Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A- Level Biology > Unit 4 > Flashcards

Unit 4 Flashcards

1
Q

Describe the role of DNA.

A

Carries genetic information, determines
our inherited characteristics.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the structure of RNA.
func=Transfers genetic information from DNA to ribosomes for protein synthesis.

A

Made up of a ribose sugar, a phosphate
group, and one of four organic bases (A,C,G,U).
It is single stranded.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How is DNA in eukaryotic cells different from in prokaryotic cells?

A

● Eukaryotic cells=
-found in nucleus
-long and linear
-Associated with histone proteins to form chromosomes.

Mitochondria and chloroplasts
contain prokaryotic-like DNA.
● Prokaryotic cells= short and circular.
Not associated with proteins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the genetic code?

A

Order of bases on DNA
Consists of codons (triplets of bases that code for a particular amino acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Identify features of the genetic code 3

A

● Non-overlapping= each triplet is only read once.
● Degenerate= more than one triplet (codon) codes for the
same amino acid
● Universal= same bases and sequences used by all species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a gene? 3

A

A sequence of bases on a DNA molecule
- that codes for a specific sequence of amino acids to make a polypeptide.
Can also code for functional RNA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a locus?

A

The fixed position on a DNA molecule occupied by a gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is an allele?

A

Different versions of the same gene, found at the same locus on a
chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are exons and introns?
(introns, between exons within genes)

A

Exons= regions of DNA that code for amino acid sequences. Separated by
one or more introns.

Introns= regions of DNA that do not code for anything.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the genome?

A

The complete set of genetic information contained in the cells of an organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the proteome?

A

The complete set of proteins that can be produced by a cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the structure of messenger RNA (mRNA) 4

A

-long
-uracil instead of thymine
-single strand
-Its base sequence is complementary to the DNA it was
transcribed from

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Suggest advantages of using mRNA rather than DNA for translation. 3

A

● shorter & contains uracil = breaks down quickly so no excess polypeptide forms
● single-stranded & linear = ribosome moves along strand & tRNA binds to exposed bases
● contains no introns

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the structure of transfer RNA
(tRNA).

A

-A single strand of around 80 nucleotides
- folded over into a clover leaf shape
-one end is an anti-codon
-on the opposite end is an amino acid binding site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Outline the process of transcription happens in the nucleus 6

the production of mRNA from DNA
RNA polymerase in joining mRNA nucleotides.

A

-Hydrogen bonds between DNA bases break
-Only one DNA strand act as a template
-Free adjacent RNA nucleotides align by complementary base pairing
-In RNA, Uracil is used instead of thymine
-RNA polymerase joins RNA nucleotides together by phosphodiester bonds from pre-mRNA
-pre-mRNA is spliced to remove introns, forming mRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens to mRNA after transcription (copy)?2

A

-In eukaryotic cells, pre-mRNA must be spliced to remove introns, leaving only the coding regions.
-Then it moves out of the nucleus and attaches to a ribosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Outline the process of translation. 7
-happens in the cytoplasm on ribosomes
-proteins produced

A

-mRNA attaches to ribosomes
-tRNA anticodons bind to complementary mRNA codons
-tRNA brings a specific amino acid.
-Amino acids join by peptide bonds.
-Amino acids join together with the use of ATP
-tRNA released after amino acid joined to the polypeptide
-The ribosome moves along the mRNA to form the polypeptide;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a mutation

A

An alteration to the DNA base sequence.
Often arise spontaneously during DNA
replication.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why might a mutation not lead to change in the amino acid sequence?

