Unit Fo

Question 1

What is the nucleotide structure of DNA?

Answer 1

Deoxyribose attached to phosphate and a base

Nucleotides are the building blocks of DNA.

Question 2

What bonds join adjacent nucleotides in DNA?

Answer 2

Phosphodiester bonds

These bonds form the backbone of the DNA structure.

Question 3

How is eukaryotic DNA different from prokaryotic DNA?

Answer 3

Eukaryotic DNA is longer, linear, associated with histone proteins, and contains introns

Prokaryotic DNA is circular and not associated with proteins.

Question 4

What is a chromosome?

Answer 4

Long, linear DNA + its associated histone proteins

Chromosomes are found in the nucleus of eukaryotic cells.

Question 5

What is a gene?

Answer 5

A sequence of DNA (nucleotide) bases that codes for the amino acid sequence of a polypeptide or a functional RNA

Genes are fundamental units of heredity.

Question 6

What is a locus?

Answer 6

Fixed position a gene occupies on a particular DNA molecule

The locus is specific to a particular gene.

Question 7

Describe the nature of the genetic code.

Answer 7

Triplet code, universal, non-overlapping, degenerate

This means that the same triplets code for the same amino acids across all organisms.

Question 8

What is a non-coding base sequence?

Answer 8

DNA that does not code for amino acid sequences or polypeptides

Found between genes (non-coding multiple repeats) and within genes (introns).

Question 9

What are introns and exons?

Answer 9

Exon: Base sequence of a gene coding for amino acid sequences. Intron: Base sequence that doesn’t code for amino acids in eukaryotes

Exons are expressed sequences, while introns are removed during RNA processing.

Question 10

Define ‘genome’.

Answer 10

The complete set of genes in a cell

This includes genes in mitochondria and chloroplasts.

Question 11

Define ‘proteome’.

Answer 11

The full range of proteins that a cell can produce

Coded for by the cell’s DNA or genome.

Question 12

What are the two stages of protein synthesis?

Answer 12

Transcription and Translation

Transcription occurs in the nucleus, while translation occurs at ribosomes.

Question 13

How is mRNA formed by transcription in eukaryotic cells?

Answer 13

Hydrogen bonds break, one strand acts as a template, RNA nucleotides align, RNA polymerase forms phosphodiester bonds, pre-mRNA is spliced to form mature mRNA

Uracil replaces thymine in RNA.

Question 14

What is a gene mutation?

Answer 14

A change in the base sequence of DNA on chromosomes

Examples include base deletion or substitution.

Question 15

What is a mutagenic agent?

Answer 15

A factor that increases the rate of gene mutation

Examples include ultraviolet (UV) light and alpha particles.

Question 16

Describe the effects of a substitution mutation.

Answer 16

Changes one triplet, possibly changing one amino acid in the polypeptide

Tertiary structure may change or remain the same due to the degenerate nature of the genetic code.

Question 17

Describe the effects of a deletion mutation.

Answer 17

Changes sequence of DNA triplets, causing a frameshift and altering the primary structure of the polypeptide

This can significantly change protein function.

Question 18

What are homologous chromosomes?

Answer 18

Same length, same genes at same loci, but may have different alleles

They pair during meiosis.

Question 19

What is the difference between diploid and haploid cells?

Answer 19

Diploid: 2 complete sets of chromosomes (2n); Haploid: 1 set of unpaired chromosomes (n)

This distinction is crucial for understanding meiosis.

Question 20

Explain how crossing over creates genetic variation.

Answer 20

Non-sister chromatids exchange alleles at chiasmata, creating new combinations of alleles

This occurs during prophase I of meiosis.

Question 21

What is the importance of meiosis?

Answer 21

Creates haploid gametes, restores diploid number at fertilization, and creates genetic variation

This is essential for sexual reproduction.

Question 22

How does independent segregation create genetic variation?

Answer 22

Homologous pairs randomly align at the equator during metaphase I, leading to different combinations in daughter cells

This process occurs in meiosis.

Question 23

What are the outcomes of mitosis?

Answer 23

Produces 2 genetically identical daughter cells

Maintains chromosome number.

Question 24

What are the outcomes of meiosis?

Answer 24

Produces 4 genetically varied daughter cells

Halves the chromosome number.

Question 25

What is meiosis?

Answer 25

A process that creates haploid gametes through two divisions, reducing the chromosome number by half. ## Footnote Meiosis results in genetic variation through independent segregation and crossing over.

Question 26

How can you recognize where meiosis and mitosis occur in a life cycle?

Answer 26

Mitosis occurs where chromosome number is maintained (e.g., diploid to diploid or haploid to haploid), while meiosis occurs where chromosome number halves (e.g., diploid to haploid).

Question 27

How do mutations in the number of chromosomes arise?

Answer 27

They arise spontaneously by chromosome non-disjunction during meiosis, leading to gametes with extra (n+1) or missing (n-1) chromosomes.

Question 28

How can the number of possible combinations of chromosomes in daughter cells following meiosis be calculated?

Answer 28

Using the formula 2^n, where n represents the number of pairs of homologous chromosomes.

Question 29

How can the number of possible combinations of chromosomes following random fertilisation of two gametes be calculated?

Answer 29

(2^n)^2, where n represents the number of pairs of homologous chromosomes.

Question 30

True or False: All mutations result in a change in amino acid sequence.

