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Molecular Biology Flashcards

1
Q

What is genetics?

A

This is the study of enes, genetic variation, and heredity in organisms.

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2
Q

what are genes?

A

These are hereditary units that reside in DNA

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3
Q

What are gene locus?

A

This is a specific area on a chromosome that is occupied by each gene.

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4
Q

What is the blending theory?

A

it was thought that parents produce hereditary fluids that mix together to form offspring with a mixture of characteristics of their parents.

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5
Q

What was the main problem with the blending theory?

A

Children weren’t always a mixture of both parents characteristics, sometimes children only had one parents characteristics or neither.

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6
Q

Why was mender’s work successful?

A
  1. He could self-fertilise the plant
  2. He cold prevent self-fertilisation by amputating the anthers
  3. He cold pollenate pollen less flowers by brushing on pollen form another flower.
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7
Q

Why did Wendell use the pea plant?

A
  1. Each pea in a pod was a progeny of a separate mating. egg being fertilised by male
  2. Seeds developed only after fertilisation
  3. These plants breed true- mutations rarely happened.
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8
Q

What were the traits considered by Mendell?

A

Height, seed colour, seed shape, flower colour, flower position, pod colour and pod shape

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9
Q

Why use a monohybrid cross?

A

It would be difficult to study all the traits of an organism by grouping them together so when you use a monohybrid cross it allows you to easily examine the specific genes and traits.

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10
Q

What are alleles?

A

These are a pair that that is found within the gene that can either be dominant x dominant, dominant x recessive and recessive x recessive

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11
Q

What is menders law of segregation?

A

the characteristics of an organism are controlled by genes occurring in pairs. Of such a pair of genes only one can be carried in any gamete. So that the members of a pair are carried in different gametes.

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12
Q

What is phenotype?

A

Phenotype is the resulting physical characteristics of the alleles/genes.

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13
Q

What is genotype?

A

Genotype is the specific type of pair of the alleles.

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14
Q

What is mendell’s second law?

A

Each member of a pair of alleles segregates independently and may combine randomly in a gamete with either member of a pair.

This is basically saying that when the male and female gamete combine (remember the first law says that male and female gametes only take one allele) they can combine randomly so yes the possible offspring can be 1:2 rr, Rr, Rr but because its random the person can still sendup have three Rr children.

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15
Q

What is an incomplete dominance?

A

this is when offspring produces a blended phenotype which is a combination of the parents phenotype while also no being it at all. example Red and white flowers produce a pink flower offspring

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16
Q

What is codominace?

A

This is when offspring is a blend of the two parents opposing phenotypes and it is visible that the offspring has characteristics from the parents. e.g red and white flowers produce offspring with red and white polka dots.

Because it is unsure which of the alleles is dominant. they may use wo different letters RR + WW = RW

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17
Q

What is pleiotropism?

A

when one gene influences two or more seemingly unrelated phenotypic traits.

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18
Q

What is the major effect?

A

This is the trait that is clearly evident

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19
Q

what are secondary traits?

A

These are less evident traits than the major effect

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20
Q

What is polygenic inheritance?

A

This is when a trait displays continuous variation. like height or skin colour is instantly varies and these traits are determined by a number of different genes present at different loci.

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21
Q

How does the environment affect phenotype?

A

a light skinned person living in a sunny area will be of a darker skin colour than a light skinned person living in a cool overcast environment

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22
Q

What is penetrant and non-pentrant?

A

A gene that expresses itself is penetrant while a gene that doesnt express itself is non-penetrant

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23
Q

what is percentage penetrance?

A

This is the percentage of individuals that may and do show the effect of a gene in their gene

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24
Q

What is expressivity?

A

this is the percentage a gene affects the phenotype.

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25
Q

what are lethal genes?

A

these are genes whose effects are so drastic that they result in the death of the bearer of certain genotypes

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26
Q

what is epistasis?

A

The expression of a pair of alleles is influenced by the genotype at other loci on the chromosomes.
e.g Aabb ( bb causes a reaction)

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27
Q

Recessive epistasis?

A

AAbb

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28
Q

Dominant epistasis?

A

AaBB

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29
Q

What is Monoecious?

A

This is what plant is called when both male and female flowers occur on the plant.

