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Biology Paper 1 Summary > Topic 4 > Flashcards

Topic 4 Flashcards

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1
Q

what are the similarities between the DNA is euk and pro cells

A
  • both made of DNA nucleotides
  • nucleotides joined by phosphodiester bonds to make polymer chain
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2
Q

differences between DNA in euk and pro cells

A
  • euk is longer / pro is shorter
  • euk is linear / pro is circular
  • euk has histones / pro doesnt associate with proteins
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3
Q

describe the DNA of mitochondria and chloroplasts

A
  • shorter
  • circular
  • doesnt associate with proteins
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4
Q

what is a gene

A

a base sequence of DNA that codes for
- amino acid sequence of polypeptide
- a functinal RNA

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5
Q

whats the locus

A

fixed occupied postion of a gene on a chromosome

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6
Q

how many DNA bases code for an amino acid

A

three

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7
Q

three features of genetic code

A
  1. degenerate
  2. non-overlapping
  3. universal
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8
Q

explain the degenerate feature of the genetic code

A
  • theres more than one triplet base that codes for each amino acid
  • genetic code has to code for 20 amino acids
  • four DNA bases (ATCG) and so therefore three bases are needed to make enough combinations for at least 20 amino acids
    > 4 x 4 x 4 = 64 amino acids
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9
Q

why is the degenerate feature an advantage

A

if a point mutation occurs, despite the triplet bases being different, the coding for the amino acid could still be the same

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10
Q

explain the universal feature of the genetic code

A

all dna bases code for the same amino acid in all organisms

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11
Q

explain the non-overlapping feature of the genetic code

A
  • each base is only part of one triplet
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12
Q

why is non-overlapping an advantage

A

if point mutation occurs, only one triplet is affected so only one amino acid will change

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13
Q

what are introns

A

sections of DNA bases that do not code for polypeptides
> only found in eukaryotic DNA

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14
Q

what are exons

A

sequences of DNA that code for amino acids

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15
Q

whats a codon

A

triplet on mRNA that codes for a specific amino acid

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16
Q

whats a start codon

A

three bases at the start of every gene that initiates translation

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17
Q

whats a genome

A

an organisms complete set of genes in a cell

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17
Q

whats a stop codon

A

three bases at the end of every gene that cause ribosomes to detach and stop translation

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18
Q

whats a proteome

A

full range of proteins that a cell can produce

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19
Q

should genome change

A

no
> unless theres a mutation

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20
Q

should proteome change

A

yes > constantly changing depending on what proteins are needed

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21
Q

what does mRNA stand for

A

messenger RNA

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22
Q

what is mRNA, where is it found and made

A
  • short, single stranded molecules
  • found in cytoplasm and nucleus
  • made during transcription and is complemnetary to the DNA base sequence
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23
Q

whats tRNA, where is it found

A

transfer RNA
cytoplasm

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24
Q

describe features of tRNA and what theyre for

A
  • has amino acid attachment site
  • anticodon at base of molecule > complementary to mRNA codons
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25
Q

what does tRNA look like

A
  • single polynucleotide strand folded into a clover shape with hydrogen bonds between base pairs to hold the shape
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26
Q

what are the two steps of protein synthesis

A

transcription and translation

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27
Q

whats transcription

A

one gene on the DNA stand is copied into mRNA

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28
Q

whats translation

A

mRNA from transcription joins with a ribosome and corresponding tRNA molecules bring the specific amino acids the codon codes for

29
Q

outline steps of transcription

A
  1. DNA helix unwinds to expose bases to act as a template
  2. hydrogen bonds broken by DNA helicase between bases
  3. free mRNA nucleotides align with complementary bases with template DNA strand
  4. RNA polymerase joins the mRNA nucleotides > forms RNA polymer chain
  5. leaves nucleus via nuclear pores after modifications
30
Q

what are the modifications to the pre mRNA before it leaves the nucleus as a mRNA strand

A

splicing
> the introns are spliced out by a splicesome leaving just the exons (coding regions)

