Download 3.4: Genetic information, variation and

3.4: Genetic information, variation and relationships between organisms
External Assessments:
Internal Assessments:
AS – Paper 1 and Paper 2
1. DNA, protein synthesis and mutations
exam questions (due:
A-level – Paper 1 and Paper 3
Required Practicals:
6. Use of aseptic techniques to investigate the effect
of antimicrobial substances on microbial growth.
Comments:
2. Classification and biodiversity exam
questions (due:
)
3. End of topic test
)
3.4: Genetic information, variation and relationships between organisms
3.4.1 DNA, genes and chromosomes
How does the DNA in prokaryotic organisms differ from the DNA in eukaryotic organisms?
How is DNA stored in eukaryotes?
In which eukaryotic organelles is DNA found?
Compare the DNA in prokaryotic organisms with
the DNA in eukaryotic organisms:
Aside from the nucleus, in which eukaryotic
organelles is DNA found?
How does the structure of this DNA compare
with that found in the nucleus?
Key words: prokaryotic cell;
eukaryotic cell; chromosome;
chromatid; centromere; histone; DNA
molecule, histones; coiled;
supercoiled; chromosome
Annotate the diagram to show how DNA is packed
into a chromosome:
3.4: Genetic information, variation and relationships between organisms
3.4.1 DNA, genes and chromosomes
Key words:
What is a gene?
What is the genetic code?
Does all of the DNA in cells code for proteins?
DNA; gene; locus; triplet; polypeptide;
RNA; non-coding; exon; intron; universal;
degenerate; non-overlapping
What is a gene?
How does DNA enable cells to produce proteins?
What do we mean by the term locus of a gene?
The genetic code is described as ‘universal, degenerate
and non-overlapping’. Explain what this means.
What do we mean by the terms intron and exon?
Give one other reason why not all of the DNA in a
nucleus codes for polypeptides.
3.4: Genetic information, variation and relationships between organisms
3.4.2 DNA and protein synthesis
Key words:
What are genomes and proteomes?
What is the structure of messenger RNA (mRNA)?
What is the structure of transfer RNA (tRNA)?
How do mRNA and tRNA contribute to protein synthesis?
Genome; proteome; ribonucleic acid;
messenger RNA; transfer RNA; codon;
anticodon
Explain what we mean by the following terms:
a) Genome
b)
Proteome
Describe the structure and role of messenger RNA:
Describe the structure and role of transfer RNA:
3.4: Genetic information, variation and relationships between organisms
3.4.2 DNA and protein synthesis
Key words:
How is pre-mRNA produced from DNA in the process called
transcription?
How is pre-mRNA modified to form mRNA?
Nucleotides; transcription; DNA replication; DNA
helicase; hydrogen bonds; template strand;
RNA polymerase; splicing; pre-mRNA
Describe the process of transcription, using the diagrams
to help:
Describe the process of splicing, using the diagrams to
help:
3.4: Genetic information, variation and relationships between organisms
3.4.2 DNA and protein synthesis
Key words:
How is a polypeptide synthesised during the process of translation?
What are the roles of messenger RNA and transfer RNA in translation?
Codon; anticodon; peptide bond;
translation; ribosome; ATP
Describe the process of translation in protein synthesis. In your answer, explain the roles of the ribosome, mRNA,
tRNA and ATP.
3.4: Genetic information, variation and relationships between organisms
3.4.3 Genetic diversity can arise as a result of mutation or during meiosis
Key words:
What is a gene mutation and how do they occur?
How do deletion and substitution of bases result in mutations?
Why do some mutations not result in changed amino acid sequences?
How do mutations in chromosome number occur?
Mutation; base deletion; base
substitution; frame shift;
mutagenic agent; nondisjunction
What is a gene mutation?
What is a mutagenic agent?
When in the life of a cell do gene mutations occur?
Give some examples of mutagenic agents.
What is meant by the statement, ‘base substitution can
lead to mutations’?
What is meant by the statement, ‘base deletion can lead
to mutations’? Use the term frame shift in your answer.
Explain what we mean by non-disjunction of chromosomes and how it can lead to a mutation in a cell:
3.4: Genetic information, variation and relationships between organisms
3.4.3 Genetic diversity can arise as a result of mutation or
during meiosis
What is the purpose of meiosis?
