Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

IGCSE Biology > Topic 6 (mini test: units 17-18) > Flashcards

Topic 6 (mini test: units 17-18) Flashcards

1
Q

What are chromosones?

A

Made of DNA,
which contains genetic information in the form
of genes.

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

What is a gene?

A

A length of DNA that codes for a protein.

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

What is an allele?

A

An alternative form of a gene/variant gene.

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

What do the base sequences in DNA determine?

A

The sequence of amino acids used to
make a specific protein.

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

What do different sequences of amino acids do?

A

Give shapes to different shaped protein molecules.

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

How does the DNA control cell function?

A

Controlling the production of proteins, including
enzymes, membrane carriers and receptors for
neurotransmitters.

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

How is a protein made?

A
  • the gene coding for the protein remains in
    the nucleus
  • messenger RNA (mRNA) is a copy of a gene
  • mRNA molecules are made in the nucleus
    and move to the cytoplasm
  • the mRNA passes through ribosomes
  • the ribosome assembles amino acids into
    protein molecules
  • the specific sequence of amino acids is
    determined by the sequence of bases in the
    mRNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is DNA copied?

A

Transcription, translation.

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

Most body cells in an organism
contain the same genes but why are only some expressed?

A

Many genes in a
particular cell are not expressed because the cell
only makes the specific proteins it needs.

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

What is a haploid nucleas?

A

A nucleus containing a single set of chromosomes.

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

What is a diploid nucleas?

A

A nucleus containing two sets of chromosomes.

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

What is in a diploid cell?

A

There is a pair of each
type of chromosome and in a human diploid cell
there are 23 pairs.

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

What is mitosis?

A

Nuclear division giving rise to genetically identical cells.

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

What is the role of mitosis?

A

Growth, repair of
damaged tissues, replacement of cells and
asexual reproduction.

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

What occurs before mitosis?

A

Exact replication of chromosomes occurs before mitosis.

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

What happens during mitosis?

A

The copies of
chromosomes separate, maintaining the
chromosome number in each daughter cell.

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

What are stem cells?

A

Unspecialized cells that
divide by mitosis to produce daughter cells that can become specialized for specific function.

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

What is meiosis used for?

A

Involved in the production of gametes

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

What is meiosis?

A

Reduction division in which
the chromosome number is halved from diploid
to haploid resulting in genetically different cells.

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

What is inheritance?

A

The transmission
of genetic information from generation to
generation.

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

What is a genotype?

A

The genetic make-up of an
organism and in terms of the alleles present.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a phenotype?

A

The observable features of
an organism.

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

What does homozygous mean?

A

Having two identical
alleles of a particular gene.

24
Q

What will happen when two homozygous individuals breed with each other?

A

Pure breeding.

25
What does heterozygous mean?
Having two different alleles of a particular gene.
26
Can heterozygous individuals pure breed?
No.
27
What is a dominant allele?
An allele that is expressed if it is present in the genotype.
28
What is a recessive allele?
An allele that is only expressed when there is no dominant allele of the gene present in the genotype.
29
What is codominance?
A situation in which both alleles in heterozygous organisms contribute to the phenotype.
30
What is a sex-linked characteristic?
A feature in which the gene responsible is located on a sex chromosome and that this makes the characteristic more common in one sex than in the other
31
What is an example of a sex-linked trait?
Red-green colour blindness
32
What is variation?
Differences between individuals of the same species
33
What is continuous variation?
Results in a range of phenotypes between two extremes; examples include body length and body mass
34
What is discontinuous variation?
Results in a limited number of phenotypes with no intermediates; examples include ABO blood groups, seed shape in peas and seed colour in peas
35
What is discontinuous variation usually caused by?
Genes.
36
What is continuous variation caused by?
Environmental and genetic
37
What is a mutation?
A random change in the base sequence of DNA.
38
How do mutations occur?
The way in which new alleles are formed.
39
How does genetic variation occur in populations?
Mutation, meiosis, random mating/fertilisation
40
What are things that can increase the rate of mutation?
Ionizing radiation and some chemicals
41
What is an adaptive feature?
An inherited feature that helps an organism to survive and reproduce in its environment
42
What are hydrophytes?
Plants adapted to live in extremely wet conditions
43
What are 3 common adaptations of hydrophytes?
- Large air spaces in leaves (flotation, keep leaf close to surface of water for more light exposure - photosynthesis) - Small roots (extract nutrients from the water through tissues, water in excess) - Stomata usually open all the time - found on upper epidermis of leaf (allows easier gaseous exchange)
44
What are xerophytes?
Plants adapted to live in extremely dry conditions
45
6 Common adaptations for xerophytes:
- Thick waxy cuticle (reduces water loss) - Sunken stomata - Leaf rolled with stomata inside and inner surface covered with hairs - Small leaves - Extensive shallow roots - Thickened leaves/stems
46
How does the thick waxy cuticle help xerophytes?
It cuts down water loss by - acting as a barrier to evaporation - shiny surface reflects heat, therefore lowering the temperature of the water
47
How does sunken stomata help xerophytes?
Stomata may be sunk in pits in the epidermis; moist air trapped here lengthens the diffusion pathway, reducing evaporation rate
48
How does the leaf rolled with stomata inside and an inner surface covered with hairs help xerophytes?
Traps moist air, prevents air movement across stomata which reduces transpiration
49
How do small leaves help xerophytes?
Small, needle-shaped leaves reduce the surface area (the evaporating surface)
50
How do extensive shallow roots help xerophytes?
Allow for quick absorption of large quantities of water when it rains
51
How do thickened leaves/stems help xerophytes?
Contain cells that store water
52
What is adaptation?
The process resulting from natural selection, by which populations become more suited to their environment over many generations
53
What is natural selection?
Natural selection allows for genetic variation within populations - allowing the one with traits most compatible to the environment to have a higher probability of surviving. These organisms have a greater chance of reproduction by individuals that are better adapted to the environment than others. These individuals pass their alleles onto the next generation
54
What is selective breeding?
The selection by humans of individuals with desirable features and crossing them to produce the next generation. The selection of offspring showing the most desirable features and repeat the process.
55
What is an example of natural selection?
The development of strains of antibiotic resistant bacteria
56
Why is selective breeding by artificial selection is carried out over many generations?
To improve crop plants and domesticated animals
57
What are the differences between natural and artificial selection?
- Natural selection occurs naturally (artificial only occurs when humans intervene) - Natural results in development of populations with features that are better adapted to their environment and survival (artificial results in development of populations with features that are useful to humans and not necessarily to survival) - Natural selection usually takes a long time to occur ( artificial takes less time to occur as only individuals with the desired features are allowed to reproduce)

IGCSE Biology (10 decks)

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