between the genome and the transcriptome+proteome?

A

Genome is stable whereas the transcriptome+proteome are dynamic

47
Q

What are blocks of tandem repeats called?

A

Satellite DNA

48
Q

What are the two types of Satellite DNA?

A

mini satellite-highly polymorphic, up to 1000 copies in one block
micro satellite-small arrays of simple sequence repeats (usually intronic DNA)

49
Q

Give three roles of multiple repeated sequences

A

Telomeres, centromeres and mini satellites

50
Q

What is the role of telomeres?

A

Allow replication to the tip of chromosomes, deletions immediately below telomeres due to instability of long tracts of repeats

51
Q

What is the role of centromeres?

A

Essential for segregation during cell division

52
Q

Give issues that result from mini satellites

A

can cause mispairing during cell division to give:
large scale duplication/deletion between homologous chromosomes or translocation of DNA between non-homologous chromosomes

53
Q

What is a chromosome?

A

A single DNA molecule

54
Q

What is a gene?

A

Sequence of DNA nucleotides (arranged one after the other along a chromosome with stretches of non-coding DNA between→exon-intron-exon-intron-exon)

55
Q

What are mitotic chromosomes formed from?

A

Highly packed chromatin

56
Q

What is the difference between euchromatin and heterochromatin?

A

Euchromatin contains loose chromatin structure (active)

Heterochromatic contains tightly packed chromatin structure (inactive)

57
Q

What is the purpose of mitosis?

A

cell division/organismal growth and genetically identical products

58
Q

What occurs to chromosomes during interphase and mitosis?

A

Interphase=duplication via replication origin sites (doubles no. of chromosomes)
Mitosis and Cytokinesis=division and segregation of chromosomes into two genetically identical cells

59
Q

What does a diploid cell (2n) form when it undergoes mitosis?

A

Two diploid cells (2n x2)

60
Q

What are the stages of Mitosis?

A

(interphase), Prophase, Prometaphase, Metaphase, Anaphase, Telophase, (cytokinesis)

61
Q

Describe Prophase in mitosis

A

chromosomes condense, nuclear envelope disappears, spindle assembles outside the nucleus-contains spindle pole and branching of microtubules (some pull DNA apart-kinetochore microtubules, some push microtubules from other pole away-interpolar microtubules)

62
Q

Describe Prometaphase in mitosis

A

spindle microtubules bind to chromosomes via kinetochore that develops around the centromere

63
Q

Describe Metaphase in mitosis

A

spindle gathers chromosomes to the equator, tension on kinetochores at centromeres facing opposite directions

64
Q

What is the M-phase checkpoint?

A

occurs after Metaphase, ensuring all chromosomes attached to all microtubules-preventing non-disjunction (too many chromosomes on one pole, not enough on the other)

65
Q

Describe Anaphase in mitosis

A

chromosomes at spindle poles, kinetochore microtubules begin to disappear, interpolar microtubules elongate to push apart poles

66
Q

Describe Telophase in mitosis

A

nuclear membrane begins to reform, chromosomes decondense, nucleoli reappear

67
Q

Describe Cytokinesis

A

initiation of plasma membrane cleavage splitting the cell into two via contraction of ring of actin and myosin filaments at cleavage burrows

68
Q

What is the purpose of meiosis?

A

gametogenesis

69
Q

What are the functions of meiosis?

A 
reduction division (haploid cell-23 c'somes per gamete (22 autosomal and X/Y)
re-assortment of genes (independent segregation of c'somes and crossing over)
70
Q

What is the only difference seen in Meiosis I from Mitosis?

A

Crossing over occurs at Metaphase I

71
Q

What are the two ways in which genetic variability is brought about during Meiosis?

A 
Independent reassortment (possibilities of haploid cells=2^number of c'somes-each c'some may be from mother/father)
Re-assortment via crossing over (exchange of genetic material between chromosomes when moving to the cell's equator-physical manifestations/link=chiasmata)
72
Q

What are the two differences seen in Meiosis II from Mitosis?

A

Metaphase II→kinetochores point in opposite directions, not the same direction, which cause cohesions in the centromere to split, sister chromatids separate
Anaphase II→sister chromatids at spindle poles

73
Q

Which requires a greater number of cell divisions to be produced: a human sperm cell or an egg cell?

A

Human sperm cell

74
Q

When is Meiosis I completed in an egg cell?

A

Ovulation

75
Q

When is Meiosis II completed in an egg cell?

A

Fertilisation

76
Q

How is Meiosis used to create an egg cell with large amounts of content?

A

Every cell division forms a larger cell and a much smaller polar body which is non-functional due to most cytoplasm going to potentially fertilising egg

MTM (7 decks)

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