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30
Q

What is heterogametic sex?

A

because the male has two kinds of sec chromosomes X&Y he is called this.

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31
Q

What is homogametic sex?

A

Since the female has one sex chromosome she is called homogametic sex

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32
Q

What are the four basic biological macromolecules?

A

carbohydrates, lipids, proteins, nucleic acids.

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33
Q

What are nucleic acids?

A

include DNA and RNA; composed of monomers nucleotides; information storage. Nucleic acids contain instructions for protein synthesis and allow organisms to transfer genetic information from one generation to the next

34
Q

What is molecular biology?

A

Analysis of the flow of information among DNA, RNA & protein

35
Q

what is DNA?

A

is the hereditary material in humans and almost all other organisms. encoded all the information needed to create and direct the chemical machinery of life

36
Q

What is Griffith and the transforming principle?

A

Work with the bacterium
Streptococcus pneumoniae showed that genetic material could be transferred; molecule of inheritance (transforming principle).
The presence of the dead S strain resulted in the transformation of the R strain.

37
Q

What is the chemical structure of DNA?

A

DNA consists of alternating units of phosphate and sugar (deoxyribose), connected to each sugar is one of the nitrogenous bases

38
Q

What are the different kinds of nitrogenous bases?

A

purine - A & G

pyrimidine - T & C

39
Q

What is a glycosidic linkage/bond?

A

This is a type of covalent bond that attaches a base to a sugar.

40
Q

What is a phosphodiester bond?

A

A phosphodiester bond occurs when exactly two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds.

41
Q

what is a hydroxyl group?

A

A hydroxy or hydroxyl group is the entity with the formula OH. It contains oxygen bonded to hydrogen.

42
Q

Where in DNA is a phosphodiester bond?

A

The PO-4 linkage

43
Q

what is antiparallel arrangement?

A

This is a term applies to two strands of DNA and how they move in opposite directions but are complementary.

44
Q

Who did the study on Relative amounts of nitrogen bases in different
samples of DNA?

A

Chargaff & Davidson 1955

45
Q

How to find the DNA content of a cell?

A

The amount of purines (A+G) is equal tot he amount of pyrimidines (C+T)

46
Q

How does x ray crystallography and diffraction work?

A

If the substance has a repeating structure, the pattern of scattering, known as the diffraction pattern, is mathematically related to the structural
arrangement of the atoms causing the scattering

47
Q

What are the main points of the Watson and crick model?

A
  1. Two polynucleotide chains coiled around a central axis.
  2. Two chains are antiparallel.
  3. The bases of both strand are lying inside of the structure and stacking flat on one another, 0.34 nm apart.
  4. The two strands are held together by hydrogen bonds.
  5. One complete turn of the helix is 3.4 nm long and contains 10 bases.
  6. The double helix measures 2 nm in diameter.
48
Q

What are the functions of DNA?

A

HETEROCATALYTIC: directs the synthesis of other molecules
AUTOCATALYTIC: directs the synthesis of itself

49
Q

What are the nitrogen bases in dna?

A

Adenine - deoxyadenosine triphosphate
Cytosine - deoxycytidine triphosphate
Guanine - deoxyguanosine triphosphate
Thymine - deoxythymidine triphosphate

50
Q

What are the nitrogen bases in RNA?

A

Adenine - deoxyadenosine triphosphate
Cytosine - deoxycytidine triphosphate
Guanine - deoxyguanosine triphosphate
Uracil - uridine triphosphate

51
Q

What are the functions of RNA?

A
  1. Genetic - i.e. makes up the genome

2. non-genetic - i.e. carries out the instructions of DNA, no genetic role

52
Q

What is the composition of chromatin?

A

1/3 DNA, 1/3 Histones, 1/3 non-histone proteins

53
Q

What are the different types of histone proteins?

A

H1, H2A, H2B, H3, H4

54
Q

How are nucleosomes formed?

A

DNA wraps around histone cores to produce a bead-like structure

55
Q

What are the three levels of reversible organization of DNA?

A

nucleosome/ 10 nm fibre
30 nm fibre
radial loop-scaffold

56
Q

How is prokaryotic DNA condensed?

A

circular unfolded
folded
supercoiled

57
Q

what did Meselson and Stahl (1958) create?

