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BIOLOGY YEAR 1 > Genetic information, variation and relationships between organisms > Flashcards

Genetic information, variation and relationships between organisms Flashcards

1
Q

Differences between DNA in eukaryotes and DNA in prokaryotes

A

Eukaryotes- packaged as chromosomes (DNA associated with histones forming chromatin)
DNA is longer, linear
Prokaryotes-free floating in cytoplasm in circular strand not associated with histones so no chromosomes
DNA is shorter, circular

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2
Q

What is a gene?

A

A base sequence that codes for
-the amino acid sequence of a polypeptide
-a functional RNA (rRNA and tRNA)

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3
Q

What is a locus?

A

The fixed position that a gene occupies

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4
Q

What are the 3 characteristics of the genetic code and what do they mean?

A
  1. Degenerate- each amino acid is coded for by more than 1 triplet (3 DNA bases)
  2. Non-overlapping- each triplet code is discrete
  3. Universal- same sequence of bases code for same amino acids in all organisms
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5
Q

Describe the structure of a tRNA molecule

A

clover-shaped: single stranded held in shape by disulfide bonds
has an amino acid binding site specific to an amino acid
has an anti-codon (3 DNA bases) complementary to codon on mRNA

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6
Q

Describe the process of transcription

A

The hydrogen bonds between bases break the unwind sections of DNA
Only 1 strand acts as a template (‘antisense’ strand) unlike in DNA replication
Complementary free mRNA nucleotides line up along exposed DNA bases (Uracil not Thymine of mRNA)
RNA polymerase catalyses formation of phosphodiester bonds between mRNA nucleotides forming pre-mRNA
pre-mRNA is spliced removing introns to form mature mRNA that leaves the nucleus via a nuclear pore

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7
Q

Describe the process of translation

A

The mRNA attaches to a ribosome
2 tRNA molecules and their amino acids associated with the ribosome
The anticodon forms hydrogen bonds with the complementary codon on mRNA
Peptide bonds are formed between amino acids in a condensation reaction using ATP and enzymes
Ribosome moves along mRNA until stop codon is reached
Polypeptide is formed

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8
Q

Define the genome

A

An organism’s complete set of DNA, including all of its genes

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9
Q

Define the proteome

A

The full range of different proteins that a cell is able to produce at a given time

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10
Q

Define a gene mutation

A

A change in the sequence of bases in DNA
-causes change in polypeptide chain
-caused by errors during DNA replication

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11
Q

What causes mutations?

A

-mutagenic agents (ionising radiation like UV)
-environmental or external factors
-INCREASE MUTATION RATE
-MORE MUTATIONS PER UNIT TIME

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12
Q

What is base substitution?

A

When a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base

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13
Q

What can base substitutions lead to?

A

-different codon so different amino acid coded for, change in location of hydrogen, ionic and disulfide bonds causing change in tertiary structure of the protein- change in protein function
-or same amino acid may be coded for as DNA is degenerate
-may code for stop codon- so polypeptide chain would be incomplete

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14
Q

What is a base deletion?

A

A nucleotide (and therefore base) is removed from a base sequence
-this changes the reading frame, shifting to the left

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15
Q

What can base deletions lead to?

A

-change in way triplets are read so change in amino acid sequence, change in function of polypeptide

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16
Q

How would a base addition affect the reading frame

A

Shift to the right

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17
Q

What are chromosome mutations?

A

Changes in structure or number of whole chromosomes
-caused by errors in cell division

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18
Q

What is non-disjunction and how does this lead to polyploidy and aneuploidy?

