Paper 1: Topic 1 Cell Biology - Cell division (LV) Flashcards
(126 cards)
1
Q
Name the genetic material found in all living cells
A
DNA
2
Q
State where the genetic material is located in eukaryotic cells
A
Contained inside the nucleus
3
Q
State where the genetic material is located in prokaryotic cells
A
Free in the cytoplasm
Exists as a nucleoid and some bacteria can also have additional small loops of DNA called plasmids
4
Q
Describe how DNA is arranged in eukaryotic cells
A
As a linear chromosomes
5
Q
Explain the term chromosome
A
A coiled length of DNA
6
Q
State how many chromosomes are found in human somatic (body) cells
A
46
7
Q
State how many chromosomes are found in human gametes
A
23
8
Q
Explain the term diploid
A
A full set of chromosomes
This is represented as ‘2n’
9
Q
Explain the term haploid
A
Half a set of chromosomes
This is represented as ‘n’
10
Q
Explain the term ‘cell cycle’
A
A series of events in which a cell grows, replicates its DNA and then divides to form daughter cells
11
Q
How do human somatic cells divide?
A
Mitosis
12
Q
What is the function of mitosis?
A
To produce two GENETICALLY identical daughter cells
13
Q
Why do multicellular organisms use mitosis?
A
To produce new cells:
a) For growth of tissues and organs
b) To repair damaged tissues and organs
* Remember do not just say “growth and repair” you must say ‘of tissues and organs’ as well*
14
Q
Describe what happens to the chromosome number when a cell undergoes mitosis
A
It is maintained/kept constant
i.e. remains as 2n (diploid)
15
Q
State the 3 main events during mitosis
A
DNA replication
Division of DNA
Splitting of the cell into 2
16
Q
Explain what events occur inside a human somatic (body) cell BEFORE it takes part in mitosis
A
The cell increases in size
The sub-cellular structures (organelles) are replicated
The DNA is replicated (copied) so that there is double the quantity of DNA inside the cell
17
Q
Describe the shape of a chromosome after it has replicated
A
It will appear as a cross
The 2 strands of DNA are held together by a centromere
18
Q
Describe the relationship between the 2 arms of a chromosome after it has replicated
A
They are genetically identical
This means they carry the same genes and alleles
19
Q
Describe the main events that take place during mitosis Hint: 6 key events
A
- The chromosomes line up in the middle of the cell along the equator
- Special protein fibres pull the chromosomes apart
- Half of each chromosome is pulled to the opposite pole of the cell
- Membranes form around the outside of each set of chromosomes (to form 2 nuclei inside the one cell)
- The cell splits equally into 2
20
Q
Describe how prokaryotic cells divide
A
Binary fission
21
Q
Explain the key events that occur during binary fission Hint: 4 events
A
- The circular DNA (nucleoid) and plasmids replicate
- The cell increases in size and the circular DNA moves to the poles of the cell
- The cytoplasm divides and new cell walls are formed
- 2 daughter cells are formed each has a circular DNA but they can have variable numbers of plasmids
22
Q
Describe the main features of cell division in bacteria
A
Occurs by binary fission
Occurs very quickly (~once every 20 minutes)
23
Q
How can you calculate the number of bacteria present after a given period of time?
A
Calculate the number of minutes in the time period
Divide the number of minutes by 20 (to calculate the number of divisions the bacteria will undertake).
Call this answer ‘x’
Calculate 2 to the power ‘x’ i.e. 2x
This will be the number of cells present after the specified time period.
24
Q
Define the term stem cell
A
An unspecialised cell that can replicate to produce more unspecialised cells
All these cells can then differentiate to become specialised cells
25
Explain the term differentiation
The process of an unspecialised cell changing its shape, chemical content and organelle content to become a specialised cell
26
What controls differentiation?
The switching on and off of certain genes inside the unspecialised cell
27
State 2 sources of stem cell
Early embryos
Umbilical cord (after birth)
Adult bone marrow
28
What is special about early embryo stem cells?
They can differentiate into ANY type of specialised cell
29
How are adult stem cells different from embryo stem cells?