What happens during meiosis?
What is meiosis? Use the diagram in your explanation.
Key words:
Meiosis; gametes; diploid; haploid; crossing
over; independent segregation; genetic
recombination; sister chromatids
3.4: Genetic information, variation and relationships between organisms
3.4.3 Genetic diversity can arise as a result of mutation or during
meiosis
Why is meiosis important and how does it lead to genetic variation?
What are the similarities and differences between mitosis and meiosis?
Explain how the following processes lead to an increase
in genetic variation:
a) Independent segregation (assortment)
Key words:
Mitosis; meiosis; gametes; diploid; haploid; crossing
over; independent segregation; genetic recombination;
alleles; genes
Explain why meiosis is important in organisms that reproduce
sexually.
Compare mitosis and meiosis:
Feature
b) Crossing over
Purpose
Number of cell
divisions
Number of daughter
cells produced
c) Random fertilisation
Genetic variation
between daughter
cells
Genetic variation
between daughter
and parent cells
Mitosis
Meiosis
3.4: Genetic information, variation and relationships between organisms
3.4.4 Genetic diversity and adaptation
Key words: Genetic diversity; alleles; genes;
What is genetic diversity and how does it lead to natural selection?
What is natural selection?
natural selection; mutation; reproductive success;
allele frequency
What is genetic diversity?
What are the causes of genetic diversity?
Complete the description of natural selection:
1. Random mutation can result in new …………...
of a gene.
2. Many mutations are harmful, but in certain
environments, the new ………….. might benefit
the organism, leading to increased
……………………………………………
3. The advantageous …………… is inherited by
members of the next generation.
4. Over many generations, the new …………...
increases in ………………. in the population.
Explain how the over-use of antibiotics and natural
selection have led to the formation of antibioticresistant strains of bacteria, such as MRSA.
3.4: Genetic information, variation and relationships between organisms
3.4.4 Genetic diversity and adaptation
Key words: Genetic diversity; alleles; genes;
What are directional and stabilising selection?
Why is natural selection important?
natural selection; mutation; reproductive success;
allele frequency ; directional; stabilising
Natural selection produces organisms that are
better adapted to their environments. The
adaptations may be anatomical, physiological or
behavioural.
Research one example of an organism adapted
in each of these ways and explain how the
adaptation is advantageous to the organism.
Anatomical:
Physiological:
Behavioural:
What is directional selection? Use the example
of antibiotic resistance in bacteria to illustrate your
answer.
What is stabilising selection? Use the example
of human birth weights to illustrate your answer.
Exam questions: DNA, Protein Synthesis and Mutations
Complete the table to show the differences between
DNA, mRNA and tRNA.
(2 marks)
In the space below, give the sequence of bases on the
mRNA produced by splicing this piece of pre-mRNA.
(1 mark)
The genetic code is described as being degenerate.
What does this mean?
(1 mark)
The diagram shows the bases on one strand of a piece
of DNA.
What is a codon?
(2 marks)
What is the role of RNA polymerase during
transcription?
(1 mark)
In the space below, give the sequence of bases on the
pre-mRNA transcribed from this strand.
(2 marks)
Exam questions: DNA, Protein Synthesis and Mutations
Figure 3 shows a pair of chromosomes at the
start of meiosis. The letters represent alleles.
The cell containing this pair of chromosomes
divided by meiosis. Figure 4 shows the
distribution of chromosomes from this pair in four
of the gametes produced.
What is an allele?
Some of the gametes formed during meiosis
have new combinations of alleles.
Explain how the gametes with the combinations
of alleles Ef and eF have been produced.
(1 mark)
Explain the appearance of one of the
chromosomes in Figure 3.
(2 marks)
(2 marks)
Exam questions: DNA, Protein Synthesis and Mutations
Only a few gametes have the new combination of
alleles Ef and eF. Most gametes have the
combination of alleles EF and ef. Suggest why
only a few gametes have the new combination of
alleles, Ef and eF.
(1 mark)
Figure 5 shows a cell with six chromosomes.
This cell produces gametes by meiosis. Draw a
diagram to show the chromosomes in one of the
gametes.
(2 marks)
How many different types of gametes could be
produced from this cell as a result of
different combinations of maternal and paternal
chromosomes?
