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Flashcards in MGD 2- Genes Deck (82)
1

What is a nucleoside?

Base + Sugar via beta-glycosidic bond

2

What is a nucleotide?

Base + Sugar + Phosphate, via phosphodiester bond

3

Name the sugar type in DNA:

Deoxyribose

4

Name the sugar type in RNA:

Ribose

5

Which type of nucleic acid is single-stranded?

RNA

6

Name the base types present in RNA:

A, C, G, U

7

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

Top strand is 5' to 3', left to right

8

Why is the 5' end of DNA delta negative?

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

9

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

Mg2+
Na+

10

What is the secondary structure of DNA?

Right-handed double helix

11

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

3.4 A

12

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

10 bp

13

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

20 A

14

What RNA secondary structure can form?

Stem-loop

15

What bond joins nucleotides in DNA?

3' to 5' Phosphodiester link

16

Name the purine bases of DNA:

Adenine
Guanine

17

Name the pyrimidine bases of DNA:

Cytosine
Thymine

18

Name the pyrimidine bases of RNA:

Cytosine
Uracil

19

How many rings does a purine base have?

2 rings

20

How many rings does a pyrimidine base have?

1 ring

21

Name 3 types of non-covalent interactions:

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

22

Describe the 3 steps from DNA to chromosome formation:

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

23

Which histones form a histone octamer?

2 x (H2A, H2B, H3, H4)

24

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

Linker DNA

25

What formation is the DNA in to form euchromatin?

Beads-on-a-string

26

What formation is the DNA in to form heterochromatin?

Solenoid 30nm fiber

27

How many chromosomes encode the entire human genome?

24 (22 autosomes plus X and Y)

28

How many chromosomes do humans have?

23 pairs of chromosomes = 46

29

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

P arm

30

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

Q arm

31

Which enzyme is required for DNA elongation?

DNA polymerase

32

What enzyme drives the forward reaction of DNA replication?

Pyrophosphatase (Cleaves PPi into 2Pi)

33

Name the 4 enzymes required for DNA replication:

DNA Helicase
Primase
DNA polymerase
DNA ligase

34

What enzyme forms the DNA replication 'bubble'?

DNA helicase, as it unwinds the DNA double helix

35

Which prime end of DNA can DNA polymerase elongate?

3' - OH

36

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

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

37

Which enzyme can seal the nick between okazaki fragments?

DNA ligase

38

What is the role of mitosis?

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

39

Name the 5 stages of Mitosis:

1- Prophase
2- Prometaphase
3- Metaphase
4- Anaphase
5- Telophase

40

What 2 events happen in prophase of mitosis?

1- Chromosomes condense
2- Nuclear membrane breaks down

41

What happens in Prometaphase?

Kinetochore spindle fibres attach to centromeres of chromosomes

42

What happens in Metaphase?

Chromosomes line up on equator of cell

43

What happens in Anaphase?

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

44

What 4 events happens in Telophase?

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

45

Define genotype:

Genetic make-up of an organism

46

Define phenotype:

Expression of the genotype - observable characteristics

47

Define gene:

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

48

Define allele:

Alternative version of a gene

49

Define dominant:

If phenotypic trait is present in homozygotes and heterozygotes

50

Define recessive:

If phenotypic trait is present only in homozygotes

51

Define co-dominance:

If both alleles in a heterozygote contribute to the phenotype

52

Define complementation:

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

53

2 albino individuals can have an unaffected child. How?

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

54

Define incomplete penetrance:

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

55

How many DNA molecules is present in a "replicated" chromosome?

2

56

Define genome:

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

57

What are the 2 types of cell division?

1- Mitosis
2- Meiosis

58

Which type of cell division creates genetic diversity?

Meiosis

59

How does meiosis produce genetic diversity?

Crossing over of homologous chromosomes in Prophase 1
Independent segregation of chromosomes in Anaphase 1

60

In which phase of meiosis does independent assortment take place?

Anaphase 1

61

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

Prophase 1

62

What occurs in G1 of the cell cycle?

Cellular contents (excluding DNA) is replicated

63

What occurs in S stage of the cell cycle?

DNA synthesis and replication

64

What occurs in G2 of the cell cycle?

Double check of chromosomes for error, and makes repairs

65

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

4 chromatids

66

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

46 replicated chromosomes at the start
23 replicated chromosomes at the end

67

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

G0

68

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

1 egg cell precursor (n)
3 polar bodies

69

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

4 sperm (n)

70

What is the equation to calculate recombination frequency?

(Number of recombinants / total progeny) x 100

71

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

They are on the same chromosome

72

What pattern of inheritance does Sickle Cell disease follow?

Autosomal recessive

73

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

25% chance

74

Which pattern of inheritance can skip generations?

Autosomal recessive

75

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

Autosomal dominant

76

Huntingdon's disease follows which pattern of inheritance?

Autosomal dominant

77

Haemophilia A follows which pattern of inheritance?

X-linked recessive

78

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

Homozygous females,
Hemizygous males

79

Define cloning:

To make an identical copy of something

80

What do you need to carry out a PCR reaction?

- Thermocycler
- Taq. polymerase
- dNTPs
- DNA to be copied
- DNA primers
- Mg2+

81

How is a PCR reaction performed?

- 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

Define cloning vector:

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