topic 4

Question 1

What is the difference between eukaryotic and prokaryotic DNA?

Answer 1

Eukaryotic DNA is longer, linear, associated with histones, and contains introns. Prokaryotic DNA is shorter, circular, not associated with proteins, and lacks introns.

Question 2

What is a gene?

Answer 2

A sequence of DNA bases that codes for a polypeptide or functional RNA.

Question 3

What is the genetic code?

Answer 3

It is a triplet, universal, non-overlapping, and degenerate code where each triplet codes for one amino acid.

Question 4

What is transcription?

Answer 4

The process where a segment of DNA is used as a template to form pre-mRNA in eukaryotes.

Question 5

How is pre-mRNA processed in eukaryotic cells?

Answer 5

Introns are removed by splicing to form mature mRNA.

Question 6

How does translation work?

Answer 6

mRNA binds to a ribosome, tRNA with complementary anticodons brings specific amino acids, and peptide bonds form using ATP.

Question 7

What is a gene mutation?

Answer 7

A change in the base sequence of DNA, which can occur spontaneously during DNA replication.

Question 8

What are the effects of a substitution mutation?

Answer 8

It may change one amino acid or have no effect due to the degeneracy of the genetic code.

Question 9

What are the effects of a deletion mutation?

Answer 9

It causes a frameshift, altering every amino acid after the mutation, potentially changing the protein’s tertiary structure.

Question 10

What is meiosis?

Answer 10

A type of cell division that results in four genetically different haploid cells through two nuclear divisions.

Question 11

How does crossing over increase genetic variation?

Answer 11

It swaps alleles between homologous chromosomes during meiosis I, creating new allele combinations.

Question 12

How does independent segregation increase genetic variation?

Answer 12

Homologous chromosomes line up randomly during meiosis I, resulting in different combinations in gametes.

Question 13

What is genetic diversity?

Answer 13

The total number of different alleles in a population.

Question 14

What are the types of adaptations?

Answer 14

Anatomical (structure), physiological (function), and behavioral (actions) that enhance survival.

Question 15

What is natural selection?

Answer 15

A process where individuals with beneficial mutations survive and reproduce, increasing allele frequency over generations.

Question 16

What is the index of diversity formula?

Answer 16

d = N(N-1) / Σn(n-1), where N is total individuals and n is individuals per species.

Question 17

Why is the index of diversity more useful than species richness?

Answer 17

Because it accounts for both species count and their population sizes.

Question 18

What is a species?

Answer 18

A group of organisms that can interbreed to produce fertile offspring.

Question 19

Why is courtship behaviour important?

Answer 19

It ensures mating between same species and synchronises mating.

Question 20

What is binomial naming?

Answer 20

Each species has a two-part name: genus and species.

Question 21

What are the taxonomic ranks?

Answer 21

Domain, kingdom, phylum, class, order, family, genus, species.

Question 22

What is phylogenetics?

Answer 22

Study of evolutionary relationships using common ancestors.

Question 23

How can DNA sequences show evolutionary relationships?

Answer 23

More similar DNA indicates more recent common ancestry.

Question 24

How can protein structure show evolutionary relationships?

Answer 24

Similar protein sequences imply close relatedness due to fewer mutations.

Question 25

What is a community in ecology?

Answer 25

All the populations of different species in a habitat.

Question 26

What is biodiversity?

Answer 26

The variety of living organisms in an ecosystem.

Question 27

Why is a hierarchy important in classification?

Answer 27

It groups organisms without overlap based on evolutionary relationships.

Question 28

What are the benefits of phylogenetic classification?

Answer 28

Reflects evolutionary history and avoids ambiguity in naming.

Question 29

Why is standard deviation important in studies of variation?

Answer 29

It shows variability and helps determine significance in differences.

Question 30

Why are random samples used in diversity studies?

Answer 30

To avoid bias and get representative data.

Question 31

What does a high index of diversity mean?

Answer 31

Many species are present and relatively even in number.

Question 32

What is the role of sample size in diversity studies?

