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CELS 191 > Molecular Biology and Genetics > Flashcards

Molecular Biology and Genetics Flashcards

1
Q

What is a sex-linked chromosome?

A

Genes that appear on the sex chromosomes

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2
Q

What are linked genes?

A

Two genes on the same chromosome

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3
Q

What are some examples of sex-linked traits

A

Red/green colour blindness

Haemophilia

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4
Q

Define autosomes

A

Chromosomes that are not sex chromosomes

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5
Q

What is haploid/diploid sex determination?

A

When an individual with a haploid set of chromosomes is (for example) male and an individual with a diploids set of chromosomes is female

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6
Q

How is sex determined in humans?

A

the presence of the Y chromosome ensures that an individual is male because it encodes the development of the testis

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7
Q

How do you describe individuals which have two different sex chromosomes (such as males in humans or females in birds)

A

Heterogametic

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8
Q

How do you describe individuals which have two of the same sex chromosomes (such as females in humans or males in birds)

A

Homogametic

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9
Q

Define hemizygous

A

eg. a male is hemizygous
Males can not be homozygous or heterozygous because they only have one X chromosomes which means they cannot have two different alleles for the same trait

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10
Q

If a trait is a sex-linked trait then it appear on the _______ chromosome

A

X

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11
Q

X-linked DOMINANT alleles will show more in

A

females

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12
Q

X-linked RECESSIVE alleles will show more in

A

males

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13
Q

Explain the predicted phenotypes of the two sons and two daughters of parents if the
- mum is a normal homozygous female
- dad is a colour blind male
and colour blindness is a recessive sex-linked trait

A
  • the mother can only produce eggs that have X chromosomes that are normal (eg. n,n)
  • the father can produce sperm with either an X chromosome (that will be colour blind - c) and produce a girl, or a Y chromosome and produce a boy
  • the daughters of this couple will have two X chromosomes, one from mum and one from dad so will both have the genotype XnXc and be carries
  • the sons of this couple will carry the Y chromosome which means they can not inherit the c from their dad so must both have the genotype XnY and be normal
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14
Q

Explain the predicted phenotypes of the two sons and two daughters of parents if the
- mum is a carrier female
- dad is a normal male
and colour blindness is a recessive sex-linked trait

A
  • the mother can produce eggs that have X chromosomes are with normal (n) or colour blind (c)
  • the father can produce sperm with either an X chromosome (that will be normal - n) and produce a girl or, a Y chromosome and produce a boy
  • the sons of this couple will inherit the Y chromosome from the dad but can inherit the normal (n) X chromosome from mum or the colour blind (c) X chromosome from mum
  • half the sons will have the genotype XnY and be normal and half will have the genotype XcY and be colour blind
  • the daughters of this couple will inherit the Xc from their dad and either the Xc or Xn from their mum
  • half the daughters will have the genotype XnXn and be normal and half the daughters will have the genotype XnXc and be carriers
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15
Q

Linked genes show a bias towards

A

parental phenotypes

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16
Q

Independent assortment creates new combinations of ________ genes

A

unlinked

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17
Q

Crossing over creates new combinations of ________ genes

A

linked

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18
Q

What does Mendel’s 1st Law (Law of Segregation) state?

A

Genes segregate at meiosis so that each gamete contains only 1 of the two possessed by the parent

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19
Q

What does Mendel’s 2nd Law (Law of Independent Assortment) state?

A

Alleles of different genes assort independently during gamete formation

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20
Q

Define a population

A

Localised groups of individuals of the same species

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21
Q

Define the gene pool

A

total aggregate of genes (and their alleles) in the population at one time

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22
Q

Why might we have to estimate the frequencies of genotypes in a population?

A
  • to predict how many individuals in a population will inherit a genetic disease
  • to estimate the proportion of individuals in a population who are carriers of a genetic disease
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23
Q

p + q = ?

where p = ________ and q = ________

A

1
p = frequency of dominant alleles
q = frequency of recessive alleles

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24
Q

What is the Hardy-Weinberg equation and when would it be used?