Embryo stem cells can differentiate into any type of specialised cell but adult stem cells can only differentiate into certain types of specialised cells e.g. red blood cells
30
How can stem cells be used in medical research
Either type of stem cell can be grown in science laboratories to produce clones
These clones can then be stimulated to differentiate into specific specialised cells
31
Explain what is meant by the term ‘specialised cell’
A cell that has changed its shape, chemical content and/or the organelle content of itself to become suited for a specific function
32
Describe what changes occur in stem cell when it differentiates into a red blood cell
Change in shape = it changes from spherical to biconcave
Change in chemical content = it produces a lot of haemoglobin
Change in organelle content = it breaks down its mitochondria and nucleus
33
State 3 examples of how stem cells can be use to cure disease
1. Adult stem cells taken from the bone marrow of a healthy person can be used to replace faulty blood cells in a patient
2. Embryonic stem cells can be used to replace faulty cells e.g. insulin producing cells can be used to treat people with diabetes nerve cells can be used to treat people with spinal cord injuries (paralysis)
3. Stem cells can be used for therapeutic cloning – they are taken from the patient stimulated to differentiate into the required specialised cells and then returned to the same patient.
34
What is the advantage of using a patient’s own stem cells in therapeutic cloning?
The specialised cells formed from the patient’s stem cells are genetically identical to the patient’s cells and are therefore not rejected
35
What are carried on each chromosome?
Each chromosome carries a large number of genes.
36
What is a gene?
A section of DNA that codes for the production of one specific protein
37
Describe how chromosomes are normally found in somatic (body) cells
In body cells the chromosomes are normally found in pairs.
38
Where are stem cells found in plants?
In the meristematic tissue i.e. root tips and shoot tips
39
What is special about meristematic tissue in plants?
Meristem tissue in plants can differentiate into ANY type of plant cell, THROUGHOUT the life of the plant.
40
State two concerns people have with stem cell treatments
The use of stem cells has potential risks such as transfer of viral infection
Some people have ethical or religious objections.
41
State an advantage for horticulturists who using plant stem cells
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
42
State 2 benefits of the use of plant stem cells in research and treatments
Rare species can be cloned to protect from extinction.
Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
43
1. Asexual reproduction
2. Sexual reproduction
Name the two types of reproduction
44
* Asexual reproduction involves only one parent and no fusion of gametes
* There is no mixing of genetic information
* This leads to genetically identical offspring (clones)
* Only mitosis is involved
Define asexual reproduction
45
* Reproduction that involves two parents
* It involves the mixing of genetic information
* This leads to variety in the offspring
* The formation of gametes involves meiosis
* It involves the fusing of gametes
Define sexual reproduction
46
1. sperm
2. ova (egg cells)
State the 2 types of gametes that are involved in sexual rep
47
1. pollen
2. ova (egg cells)
State the 2 types of gametes that are involved in sexual rep
48
1. Produces variation in the offspring
2. If the environment changes variation gives a survival advantage by natural selection
3. Natural selection can be speeded up by humans in selective breeding to increase food production
Give 3 advantages of sexual reproduction
49
1. Only one parent needed
2. More time and energy efficient as do not need to find a mate
3. Faster than sexual reproduction
4. Many identical offspring can be produced when conditions are favourable
Give 4 advantages of asexual reproduction
50
* Malarial parasites
* Fungi
* Plants e.g. strawberry plants
Name 3 organisms that reproduce by both asexual and sexual r
51
Malarial parasites reproduce asexually in the human host, but sexually in the mosquito
State how malarial parasites demonstrate both sexual and ase
52
* Many fungi reproduce asexually by spores
* They also reproduce sexually by spores to give variation
*Remember:* fungal spores can be produced asexually and sexually
State how fungi demonstrate both sexual and asexual reproduc
53
* When conditions are favourable the fungi can produce spores asexually to make many identical spores in a short period of time
* When conditions are unfavourable fungi can produce spores sexually to make genetically different spores to increase the chances of surviving the environmental conditions
Explain why it is an advantage for fungi to be able to produ
54
* Flowering plants produce seeds sexually
* They also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils
State how some plants demonstrate both sexual and asexual re
55
Mitosis
State the type of cell division involved in asexual reproduc
56
Meiosis
State the type of cell division involved in sexual reproduct
57
Meiosis
Which type of reproduction involves the production of haploi
58
Fertilisation
State the term that describes the fusing of two gametes to f
59
* Half the full number i.e. haploid (n)
* For human cells this is 23
How many chromosomes are found in a gamete?
60
* A full set of chromosomes i.e. diploid (2n)
* For human cells this is 46
How many chromosomes are found in a somatic (body) cell?