Answer 32

Larger samples increase reliability and representation.

Question 33

What does the presence of clear zones in antimicrobial testing show?

Answer 33

The antimicrobial is effective at killing or inhibiting bacteria.

Question 34

How can antimicrobial effect be visualised?

Answer 34

By measuring inhibition zones around discs on an agar plate.

Question 35

Why are control discs used in antimicrobial experiments?

Answer 35

To ensure observed effects are due to the antimicrobial.

Question 36

Why must the petri dish be taped but not sealed completely?

Answer 36

To allow oxygen in and prevent anaerobic bacterial growth.

Question 37

What is the difference between observable characteristics and genetic markers?

Answer 37

Observable traits can be affected by environment; genetic markers are not.

Question 38

Why was DNA sequencing adopted for measuring diversity?

Answer 38

It provides direct and precise comparisons of genetic material.

Question 39

What statistical tests are used to analyse biodiversity data?

Answer 39

T-tests, chi-squared, correlation coefficient.

Question 40

Why does species richness not always indicate true diversity?

Answer 40

It ignores the population size of each species.

Question 41

What is a genome?

Answer 41

The complete set of genes in a cell, including mitochondrial or chloroplast genes.

Question 42

What is a proteome?

Answer 42

The full range of proteins a cell can produce.

Question 43

How is tRNA different from mRNA?

Answer 43

tRNA is folded with base pairing and has an anticodon and amino acid binding site; mRNA is linear and has codons.

Question 44

What does RNA polymerase do in transcription?

Answer 44

It joins adjacent RNA nucleotides via phosphodiester bonds.

Question 45

How does a mutation cause a non-functional protein?

Answer 45

It changes the amino acid sequence, altering the protein’s tertiary structure.

Question 46

What is a mutagenic agent?

Answer 46

A factor that increases mutation rate, like UV radiation or chemicals.

Question 47

What are homologous chromosomes?

Answer 47

Chromosomes with the same genes at the same loci, possibly with different alleles.

Question 48

What is the result of meiosis?

Answer 48

Four genetically different haploid cells.

Question 49

Why is the chromosome number halved in meiosis?

Answer 49

Because homologous chromosomes are separated in the first division.

Question 50

What causes chromosome mutations?

Answer 50

Non-disjunction during meiosis, leading to gametes with n+1 or n-1 chromosomes.

Question 51

How do random fertilisation and meiosis generate variation?

Answer 51

By combining alleles in new ways through crossing over and independent assortment.

Question 52

How do mitosis and meiosis differ?

Answer 52

Mitosis produces 2 identical diploid cells; meiosis makes 4 varied haploid cells.

Question 53

What is the importance of meiosis?

Answer 53

It creates genetic diversity and maintains chromosome number across generations.

Question 54

How can you calculate combinations of chromosomes from meiosis?

Answer 54

2^n where n = number of homologous chromosome pairs.

Question 55

How is the number of combinations after fertilisation calculated?

Answer 55

(2^n)^2 where n is the number of homologous chromosome pairs.

Question 56

What is evolution?

Answer 56

A change in allele frequency over generations via natural selection.

Question 57

What are the steps of natural selection?

Answer 57

Mutation → Advantage → Reproductive success → Inheritance → Allele frequency change.

Question 58

What is directional selection?

Answer 58

Favors individuals at one extreme of the trait distribution.

Question 59

What is stabilising selection?

Answer 59

Favors the average phenotype and reduces variation.

Question 60

Give an example of directional selection.

Answer 60

Antibiotic resistance in bacteria.

Question 61

Give an example of stabilising selection.

Answer 61

Human birth weight.

Question 62

Why does antibiotic resistance occur?

Answer 62

Mutations give some bacteria resistance, allowing survival and reproduction in presence of antibiotics.

Question 63

What is the principle behind the aseptic technique?

Answer 63

Prevent contamination by killing or excluding unwanted microbes.

Question 64

Why are agar plates incubated at 25°C?

Answer 64

To prevent growth of human pathogens.