A

p² + 2pq + q² = 1

It would be used to predict the number of genotypes in a population

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25
Q

What do p², 2pq and q² represent in the Hardy-Weinberg equation?

A
  • p² = the proportion of homozygous dominant genotypes there are in the population
  • q² = the proportion of homozygous recessive genotypes there are in the population
  • 2pq = the proportion of heterozygous dominant genotypes there are in the population
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26
Q

What are 7 ways allele frequencies can change?

A
  1. non-random mating
  2. random genetic drift
  3. bottleneck effect
  4. founder effect
  5. natural selection
  6. gene flow or migration
  7. mutation
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27
Q

What are two types of non-random mating?

A
  • assortative mating

- inbreeding

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28
Q

Define assortative mating

A

Intentionally choosing mates that look identical to you or the complete opposite

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29
Q

Define inbreeding

A

Breeding between related individuals

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30
Q

Define random genetic drift

A

A random change in allele frequencies due to sampling error over generations

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31
Q

Define bottleneck

A

A random event causes a collapse of the population so that only a few individuals survive. This causes a change in allele frequency as some alleles become fixed and some become lost

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32
Q

Define the founder effect

A

A few individuals leave a population and establish new population in a new location, so there is reduced genetic diversity in new population

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33
Q

What are 5 types of natural selection?

A
  1. stabilising selection
  2. disruptive selection
  3. directional selection
  4. sexual selection
  5. frequency dependent selection
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34
Q

Define stabilising selection and give an example

A

Extreme variations are selected against and middle range are retained in greater numbers. This reduces variation but does not change the mean.
eg. birth weight in babies

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35
Q

Define directional selection and give an example

A

When the adaptive phenotype is shifted in one direction and one phenotype is favoured over others. This changes the mean towards one extreme
eg. taller giraffes are favoured or wild mustard evolving to cabbage, cauliflower, Brussel sprouts, kale, broccoli

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36
Q

Define disruptive selection and give an example

A

Phenotypic extremes are favoured at the expense of intermediate phenotypes. This means two peaks form
eg. beak size in West African black bellied seed crackers

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37
Q

Define sexual selection and give an example

A

Females are more likely to mate with males with an attractive phenotype
eg. Females like males with long tails therefore long tailed males are more likely to mate so over time we have a population with longer tails

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38
Q

Define frequency dependent selection

A

Over a long period of time, natural selection maintains an equal proportion of differing phenotypes
eg. left or right mouthed Perissodus microlepis (one year there is a higher frequency of right mouthed individuals but then the fish they feed on stop them from feeding so the next year left mouthed individuals are more common and so on

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39
Q

Define a cline and give an example

A

The gradual geographic change in genetic/phenotypic composition
eg. more clovers producing cyanide in warmer climates

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40
Q

Describe how a mutation can act within a population

A
  • Mutations occur randomly
  • very slow to act
  • usually disadvantageous
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41
Q

Define migration

A

an individual from another population successfully mates (and contributes) to the gene pool

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42
Q

What does migration do to a population?

A
  • brings new alleles
  • changes proportions of existing alleles
  • changes population size
  • makes two populations more similar
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43
Q

What is the role of primase?

A

It makes RNA primers in the 5 to 3 direction. The RNA primer is the starting point for DNA polymerisation and it provides the 3` OH group

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44
Q

What is the role of DNA polymerase |||?

A

It is the enzyme that synthesises a new DNA strand by adding complementary nucleotides to the parent strand. DNA polymerase ||| uses the 3 OH group from the RNA primer to start building DNA in the 5 to 3` direction

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45
Q

What is the role of helicase?

A

It is the enzyme that pulls strands of DNA apart at the origin of replication

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46
Q

Why does helicase pull DNA apart at the origin of replication?

A

Because the origin of replication is an A/T rich region which means that there are only two H bonds to break instead of three

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47
Q

What is the role of topoisomerase?

A

It cuts off the DNA and sticks it back together to remove the pressure from it being twisted so hard when helicase pulls the strands apart. The DNA is no longer twisted when it is put back together

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48
Q

What is the role of single stranded DNA binding proteins?

