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A Level Biology > Chapter 3.4 Genetic Info & Variation > Flashcards

Chapter 3.4 Genetic Info & Variation Flashcards

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1
Q

Compare prokaryotic + eukaryotic cells DNAs

A

prokaryotic
Short
Circular strands
Not associated with proteins

eukaryotic
Very long
Linear strands
Associated with proteins called histones

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2
Q

Apart from nucleus
where else is DNA found in eukaryotic cells
+ describe its structure

A

In EUKARYOTIC CELLS
Mitochondria & chloroplast contain DNA
+this DNA is short, circular & not associated with proteins (like prokaryotic DNA)

{This DNA can be used to synthesis their own proteins/enzyme that are used inside the organelle itself }
think about the extra reading about how there is a theory that both these organelles where bacteria cells themselves at some point which would explain the need for DNA

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3
Q

Def of gene

A

A base sequence of DNA that codes for the amino acid sequence of a polypeptide and a functional RNA

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4
Q

Why is the genetic code
1) universal
2) non-overlapping
3) degenerate

A

-universal= the same triplet (codon) code used by all organism
- Non-overlapping=
-Degenerate= most amino acids code for more than one codon

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5
Q

Def of genome?

A

The complete set of genes in a cell

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6
Q

Def of proteome

A

The full range of proteins a cell is able to produce

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7
Q

Compare structures of mRNA & tRNA

A

mRNA tRNA
-straight chain. - folded into a clover leaf shape
- variable in length. - fixed length (3 bases)
- longer chains. - shorter chains
- doesn’t attach amino acids. - attachment site for amino acids to bind
[- only polypeptide bonds - regions of H bonds within ]

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8
Q

Explain transcription process

A

Transcription - making an mRNA copy of DNA nucleotide sequence in a gene

1) DNA helicase unzips the DNA molecule
2) Free RNA nucleotides form complementary base pairs with nucleotides from non-sense strand of exposed DNA
3) enzyme RNA polymerase joins RNA nucleotides together using phosphodiester bonds to make mRNA
4) mRNA is a copy of the ‘sense’ strand of DNA (but U replaces T bases)

if prokaryotic then mRNA produced is ready for use in translation at this stage
if eukaryotic the pre-mRNA is then processed
inrons- non coding sections-are removed and
exons- coding sections- get spliced together to from mRNA ready for translation

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9
Q

Explain translation process

A

Translation- occurs at ribosomes + is when mRNA codons are used to create a sequence of amino acids in a polypeptide chain

1) mRNA binds to ribosome at start codon
2) tRNA molecule’s anticodon binds to each complementary codon on mRNA
3) amino acids carried by tRNA molecules join by peptide bonds to from polypeptide chain
(These peptide bonds are formed using enzyme + ATP which is hydrolysed to provide required energy)
4) final protien is release from ribosome where it can then fold into its final structure

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10
Q

Draw diagram to show structure of tRNA molecule

A

See notes

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11
Q

Def of anticodon (tRNA)

A

A triplet of bases complementary to codon on mRNA molecule

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12
Q

Mutation

A

Change to quantify or structure of DNA of an organism

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13
Q

Gene mutation

A

Change to one or more nucleotide bases in the DNA of gene/ rearrangement in the sequence of bases of a gene

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14
Q

Types of gene mutations and what they are?

A

1) substitution
Replacement of 1 nucleotide with a different nucleotide
2) insertion
Addition of 1 or more nucleotides
3) deletion
Loss of one or more nucleotides
4) inversion
A cut portion is inverted 180o then rejoined to the same place within the gene
5) duplication
A whole gene/section is duplicated so that 2 copies of gene/section appear on the same chromosome
6) translocation
The section of the gene is cut off and attached to a separate gene

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15
Q

When can substitutions be harmful or neutral

A

HARMFUL
- if the replacement nucleotide causes the amino acid to change which leads to an unfunctional or harmful protein.

NEUTRAL
- if the replacements nucleotide is in the non coding region (intron region removed) then no effect will be seen in proteins produced
- if the replacement nucleotide still forms the same protein

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16
Q

Why might a time shift not be formed during insertion or deletion of DNA

A

-If 3 nucleotides are added or removed
- if the nucleotide is added to the ends

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17
Q

Types of chromosome mutations?