A

Non-disjunction: chromosomes do not separate during meiosis
causing…
-POLYPLOIDY- when organisms have 3 or more sets of chromosomes rather than 2
-ANEUPLOIDY-when organisms have 1 more or 1 fewer chromosomes

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19
Q

Define ‘gene’ mutation and explain how a gene mutation can have no effect on an individual or a positive effect on an individual

A

-A change in the base/nucleotide
-results in formation of new allele

No effect:
-mutation is in intron
-changes amino acid but not effect on tertiary structure

Positive effect:
-results in change in polypeptide that positively changes the properties
-may result in increased reproductive success

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20
Q

Describe the structure of proteins

A

-polymer of amino acids
-joined by peptide bonds
-formed by condensation
-primary structure is sequence of amino acids
-secondary structure is folding of polypeptide chain due to hydrogen bonding
-tertiary structure is 3-D folding due to hydrogen, ionic and disulfide bonding
-quaternary structure is 2 or more polypeptide chains

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21
Q

Describe what happens to chromosomes during meiosis

A

-chromosomes condense
-chromosomes associate in homologous pairs
-homologous pairs line up at equator
-and spindle fibres attach to the centromere
-crossing over occurs
-homologous pairs pulled to opposite poles of the cell in first division
-sister chromatids pulled apart to opposite poles by spindle fibres in second division

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22
Q

Describe and explain the processes that occur during meiosis that increase genetic variation and how is this an advantage for a species

A

-chromosomes in homologous pairs
-independent segregation
-maternal and paternal chromosomes re-shuffled in any combination
-crossing over where alleles are exchanged between homologous chromosomes
-both result in new combination of alleles

-different adaptations
-pass on alleles
-more likely to survive and reproduce
-less vulnerable to selection pressures

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23
Q

Difference between diploid and haploid cells

A

Diploid- have the full set of chromosomes (2n)
Haploid- have half the set of chromosomes (n)