A

They stop the newly separated DNA from snapping back together.
The cells like to break down single stranded molecules so the SSBP protect the DNA from this happening

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49
Q

What is the role of DNA polymerase |?

A

It removes the RNA primer and will use the 3` OH groups from the Okazaki fragments next door to fill the gap between the neighbouring Okazaki fragment

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50
Q

What is the role of DNA ligase?

A

It makes a phosphodiester bond between the 5 phosphate group and the 3 OH group of neighbouring Okazaki fragments

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51
Q

Describe how leading strands are synthesised

A
  1. helicase separates the strands of DNA
  2. single stranded DNA binding proteins hold the strands apart and protect the strands
  3. Primase builds a primer in the 5 to 3 direction
  4. DNA polymerase ||| extends from the primer by adding nucleotides in the 5’ to 3` direction
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52
Q

Describe how the lagging strand is synthesised

A
  1. helicase separates the strands of DNA
  2. single stranded DNA binding proteins hold the strands apart and protect the strands
  3. Primase builds a primer in the 5 to 3 direction
  4. DNA polymerase ||| extends from the primer by adding nucleotides in the 5’ to 3` direction
  5. DNA polymerase | removes the RNA primer and fills the gaps between the Okazaki fragments by building DNA nucleotides from the 3’ OH group of the RNA polymer
  6. DNA ligase makes a phosphodiester bond between the 5 phosphate group and the 3 OH group of neighbouring Okazaki fragments
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53
Q

When can DNA errors be corrected?

A

During replication or after replication

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54
Q

DNA errors are fixed during replication by

A

an exonuclease

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55
Q

DNA errors are fixed after replication by

A

an endonuclease

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56
Q

How does an exonuclease fix errors in DNA during replication?

A

DNA polymerase ||| acts as an exonuclease and removes the incorrect base from the 3 end and works towards the 5 end removing the incorrect base. DNA polymerase then adds the correct base

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57
Q

How does an endonuclease fix errors in DNA after replication?

A
  • the endonuclease removes a chunk of bases including the incorrect one
  • this takes a chunk out of the strand
  • a DNA polymerase adds the correct bases
  • DNA ligase forms the phosphodiester bonds between the new bases and the existing ones
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58
Q

What is PCR and why is it important?

A

Polymerase Chain reaction

to amplify of a specific (target) region of DNA.

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59
Q

Which PCR components are the same as in vivo DNA replication?

A

DNA template
Primers
DNA polymerase
dNTPs

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60
Q

What is the role of the DNA template in PCR?

A

It is the DNA molecule to which complementary nucleotides can be matched to make identical copies via DNA synthesis

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61
Q

What is the role of the primers in PCR?

A

they provide a free 3` OH group to initiate DNA synthesis

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62
Q

What is the role of the DNA polymerase in PCR?

A

it is the enzyme which adds nucleotides complementary to the DNA template and joins them together forming the phosphodiester bond

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63
Q

What is the role of the dNTPs in PCR?

A

free nucleotide blocks (equal amounts of A, C, G and T) used by the DNA polymerase

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64
Q

What are the three steps of PCR?

A

Denaturation
Annealing
Extension

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65
Q

Describe the process of denaturation in PCR

A

The double stranded DNA is denatured (separated) by briefly heating the sample to 95°C.

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66
Q

Describe the process of annealing in PCR

A

the sample is cooled to allow annealing (joining) of the primers to the single strands of DNA. The annealing temperature depends on the primer sequence, but is generally between 45-70°C.

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67
Q

Describe the process of extension in PCR

A

the temperature is increased to 72°C and the DNA polymerase makes the new DNA strand, starting at the primers and adding new nucleotides to match the existing strand in the 5’ to 3’ direction

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68
Q

What is the consequence of errors in DNA replication not being fixed?

A

The DNA error becomes part of the template, there is a permanent DNA change and mutation

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69
Q

What is a karyotype?

A

An ordered, visual representation of chromosomes in a cell

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70
Q

What is a locus?