61
* Sexual reproduction involves the fusing of two gametes
* Each gamete contains genetic material from each parent
* The zygote will have half the DNA from the mother and half from the father
* This mixture of genetic information produces variation
Explain why sexual reproduction causes greater genetic varia
62
1. It increases genetic variation
2. Genetic variation increases the chances of survival of the species if there is a change in the environment
3. Genetic variation will mean some individuals will be better adapted to the environment and therefore more likely to survive and breed and pass the successful alleles on to the next generation (called natural selection)
4. Scientists can use selective breeding to speed up natural selection
State the 4 advantages of sexual reproduction
63
1. Only one parent is required (so there is no need to find a mate)
2. This means asexual reproduction uses less energy (no energy used in finding a mate, producing gametes)
3. It is also faster (as no time is used in finding a mate)
4. Many genetically identical offspring can be produced when conditions are favourable
5. It maintains genetic stability by producing genetically identical cells
State the 5 advantages of asexual reproduction
64
* Gametes must contain half the chromosomes number so that when 2 gametes fuse during fertilisation the chromosome number is restored
* If the gametes had a full set of chromosomes (2n) then the chromosome number would double at each generation
Explain the importance of producing haploid gametes
65
2
How many daughter cells are produced in mitosis?
66
4
How many daughter cells are produced in meiosis?
67
1. Copies of the genetic information are made
2. The cell divides once to form two daughter cells, each with a full set of chromosomes(2n)
3. All gametes are genetically identical to each other.
State the 3 main stages of mitosis
68
1. Copies of the genetic information are made
2. The cell divides twice to form four gametes, each with a single set of chromosomes
3. All gametes are genetically different from each other
State the 3 main stages of meiosis
69
In the reproductive organs
* testes
* ovaries
State where meiosis occurs
70
Mitosis
State the type of cell division that occurs in an embryo to
71
The number of cells increases The number of cells doubles after each division
How does the cell number change as the embryo forms a fetus?
72
Differentiation
As the embryo develops the cells become specialised. Name t
73
Gamete → zygote → embryo → fetus → organism
Put these structures in order of increasing complexity:Gamet
74
* Runners e.g. strawberry plants
* Bulbs e.g. daffodils
Give an example of asexual reproduction in plants
75
23
*Please note the questions asked you for the number of **PAIRS***
How many pairs of chromosomes are found in a somatic (body)
76
Sex chromosomes
What is the name for the pair of chromosomes that determines
77
XX
What 2 sex chromosomes are found in all somatic (body) cells
78
XY
What 2 sex chromosomes are found in all somatic (body) cells
79
100%
What percentage of female ova will carry an X chromosome?
80
50%
What percentage of male sperm will carry an X chromosome?
81
50%
What percentage of male sperm will carry a Y chromosome?
82
* Male
* If the ovum is fertilised by a sperm carrying an X chromosome the individual will be female.
* If the ovum is fertilised by a sperm carrying a Y chromosome the individual will be male.
State gamete will determine the sex of a human at fertilisat
83
XY
State the genotype of a human male
84
XX
State the genotype of a human female
85
1. Asexual reproduction
2. Sexual reproduction
Name the two types of reproduction
86
* Asexual reproduction involves only one parent and no fusion of gametes
* There is no mixing of genetic information
* This leads to genetically identical offspring (clones)
* Only mitosis is involved
Define asexual reproduction
87
* Reproduction that involves two parents
* It involves the mixing of genetic information
* This leads to variety in the offspring
* The formation of gametes involves meiosis
* It involves the fusing of gametes
Define sexual reproduction
88
1. sperm
2. ova (egg cells)
State the 2 types of gametes that are involved in sexual rep
89
1. pollen
2. ova (egg cells)
State the 2 types of gametes that are involved in sexual rep
90
1. Produces variation in the offspring
2. If the environment changes variation gives a survival advantage by natural selection
3. Natural selection can be speeded up by humans in selective breeding to increase food production
Give 3 advantages of sexual reproduction
91
1. Only one parent needed
2. More time and energy efficient as do not need to find a mate
3. Faster than sexual reproduction
4. Many identical offspring can be produced when conditions are favourable
Give 4 advantages of asexual reproduction
92
* Malarial parasites
* Fungi
* Plants e.g. strawberry plants
Name 3 organisms that reproduce by both asexual and sexual r
93
Malarial parasites reproduce asexually in the human host, but sexually in the mosquito
State how malarial parasites demonstrate both sexual and ase
94
* Many fungi reproduce asexually by spores
* They also reproduce sexually by spores to give variation
*Remember:* fungal spores can be produced asexually and sexually
State how fungi demonstrate both sexual and asexual reproduc
95
* When conditions are favourable the fungi can produce spores asexually to make many identical spores in a short period of time
* When conditions are unfavourable fungi can produce spores sexually to make genetically different spores to increase the chances of surviving the environmental conditions
Explain why it is an advantage for fungi to be able to produ
96
* Flowering plants produce seeds sexually
* They also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils
State how some plants demonstrate both sexual and asexual re
97
Mitosis
State the type of cell division involved in asexual reproduc
98
Meiosis
State the type of cell division involved in sexual reproduct
99
Meiosis
Which type of reproduction involves the production of haploi
100
Fertilisation
State the term that describes the fusing of two gametes to f
101
* Half the full number i.e. haploid (n)
* For human cells this is 23
How many chromosomes are found in a gamete?