31
Q

why does transcription in prokaryotes create mRNA directly and not pre mRNA

A

because prokaryotes DNA do not contain introns

32
Q

outline steps of translation

A
  1. mRNA attaches to a ribosome in the cytoplasm at the start codon
  2. tRNA molecule with complementary anticodon at its start codon aligns opposite the mRNA > held in place with ribosome
  3. ribosome moves along one codon along mRNA to allow for another complementary tRNA molecule to attach
  4. the amino acids delivered by the tRNA are joined with a peptide bond > requires ATP and enzyme
  5. continues until ribosome reaches stop codon at the end of the mRNA and detaches
33
Q

why does the stop codon allow for the ribosome to detach

A

it doesnt code for an amino acid

34
Q

what is a gene mutation

A

change in the base sequence

35
Q

what is the effect of mutagenic agents on gene mutations

A

random mutations are more likely to occur

36
Q

examples of mutagenic agents

A
  • high energy radiation
  • ionising radiation
  • chemicals
37
Q

what can a gene mutation result in happening to the base sequence

A

bases being deleted or substituted for different ones

38
Q

explain what frameshift is

A

one base is deleted so all of the base codons change and different amino acids could be coded for

39
Q

why is it possible for a base substitution to have no impact on the overall coding

A
  • genetic code is degenerate
  • multiple codons code for the same DNA base
40
Q

what are chromosome mutations

A

changes in the number of chromosomes

41
Q

what is non-disjunction

A

when chromosomes or chromatids dont split equally during anaphase
or meiosis 1 / 2

42
Q

what is polyploidy

A

changes in whole sets of chromosomes

43
Q

when does polyploidy occur

A

when organisms have three or more sets of chromosomes rather than two
> common in plants
> fatal in humans

44
Q

what is aneuploidy

A

changes in the number of individual chromosomes

45
Q

how does aneuploidy occur

A

individual homologous pairs of chromosomes fail to separate during meiosis

46
Q

what are the two ways variation is introduced in meiosis

A

independant segregration
crossing over
> occur in meiosis 1

47
Q

what is independant segregration

A

when the homologous pairs of chromosomes line up opposite eachother at the equator and the pairs seperate randomly

48
Q

what is crossing over

A

when homologous pairs line up opposite eachother at equator and parts of the chromatids twist around eachother
- this causes tension on the chromatids and breaks them
- broken parts of the chromatid recombine with another chromatid > resulting in new combinations of alleles

49
Q

compare mitosis and meiosis

A
  • meiosis is two divisions / mitosis is one
  • meiosis produces haploids / mitosis produces diploids
  • meiosis introduces genetic variation / mitosis creates genetically identical cells
50
Q

how can you identify meiosis in a life cycle

A

diploid (2n) > haploid (n)

51
Q

what is genetic diversity

A

number of different alleles of genes in a population

52
Q

what is natural selection

A

process that leads to evolution in populations

53
Q

what is evolution

A

change in the allele frequency over many generations in a population

54
Q

what type of adaptations can natural selection result in

A

anatomical
physiological
behavioural

55
Q

outline the process of natural selection

A
  1. new alleles for a gene are created from random mutations
  2. if the allele is advantageous, survival increases > more reproduction
  3. reproduction passes on the advantageous allele to next generation
  4. new allele has increased in frequency over many generations
56
Q

how do you know if organisms are part of the same species

A

both can have fertile offspring

57
Q

why is courtship behaviour essential

A

enables successful mating and for species recognition

58
Q

what is courtship behaviour

A

a sequence of actions which is unique to each species to help animals recognise their own species and help reproduction

59
Q

who usually performs the courtship ritual

A

the males

60
Q

how can courtship rituals be observed to conclude the relations between the species

A

the more similar the ritual, the closer in relation they are

61
Q

what is phylogenetic classification

A

arranging species into groups according to their evolutionary origins and relationships

62
Q

whats the order of hierarchy

A

domain
kingdom
phylum
class
order
family
genus
species

63
Q

what is a hierarchy

A

smaller groups arranged within larger groups

64
Q

how does binomial system work

A

first name is genus
second name is species
same species = closely related

65
Q

what is species diversity

A

number of diff species and individuals within each species in a community

66
Q

what is genetic diversity

A

the variety of genes amongst all the individuals in a population of one species

67
Q

what is ecosystem diversity

A

range of different habitats

68
Q

what is species richness

A

number of different species in a community

69
Q

what are farming techniques to balance between conservation and farming

A
  1. destruction of hedgerows
  2. selective breeding
  3. monocultures
  4. over-grazing
  5. filling in ponds and draining wetlands
70
Q

how do you measure biodiversity

A

index of diversity
N = total num of organisms of all species
n = total num of organisms of a particular species
D = Simpsons diversity index
(1 is lowest value for D > the higher it is, the greater the species diversity

71
Q

what can we compare to invesitgate relationships between species

A

amino acid sequence
mRNA base sequence
DNA base sequence
observable traits

Biology Paper 1 Summary (4 decks)

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