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

Genetic information, variation and relationships between organisms Flashcards

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1
Q

How is DNA organized in prokaryotic cells?

A

DNA is short, circular, and not associated with proteins in prokaryotic cells.

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2
Q

How is DNA organized in the nucleus of eukaryotic cells?

A

DNA is long, linear, and associated with histone proteins, forming chromosomes.

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3
Q

How is DNA in mitochondria and chloroplasts similar to prokaryotic DNA?

A

Mitochondrial and chloroplast DNA is short, circular, and not associated with proteins, just like prokaryotic DNA.

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4
Q

What is a gene?

A

A gene is a base sequence of DNA that codes for: The amino acid sequence of a polypeptide and a functional RNA (e.g., ribosomal RNA and tRNA).

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5
Q

What is a locus?

A

A locus is the fixed position of a gene on a DNA molecule.

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6
Q

What is a triplet?

A

A triplet is a sequence of three DNA bases that codes for a specific amino acid.

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7
Q

What are the three key properties of the genetic code?

A

Universal – The same triplet codes for the same amino acid in all organisms.
Non-overlapping – Each base is read once in a sequence.
Degenerate – Multiple triplets can code for the same amino acid.

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8
Q

What are non-coding multiple repeats?

A

These are repeated base sequences between genes that do not code for polypeptides.

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9
Q

What are exons?

A

Exons are coding sequences within a gene that code for amino acid sequences.

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10
Q

What are introns?

A

Introns are non-coding sequences within a gene that separate exons.

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11
Q

What is the genome?

A

The genome is the complete set of genes in a cell.

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12
Q

What is the proteome?

A

The proteome is the full range of proteins that a cell can produce.

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13
Q

What is the structure of mRNA?

A

Single-stranded
Linear molecule
Carries the genetic code from DNA to the ribosome

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14
Q

What is the structure of tRNA?

A

Single-stranded, folded into a cloverleaf shape
Contains an anticodon (three bases complementary to an mRNA codon)
Has an amino acid binding site at the other end

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15
Q

What is transcription?

A

Transcription is the process of producing mRNA from DNA.

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16
Q

What is the role of RNA polymerase in transcription?

A

RNA polymerase joins mRNA nucleotides together to form a strand of mRNA.

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17
Q

How does transcription differ in prokaryotes and eukaryotes?

A

Prokaryotes: Transcription directly produces mRNA.
Eukaryotes: Transcription produces pre-mRNA, which is then spliced to remove introns and form mRNA.

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18
Q

What is translation?

A

Translation is the process of producing polypeptides from mRNA codons.

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19
Q

What are the key components involved in translation?

A

mRNA – Carries the codons.
tRNA – Brings specific amino acids to the ribosome.
Ribosomes – Site of protein synthesis.
ATP – Provides energy for peptide bond formation.

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20
Q

How does the base sequence of nucleic acids relate to polypeptides?

A

The sequence of bases in DNA/mRNA determines the sequence of amino acids in a polypeptide through the genetic code.

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21
Q

What types of data might be used to interpret the role of nucleic acids?

A

Experimental results showing mutations and their effects on proteins.
mRNA codon sequences matched to amino acid sequences.
Gel electrophoresis data on DNA/RNA fragments.

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22
Q

What is a gene mutation?

A

A gene mutation is a change in the base sequence of DNA within a chromosome.

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23
Q

When do gene mutations occur?

A

They arise spontaneously during DNA replication.

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24
Q

What are the two main types of gene mutations?

A

Base deletion – A base is removed, causing a frameshift mutation.
Base substitution – A base is swapped for another, which may or may not change the amino acid sequence.