A

a place or location on a chromosomes where we find a gene

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71
Q

What are the phases of the cell cycle?

A

Interphase

Mitotic phase

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72
Q

What occurs during interphase?

A

G1
S phase
G2

73
Q

What happens during S phase?

A

DNA replication

74
Q

What occurs during the mitotic phase?

A

Mitosis and cytokinesis

75
Q

What is mitosis?

A

A type of cell division that produces two genetically identical daughter cells

76
Q

What are the 5 stages of mitosis?

A 
prophase
prometaphase
metaphase
anaphase
telophase
77
Q

Describe what happens during prophase

A
  • the chromosomes have condensed and become visible

- centrosomes form early mitotic spindles and move towards each cell pole

78
Q

Describe what happens during prometaphase

A
  • the nuclear envelope fragments
  • the kinetochore microtubules connect to the kinetochores
  • the centrosomes have moved to each pole of the cell
79
Q

Describe what happens during metaphase

A
  • the pairs of sister chromatids line up along the metaphase plate
80
Q

Describe what happens during anaphase

A
  • the kinetochore microtubules shorten pulling the sister chromatids apart
  • the non-kinetochore microtubules lengthen to start to push the ends of the cells apart
81
Q

Describe what happens during telophase/cytokinesis

A
  • separate nuclei begin to form

- the cells separate

82
Q

What is the sexual life cycle?

A
  • meiosis to form egg and sperm
  • fertilisation to form diploid gametes
  • mitosis and development
  • make gametes via meiosis
83
Q

What is the purpose of meiosis?

A

To make unique haploid gametes

84
Q

Describe what happens during prophase 1 of meiosis

A
  • homologous chromosomes align and synapse
  • crossing over occurs between non-sister chromatids at the chiasmata
  • centrosomes form early mitotic spindles and move towards each cell pole
85
Q

Describe what happens during metaphase 1 of meiosis

A
  • Paired homologous chromosomes move to the metaphase plate

- The chiasmata line up on the metaphase plate

86
Q

What is the chiasmata?

A

the point at which crossing over and exchange of genetic material occur between the strands of homologous chromosomes

87
Q

Describe what happens during anaphase 1 of meiosis

A
  • recombined homologous chromosomes separate

- sister chromatids remain attached

88
Q

Describe what happens during telophase and cytokinesis of meiosis 1

A
  • the haploid cells with duplicated chromosomes (the pair of sister chromatids) form
  • they are haploid because only half the genetic information is in each cell
89
Q

After telophase and cytokinesis of meiosis 1, are the cells diploid or haploid

A

Haploid because they only have half the genetic information in each cell

90
Q

Meiosis || is the same as

A

mitosis

91
Q

How does sexual reproduction produce genetic diversity?

A
  • independent assortment of chromosomes
  • crossing over
  • random fertilisation of gametes
92
Q

What is segregation and how does it increase sexual diversity?

A

Alleles segregate randomly into each gamete. When gametes are formed, each allele of one parent segregates randomly into the gametes, so half of the parent’s gametes carry each allele.

93
Q

What is independent assortment and how does it increase sexual diversity?

A

It is random whether a homologous pair of chromosomes lines up maternal:paternal or paternal:maternal which means that alleles of two different genes get sorted into gametes independently of one another.

94
Q

What is crossing over and how does it increase sexual diversity?

A

The exchange of genetic material between non-sister chromatids of homologous chromosomes at the chiasmata during meiosis, which results in new allelic combinations in the daughter cells.

95
Q

Crossing over creates new variations of

A

linked genes

96
Q

Independent assortment creates new variations of

A

unlinked genes

97
Q

What is aneuploidy? Give an example

A

An abnormal number of a particular chromosome

eg. trisomy 21 (3 copies of chromosomes 21) causing Down Syndrome

98
Q

What can cause Down Syndrome?

A

Non-disjunction

99
Q

What is non-disjunction?

A

the failure of chromosomes to correctly separate during meiosis (could be the first or second division)

100
Q

What are the sex chromosomes for an individual with Klinefelter Syndrome?