A

1) POLYPLOIDY (changes in the whole sets of chromosomes)
- organism have 3 or more sets of chromosomes rather that usual 2
mostly occurs in plants

2) HYBRIDS (changes in wholes sets of chromosomes)
- can be formed by combining sets of chromosomes from different species closely related
A new species may arise if the chromosome number of the hybrid is a multiple of the original chromosome number (because meiosis can occur)
mostly occurs in plants

3) NON-DISJUNCTION
- during meiosis
Homologous pairs of chromosomes fail to separate during meiosis
A gamete will have either 1 or more or 1 fewer chromosomes
mostly occurs in plants

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18
Q

Types of chromosome mutations?

A

1) POLYPLOIDY (changes in the whole sets of chromosomes)
- organism have 3 or more sets of chromosomes rather that usual 2
mostly occurs in plants

2) HYBRIDS (changes in wholes sets of chromosomes)
- can be formed by combining sets of chromosomes from different species closely related
A new species may arise if the chromosome number of the hybrid is a multiple of the original chromosome number (because meiosis can occur)
mostly occurs in plants

3) NON-DISJUNCTION
- during meiosis
Homologous pairs of chromosomes fail to separate during meiosis
A gamete will have either 1 or more or 1 fewer chromosomes
mostly occurs in plants

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19
Q

Def of mutagenic agent

A

An outside factor that increases the basic mutation rate

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20
Q

Causes of mutations (chromosome/gene)?

A
  • mutations occur spontaneously
    During DNA replication
  • mutagenic agents
    1) high energy ionising radiation
    Can distrust structure of DNA

2) chemicals (NO2 & Benzopyrene)
NO2- disrupt DNA structure interfere with transcription
Benzopyrene - inactivates a tumour supressor gene TP53 leading to cancer

Benzopyrene is found in tobacco smoke & NO2 from burning fossil fuels

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21
Q

define degeneracy and explain its significance in genetic mutation

A
  • 1 or more triple codes can code for the same amino acid
  • substitution replacement of bases in the triplet code can code for the same amino acid (silent mutations can arise)
  • 3rd bases in triplet most likely to result in scilent mutation
    (as which amino acid of the 3rd base in a triplet can have multiple bases & still result in coding for same amino acid)
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22
Q

impacts/outcomes of silent mutations?

A

silent mutations
- new allele formed but degeneracy means amino acid not affected
- new allele friend in intron that is removed during slicing of mRNA
- new allele doesn’t affect tertiary protein structure (recessive)
*no affect to reproduction/survival

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23
Q

Impacts/outcomes of harmful mutations?

A

harmful mutations
- new allele formed results in charge in polypeptide that negatively changes the tertiary properties
- may result in decreased survival and reproduction

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24
Q

Impacts/outcomes of beneficial mutations?

A

beneficial mutations
- new allele is formed resulting in change in polypeptide that positivity changes tertiary properties
- may result in increased survival & reproduction

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25
Q

Difference between haploid and diploid cells

A

Diploid cells
- contain 2 types of each chromosome (homologous chromosomes)
- produced by mitosis cell division

Haploid cells
- only contins 1 type of each chromosome
- produced via meiosis cell division

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26
Q

Purpose of meiosis

A

To produce gamates that each contian
1) a haploid number of chromosomes
2) a different combination of alleles (i.e show variation )

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27
Q

Describe + explain the process of crossing over/recombination
+how it leads to genetic variation during meiosis?

A

During prophase 1 homologous pairs of chromosomes associate (form bivalent )
Chiasmata form (sister chromatids attach)
Lengths of chromatids/alleles are exchanged
Producing new combination of alleles

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28
Q

Describe + explain the process of independent segregation
+how it leads to genetic variation during meiosis?

A

During metaphase 1, pairs of homologous chromosomes (bivalent)
Line up at equator, each pair line up randomly
This results in gamates that are genetically unique
(Gamates each carry a different combination of maternal &paternal chromosomes)

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29
Q

Def of variation

A
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30
Q

Name + explain the 3 events in meiosis/sexual reproduction that cause genetic variation

A

1) independent segregation
- produces gametes with random combination of maternal & paternal chromosomes
2) crossing over
- new combination of alleles produced as portions of sister chromatids are exchanged
3) random fusion of gametes
- produces offspring with unique combination of maternal & paternal alleles

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31
Q

Def of natural selection

A

natural selection = the process that removes the least well-adapted organisms with least beneficial alleles from population

32
Q

What are selection pressures?
+give examples

A

Are factors hat cause poorly adapted organism to die
-i.e. they remove the least beneficial alleles from the population

Examples
+ predictors, diseases, competition for food/mates/breeding sites

33
Q

What is discontinuous/ discrete data for variation?