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25
Why don’t all base substitutions affect the amino acid sequence?
Due to the degenerate nature of the genetic code, some substitutions result in the same amino acid being encoded.
26
What are mutagenic agents?
Mutagenic agents increase the rate of gene mutation and include: Radiation (e.g., X-rays, UV light) Chemicals (e.g., benzene, tobacco smoke) Viruses
27
How do chromosome mutations occur?
They can arise due to chromosome non-disjunction during meiosis, where chromosomes fail to separate properly.
28
What is the purpose of meiosis?
Meiosis produces genetically different haploid gametes for sexual reproduction.
29
How many daughter cells does meiosis produce?
Meiosis results in four haploid daughter cells from a single diploid parent cell.
30
What are the two key processes in meiosis that increase genetic variation?
Independent segregation of homologous chromosomes. Crossing over between homologous chromosomes.
31
What is independent segregation?
The random separation of homologous chromosomes during meiosis I, leading to genetic variation.
32
What is crossing over?
The exchange of genetic material between homologous chromosomes during meiosis I, creating new allele combinations.
33
How does random fertilisation increase genetic variation?
Any random sperm can fertilise any random egg, creating unique combinations of alleles in offspring.
34
What diagrams should students be able to complete?
Diagrams showing the chromosome content of cells after meiosis I and meiosis II when given the parent cell’s chromosome number.
35
How can you explain the different outcomes of mitosis and meiosis?
Mitosis produces two genetically identical diploid cells for growth and repair. Meiosis produces four genetically different haploid gametes for reproduction.
36
How can meiosis be recognized in an unfamiliar life cycle?
Look for a reduction in chromosome number, indicating gamete production.
37
What is genetic diversity?
Genetic diversity is the number of different alleles of genes in a population.
38
Why is genetic diversity important?
It allows natural selection to occur by providing variation within a population.
39
How can random mutation lead to evolution?
Random mutation can create new alleles of a gene. Many mutations are harmful, but some may provide an advantage in certain environments. Organisms with the advantageous allele have increased reproductive success. Over generations, the frequency of the advantageous allele increases in the population.
40
What are the key types of selection?
Directional selection – Favors individuals with an extreme characteristic (e.g., antibiotic resistance in bacteria). Stabilising selection – Favors individuals with average characteristics, reducing variation (e.g., human birth weights).
41
How does natural selection lead to adaptation?
Organisms become better suited to their environment through adaptations that increase survival and reproduction.
42
What are the three types of adaptations?
Anatomical – Physical structures (e.g., thick fur in arctic animals). Physiological – Internal functions (e.g., enzymes working at extreme temperatures). Behavioural – Actions that increase survival (e.g., migration patterns).
43
How does selection cause changes in a species' population?
Selection increases the frequency of beneficial alleles and reduces less advantageous ones, leading to evolutionary change.
44
How can selection data be interpreted?
By analyzing: Changes in allele frequencies over time. Graphs showing selection pressures (e.g., antibiotic resistance trends). Environmental factors affecting survival and reproduction.
45
How do adaptation and selection contribute to biodiversity?
Different selection pressures in different environments lead to species diversity and evolution of new species.
46
What defines two organisms as belonging to the same species?
They must be able to produce fertile offspring.
47
Why is courtship behavior important?
It ensures: Recognition of the same species for successful mating. Identification of a mate capable of breeding. Synchronization of mating behaviors for reproduction.
48
What is a phylogenetic classification system?
It groups species based on their evolutionary origins and relationships.
49
What is a hierarchy in classification?
A system where smaller groups (taxa) are nested within larger groups with no overlap.
50
What are the main taxa in classification?
Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
51
What is a taxon?
A group of organisms classified together based on shared characteristics.
52
How are species universally identified?
Using the binomial system, which includes the genus and species names (e.g., Homo sapiens).
53
Why is the binomial system used?
It provides a universal and standardized way to name species.
54
How does immunology help clarify evolutionary relationships?
Similar antibody-antigen reactions suggest a close evolutionary relationship.
55
How does genome sequencing clarify evolutionary relationships?
Comparing DNA base sequences reveals genetic similarities and evolutionary links between species.
56
What is biodiversity?
Biodiversity refers to the variety of living organisms in a given area, from a small habitat to the entire Earth.
57
What is species richness?
Species richness is a measure of the number of different species in a community.
58
What is an index of diversity?
It describes the relationship between: The number of species in a community. The number of individuals in each species.
59
What is the formula for the index of diversity (d) ?
​d=N(N-1)/sigma n(n-1) Where: 𝑁 N = total number of organisms of all species 𝑛 n = total number of organisms of each species
60
What does a high index of diversity indicate?
A greater variety of species and a more stable ecosystem.
61
How do farming techniques reduce biodiversity?
Monocultures (growing one crop) reduce species variety. Pesticides & herbicides kill non-target species. Removal of hedgerows destroys habitats. Overuse of fertilizers disrupts ecosystems.
62
How can farming and conservation be balanced?
Hedgerow planting to support wildlife. Crop rotation to maintain soil health. Reducing pesticide use to protect beneficial species. Maintaining natural meadows and wetlands.
63
What are the four methods used to compare genetic diversity within or between species?
Measurable or observable characteristics (e.g., flower color, blood type). Base sequence of DNA (direct genetic comparison). Base sequence of mRNA (reflects active genes). Amino acid sequence of proteins (determined by DNA/mRNA).
64
Why is comparing DNA sequences more reliable than observable characteristics?
Observable traits are influenced by environmental factors and polygenic inheritance, making them less accurate for measuring genetic differences.
65
How has gene technology changed the study of genetic diversity?
Scientists now directly sequence DNA rather than inferring genetic differences from physical traits.
66
What can similarities in DNA base sequences or amino acid sequences indicate?
A closer evolutionary relationship between organisms.
67
What are the key steps in a quantitative investigation of variation?
Collecting random samples (to avoid bias). Calculating the mean of the collected data. Determining the standard deviation (to measure data spread).
68
Why is random sampling important?
It reduces bias and makes results representative of the whole population.
69
How can mean values and standard deviations be interpreted?
A higher mean suggests greater average trait size. A larger standard deviation indicates greater variation within the population.
70

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