A

XXY

101
Q

What are the sex chromosomes for an individual with Turner Syndrome?

A

XO

102
Q

If a pair of chromosomes fails to disjoin at anaphase of meiosis |, what will be the likely chromosomes numbers (N) for the four resulting gametes?

A

N + 1
N + 1
N - 1
N - 1

103
Q

What is polyploidy?

A

Possession of multiple sets of chromosomes

104
Q

What are 6 chromosomal abnormalities?

A
  1. non-disjunction
  2. aneuploidy
  3. deletion
  4. duplication
  5. inversion
  6. translocation
105
Q

Describe a deletion chromosomal abnormalities

A

The removal of a chromosomal segment

eg. ABCDEFG is now ABCEFG

106
Q

Describe a duplication chromosomal abnormalities

A

the repeating of a segment

eg. ABCDEFG is now ABCBCDEFG

107
Q

Describe an inversion chromosomal abnormalities

A

the reversal of a segment within a chromosome

eg. ABCDEFG is now ADCBEFG

108
Q

Describe a translocation chromosomal abnormalities

A

The movement of a segment from one chromosome to a non-homologous chromosome
eg. ABCDEFG and MNOPQR are now MNOCDEFG and ABPQR

109
Q

Give an example of a syndrome caused by a deletion

A

Lejeune syndrome/Cri du chat caused by the deletion of the short arm of chromosome 5

110
Q

Give two examples of conditions caused by an inversion

A

Philadelphia translocation t(9;22) which means that some of chromosome 22 and chromosome 9 have swapped over. This can cause myeloid leukemia

Or Familial Down syndrome from t(14;21) where a bit of 21 has broken off and joined with 14 and the rest of 21 has broken off and disappeared. If paired with a normal gamete, trisomy 21 can occur (Down syndrome)

111
Q

Why does the lagging strand have to be synthesised as smaller fragments and what are these fragments called?

A

They have to be synthesised as smaller fragments so that they can be synthesised in the 5 -> 3 direction, despite this being opposite to the required direction. These fragments are called Okazaki fragments

112
Q

In DNA replication, why is the primer removed and replaced?

A

Because the primer is RNA and it needs to be DNA

113
Q

Where does DNA replication start?

A

At the Origin of Replication (OoR)

114
Q

How many OoR does a human have and why?

A

A eukaryote has many OoR because replication is faster if it occurs simultaneously in many different locations rather

115
Q

What is “the flow” of the Central Dogma of Molecular biology; what are the macromolecules and what is their function?

A

It outlines the process of how information coded for in DNA can flow in proteins. This process is described in two stages; transcription and translation.

116
Q

What are the three stages of transcription?

A

Initiation
Elongation
Termination

117
Q

What macromolecule is being synthesised in transcription and in which direction is the synthesis proceeding?

A

RNA is synthesised in the 5’ -> 3’ direction

118
Q

What is transcription?

A

the process of converting DNA into RNA

119
Q

What is translation?

A

the synthesis of proteins by ribosomes using mRNA as a set of instructions

120
Q

What is the template for transcription and in which direction does it run?

A

DNA contains both a complementary strands: coding strand (5’ -> 3’) and a template strand (3’ -> 5’). The coding strand is the strand that contains the information that codes for a protein. The template strand is the one that is used during transcription so when mRNA bases are added complementary to the template strand, the mRNA will be identical to the required coding strand.

121
Q

What happens during initiation of transcription?

A
  • RNA polymerase || binds to the DNA strands at the promoter region and separates the two strands.
  • this forms a transcriptional initiation complex
  • RNA pol || contains a 3’ OH group which means that it can start mRNA synthesis without the use of a primer.
122
Q

What happens during elongation of transcription?

A
  • RNA pol || separates only about 20 or 30 nucleotides and moves along the template strand (running 3’ -> 5’), adding complementary mRNA bases in the 5’ -> 3’ direction.
  • Instead of adding Thymine complementary to Adenine, RNA pol || adds Uracil.
123
Q

Which parts of a gene is transcribed from DNA to mRNA?

