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ESA1 > MGD 2- Genes > Flashcards

MGD 2- Genes Flashcards

1
Q

What is a nucleoside?

A

Base + Sugar via beta-glycosidic bond

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2
Q

What is a nucleotide?

A

Base + Sugar + Phosphate, via phosphodiester bond

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3
Q

Name the sugar type in DNA:

A

Deoxyribose

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4
Q

Name the sugar type in RNA:

A

Ribose

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5
Q

Which type of nucleic acid is single-stranded?

A

RNA

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6
Q

Name the base types present in RNA:

A

A, C, G, U

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7
Q

What is the conventional way to represent a DNA base sequence?

A

Top strand is 5’ to 3’, left to right

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8
Q

Why is the 5’ end of DNA delta negative?

A

Due to the negative charges present on the phosphate group at physiological pH

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9
Q

Which ion(s) are necessary to stabilise the negative charges of the phosphate group in DNA?

A

Mg2+

Na+

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10
Q

What is the secondary structure of DNA?

A

Right-handed double helix

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11
Q

What is the distance (in angstroms) between stacking bases?

A

3.4 A

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12
Q

How many base pairs form 1 turn of the DNA double helix?

A

10 bp

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13
Q

What is the diameter (in Angstroms) of the DNA double helix?

A

20 A

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14
Q

What RNA secondary structure can form?

A

Stem-loop

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15
Q

What bond joins nucleotides in DNA?

A

3’ to 5’ Phosphodiester link

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16
Q

Name the purine bases of DNA:

A

Adenine

Guanine

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17
Q

Name the pyrimidine bases of DNA:

A

Cytosine

Thymine

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18
Q

Name the pyrimidine bases of RNA:

A

Cytosine

Uracil

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19
Q

How many rings does a purine base have?

A

2 rings

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20
Q

How many rings does a pyrimidine base have?

A

1 ring

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21
Q

Name 3 types of non-covalent interactions:

A

1- Electrostatic interactions
2- Hydrogen bonds
3- Van der Waals interactions

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22
Q

Describe the 3 steps from DNA to chromosome formation:

A

1) -ve DNA is wrapped around +ve histone octamers
2) Beads-on-a-string is coiled into Solenoid 30nm fiber
3) Solenoid associates with scaffolding proteins into a Chromosome

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23
Q

Which histones form a histone octamer?

A

2 x (H2A, H2B, H3, H4)

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24
Q

What is the name of the DNA which is not wrapped around histones in the beads-on-a-string formation?

A

Linker DNA

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25
Q

What formation is the DNA in to form euchromatin?

A

Beads-on-a-string

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26
Q

What formation is the DNA in to form heterochromatin?

A

Solenoid 30nm fiber

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27
Q

How many chromosomes encode the entire human genome?

A

24 (22 autosomes plus X and Y)

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28
Q

How many chromosomes do humans have?

A

23 pairs of chromosomes = 46

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29
Q

What is the name given to the short arm of a chromosome?

A

P arm

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30
Q

What is the name given to the long arm of a chromosome?

A

Q arm

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31
Q

Which enzyme is required for DNA elongation?

A

DNA polymerase

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32
Q

What enzyme drives the forward reaction of DNA replication?

A

Pyrophosphatase (Cleaves PPi into 2Pi)

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33
Q

Name the 4 enzymes required for DNA replication:

A

DNA Helicase
Primase
DNA polymerase
DNA ligase

34
Q

What enzyme forms the DNA replication ‘bubble’?

A

DNA helicase, as it unwinds the DNA double helix

35
Q

Which prime end of DNA can DNA polymerase elongate?

A

3’ - OH

36
Q

How does DNA polymerase elongate the 5’ end of DNA?

A

Primase forms an RNA primer with a 3’ end which DNA polymerase can elongate. The primer is later removed and replaced with DNA.

37
Q

Which enzyme can seal the nick between okazaki fragments?

A

DNA ligase

38
Q

What is the role of mitosis?

A

Cellular division of somatic cells to produce 2 identical daughter cells, to allow growth, maintenance and repair.

39
Q

Name the 5 stages of Mitosis:

A 
1- Prophase
2- Prometaphase
3- Metaphase
4- Anaphase
5- Telophase
40
Q

What 2 events happen in prophase of mitosis?

A

1- Chromosomes condense

2- Nuclear membrane breaks down

41
Q

What happens in Prometaphase?

A

Kinetochore spindle fibres attach to centromeres of chromosomes

42
Q

What happens in Metaphase?