A
  • a character with only a small number of different possible values
    Caused by:
    Only one gene (very small number of genes)
    Not affected by environmental factors
    (E.g eye colour, sex)
34
Q

What is continuous data for variation?

A
  • a characteristic with a large range of possible values
    Caused by:
    Several genes working together (polygenic trait)
    Environmental factors make significant contribution
    E.g. height, skin colour
35
Q

Steps of natural selection (to be adapted to any question)

A

variation
> any population there is a range of characteristics caused by different alleles
overproduction
> more offspring are produced than will survive
survival of the fittest and reproduction
> only the best adapted organisms with most beneficial alleles will survive and reproduced, passing on the most beneficial alleles to their offspring
repeat
> this is repeated over many generation, until all individuals in population have the characteristic
mention frequency of alleles
THIS WILL LEAD TO AN INCREASE OF FREQUENCY OF THE beneficial ALLELE.

36
Q

Def of evolution?

+why is it important for species?

A

The formation of new species from pre-existing species over time, as a result of changes to gene pools and allele frequencies from generation to generation

+evolution allows species to survive by adapting to changes in their environments

37
Q

What does evolution require?

A

Variation - the population must contain individuals with diff alleles
Natural selection - process which causes least well adapted individuals to die out.

38
Q

Why are bacteria able to pass on genes more quickly than humans

A

Bacteria are unique since they can pass on genes
vertically (like humans) as well as Horizontally

39
Q

Describe aseptic techniques that could be used to transfer 0.3cm3 of bacteria liquid culture form bottle onto an agar plate

A

Disinfect bench and wash hands - prevent contamination by destroying other MOs
Work close to lit Bunsen - creates updraft of air away from work station
Flame mouth of bottle - prevents contamination of reagents by airborne MOs
Sterilise tools in ethanol then through flame - prevents contamination by killing MOs

Never completely remove lid of pétri dish - prevent contamination
Tape to secure lid - keeps cultures aerobic to reduce more harmful anaerobic ones growing
Incubate at 25oc upside down- prevent condensation falling on bacteria & prevent more harmful bacteria growing*
Sterilise all equipment at the end - prevents releasing bacteria into environment

40
Q

Describe and explain the appearance of the chromosome at the start of mitosis

A

2 chromatids, attached at centromere

41
Q

Describe the role of spindle fibres during mitosis

A

1- attachment of centromeres
2- separation of chromatids

42
Q

Def of genetic diversity

A

The number of different alleles of genes in a population

43
Q

Def of species

A

A group of organism with similar characteristics that are capable of breeding to produce living, fertile offspring

44
Q

What is courtship behaviour?

A

Courtship behaviour is carried out by organisms to allow them to recognise members of their own species and to attract a mate of the same species capable of breeding

45
Q

Role of courtship behaviour in species recognition?

A

Courtship behaviour is species specific- only members of the same species will do & respond to the courtship behaviours.

This allows members of the same species to recognise each other, prevent interbreeding and result in successful reproduction

46
Q

Name two 5 examples of courtship behaviours?

A

1) Using sounds
- male red deers make roaring noise to attract mate
2) visual displays
- male peacocks displaying their tail feathers
3) releasing chemicals/scents
- bumble bees produce pheromones to attract mates
4) dancing
- blue footed booby bird performs complex dance to show off their blue feet
5) Building things
- bowerbird construct bowers to find mate

47
Q

How does a phylogenetic classification arrange species? + how do we display this information

A

Phylogenetic classification system
Arranges species in groups based on their evolutionary origins and relationships

(Basically they tell us who’s related to whom and how closely related they are)
+ can be shown on a phylogenetic tree

48
Q

What are the 8 groups to classify organisms?

A

DOMAINS
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES

49
Q

How do we organise the levels of classification?
+ what is a Taxon?

A

8 levels of groups (D,K,P,C,O,F,G,S)
+ Each of these groups is called a Taxon
These groups are arranged into a hierarchy, with larger group at the top and the smallest groups at the bottom.
Organisms can only belong to one group at each level in the hierarchy- no overlap.

50
Q

What is binomial naming system (binomial nomenclature) for classification?

A

All species of plants and Ana I als are given a genus name (general) followed by species (specific) name both of which are in Latin

E.g Vulpes ferrilate - Tibetan fox
The genus name should have a capital letter to start
Species name is all lower case
To show it should be in italics you underline the word

51
Q

Def of phylogeny?

A

The study of evolutionary relationships
(Comparing DNA and protein sequences to find closest relatives)

52
Q

explain why a protein has an identical amino acid sequence in all species of ape?

