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Biology > 3.4 Genetic information, variation and relationships between organisms > Flashcards

3.4 Genetic information, variation and relationships between organisms Flashcards

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1
Q

What is an allele?

A

Different version of a gene

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2
Q

Explain how DNA replicates.

A

Semi-conservative replication:
- DNA helicase breaks hydrogen bonds
- Produces two template strands
- DNA nucleotides line up by complimentary base pairs
- DNA polymerase joins nucleotides together by phosphodiester bonds, forming sugar phosphate backbone

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3
Q

What are 2 advantages of DNA molecules having two DNA strands?

A
  1. Protects bases
  2. Makes semi-conservative replication possible
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4
Q

Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells.

A

Compare
- Both have identical nucleotide structure
- Phosphodiester bond

Contrast
- Eukaryotic DNA is longer
- Histones
- Introns/exons
- Ciruclar vs linear

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5
Q

Describe how the DNA in a chloroplast is different to the DNA in the nucleus of a eukaryotic cell.

A
  • Chloroplast DNA is circular, nucleus is linear
  • Chloroplast DNA not associated with histones, nucleus is
  • Chloroplast DNA has no introns, nucleus does
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6
Q

Describe the nature of the genetic code (3)

A
  • Degenerate
  • Non-overlapping
  • Universal
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7
Q

Define ‘non-coding base sequence’ and describe where the non-coding sections of the DNA are positioned in the genome.

A
  • DNA that does not code for a polypeptide
  • Positioned between genes
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8
Q

What is a homologous pair of chromosomes?

A

Parent chromosomes that carry the same genes (same loci) and code for the same characteristics

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9
Q

What is the proteome?

A

All of the proteins produced by the genome

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10
Q

What is an autosome?

A

A non-sex chromosome

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11
Q

Give 2 ways in which the structure of tRNA differs from mRNA.

A
  • mRNA is a single helix, tRNA has a clover leaf shape
  • mRNA contains codons, tRNA contains anticodons
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12
Q

Describe how a gene is transcribed in the nucleus of a cell.

A
  • DNA helicase breaks hydrogen bonds
  • One strand acts as a template, RNA nucleotides pair up with complimentary bases on the template strand
  • RNA polymerase forms the sugar phosphate backbone (phosphodiester bonds) to proude a pre-mRNA molecule
  • Molecule is spliced to remove introns and produce the mRNA
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13
Q

Describe the process of translation.

A
  • mRNA associates with a ribosome
  • tRNA has complimentary anticodon to each codon of this mRNA molecule
  • Each tRNA molecule also has a specific amino acid
  • As each codon is read by the ribosome the amino acid from the complimentary tRNA is added in the correct sequence to form a polypeptide chain by condensation reactions (peptide bonds)
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14
Q

What point mutations cause a frame shift?

A

Addition and deletion

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15
Q

What are the 3 impacts that base substitution can have on a protein?

A
  1. Silent- codes for same amino acid (degenerate nature of genome)
  2. Nonsense- codes for a stop codon
  3. Missense- codes for new amino acid
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16
Q

How can a base substitution lead to the formation of a non-functioning enzyme?

A
  • Base substitution causes amino acid sequence chnages as new amino acid coded for
  • This changes the ionic/hydrogen/disulphide bonds and so tertiary structure of enzyme changes
  • Active site changes shape, no longer complimentary to substrate so fewer E-S complexes form
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17
Q

Give 2 factors that could increase the frequency at which a mutation in DNA occurs.

A
  1. Exposure to ionising radiation (x-rays)
  2. Exposure to carcinogens (tobacco tar)
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18
Q

Name the processes that occur during meiosis that increase genetic variation.

A
  1. Crossing-over
  2. Independent assortment
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19
Q

Describe the process of crossing-over and explain how it increases genetic diversity.

A
  • Homologous pair of chromosomes form a tetrad during prophase I
  • 2 non-sister chromatids form a chiasma at the point they cross and exchange equal lengths of alleles
  • This produces new combinations of alleles
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20
Q

Describe the process of independent assortment and explain how it increase genetic diversity.

A
  • It is the random orientation of homologous chromosome pairs along the spindle fibres during metaphase I
  • Maternal and paternal chromosomes reshuffled
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21
Q

What are the stages of meiosis?

A

Meiosis I (interphase + pmat + cytokinesis)
Meiosis II (pmat + cytokinesis)

22
Q

How many daughter cells does meiosis produce?
Are they haploid or diploid?

A

4 haploid daughter cells

23
Q

What is the formula to calculate the number of combinations of chromosomes after the random fertilisation of two gametes?