Answer 30

False ## Footnote Due to the degenerate nature of the genetic code, many mutations do not affect the amino acid sequence.

Question 31

What is genetic diversity?

Answer 31

The number of different alleles of genes in a population.

Question 32

What are alleles and how do they arise?

Answer 32

Variations of a particular gene at the same locus with different DNA base sequences, arising by mutation.

Question 33

What is a population?

Answer 33

A group of interbreeding individuals of the same species.

Question 34

Explain the importance of genetic diversity.

Answer 34

It enables natural selection, allowing advantageous alleles to contribute to survival and reproductive success.

Question 35

What is evolution?

Answer 35

The change in allele frequency within a population over many generations through natural selection.

Question 36

List the principles of natural selection in the evolution of populations.

Answer 36

* Mutation * Advantage * Reproductive success * Inheritance * Allele frequency

Question 37

Describe three types of adaptations.

Answer 37

* Anatomical - structural features * Physiological - chemical processes * Behavioural - actions that increase survival

Question 38

What is directional selection?

Answer 38

A type of selection where organisms with an extreme variation of a trait have a selective advantage.

Question 39

What is stabilising selection?

Answer 39

A type of selection that favors average or modal variations of traits, maintaining stability in a population.

Question 40

Describe the method to investigate the effect of antimicrobial substances on microbial growth.

Answer 40

Prepare the area with aseptic techniques, transfer bacteria to agar, place antimicrobial discs, incubate, and measure inhibition zones.

Question 41

Why is it important to maintain a pure culture of bacteria?

Answer 41

To prevent competition from other bacteria and avoid potential health risks.

Question 42

What is a species?

Answer 42

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

Question 43

What is a phylogenetic classification system?

Answer 43

A system that arranges species into groups based on evolutionary origins and relationships.

Question 44

What are the taxa in the hierarchy of classification?

Answer 44

* Domain * Kingdom * Phylum * Class * Order * Family * Genus * Species

Question 45

What is biodiversity?

Answer 45

The variety of living organisms, including species, genetic, and ecosystem diversity.

Question 46

What is species richness?

Answer 46

A measure of the number of different species in a community.

Question 47

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

Answer 47

It accounts for both the number of species and the number of individuals in each species.

Question 48

What is the formula for index of diversity?

Answer 48

d = N(N - 1) / Σn(n - 1)

Question 49

Explain how some farming techniques reduce biodiversity.

Answer 49

* Removal of woodland and hedgerows reduces plant variety * Monoculture limits food sources * Herbicides and pesticides decrease populations of non-target species

Question 50

What is an advantage of binomial naming?

Answer 50

It is universal, reducing confusion from multiple common names for organisms.

Question 51

What is required to increase biodiversity?

Answer 51

Conservation ## Footnote Conservation practices are essential for enhancing biodiversity, especially in agricultural settings.

Question 52

How can conservation practices impact farmers?

Answer 52

They can reduce yields, thus impacting profit/income ## Footnote Conservation measures might require reducing land area for crop growth, which can lead to increased competition and pest populations.

Question 53

What financial mechanisms are offered to offset losses from conservation?

Answer 53

Financial incentives and grants ## Footnote These are provided to support farmers who implement biodiversity-friendly practices.

Question 54

Give examples of how biodiversity can be increased in agriculture.

Answer 54

* Reintroduction of field margins and hedgerows * Reduce use of pesticides * Intercropping * Crop rotation with nitrogen-fixing crops ## Footnote These practices help promote biodiversity while maintaining agricultural productivity.

Question 55

What is species richness?

Answer 55

A measure of the number of different species in a community/habitat/ecosystem/area ## Footnote It is often confused with the population of a single species.

Question 56

True or False: Farming techniques reduce biodiversity by causing less food overall.

Answer 56

False ## Footnote Farming techniques may reduce the variety of food sources, which is crucial for biodiversity.

Question 57

How can genetic diversity within or between species be measured?

Answer 57

* Comparing frequency of measurable or observable characteristics * Comparing base sequence of DNA * Comparing base sequence of mRNA * Comparing amino acid sequence of proteins ## Footnote These methods help in understanding the relationships between organisms.

Question 58

What does a greater number of differences in DNA sequences indicate?

Answer 58

More distantly related organisms or an earlier common ancestor ## Footnote This is due to the accumulation of mutations over time.

Question 59

How have methods of investigating genetic diversity changed over time?

Answer 59

Shifted from inferring DNA differences based on observable characteristics to direct investigation of DNA sequences ## Footnote Early methods were limited by environmental influences and polygenic traits.

Question 60

What are key considerations in quantitative investigations of variation within a species?

Answer 60

* Collect data from random samples * Use a large sample size * Ethical sampling * Calculate mean values and standard deviation * Use named statistical tests ## Footnote These practices help ensure that the data is reliable and representative.

Question 61

What does a higher standard deviation indicate?

Answer 61

Higher variation ## Footnote A higher standard deviation shows that the values are more spread out from the mean.

Question 62

What does it mean if the standard deviations of two data sets overlap?

Answer 62

Any difference may be due to chance and not significant ## Footnote Overlapping standard deviations suggest that the data sets are not significantly different.

Question 63

True or False: Comparing DNA and amino acid sequences provides a vague measure of genetic diversity.

Answer 63

False ## Footnote It is essential to specify that comparing DNA base sequences and amino acid sequences allows for a precise measurement of genetic diversity.