A

demonstrated that DNA replication is semi-conservative in E. coli (14N,15N, CsCl density gradient centrifugation)

58
Q

Which model of DNA replication applies to E. coli?

A

Semi-conservative

59
Q

What kind of DNA molecule does eukaryotic and prokaryotic (bacteria)?

A

bacteria (prokaryote) - circular DNA molecule

eukaryote - linear DNA molecule

60
Q

what is the transforming principle?

A

Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA (not proteins) can transform the properties of cells, clarifying the chemical nature of genes. Avery, MacLeod and McCarty identified DNA as the “transforming principle” while studying Streptococcus pneumoniae, bacteria that can cause pneumonia

61
Q

How is a bee attached to a sugar?

A

Via a glycosidic linkage

62
Q

What is a nucleoside?

A

This is a base that is bonded to a sugar without a phosphate (PO4)

63
Q

Describe the deoxyribose sugar

A

A pentose, a 5-carbon sugar.

4 carbons and an oxygen make up the 5-membered ring; the other carbon branches off the ring.

64
Q

what is a phosphodiester bond?

A

This is the phosphate (PO4) linkage in DNA

65
Q

What is a base pair?

A

This is a pair of complementary bases. e.g AT GC

66
Q

What are the requirements for semi-conservative replication?

A
  1. DNA must act as a template for complementary base pairing
  2. dATP, dGTP, dCTP, and dTTP
  3. RNA primer
  4. The enzyme DNA polymerase must be present catalyze the formation of phosphoester bonds between the dNTPS
  5. The reaction involved in replication is endergonic; a source of chemical energy must be present
67
Q

What kind of reaction is DNA replication?

A

Endergonic -

Which means a source of chemical energy must be present

68
Q

Describe the DNA replication process?

A
  1. Begins with the unwinding of the double helix to expose the bases in each DNA strand
  2. Each unpaired nucleotide in the template will attract a complementary nucleotide and base pair via hydrogen bonding (after the formation of a primer)
  3. Enzymes link the aligned nucleotides by phosphodiester bonds to form a continuous strand
69
Q

What is bidirectional replication?

A

Bidirectional replication involves replicating DNA in two directions at the same time resulting in a leading strand (were replication occurs more rapidly) and a lagging strand (with slower replication).

70
Q

How does bidirectional replication take place in prokaryotes (bacteria)?

A

In bacteria, a single ori is found. Bidirectional replication
starts at the origin of replication and proceeds until the new strands meet each other on the opposite
side of the chromosome

71
Q

Which strand is copied with Okazaki fragments?

A

lagging (5’ - 3’)

72
Q

What are the different proteins required for DNA replication?

A 
DNA helicase
Single-strand binding proteins
Topoisomerase 
Primase 
DNA polymerase
DNA ligase
73
Q

What events must occur in order to complete the synthesis of the new daughter DNA strands?

A

(1) removal of the RNA primers,
(2) synthesis of DNA in the area where the primers have been removed
(3) the covalent joining of adjacent fragments of DNA

74
Q

What are exonuclease?

A

Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3′ or the 5′ end occurs. This is helpful in proof reading.

75
Q

What are the telomere sequence in humans?

A

TTAGGG

76
Q

What is the messenger hypothesis for RNA?

A

An RNA molecule forms as a complementary copy of one DNA strand of a gene & travels to the cytoplasm where it serves as template for the synthesis of a protein.

77
Q

What is the adapter hypothesis for RNA?

A

An adapter molecule binds to specific amino acids at one region & recognizes the sequence of nucleotides at another region

78
Q

What is transcription?

A

Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA).

79
Q

What are the requirements for Transcription: DNA-directed RNA synthesis?

A

DNA template
ribonucleoside triphosphates
RNA polymerase
(+ various accessory proteins called transcription factors)

80
Q

What is open reading frame?

A

Coding region

81
Q

What are the uses for the different kinds of polymerases?

A

eukaryotes have three RNA polymerases (I, II, and III)

  1. RNA polymerase II is used for mRNA synthesis +snRNA
  2. pol I for rRNA
  3. pol III for tRNA
82
Q

What is a transcription bubble?

A

The region that is unwound by RNA polymerase to allow transcription and rewound behind the enzyme.

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