102
* A full set of chromosomes i.e. diploid (2n)
* For human cells this is 46
How many chromosomes are found in a somatic (body) cell?
103
* Sexual reproduction involves the fusing of two gametes
* Each gamete contains genetic material from each parent
* The zygote will have half the DNA from the mother and half from the father
* This mixture of genetic information produces variation
Explain why sexual reproduction causes greater genetic varia
104
1. It increases genetic variation
2. Genetic variation increases the chances of survival of the species if there is a change in the environment
3. Genetic variation will mean some individuals will be better adapted to the environment and therefore more likely to survive and breed and pass the successful alleles on to the next generation (called natural selection)
4. Scientists can use selective breeding to speed up natural selection
State the 4 advantages of sexual reproduction
105
1. Only one parent is required (so there is no need to find a mate)
2. This means asexual reproduction uses less energy (no energy used in finding a mate, producing gametes)
3. It is also faster (as no time is used in finding a mate)
4. Many genetically identical offspring can be produced when conditions are favourable
5. It maintains genetic stability by producing genetically identical cells
State the 5 advantages of asexual reproduction
106
* Gametes must contain half the chromosomes number so that when 2 gametes fuse during fertilisation the chromosome number is restored
* If the gametes had a full set of chromosomes (2n) then the chromosome number would double at each generation
Explain the importance of producing haploid gametes
107
2
How many daughter cells are produced in mitosis?
108
4
How many daughter cells are produced in meiosis?
109
1. Copies of the genetic information are made
2. The cell divides once to form two daughter cells, each with a full set of chromosomes(2n)
3. All gametes are genetically identical to each other.
State the 3 main stages of mitosis
110
1. Copies of the genetic information are made
2. The cell divides twice to form four gametes, each with a single set of chromosomes
3. All gametes are genetically different from each other
State the 3 main stages of meiosis
111
In the reproductive organs
* testes
* ovaries
State where meiosis occurs
112
Mitosis
State the type of cell division that occurs in an embryo to
113
The number of cells increases The number of cells doubles after each division
How does the cell number change as the embryo forms a fetus?
114
Differentiation
As the embryo develops the cells become specialised. Name t
115
Gamete → zygote → embryo → fetus → organism
Put these structures in order of increasing complexity:Gamet
116
* Runners e.g. strawberry plants
* Bulbs e.g. daffodils
Give an example of asexual reproduction in plants
117
23
*Please note the questions asked you for the number of **PAIRS***
How many pairs of chromosomes are found in a somatic (body)
118
Sex chromosomes
What is the name for the pair of chromosomes that determines
119
XX
What 2 sex chromosomes are found in all somatic (body) cells
120
XY
What 2 sex chromosomes are found in all somatic (body) cells
121
100%
What percentage of female ova will carry an X chromosome?
122
50%
What percentage of male sperm will carry an X chromosome?
123
50%
What percentage of male sperm will carry a Y chromosome?
124
* Male
* If the ovum is fertilised by a sperm carrying an X chromosome the individual will be female.
* If the ovum is fertilised by a sperm carrying a Y chromosome the individual will be male.
State gamete will determine the sex of a human at fertilisat
125
XY
State the genotype of a human male
126
XX
State the genotype of a human female
