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Biology Paper 1 > Genetics, Biodiversity And Classification 4 > Flashcards

Genetics, Biodiversity And Classification 4 Flashcards

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1
Q

What is a gene?

A

A section of DNA that contains a code for making a polypeptide and functional RNA.

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2
Q

What does locus refer to?

A

The location of a particular gene on a chromosome.

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3
Q

What is an allele?

A

A different version of the same gene.

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4
Q

What is a chromosome?

A

A threadlike structure composed of tightly coiled DNA wrapped around histones (if it is a eukaryotic cell).

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5
Q

What is a homologous chromosome?

A

A pair of chromosomes that have the same genes and therefore are the same size.

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6
Q

What is a homologous pair of chromosomes?

A

A pair of chromosomes that are homologous.

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7
Q

Where is eukaryotic DNA stored?

A

DNA is stored as chromosomes inside the nucleus.

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8
Q

What is the structure of eukaryotic DNA?

A

Eukaryotic DNA consists of linear chromosomes that are tightly coiled and wrapped around proteins called histones.

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9
Q

What is the structure of prokaryotic DNA?

A

Prokaryotic DNA molecules are shorter and circular, and they are not wound around histones but supercoil to fit in the cell.

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10
Q

What is a codon?

A

A codon is 3 bases on mRNA that code for an amino acid.

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11
Q

What is a start codon?

A

3 bases at the start of an mRNA sequence which help to initiate translation.

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12
Q

What is a stop codon?

A

3 bases at the end of every gene that do not code for an amino acid.

This causes ribosomes to detach and therefore stops translation.

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13
Q

What is the genetic code?

A

An amino acid is coded for by 3 DNA bases which are described as the ‘triplet code’.

Each amino acid is coded for by more than one triplet of bases.

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14
Q

What is meant by ‘the genetic code is degenerate’?

A

Each amino acid can be coded for by more than one triplet of bases.

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15
Q

What is the advantage of the genetic code being degenerate?

A

If a substitution mutation occurs, the new triplet of bases may still code for the same amino acid, therefore the mutation will have no impact on the final protein produced.

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16
Q

What is the advantage of the genetic code being universal?

A

Genetic engineering is possible, allowing a human gene to be inserted into another organism.

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17
Q

What is the advantage of the genetic code being non-overlapping?

A

If a point mutation occurs, it will only affect one codon and therefore one amino acid.

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18
Q

What is a triplet code?

A

An amino acid is coded for by 3 bases.

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19
Q

Give an example of genetic engineering.

A

A human gene for insulin can be inserted into bacteria to make insulin.

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20
Q

What are exons?

A

Sequences of DNA that code for amino acids.

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21
Q

What is splicing?

A

Post-transcription modification involving removing introns.

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22
Q

What is a genome?

A

The complete set of genes in a cell.

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23
Q

What is a proteome?

A

The full range of proteins that a cell is able to produce.

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24
Q

What is an anticodon?

A

3 bases on the tRNA which are complementary to the codon on mRNA.

