AQA A-level Biology - Topic 4
1. Define variation: Differences that exist between individuals
2. In what ways can variation be caused?: It can be caused by genetic
factors, such as alleles from mutations.
It can also be caused by the environment, such as climate.
Most variation is caused by a combination of genetic factors and
environmental factors
3. Why is it impossible to study a whole population?: Because it is too
large and would take too long. Instead, scientists use a sample that is
representative of the species' population
4. Why should the sample taken be random?: So you can make sure
that the sample isn't biased in any way.
5. What could you calculate to look at variation between species?: The
mean (average)
6. What is standard deviation?: It tells you how much values in a single
sample vary, by measuring the spread of values about the mean
7. What does a large standard deviation mean?: That the values in the
sample vary a lot
8. What does a small standard deviation mean?: That the values in the
,sample varies little
9. What can you use standard deviation to draw on a bar chart of mean
values?: An error bar. You would draw it one standard deviation either
side of the mean value.
10.How is DNA stored in eukaryotic cells?: 1) The DNA is linear and
exists as chromosomes
2) It is stored in the nucleus, and has to be wound up because it is so
long
3) It is wound around proteins called histones which help to
support the DNA 4)The DNA is coiled very tightly to make a
compact chromosome
11.How is DNA stored in prokaryotic cells?: 1)Prokaryotic cells carry
DNA as chromosomes, but the DNA is shorter and circular
2)It isn't wrapped around histones, so condenses into the cell by
supercoiling
12.What organelles in eukaryotic cells have their own DNA apart from the
nucleus?: The mitochondria and chloroplasts have their own DNA. It is
similar to prokaryotic DNA as it is shorter, circular and isn't wrapped
around histones.
,13.What is a gene?: A gene is a sequence of DNA bases that
codes for a polypeptide or functional RNA
14.What forms the primary structure of proteins?: The sequence of
amino acids.
15.What determines the order of amino acids in a polypeptide?: The order
of the bases
, 16.How is each amino acid coded for?: By a sequence of three bases in a
gene called a triplet
17.What is functional RNA?: It is RNA molecules other than mRNA that
perform special tasks during protein synthesis.
tRNA and rRNA
18.What is a cell's genome?: The complete set of genes in a cell
19.What is a cell's proteome?: The full range of proteins that the cell is
able to produce
20.If a gene doesn't code for polypeptides, what does it code for?:
Functional RNA such as tRNA and rRNA
21.What are introns?: Sections of a gene that codes for polypeptides,
that doesn't actually code for amino acids
22.What are exons?: The sections of a gene that actually code for amino
acids
23.When are introns removed, and why?: They are removed ng
duri synthesis so it doesn't affect the amino acid order
24.Which type of DNA does not have introns?: Prokaryotic DNA does not
1. Define variation: Differences that exist between individuals
2. In what ways can variation be caused?: It can be caused by genetic
factors, such as alleles from mutations.
It can also be caused by the environment, such as climate.
Most variation is caused by a combination of genetic factors and
environmental factors
3. Why is it impossible to study a whole population?: Because it is too
large and would take too long. Instead, scientists use a sample that is
representative of the species' population
4. Why should the sample taken be random?: So you can make sure
that the sample isn't biased in any way.
5. What could you calculate to look at variation between species?: The
mean (average)
6. What is standard deviation?: It tells you how much values in a single
sample vary, by measuring the spread of values about the mean
7. What does a large standard deviation mean?: That the values in the
sample vary a lot
8. What does a small standard deviation mean?: That the values in the
,sample varies little
9. What can you use standard deviation to draw on a bar chart of mean
values?: An error bar. You would draw it one standard deviation either
side of the mean value.
10.How is DNA stored in eukaryotic cells?: 1) The DNA is linear and
exists as chromosomes
2) It is stored in the nucleus, and has to be wound up because it is so
long
3) It is wound around proteins called histones which help to
support the DNA 4)The DNA is coiled very tightly to make a
compact chromosome
11.How is DNA stored in prokaryotic cells?: 1)Prokaryotic cells carry
DNA as chromosomes, but the DNA is shorter and circular
2)It isn't wrapped around histones, so condenses into the cell by
supercoiling
12.What organelles in eukaryotic cells have their own DNA apart from the
nucleus?: The mitochondria and chloroplasts have their own DNA. It is
similar to prokaryotic DNA as it is shorter, circular and isn't wrapped
around histones.
,13.What is a gene?: A gene is a sequence of DNA bases that
codes for a polypeptide or functional RNA
14.What forms the primary structure of proteins?: The sequence of
amino acids.
15.What determines the order of amino acids in a polypeptide?: The order
of the bases
, 16.How is each amino acid coded for?: By a sequence of three bases in a
gene called a triplet
17.What is functional RNA?: It is RNA molecules other than mRNA that
perform special tasks during protein synthesis.
tRNA and rRNA
18.What is a cell's genome?: The complete set of genes in a cell
19.What is a cell's proteome?: The full range of proteins that the cell is
able to produce
20.If a gene doesn't code for polypeptides, what does it code for?:
Functional RNA such as tRNA and rRNA
21.What are introns?: Sections of a gene that codes for polypeptides,
that doesn't actually code for amino acids
22.What are exons?: The sections of a gene that actually code for amino
acids
23.When are introns removed, and why?: They are removed ng
duri synthesis so it doesn't affect the amino acid order
24.Which type of DNA does not have introns?: Prokaryotic DNA does not