A

The coding sequence and the UTRs

124
Q

Which parts of a gene are translated from mRNA to protein?

A

The exons of the coding sequence

125
Q

What is the promoter region?

A

The DNA segment recognised by RNA polymerase to initiate transcription

126
Q

What are the 5’ and 3’ UTRs?

A

UnTranslated Regions

  • contain regulatory elements that influence gene expression at the transcriptional and translational level
  • transcribed but not translated
127
Q

What is the 5’G cap and what is its function?

A

A region prior to the 5’ UTR

  • it prevents mRNA degradation
  • regulates translation by providing ribosome binding site
128
Q

What is the Poly-A tail and what is its function?

A

A region after the 3’ UTR

  • it prevents mRNA degradation
  • regulates translation
  • regulation of nuclear export
129
Q

Explain the process of splicing

A
  • The coding sequence consists of sections called exons and introns
  • during splicing, the introns are removed
130
Q

Briefly outline the process from DNA to protein

A
  1. UTRs and coding sequence (both introns and exons) undergo transcription
  2. this forms precursor mRNA
  3. the pre-mRNA undergoes slicing and the introns are removed from the coding sequence
  4. mature mRNA is formed
  5. the mRNA undergoes translation to form a protein
131
Q

How many codons are there?

A

64

132
Q

What is a codon?

A

Three DNA bases that codes for one amino acid

133
Q

How many of the 64 codons code for an amino acid? What are the other codons for?

A

61

The other three are stop codons

134
Q

What are the three stop codons?

A

UAA, UAG, UGA

135
Q

What is the one start codon?

A

AUG

136
Q

What amino acid is the first one in a peptide sequence?

A

Methionine (MET)

137
Q

What binds to the mRNA codons and to the mRNA stop codons?

A

tRNA

138
Q

Describe the tRNA molecule

A
  • single strand of RNA
  • 70-80 nucleotides in length
  • at least one tRNA for each amino acid
  • each tRNA has a region which can bind an amino acid and a region which can interact with mRNA
139
Q

How can tRNA bind to an amino acid and interact with mRNA?

A

At one end there is an amino acid attachment site and at the other end, there is an anticodon which is complementary to the mRNA

140
Q

What is meant by “charging the tRNA”?

A

Attaching an amino acid to the tRNA

141
Q

Explain how the tRNA is charged

A

an enzyme recognises both the specific amino acid and the correct tRNA for this acid and joins them together

142
Q

How many different tRNA molecules are there?

A

20 (one for each amino acid)

143
Q

How many different amino acids are there?

A

20

144
Q

Describe the anatomy of the ribosome

A
  • it has a large subunit and a small subunit
  • it has three sites (E, P, A)
  • it has an mRNA binding site
  • it has an exit tunnel
145
Q

What is the purpose of the A site?

A

it is the aminoacyl tRNA binding site

146
Q

What is the purpose of the E site?

A

It is the exit site

147
Q

What is the purpose of the P site?

A

it is the peptidyl-tRNA binding site

148
Q

Where are the ribosomes located?

A

Bound to the rough endoplasmic reticulum

free in the cytosol

149
Q

What are the tree stages of translation?

A

Initiation
elongation
termination

150
Q

Describe initiation of translation

A
  • 5’G cap is at the 5’ end of the mRNA and this is where the ribosome binds with the mRNA
  • the small ribosomal subunit recognises G cap
  • small subunit latches onto mRNA and scans it until it finds the AUG (start) codon
  • the tRNA charged with the Met amino acid and complementary anticodon binds to the P site
  • large subunit attaches
151
Q

Describe elongation of translation

A
  • the tRNA carrying the next amino acid (eg. leu) enter through the A site
  • two things at the same time:
    1. Transfer one amino acid from tRNA in P site onto newly arrived amino acid on A site but the tRNA do not move
    2. AT THE SAME TIME: the RIBOSOME moves three nucleotides ie. One codon along. Therefore the tRNA are now in the E and P sites. tRNA with chain is now in the P site and the empty one can leave through the E site
      Bond between amino acids = peptide bond (strong)
152
Q

Where do the tRNA enter the ribosome?