A

2^n

24
Q

What causes mutations in chromosome number during meiosis?

A

Non-disjunction

25
Q

What happens if abnormal gametes (wrong number of chromosomes) are fertizlied?

A
  • Aneuploidy/polyploidy,
  • Genetic disorders like Down’s syndrome can occur
26
Q

What is the gene pool?

A

The total number of different alleles (total genetic diversity) within a population

27
Q

How is the gene pool of a population increased?

A
  • Mutations
  • Migration into area
  • Gene flow
28
Q

How is the gene pool of a population decreased?

A
  • Genetic bottlenecking
  • Founder effect
  • Genetic drift
29
Q

What is genetic bottleneck?

A
  • Population size decreases significantly due to an event
  • Smaller gene pool
  • Remaining population breed, passing on the few alleles they have amongst themselves, alleles become more common in offspring
30
Q

What is the founder effect?

A
  • Small number of individuals seperate from original population
  • Taking with them their alleles: smaller gene pool and possibly an increased proportion of individuals with a certain allele
31
Q

What is gene flow and genetic drift?

A

Gene flow = introduction of genes from one population of a species to another via migration

Genetic drift = change in frequency of genes in population due to random chance

32
Q

What are the 3 types of selection and the environment quality for each?

A
  1. Disruptive- selection pressure
  2. Directional- change in environment
  3. Stabilising- stable environment
33
Q

Name some common selection pressures.

A
  • Prey/food
  • Mates
  • Environment
  • Disease
  • Predation
34
Q

What are the 3 types of adaptions?

A
  1. Anatomical- structural features
  2. Behavioural- organism action
  3. Physiological- biological processes
35
Q

What 2 types of variation are there?

A
  1. Intraspecific variation- a species
  2. Interspecific variation- different species
36
Q

What is a species?

A

Organisms which can mate to produce fertile offspring

37
Q

Why is courtship behaviour important?

A

Ensures there is successful mating within a species

38
Q

Give 3 ways curtship behaviour can increase the probability of successful mating.

A
  • Allows individuals to recognise and attract member of same species
  • Able to identify a fertile/sexually mature mate
  • Able to identify a mate of the opposite sex
39
Q

What is classification and what 5 methods can you use to help classify organisms?

A
  • How species are organised into groups
  1. Morphology
  2. Amino acid sequence comparison
  3. Immunological comparison
  4. DNA hybridisation
  5. DNA base sequence comparison
40
Q

What is the difference between artificial and phylogenetic classification?

A
  • Artificial looks at common features and function, phylogenetic looks at evolutionary origon (common ancestors)
  • Artificial based off analagous characteristics but phylogenetic based off homologous characteristics
41
Q

What is a hierarchy?

A

Groups within groups which are non-overlapping

42
Q

How do you classify species?

A

Kingom
Phylum
Class
Order
Family
Genus
Species

43
Q

What are the 3 domains?

A
  1. Bacteria
  2. Archae
  3. Eukarya
44
Q

What are the 4 types of eukarya? How do they differ?

A
  1. Protoctista
  2. Animal
  3. Plant
  4. Fungi

cell wall (is it present, what is it made out of), how they feed (saprotroph, autotroph, heterotroph)

45
Q

How can differences in the primary structure of proteins provide evidence of phylogenetic relationships between species?

A
  • Mutations change base sequence
  • Change in amino acid sequence
  • Mutations increase over time
  • More mutations between more distantly related species
  • Distantly related species have earlier common ancestor
46
Q

What is biodiversity and what is it made up of?

A

Biodiversity = variety of organisms in a community
- Species diversity = species abundance/richness
- Ecosystem diversity = range of different habitats
- Genetic diversity = variety of genes within community

47
Q

Why is it important to have a high level of biodiversity?

A
  • Helps with survival of specie when there are selection pressures or a change in environement.
  • Protects them from loss of food sources and habitats
48
Q

What can cause a decline in biodiversity?

A
  • Over-farming/fishing
  • Climate change
  • Pollution
  • Deforestation
49
Q

How can farming lower biodiversity?

A
  • Monoculture, limited species richness and variety
  • Use of herbicides/pesticides
  • Removal of hedges and trees
  • Over-grazing by farm animals
  • Lack of biomass, other species have to compete with small remainder of food, water, space
50
Q

What conservation techniques are being used in farming?

A
  • Crop-rotation
  • Organic farming
  • Replanting trees
51
Q

How would you take a random sample in an area?

A
  • Draw a grid of area and randomly select coordinates using a random number generator
  • Take sample at area where this coordinate lies, repeat for many different coordinates (at least 20)

Biology (10 decks)

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