(1 mark)
Exam questions: DNA, Protein Synthesis and Mutations
Table 1 shows the first 12 bases on the coding strand of a
DNA molecule.
Substitution is a type of gene mutation. Use the
information in Table 2 to explain the effect on:
(i) the amino acid sequence of substitution of the third
DNA base in Table 1
(2 marks)
Table 2 shows the DNA triplets for four amino acids.
(ii) substitution of the sixth DNA base in Table 1.
(2 marks)
Complete Table 1 to show the first five bases on the
messenger RNA produced by transcription of this DNA.
(1 mark)
Give the amino acid sequence which is coded for in the
DNA sequence given in Table 1.
(1 mark)
Explain why a mutation involving the deletion of a base
might have a greater effect than a mutation involving
the substitution of one base for another.
(2 marks)
3.4: Genetic information, variation and relationships between organisms
3.4.5 Species and taxonomy
Key words:
What is a species?
What is the role of courtship in ensuring successful mating?
How are organisms classified?
Classification; courtship; pair bond;
synchronised mating; species recognition;
phylogenetic; hierarchy; taxon
Give the definition of a species.
What is a phylogenetic classification
system?
Explain how courtship behaviours lead to
successful mating.
In terms of classification, what do we mean by
a hierarchy?
Which term do we use to describe the groups
within a hierarchy?
3.4: Genetic information, variation and relationships between organisms
3.4.5 Species and taxonomy
Key words:
How are species named?
What are the principles of classification?
How have technological advances helped to clarify
evolutionary relationships between organisms?
Binomial system; generic name; species;
classification; taxonomy; domain; kingdom; phylum;
class; order; family; genus; species; phylogeny;
hierarchy
List the taxa in a hierarchy, from the largest to smallest group.
Explain what is meant by the binomial system of naming species.
Explain how immunology can give us evidence of evolutionary
relationships between organisms.
Explain how genome sequencing has helped to clarify
evolutionary relationships between organisms.
3.4: Genetic information, variation and relationships between organisms
3.4.6 Biodiversity within a community
Key words:
What is biodiversity?
What is species richness?
What is an index of diversity and how do we calculate it?
Biodiversity; species richness; diversity
index
What is biodiversity?
What is an index of diversity?
What is species richness?
Why might you choose to calculate a diversity index, rather than
just measuring species richness?
The formula for calculating the Simpson’s Diversity Index is:
Calculate the species diversity index using the
following numbers:
𝑁(𝑁 − 1)
𝑑=
𝑛(𝑛 − 1)
Where:
𝑑 = species diversity index
𝑁 = total number of organisms of all species
𝑛 = total number of organisms of each species
∑ = the sum of
Species
Numbers (n)
A
4
B
5
C
6
∑n(n-1)
d=
n(n-1)
3.4: Genetic information, variation and relationships between organisms
3.4.6 Biodiversity within a community
Key words:
How do farming techniques reduce biodiversity?
What should we consider when trying to balance farming and conservation?
Biodiversity; conservation; gene
pool; alleles; agriculture
Explain how the following farming techniques reduce biodiversity:
a) Hedgerow removal
b) Monoculture
c) Use of herbicides
Suggest how farmers might change the techniques above to help maintain higher levels of biodiversity.
Remember to consider both the economic cost to the farmer and the impact on the environment.
3.4: Genetic information, variation and relationships between organisms
3.4.7 Investigating diversity
Key words:
What different methods can we use to investigate genetic diversity within
or between species?
DNA; mRNA; base sequence; amino acid; DNA
hybridisation
How can we use observable/measurable characteristics to
investigate genetic diversity?
DNA hybridisation can give evidence for genetic diversity.
Annotate the diagram below to explain how.
How can we use DNA base sequencing to investigate genetic
diversity?
How can we use mRNA base sequencing to investigate genetic
diversity?
Why might this give different results to using DNA base sequences?
How can we use amino acid sequencing to investigate genetic
diversity?
Why might this give different results to using DNA or mRNA base
sequences?
3.4: Genetic information, variation and relationships between organisms
3.4.7 Investigating diversity
Key words:
How do we collect and process data about variation within a
species?