A

The first tRNA carrying Met comes through the P site and all the others come through the A site

153
Q

What does polymorphic means?

A

one gene that has many different alleles

154
Q

What is incomplete dominance?

A

When the heterozygous genotype codes for an intermediate phenotype that is a blend of the two phenotypes
eg. red and white giving pink

155
Q

What is co-dominance?

A

When both phenotypes exist side by side within an organism

eg. red and white giving red with white spots

156
Q

What are polygenic traits?

A

when the phenotype is controlled by many genes that have an additive effect so the characters appear continuous or quantitive

157
Q

Give 5 examples of polygenic traits

A
  1. skin colour
  2. weight
  3. IQ
  4. wool length
  5. height
158
Q

Describe the additive effect

A

the phenotype is determined by a number or alleles which could be 0 (and you could be white eg.) or 6 (and you could be black)

159
Q

Apart from the genotype, what else can affect the phenotype?

A

The environment

160
Q

What is an allopolyploid?

A

When two species interbreed to produce a new hybrid with chromosomes from each parent species. The hybrid is infertile because the chromosomes do not pair up (even if each species produces a gamete with the same number of chromosomes). To become sterile, a mitotic disjunction (chromosome doubling event) must occur

161
Q

What is lyonization?

A

The inactivation of an X chromosome in females during early embryonic development

162
Q

Why are females stripey?

A

In females during early embryonic development, one of the X chromosomes is inactivated in each cell and therefore some cells will show the phenotype of the X from dad and some will show the phenotype of X from mum.

163
Q

What are the building blocks of DNA?

A

nucleotides

164
Q

What are the three components of the building blocks of DNA?

A

A base (A,C,T or G), a phospate and deoxyribose sugar.

165
Q

There are two types of bases; what are they called and how many “rings” are there in each?

A

Pyrimidines (1 ring)

Purines (2 rings)

166
Q

Give two examples of a pyrimidine

A

Cytosine and Thymine

167
Q

Give two examples of a purine

A

Adenine and Guanine

168
Q

How does the sugar component in a DNA and RNA molecule differ?

A

The sugar component of DNA is deoxyribose with an H on the second carbon and for RNA it is ribose with and OH on the second carbon

169
Q

How do the bases in DNA and RNA differ?

A

DNA: C,G,T,A
RNA: C,G,U,A

170
Q

With what type of bond are DNA and RNA nucleotide monomers joined together?

A

A phosphodiester bond

171
Q

Particular carbons and chemical groups are involved in joining the nucleic acid monomers together. Which ones?

A

One nucleotide contains a base, a phosphate group and a sugar.
The 5th carbon (the 5’ end) is bonded to the phosphate group. This phosphate is bonded to the 3rd carbon (the 3’ end) of the next nucleotide’s sugar. The bond between the 3’ and phosphate is the phosphodiester bond.

172
Q

How many polynucleotide chains make up a DNA molecule and how are these organised in relation to each other?

A

There are two chains arranged in an antiparallel arrangement

173
Q

In which direction does a DNA chain grow when it is being synthesised?

A

From the 5’ to 3’ direction

174
Q

How is the DNA helix stabilised?
(be specific; which component of the nucleotide is involved and include the type and number of bonds between these components)

A

By hydrogen bonds between the bases of the two strands.

There are 3 H bonds between C and G and 2 H bonds between the T and A

175
Q

What nucleotide components are located on the inside of the DNA helix?

A

The bases

176
Q

What nucleotide components are located on the outside of the DNA helix?

A

The phosphate group and the sugar making a phosphate sugar backbone

177
Q

What kind of replication does DNA undergo?

A

Semi-conservative

178
Q

What were Chargaff’s significant findings?

A
  • the amount of A bases was the same as the T bases and the amount of C bases was the same as the G bases

The composition of DNA varies between species

CELS 191 (5 decks)

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