A

● Genetic code is degenerate so
mutation may end up coding for same
amino acid as the original triplet.
● Mutation may occur in intron.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a substitution mutation?
-genetic code degenerate so not all substitions result in a change in the primary structure of a polypeptide chain

A

When a nucleotide in the DNA sequence is replaced by another. This is more likely to be a quiet mutation, meaning no change occurs in the amino acid sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a deletion mutation

A
  • nucleotide in the DNA sequence
    is lost.
    -leads to a frame shift
    -entire amino acid sequence will be different.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a mutagenic agent? Give
examples of this 2

A

-Factors that increase the rate of gene
mutation.
-X-rays, UV light, gamma rays,
certain chemicals e.g. in alcohol and
tobacco.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is chromosome non-disjunction?

A

chromosomes/ chromatids fail to separate correctly in meiosis resulting in gametes with one more or less chromosome than normal

-in anaphase 1 /meiosis homologous pairs fail to separate and are not pulled to opposite poles

-in anaphase 2 sister chromatids fail to separate and are not pulled to opposite poles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is meiosis?2

A

-A form of cell division
-produces four
genetically different haploid cells (cells with half the number of chromosomes found in the parent cell) known as gametes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How does meiosis differ from mitosis?2

A

● Meiosis produces four genetically different cells with half the number of chromosomes as the parent cells.
● Mitosis produces two genetically identical cells with the same number of chromosomes as the parent cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What happens during meiosis Ⅰ?3

A
  1. Homologous chromosomes pair to form bivalents.
  2. Crossing over (exchange of sections of genetic material) occurs at chiasmata.
  3. Cell divides into two. Homologous chromosomes separate randomly. Each cell contains either
    maternal or paternal copy.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What happens during meiosis Ⅱ?2

A
  1. Independent segregation of sister
    chromatids.
  2. Each cell divides again, producing 4
    haploid cells.
28
Q

In which two ways does meiosis produce genetic variation?
2*
*= how many homologous pairs of chromosomes
2=homologous pairs

A
  1. Crossing over during meiosis Ⅰ
  2. Independent assortment (random
    segregation) of homologous
    chromosomes & sister chromatids
    Result in new combinations of alleles.
29
Q

crossing over of chromosomes 3

A

-homologous pairs of chromosomes associate to form bivalents
-chiasma forms
-equal lengths of non-sister chromatids are exchanged producing new combination of alleles

30
Q

ethical and economical argument for biodiversity

A

eth -Prevent extinction / loss of populations / reduction in populations / loss of habitats / save organisms for future generations

econ-medical / pharmaceutical uses;
commercial products, tourism; agriculture; saving local forest communities

31
Q

Define population

A

All the organisms of a particular species that live in the same place

32
Q

Define genetic diversity

A

the number of different alleles of genes in a population.

33
Q

What advantage does a high genetic
diversity provide?

A

Ability to adapt to a change in environment; allows natural selection to
occur.

33
Q

What advantage does a high genetic
diversity provide?

A

Ability to adapt to a change in environment; allows natural selection to
occur.

34
Q

Explain how natural selection results in development
of new characteristics.

A

● Random mutations result in new alleles.
● Some alleles provide an advantage, making an
individual more likely to survive and reproduce.
● Their offspring receive the new allele, and
frequency continues to increase over many
generations

35
Q

What is directional selection?

A

Occurs when environmental conditions
change. Individuals with phenotypes suited to
the new conditions will survive and pass on
their genes. Over time the mean of the
population will move towards these
characteristics

36
Q

Give an example of directional selection.

A

Antibiotic resistance. Bacteria with a mutation
allowing them to survive in the presence of
antibiotics will reproduce. Therefore frequency
of this allele will increase and the population
will shift to have greater antibiotic resistance.

37
Q

What is stabilising selection?

A

Occurs when environmental conditions
stay the same. Individuals closest to the
mean are favoured, and any new
characteristics are selected against.
Results in low diversity

38
Q

Give an example of stabilising selection.

A

Birth weight; babies that weigh around
3kg are more likely to survive than those
at lower or higher weights.