Normal distribution; mean; standard deviation;
sample; population; random
How could you collect a random (unbiased) sample of data involving:
a) The length of leaves in a shaded field and a sunny field?
b) The heights of students in a school?
Explain what the graphs above suggest about the
variation shown by the samples measured.
Calculate the mean, median, mode and standard deviation of the following
numbers:
1, 2, 4, 5, 7, 15, 10, 19, 20, 13, 14, 15, 21, 7, 5, 3, 17, 16, 7, 2
The equation for standard deviation is:
𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛 =
(𝑥 − 𝑥)2
𝑛
Where:
∑ = the sum of
𝑥 = measured value (from the sample)
𝑥 = mean value
𝑛 = the total number of values in the sample
Mean:
Median:
Mode:
Standard deviation:
Exam questions: Classification and Biodiversity
An order is a taxonomic group. All seals belong to the
same order. Name one other taxonomic group to which all
seals belong.
How many different genera are shown in this diagram?
(1 mark)
(1 mark)
All the seals shown in the diagram are members of the
Phocidae. Phocidae is an example of a taxonomic
group. Of which taxonomic group is it an example?
The diagram shows how some species of seal are
classified.
(1 mark)
The diagram is based on the evolutionary history of the
seals. What does the information in the diagram
suggest about the common ancestors of Mirounga
angustirostris, Mirounga leonina and Monachus
tropicalis?
(1 mark)
Exam questions: Classification and Biodiversity
Cytochrome c is a protein found in all eukaryotes. In
humans it consists of 102 amino acids. Biologists have
compared the amino acid sequence in some other
species with that in humans. The table shows amino acids
9 to 13 in the amino acid sequences of cytochrome c from
four species.
Suggest one advantage of using cytochrome c to
determine relationships between species.
(1 mark)
Comparing the base sequence of a gene provides
more information than comparing the amino acid
sequence for which the gene codes. Explain why.
What do the results suggest about the relationship
between humans and the other three species?
(2 marks)
(2 marks)
Exam questions: Classification and Biodiversity
Hummingbirds belong to the order Apodiformes. One genus in this order is Topaza.
Name one other taxonomic group to which all members of the Apodiformes belong.
(1 mark)
Name the taxonomic group between order and genus.
(1 mark)
The crimson topaz and the fiery topaz are hummingbirds.
Biologists investigated whether the crimson topaz and the fiery topaz are different species of hummingbird, or different
forms of the same species.
They caught large numbers of each type of hummingbird. For each bird they
•
recorded its sex
•
recorded its mass
•
recorded the colour of its throat feathers
•
took a sample of a blood protein.
The table shows some of
their results.
Exam questions: Classification and Biodiversity
Explain how the standard deviation helps in the interpretation of these data.
(2 marks)
In hummingbirds throat colour is important in courtship. Explain the evidence in the table that shows
that the crimson topaz and the fiery topaz may be different species of hummingbird.
(2 marks)
The biologists analysed the amino acid sequences of the blood protein samples from these
hummingbirds.
Explain how these sequences could provide evidence as to whether the crimson topaz and the fiery
topaz are different species.
(2 marks)
Exam questions: Classification and Biodiversity
Scientists investigated the species of insects found
in a wood and in a nearby wheat field. The
scientists collected insects by placing traps at sites
chosen at random both in the wood and in the
wheat field. The table shows the data collected in
the wood and in the wheat field.
The scientists collected insects at sites chosen at
random. Explain the importance of the sites being
chosen at random.
(1 mark)
Use the formula 𝑑 =
𝑁(𝑁−1)
𝑛(𝑛−1)
to calculate the index of
diversity for the insects caught in the wood, where
d = index of diversity
N = total number of organisms of all species
n = total number of organisms of each species
Show your working.
Answer ...................................................................
(2 marks)
Exam questions: Classification and Biodiversity
Without carrying out any further calculations, estimate whether the index of diversity for the wheat field
would be higher or lower than the index of diversity for the wood. Explain how you arrived at your
answer.
(2 marks)
A journalist concluded that this investigation showed that farming reduces species diversity.
Evaluate this conclusion.
(2 marks)
Farmers were offered grants by the government to plant hedges around their fields. Explain the effect
planting hedges could have on the index of diversity for animals.
(2 marks)