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25
What are the characteristics of mRNA?
Single-stranded, made up of codons, and a copy of one gene.
26
What is the structure of tRNA?
Single-stranded, folded to create a cloverleaf shape, held in place by hydrogen bonds, has an anticodon and amino acid binding site.
27
What is the function of mRNA?
A copy of a gene from DNA, created in the nucleus, and it then leaves the nucleus to carry the copy of the genetic code of one gene to a ribosome in the cytoplasm.
28
What is the function of tRNA?
A specific amino acid attaches at the binding site and transfers this amino acid to the ribosome to create the polypeptide chain.
29
What is transcription?
The first stage in protein synthesis where one gene in DNA is copied into mRNA. It occurs in the nucleus.
30
What is translation?
The second stage in protein synthesis where the polypeptide chain is created using both the mRNA base sequence and the tRNA. It occurs on ribosomes in the cytoplasm.
31
Which enzymes are involved in transcription?
DNA helicase and RNA polymerase.
32
What does helicase do?
Helicase catalyses the breaking of hydrogen bonds between the two strands of DNA.
33
What is the function of RNA polymerase?
RNA polymerase joins adjacent RNA nucleotides together, forming a phosphodiester bond.
34
What is pre-mRNA?
Pre-mRNA is mRNA in eukaryotes that still contains the introns.
35
How is pre-mRNA modified?
The introns are removed by a protein called a spliceosome, leaving just the exons.
36
What is ATP used for in translation?
Forming the peptide bond between amino acids.
37
What does haploid mean?
One copy of each chromosome in a cell.
38
What does diploid mean?
Two copies of each chromosome in a cell.
39
What is meiosis?
Cell division that creates genetically different gametes. ## Footnote There are two nuclear divisions in this process and it results in four haploid daughter cells.
40
What is ATP used for in translation?
Forming the peptide bond between amino acids.
41
What does haploid mean?
One copy of each chromosome in a cell.
42
What does diploid mean?
Two copies of each chromosome in a cell.
43
What is meiosis?
Cell division that creates genetically different gametes. ## Footnote There are two nuclear divisions in this process and it results in four haploid daughter cells.
44
What is independent segregation?
Homologous pairs of chromosomes randomly line up opposite each other at the equator of the cell. When they separate, it creates a large number of possible combinations of chromosomes in the daughter cells produced.
45
What is crossing over?
Homologous pairs of chromosomes line up opposite each other at the equator in meiosis 1. Parts of the chromatid twist, break, and recombine with another chromatid, resulting in new combinations of alleles in the gametes.
46
What are gametes?
Sex cells (sperm and egg).
47
How does meiosis introduce variation?
Through crossing over and independent segregation.
48
What are the types of gene mutations?
Deletion and substitution.
49
What is a frameshift?
The removal of one base changes all of the subsequent codons. All the bases shift back one position.
50
What is a chromosome mutation?
A change in the number of chromosomes that occurs during meiosis.
51
What is a deletion mutation?
A gene mutation where a base is removed from a sequence, causing a frameshift.
52
What is a substitution mutation?
A gene mutation where a base is swapped for a different one.
53
What is non-disjunction?
The chromosomes or chromatids do not split equally during anaphase.
54
What is polyploidy?
Changes in whole sets of chromosomes, mainly occurs in plants. ## Footnote Example: Organisms with three or more sets of chromosomes.
55
What is aneuploidy?
A change in the number of individual chromosomes. ## Footnote Example: 3 copies of chromosome 21.
56
What causes Down's syndrome?
Down's syndrome is caused by a chromosome mutation.
57
What is an example of aneuploidy?
Down's syndrome is an example of aneuploidy.
58
How many copies of chromosome 21 are present in Down's syndrome?
There are 3 copies of chromosome 21 in Down's syndrome.
59
What is genetic diversity?
Genetic diversity is the number of different alleles in a population.
60
What is natural selection?
Natural selection is the process that leads to evolution in populations.
61
What does natural selection result in?
Natural selection results in species becoming better adapted to their environment.
62
What is a gene pool?
A gene pool is all the genes and alleles in a population at a particular time.
63
What is allele frequency?
The proportion of organisms within the population carrying a particular allele.
64
What is evolution?
The change in allele frequency over many generations in a population.
65
What is selection pressure?
Factors that affect the survival of an organism and the driving force of natural selection.
66
What are the types of selection?
Stabilising and directional.
67
What is the definition of a species?
A group of similar organisms that can breed to make fertile offspring.
68
What is the binomial system?
A universal naming system where individuals are named after their genus and species. ## Footnote Example: Homo sapiens
69
What is courtship behaviour?
Different sequences of behaviours that animals demonstrate to attract a mate. ## Footnote Each species demonstrates its own unique behaviour.
70
What is the importance of courtship?
Helps to synchronise mating behaviour, increases the likelihood of successful mating, and enables individuals to recognise members of the same species and opposite sex.
71
What is meant by a hierarchy?
Smaller groups arranged within larger groups; there is also no overlap between groups.
72
What is phylogenetics?
The study of species' evolutionary origins and relationships.
73
What is a common ancestor?
The species from which another species evolved.
74
What is a taxon?
The term for each group in classification.
75
What are the taxa in the Linnaeus classification system?
• domain • kingdom • phylum • class • order • family • genus • species
76
What is species diversity?
The number of different species and the number of individuals within each species in a community.
77
What defines a species?
The number of different species in a particular area at the same time.
78
What is the index of diversity?
A measure of species diversity. ## Footnote A calculation to measure the relationship between the number of species in a community and the number of individuals in each species.
79
What is biodiversity?
A measure of the range of habitats, from a small local habitat to the entire Earth, and includes species diversity and genetic diversity.
80
How is standard deviation more useful than a mean?
It gives you the spread of data (variance) around the mean. Overlaps in standard deviation indicate no significant difference in the means.
81
How do you make sure your sampling is representative of the population?
Take a large sample (at least 30) and randomly sample to avoid bias.
82
How can you measure genetic diversity?
By comparing the base sequence of DNA, mRNA, and the amino acid sequence of the proteins.
83
What is genetic diversity?
The measure of how many different alleles there are for each gene.
84
What is the formula for Simpson's index of diversity?
D = N(N - 1) / En(n - 1) ## Footnote N = total number of organisms of all species; n = population size of one species; D = Simpson's index of diversity.
85
How does chloroplast/mitochondria DNA compare to prokaryotic DNA?
The DNA is similar to prokaryotic DNA in that it is short, circular, and not histone bound.
86
How does transcription differ between prokaryotes and eukaryotes?
Transcription in prokaryotic organisms results in mRNA that requires no modification because prokaryotic DNA does not contain any introns. Eukaryotic transcription results in pre-mRNA that needs introns removed.
87
What is the role of ribosomes in translation?
It holds two tRNA molecules and enables peptide bonds to form between the amino acids.
88
What is the role of tRNA in translation?
It carries a specific amino acid and anticodons align opposite complementary codons on the mRNA.
89
What are gene mutations?
A change in the base sequence of DNA, which can involve substitution or deletion.
90
When in the cell cycle do gene mutations occur?
During interphase (S phase), when DNA is replicated.

Biology Paper 1 (4 decks)

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