39
Q

Define a niche

A

The role of a species within its
environment. Species sharing the same
niche will compete with each other

40
Q

What are the three types of adaptation?
Give examples of each

A

● Anatomical (changes to body structure) e.g. oily
fur.
● Physiological (changes to bodily processes) e.g.
venom production.
● Behavioural (changes to actions) e.g. hibernation

41
Q

Define species.

A

A group of organisms that can interbreed
to produce fertile offspring

42
Q

What are the advantages of courtship behaviour?

A

Individuals can recognise sexually
mature members of their own species of
the opposite sex, synchronise mating,
form a pair bond, and successfully
breed

43
Q

Define classification

A

The process of arranging organisms into
groups.

44
Q

Name the eight groups in the
classification hierarchy, from largest to
smallest.

A

domain → kingdom → phylum → class
→ order → family → genus → species

45
Q

What system is used to give species a
universal name?

A

Binomial naming system.

46
Q

What are the two components to a
binomial name?

A

Generic name= the genus the organism
belongs to. Two closely related species
will share the same genus.
Specific name= the species the organism
belongs to.

47
Q

How are binomial names handwritten?

A

The first letter of the generic name
should be capitalised, with the rest in
lowercase. The whole name should be
underlined

48
Q

What is phylogenetic classification?

A

The process of arranging organisms into
groups based on their evolutionary
origins and relationships

48
Q

How can we clarify evolutionary
relationships between organisms?

A

Analyse their molecular differences.
Advances in immunology/genome
sequencing provide clear pictures of how
related two organisms are.

49
Q

Explain hierarchical classification.

A

● groups within groups
● no overlap between group

50
Q

Define community.

A

All the different species that live in one
area and interact with each other

50
Q

What is biodiversity?

A

The variety of living organisms. It can be
measured in terms of species diversity
(number of species in a community),
ecosystem diversity (range of different
habitats) and genetic diversity

51
Q

How do you calculate index of diversity (d)?

A

d= N(N-1)
———-
Σ n(n-1)

N= total number of
organisms of all species.
n= total number of
Σ = sum of organisms of each species.

52
Q

What impact does agriculture (farming)
have on species diversity?

A

decreases species richness
● farmland is typically used for only 1
species (monoculture)
● use of pesticides/ herbicides

53
Q

What impact does agriculture (farming)
have on genetic diversity?

A

decreases
● farmers select for certain
characteristics, which reduces number
of different alleles in the population

54
Q

How can biodiversity be increased in
areas of agriculture?

A
  1. Use hedgerows instead of fences.
  2. Grow different crops in the same area,
    or rotate crops around after a season.
  3. Limit use of pesticides and herbicides
55
Q

Name four ways we can measure
genetic diversity

A
  1. Frequency of observable characteristics.
  2. Base sequence of DNA.
  3. Base sequence of mRNA.
  4. Amino acid sequence.
56
Q

What is meant by interspecific and
intraspecific variation

A

Interspecific= differences between
individuals of different species.
Intraspecific= differences between
individuals of the same species

56
Q

What is meant by gene technology?

A

Sampling DNA or mRNA in order to read and
compare the base sequence of organisms.
Alternatively the amino acid sequence can be
studied as this will also provide information on
the organism’s mRNA and DNA sequences.

57
Q

Why do scientists prefer to use gene
technology instead of observation?

A

Simply inferring DNA differences by observing
an organism’s characteristics is not reliable;
the characteristics could be coded for by more
than one gene, or could be influenced by the
environment

58
Q

What is sampling?

A

Selecting a group of individuals to
measure that will represent the whole
target population.

59
Q

How can a random sample be achieved?

A

Create a grid for your sample area, and
then randomly generate coordinates
where a quadrat or transect can be
placed. Repeat until required sample
size is reached

60
Q

what is species richness

A

(A measure of) the number of (different) species in
a community

61
Q

non coding bases sequences

A

sequence of dna that doesn’t code of a amino acid
found within genes as introns

62
Q
A

A- Level Biology (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions