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B6 AND B5 > B6 - PMT > Flashcards

B6 - PMT Flashcards

1
Q

What is sexual reproduction?

A

● Type of reproduction.
● Involves the production of gametes by meiosis.
● A gamete from each parent fuses to form a zygote.
● Genetic information from each gamete is mixed so the
resulting zygote is unique

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2
Q

What are gametes?

A

● Sex cells (sperm cells and egg cells in
animals, pollen and egg cells in flowering
plants).
● Haploid (half the number of chromosomes).

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3
Q

What is meiosis?

A

● Form of cell division involved in the formation of
gametes (non-identical haploid cells) in reproductive
organs.
● Chromosome number is halved.
● Involves two divisions.

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4
Q

What must occur prior to meiosis?

A

Interphase - copies of genetic
information are made during this
process

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5
Q

What happens during the first stage of meiosis?

A

● Chromosome pairs line up along the cell equator.
● The pair of chromosomes are separated and move to
opposite poles of the cell (the side to which each
chromosome is pulled is random, creating variation).
● Chromosome number is halved.

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6
Q

What happens during the second stage of meiosis?

A

● Chromosomes line up along the cell equator.
● The chromatids are separated and move to opposite
poles of the cell.
● Four unique haploid gametes are produced.

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7
Q

Why is meiosis important for sexual reproduction?

2

A

● It increases genetic variation.
● It ensures that the zygote formed at
fertilisation is diploid.

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8
Q

Describe fertilisation and its resulting outcome

A

Gametes join together to restore the normal
number of chromosomes and the new cell then
divides by mitosis (which increases the number
of cells).
As the embryo develops, cells differentiate.

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9
Q

What is the advantage of sexual reproduction?

A

It creates genetic variation in offspring,
increasing the probability of a species adapting to
and surviving environmental changes.
Natural selection can be speeded up by humans
in selective breeding to increase food production.

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10
Q

Describe the disadvantages of sexual reproduction

2

A

● Two parents are required. This makes reproduction
difficult in endangered populations or in species which
exhibit solitary lifestyles.
● More time and energy is required so fewer offspring
are produced

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11
Q

What is asexual reproduction?

A

● Type of reproduction.
● Involves mitosis only.
● Produces genetically identical offspring
known as daughter cells.

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12
Q

Describe the advantages of asexual reproduction (3)

A

● Only one parent is required.
● Lots of offspring can be produced in a short period of time,
enabling the rapid colonisation of an area and reducing
competition from other species.
● Requires less energy and time as do not need a mate

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13
Q

What is the disadvantage of asexual reproduction?

A

No genetic variation (except from
spontaneous mutations) reducing the
probability of a species being able to
adapt to environmental change.

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14
Q

Describe the circumstances in which malarial

parasites reproduce sexually and asexually

A

Sexual reproduction in the mosquito.

Asexual reproduction in the human host.

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15
Q

Describe the circumstances in which fungi reproduce

sexually and asexually

A

Asexual reproduction by spores.

Sexual reproduction to give variation

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16
Q

Describe the circumstances in which plants

reproduce sexually and asexually

A

Sexual reproduction to produce seeds.
Asexual reproduction by runners (e.g.
strawberry plants) or bulb division (e.g.
daffodils)

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17
Q

What is DNA?

A 
A double-stranded polymer of
nucleotides, wound to form a double
helix.
The genetic material of the cell found in
its nucleus
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18
Q

Define genome

A

The entire genetic material of an organism

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19
Q

Why is understanding the human genome

important?

A

The whole human genome has been studied and is
important for the development of medicine in the future.
● Searching for genes linked to different types of disease.
● Understanding and treating inherited disorders.
● Tracing human migration patterns from the past

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20
Q

What is a chromosome?

A

A long, coiled molecule of DNA that
carries genetic information in the form of
genes.

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21
Q

How many chromosomes do human body cells

have?

A

46 chromosomes (23 pairs)

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22
Q

How many chromosomes do human gametes have?

23 chromosomes

A
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23
Q

Define gene
A small section of DNA that codes for a
specific sequence of amino acids which
undergo polymerisation to form a protein.

A
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24
Q

What are the monomers of DNA? (biology only)

Nucleotides

A
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25
Q 
What are DNA nucleotides made up of?
(biology only)
● Common sugar
● Phosphate group
● One of four bases: A, T, C or G
A
26
Q 
State the full names of the four bases found in
nucleotides (biology only)
● Adenine
● Thymine
● Cytosine
● Guanine
A
27
Q

Describe how nucleotides interact to form a molecule
of DNA (biology only)
● Sugar and phosphate molecules join to form a
sugar-phosphate backbone in each DNA strand.
● Base connected to each sugar.
● Complementary base pairs (A pairs with T, C pairs with G)
joined by weak hydrogen bonds

A
28
Q

Explain how a gene codes for a protein
(biology only)
● A sequence of three bases in a gene forms a triplet.
● Each triplet codes for an amino acid.
● The order of amino acids determines the structure
(i.e. how it will fold) and function of protein formed.

A
29
Q

Why is the ‘folding’ of amino acids important in
proteins such as enzymes?
(biology only) (higher only)
The folding of amino acids determines the
shape of the active site which must be
highly specific to the shape of its substrate.

A
30
Q

What is protein synthesis?
(biology only) (higher only)
The formation of a protein from a gene.

A
31
Q

What are the two stages of protein synthesis?
(biology only) (higher only)
1. Transcription
2. Translation

A
32
Q

What does transcription involve?
(biology only) (higher only)
The formation of mRNA from a DNA
template.

A
33
Q

Outline transcription (biology only) (higher only)
1. DNA double helix unwinds.
2. RNA polymerase binds to a specific base sequence of non-coding
DNA in front of a gene and moves along the DNA strand.
3. RNA polymerase joins free RNA nucleotides to complementary bases
on the coding DNA strand.
4. mRNA formation complete. mRNA detaches and leaves the nucleus

A
34
Q 
What does translation involve?
(biology only) (higher only)
A ribosome joins amino acids in a
specific order dictated by mRNA to form
a protein.
A
35
Q

Outline translation (biology only) (higher only)
1. mRNA attaches to a ribosome.
2. Ribosome reads the mRNA bases in triplets. Each triplet codes
for one amino acid which is brought to the ribosome by a tRNA
molecule (carrier molecule).
3. A polypeptide chain is formed from the sequence of amino
acids which join together.

A
36
Q

What is a mutation? (biology only) (higher only)
A random change in the base sequence of DNA which
results mostly in no change to the protein coded for, or
genetic variants of the protein (slight alteration but
appearance and function remain).
Mutations occur continuously

A
37
Q

Describe the effect of a gene mutation in coding
DNA (biology only) (higher only)
● If a mutation changes the amino acid sequence, protein
structure and function may change (an enzyme may no longer
fit its substrate binding site or a structural protein may lose its
strength).
● If a mutation does not change amino acid sequence, there is no
effect on protein structure or function.

A
38
Q

What is non-coding DNA?
(biology only) (higher only)
DNA which does not code for a protein
but instead controls gene expression

A
39
Q 
Describe the effect of a gene mutation in non-coding
DNA (biology only) (higher only)
Gene expression may be altered,
affecting protein production and the
resulting phenotype.
A
40
Q

What are alleles?

Different versions of the same gene.

A
41
Q

What is a dominant allele?
A version of a gene where only one copy
is needed for it to be expressed.

A
42
Q

What is a recessive allele?
A version of a gene where two copies
are needed for it to be expressed

A
43
Q

What is meant when an organism is homozygous?
When an organism has two copies of the
same allele (two recessive or two
dominant).

A
44
Q

What is meant when an organism is heterozygous?
When an organism has two different
versions of the same gene (one
dominant and one recessive).

A
45
Q

What is the genotype?

The genes present for a trait

A
46
Q

What is the phenotype?

The visible characteristic.

A
47
Q

How are dominant alleles represented in a punnett
square?
They are represented using uppercase
letters

A
48
Q

How are recessive alleles represented in a punnett
square?
They use the lowercase version of the
same letter as the dominant allele.

A
49
Q

Draw a Punnett square for a cross between a
homozygous recessive blue eyed female (bb) with a
heterozygous brown eyed male (Bb)

A

Gamete | B | b
b | Bb | bb
b | Bb | bb

50% brown eyes
50% blue eyes
1:!

50
Q

Draw a Punnett square for a cross between a
homozygous dominant red flower (RR) with a
homozygous recessive white flower (rr)

A

Gamete | R | R
r | Rr | Rr
r | Rr | Rr

100% red eyes

51
Q

Draw a Punnett square for a cross between two

heterozygous cystic fibrosis carriers (Ff)

A

Gamete | F | f
F | FF | Ff
f | Ff | ff

25% healthy
50% carriers
25% have CF

52
Q

What is the problem with single gene crosses?
Most characteristics are controlled by
multiple alleles rather than just one.

A
53
Q

What is an inherited disorder?
A disorder caused by the inheritance of
certain alleles

A
54
Q

Give 2 examples of inherited disorders
● Polydactyly (having extra fingers or toes) -
caused by a dominant allele.
● Cystic fibrosis (a disorder of cell
membranes) - caused by a recessive allele.

A
55
Q

How are embryos screened for inherited disorders?
During IVF, one cell is removed (from an 8 cell
embryo) and tested for disorder-causing
alleles. If the cell doesn’t have any indicator
alleles, then the originating embryo is
implanted into the uterus.

A
56
Q

What are the ethical issues concerning embryo
screening?
● It could lead to beliefs in society that being disabled or having a
disorder is less human or associated with inferiority.
● The destruction of embryos with inherited disorders is seen by
some as murder as these would go on to become human beings.
● It could be viewed as part of the concept of designer babies as it
may be for the parents convenience or wishes rather than the
child’s wellbeing

A
57
Q

What are the economic issues concerning embryo
screening?
● Costs of hospital treatment and medication
will need to be considered if it is known that
a child will have an inherited disorder and
financial support explored if necessary.

A
58
Q

What are the social issues concerning embryo
screening?
● Social care for children with inherited disorders may
need to be considered if parents are unable to provide
care.
● If an embryo is found to have an inherited disorder and
is terminated, this can prevent a child and its parents
from potential suffering in the future due to the disorder.

A
59
Q

What is gene therapy?
The insertion of a normal allele into the
cells of a person with an inherited
disorder to functionally replace the faulty
allele.

A
60
Q 
What are the ethical issues concerning gene
therapy?
● Some people believe that it is going
against and ‘playing God’.
● The introduced genes could enter sex
cells and so be passed to future
generations.
A

B6 AND B5 (6 decks)

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