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24
Q

Ways genetic variation is achieved through meiosis

A

independent segregation
crossing over
THEN random fertilisation

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25
What happens during meiosis 1?
Homologous chromosomes pair up crossing over at chiasma may take place cell divides producing 2 haploid cells (each cell contains 1 chromosome from each homologous pair)
26
What happens during meiosis 2?
Sister chromatids of each chromosome separated producing 4 haploid cells Gametes fuse together forming a zygote (diploid) during fertilisation
27
Define allele
One of a number of alternative versions of a gene
28
Define species
A group of organisms that can breed together to produce fertile offspring
29
Define population
A group of individuals of the same species that live in the same place at the same time and can interbreed
30
Define genetic diversity
The frequency of all the alleles available in a population of a species
31
How is genetic diversity brought about and why is beneficial?
Changes in DNA from mutations and meiosis- different combinations of alleles Greater variation, more individuals likely to survive if environment changes Without genetic diversity, natural selection would not occur
32
Describe evolution
A change in the inherited characteristics of a population over time through the process of natural selection
33
How does natural selection work? MODEL ANSWER to apply to scenarios
-Mutations occur with lead to new alleles and genetic variation -A new selection pressure is applied to the environment creating competition -Individuals with advantageous alleles for that environment have an advantage over others -These individuals survive and reproduce more, passing on the advantageous alleles to their offspring -The frequency of this advantageous allele and numbers of these individuals increases in subsequent generations
34
Difference between genotype and phenotype
Genotype- compete set of genes it carries Phenotype- all of its observable characteristics, which are influenced by its genotype and environment
35
Describe and explain the effect of stabilising selection of the normal distribution curve of phenotypes
-PRESERVES the population characteristics -selects phenotypes around the population mean (against both extremes) -causing curve to have higher peak and narrower spread Stable environmental conditions
36
Describe and explain the effect of directional selection on the normal distribution curve of phenotypes
-CHANGES the population characteristics -selects for phenotypes at 1 extreme of the population -curve has same shape but MEAN SHIFTS left/right Allele frequency at extreme selected for increases
37
Describe behavioural, physiological and anatomical adaptations
Behavioural- way an organism acts that increases chance of survival and reproduction Physiological- differences in biochemical pathways or enzymes Anatomical- structural features of body that increase chances of survival
38
What is courtship behaviour?
Carried out to attract a mate of the right species e.g releasing chemicals, series of displays
39
Why is courtship behaviour species specific?
- to ensure they are recognising their own species -to prevent interbreeding and so makes reproduction more successful -to produce fertile offspring -females of most species produce eggs at specific times and sometimes only a few eggs
40
How does courtship behaviour ensure survival?
-attracts same species -attracts mates -indication of sexual maturity -stimulates release of gametes -form pair bond
41
What are the features of bacteria?
Domain: group of single-celled prokaryotes -absence of membrane-bound organelles -unicellular -70s ribosomes -murein cell walls -singular circular strand of DNA
42
What are the features of archaea?
Domain: group of single-celled prokaryotes originally classified as bacteria differ from bacteria: -genes and protein synthesis more similar to eukaryotes -membranes contain fatty acids attached to glycerol by ETHER bonds -no murein in cell walls -more complex form of RNA polymerase
43
What are the features of eukarya?
Domain: group of organisms made up of one or more eukaryotic cells -membrane-bound organelles -membrane containing fatty acids attached to glycerol by ESTER bonds -not all possess cells with cell walls- no murein -80S ribosomes
44
Define classification and taxonomy
Classification- organisation of organisms into groups Taxonomy- theory and practice or biological classification (each group called a taxon)
45
Describe the difference between artificial and phylogenetic classification
Artificial- according to differences at time of study Phylogenetic- based on evolutionary relationships between organisms and common ancestors + using shared features with ancestors -arranges into hierarchy
46
Define hierarchy
A system in which smaller groups are placed within larger groups, with NO OVERLAP groups
47
Rules for binomial system:
-names printed in italics or underlined if handwritten -1st letter of genus in capitals, species name in lower case -if species name unknown, write 'sp'
48
What is the hierarchal taxonomic rank?
Domain Kingdom Phylum Class Order Family Genus Species
49
Phylogeny =
evolutionary relationships between organisms -branch points show common ancestors -closely related species diverge from each other most recently
50
How can scientists investigate diversity?
-compare observable characteristics -compare DNA base sequences -compare mRNA base sequences -compare amino acid sequences
51
Define biodiversity
Every living thing including plants, bacteria, animals and fungi in an ecosystem
52
Diff between species richness and species diversity
Species richness- number of different species in a community at a given time Species diversity- number of different species and the proportion of each species within a community
53
How do you calculate index of diversity?
d= N( N-1)/ sum of n(n-1) N= total number of organisms of ALL species n= total number of organisms or EACH species
54
Why is a high index of diversity beneficial?
-the higher the number the more diverse the habitat -so less susceptible to selection pressures -more likely to be able to cope with any changes
55
Why is random sampling used?
-to find species richness and species diversity -to prevent sampling bias and ensure results are representative and reliable
56
How are quadrats used in random sampling?
-divide area into a grid -use random number generator to obtain a series of random coordinates -place the quadrat at these coordinates and record the frequency or % cover of species investigating -repeat multiple times -calculate a mean and multiply by the total area
57
Ways to minimise effect of chance in random sampling:
-use large number of samples -analyse data using a statistical test -continue sampling until stable running mean
58
Describe negative effects of agriculture on biodiversity
-selective breeding therefore low genetic diversity -reduced space for wild animals therefore reduced species diversity -less habitats available/monoculture therefore reduced species diversity -pesticides used (enter food chain and kill) therefore reduced species diversity
59
Ways to minimise reduction of biodiversity through agriculture
-planting hedgerows increases species diversity -growing nitrogen-fixing plants instead of chemical fertilisers -using intercropping to manage pest species -introducing conservation headlands (areas where pesticides restricted)
60
Why does removing a hedgerow reduce biodiversity? MODEL ANSWER
-reduces variety of plants -reduces variety of habitats available -reduces variety of food sources available -reduces variety of herbivore species -reduces variety of carnivore species
61
How can differences in the primary structure of haemoglobin molecules provide evidence of phylogenetic relationships between species?
-mutations change base sequence -causing change in amino acid sequence -mutations build up over time -more differences between distantly related species -distantly related species have earlier common ancestors

BIOLOGY YEAR 1 (6 decks)

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