A

The more closely related the species, the more similar the amino acid sequence of their proteins/ nucleotide sequence of their genes, because there has not been enough time (in evolutionary terms) for mutations to happen

53
Q

What is measured it generate the global biodiversity map?

A

The number and population of different species

54
Q

Def of ecosystem?

A

The dynamic interaction between the community of organisms (biotic factors) and abiotic factors

55
Q

Def of producers?

A

The species that use this energy to synthesise organic molecules (create the biomass available for all other organisms)

56
Q

What do trophic leaves show?
+ what do arrows between them indicate
+ what is max number of trophic levels in ecosystem?

A

Tropic levels show the feeding relationships within ecosystem
+ arrows show direction of energy/ biomass flow
+ around 4/5 trophic levels as energy is losses between each level

57
Q

Def of decomposers?

A

Species that break down dead/decaying biomass to recycles the minerals it contains

58
Q

What is intra-specific competition?

A

Competition between individuals of the same species
- only those with most favourable alleles will survive & reproduce

59
Q

What it inter-specific competition?
+ what is a niche?

A

Competition between organisms from different species
- species better adapted will outcompete others, for this reason no 2 species will ever occupy exactly the same ecological niche

+ niche= includes position of organism in food chain, what it eats, where in the habitat it breeds and raises its young.

60
Q

What are measures of biodiversity and how are they defined?

A

Biodiversity includes the number of different species (species richness) as well as the number of individuals of each species (species evenness ) within a community

Species richness = number of different species
Species evenness= how close in numbers each species population is

61
Q

How does phylogenetic classification system arrange species?

A

In groups based on their evolutionary origins and relationships

62
Q

Why is more information given if we use base sequences instead of amino acid sequences when comparing evolutionary origins?

A

Over time the nucleotide sequences of different species will change due to mutations. Since the genetic code is degenerate many of these changes will not change the amino acid, so would be missed if only the protein sequence was compared.

63
Q

Explain how comparing amino acid sequences of cytochrome C protein allows evolutionary relationships to be determined?

A

Mutations in DNA lead to different amino acid sequences. More differences means longer period of time when natural mutations can occur. Longer periods of time shows a longer time since evolutionary close relationships

64
Q

Cytochrome C and anitbofy explain

A
65
Q

What is DNA hybridisation?

A

The DNA from two different sources binding together held by H bonds

66
Q

Explain why more closely related hybridised DNA strands would separate at higher temperatures

A

Heat is required to break the hydrogen bonds between DNA stands that form between complementary bases.
Hybrids with similar sequences will form more H bonds between stands therefore require more energy and separate at higher temperatures to those less similar

67
Q

Def of hierarchy?

A

System of groups ranked successively/ one above each other
(System where smaller groups are placed within larger groups, with no overlap between groups)

68
Q

Def of phylogenetic group

A

Group of evolutionary-related species sharing a common ancestry

69
Q

Formula of index of diversity (d)

+ what does a higher number mean?

A

D = N(N - 1)
———————
Sum of n(n - 1)

D- diversity index
N- total number of organisms of all species
n - total number of organism of one species

+ higher number the more diverse the area is

70
Q

What are the groups in phylogenetic classification called

A

Taxon (Plural= taxa)

71
Q

What does index of biodiversity show?

A

Relationship between number of species in a community and the number of individuals in each species

72
Q

What does index of biodiversity show?

A

Relationship between number of species in a community and the number of individuals in each species

73
Q

How do farming techniques reduce biodiversity?

A

-Farmer select species for qualities that make them productive decreasing other species.
- Area can only support certain amount of biomass - if one species dominates other species have less space and compete with each other decreasing their populations.
This reduces species diversity
- Harvesting reduces the food supply for some animals like birds
- Pesticides and other chemicals can be harmful to insects reducing their populations
- removing hedgerows and woodland areas which reduces habitat
- filling ponds/marshes
- lack of intercropping or over sowing

74
Q

Conservation methods to balance farming and biodiversity

A
  • maintain existing hedgerows
  • plant hedges rather than fences as boundaries
  • maintain existing ponds and create ditches
  • plant trees on areas with low species diversity instead of designated area
  • use biological control methods rather than pesticides
  • organic fertilisers
  • consistent crop rotation
75
Q

identify genetic diversity within or between species using?

A

1) frequency of measurable or observable characteristics
2) base sequence of DNA
3) base sequence of RNA
4) the amino acid sequence of the protein encoded by DNA and mRNA

A Level Biology (10 decks)

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