A

Chromosomes line up on equator of cell

43
Q

What happens in Anaphase?

A

Spindle fibres contract, causing centromeres to divide and sister chromatids move apart towards the poles of the cell

44
Q

What 4 events happens in Telophase?

A

1- Nuclear membrane reforms
2- Chromosomes decondense
3- Spindle fibers disappear
4- Cleavage furrow develops

45
Q

Define genotype:

A

Genetic make-up of an organism

46
Q

Define phenotype:

A

Expression of the genotype - observable characteristics

47
Q

Define gene:

A

Transcription unit, a section of DNA within a chromosome which contains the code for a protein, and associated sequences necessary for its expression.

48
Q

Define allele:

A

Alternative version of a gene

49
Q

Define dominant:

A

If phenotypic trait is present in homozygotes and heterozygotes

50
Q

Define recessive:

A

If phenotypic trait is present only in homozygotes

51
Q

Define co-dominance:

A

If both alleles in a heterozygote contribute to the phenotype

52
Q

Define complementation:

A

If more than 1 gene is responsible for phenotype, a child of 2 affected parents can be unaffected

53
Q

2 albino individuals can have an unaffected child. How?

A

Complementation - more than 1 gene is responsible for the phenotype.

54
Q

Define incomplete penetrance:

A

When the presence of a particular allele results in a defined phenotype in some, but not in all.

55
Q

How many DNA molecules is present in a “replicated” chromosome?

A

2

56
Q

Define genome:

A

The complete set of genetic material in a haploid set of chromosomes

57
Q

What are the 2 types of cell division?

A

1- Mitosis

2- Meiosis

58
Q

Which type of cell division creates genetic diversity?

A

Meiosis

59
Q

How does meiosis produce genetic diversity?

A

Crossing over of homologous chromosomes in Prophase 1

Independent segregation of chromosomes in Anaphase 1

60
Q

In which phase of meiosis does independent assortment take place?

A

Anaphase 1

61
Q

In which phase of meiosis does crossing over of homologous chromosomes occur?

A

Prophase 1

62
Q

What occurs in G1 of the cell cycle?

A

Cellular contents (excluding DNA) is replicated

63
Q

What occurs in S stage of the cell cycle?

A

DNA synthesis and replication

64
Q

What occurs in G2 of the cell cycle?

A

Double check of chromosomes for error, and makes repairs

65
Q

How many chromatids are present in 1 tetrad in meiosis 1?

A

4 chromatids

66
Q

How many replicated chromosomes are present at the start of Meiosis, and how many are present at the end?

A

46 replicated chromosomes at the start

23 replicated chromosomes at the end

67
Q

Terminally differentiated cells are locked in which stage of the cell cycle?

A

G0

68
Q

What is the result after meiosis of 1 oocyte (2n)?

A

1 egg cell precursor (n)

3 polar bodies

69
Q

What is the result after meiosis of 1 spermatocyte (2n)?

A

4 sperm (n)

70
Q

What is the equation to calculate recombination frequency?

A

(Number of recombinants / total progeny) x 100

71
Q

If the recombination frequency is less than 50 percent, what can be inferred?

A

They are on the same chromosome

72
Q

What pattern of inheritance does Sickle Cell disease follow?

A

Autosomal recessive

73
Q

Mating between 2 heterozygotes carrying an autosomal recessive disease gives what chance of having an affected child?

A

25% chance

74
Q

Which pattern of inheritance can skip generations?

A

Autosomal recessive

75
Q

A pedigree in which all generations are affected, and affects equally men and women most likely follows which pattern of inheritance?

A

Autosomal dominant

76
Q

Huntingdon’s disease follows which pattern of inheritance?

A

Autosomal dominant

77
Q

Haemophilia A follows which pattern of inheritance?

A

X-linked recessive

78
Q

Describe the individuals affected by an X-linked recessive disorder:

A

Homozygous females,

Hemizygous males

79
Q

Define cloning:

A

To make an identical copy of something

80
Q

What do you need to carry out a PCR reaction?

A
  • Thermocycler
  • Taq. polymerase
  • dNTPs
  • DNA to be copied
  • DNA primers
  • Mg2+
81
Q

How is a PCR reaction performed?

A
  • DNA heated to 95’C = form ssDNA
  • Cooled to 50’C = primers anneal to ssDNA
  • Heat to 72’C = optimum temp for T. pol
  • Repeat = exponential increase of target DNA
82
Q

Define cloning vector:

A

A small piece of DNA taken from a virus or a plasmid that can be stably maintained in an organism

ESA1 (22 decks)

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