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S2 GCSE Biology Unit 2 > Unit 2 - Topic 10 - Cell Division and Genetics > Flashcards

Unit 2 - Topic 10 - Cell Division and Genetics Flashcards

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1
Q

Definition: Chromosome

A

Long strand of DNA (genetic structures) located in the nucleus.

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2
Q

Definition: Gene

A

Short strand of DNA (located on a chromosome) which codes for a particular characteristic or amino acid, which are the building blocks for proteins.
Genes are often described as functional units.

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3
Q

Definition: Allele

A

Alternative form of a gene for a particular characteristic.

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4
Q

Definition: Gene Locus

A

Position of a gene on a chromosome.

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5
Q

Definition: Genotype

A

The genetic arrangement of alleles (genetic make-up) for one or more traits.

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6
Q

Definition: Phenotype

A

The actual appearance of a particular trait. This may also be influenced by the environment (diet, sunlight, etc).

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7
Q

Definition: Homozygous

A

If the individual has two identical alleles on a chromosome for a characteristic, e.g. AA or aa.

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8
Q

Definition: Heterozygous

A

If the individual has two different alleles on a chromosome for a characteristic, e.g. Aa.

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9
Q

Definition: Recessive

A

The allele is only expressed in the homozygous form.

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10
Q

Definition: Dominant

A

The allele that is expressed in both the homozygous and the heterozygous forms.

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11
Q

Definition: Test Cross

A

A test carried out to confirm the genotype of an individual with a dominant phenotype by breeding the individual with a pure bred homozygous recessive (i.e. to determine if the individual is heterozygous or homozygous dominant).

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12
Q

Definition: Hereditory

A

Transfer of genetic information (alleles) from one generation to the next.

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13
Q

Definition: Homologous Chromosomes

A

A pair of chromosomes that are the same length and have the same genes for the same characteristics.

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14
Q

Definition: Monohybrid Inheritance

A

When only one factor is considered in a genetic cross.

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15
Q

Definition: Mutation

What are the two different types of genetic mutation?

A

A random genetic change to the structure or number of chromosomes.

  • There are two types of mutations:
    1. Gene mutation
    2. Chromosome mutation
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16
Q

What is dry mass and how is it calculated?

A

Dry mass is the mass of the organism after all the water content is removed. It is found by drying in an incubator until there is a constant mass.

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17
Q

Name five methods of measuring growth

A 
Height
Mass
Cell length
Number of cells
Dry mass
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18
Q

What are the advantages and disadvantages of using cell length as a method of measuring growth?

A

Advantages
- Easy to measure under a microscope.

Disadvantages

  • Often irregular shape.
  • No reference to number of cells.
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19
Q

What are the advantages and disadvantages of using number of cells as a method of measuring growth?

A

Advantages
- Good indication of overall size.

Disadvantages

  • Organisms may contain millions of cells - difficult to estimate or count them all.
  • Doesn’t take account of size of cells.
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20
Q

What are the advantages and disadvantages of using dry mass as a method of measuring growth?

A

Advantages
- Accurate indication of growth.

Disadvantages

  • Time consuming.
  • Organism or part (e.g. leaf) is killed during process.
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21
Q

What is the role of mitosis?

A

Growth
Replacement of worn out cells
To repair damaged tissue

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22
Q

Name the steps and processes that occur in mitosis.

A
  1. Chromosome condensation - Chromosomes condense, thicken and become more visible before DNA replication.
  2. Each chromosome duplicates by splitting lengthwise (this duplicates genetic material) into two identical chromatids held together by a centromere.
  3. Chromatids (still joined by centromere) line up along the centre (equator) of the cell.
  4. Chromatids in each chromosome separate and are pulled to opposite ends of the cell by spindle fibres which form at opposite poles of the cell.
  5. Once chromatids reach the opposite ends of the cell the nuclear membrane dissolves and the cell divides.
  6. The two new (daughter) cells contain exactly the same chromosomes as each other and the parent cell.
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23
Q

What are the two different types of cell division?

A

Mitosis

Meiosis

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24
Q

What is asexual reproduction?

A

Asexual reproduction is a type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only (becoming genetically identical, i.e. a clone) it does not involve the fusion of gametes.
Asexual reproduction involves cell division by mitosis.

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25
Q

Give some examples of asexual reproduction in nature.

A

Daffodils forming daughter bulbs.

Strawberry runners producing new plants.

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26
Q

What is a clone?

A

A clone is a cell/organism which is genetically identical to the parent cell/organism. The process occurs through asexual reproduction by mitosis, involving only one parent cell.

27
Q

What are the advantages of plant cloning?

A
  1. Only one parent plant is needed.
  2. Conservation of endangered species.
  3. Plants with desirable characteristics and qualities can be replicated.
  4. Relatively quick.
  5. Relatively cheap.
  6. Relatively easy.
  7. Multiple cuttings can be taken from the same plant.
28
Q

What are the disadvantages of plant cloning?

A
  1. Lack of variation means that all plants are equally susceptible to disease.
29
Q

What is tissue culture?

A

Tissue culture is a particular type of cloning in plants that can be used to produce a very large number of identical plants. It can be carried out in the laboratory all year round, and if carried out in sterile conditions can produce disease-free varieties.

30
Q

Describe the steps necessary to carry out tissue culture.

A
  1. Get a plant with desirable characteristics.
  2. Use a sterile scalpel to cut explants from the plant stem.
  3. Place the explants in nutrient jelly.
  4. Each explant will grow into a small plant, genetically identical to the parent plant.
31
Q

What is cancer?

A

Cancer is a term used to describe a range of diseases caused by uncontrolled cell division.

32
Q

What are some of the causes of cancer?

A
  1. UV radiation.
    - UV radiation from the Sun or sun beds can cause skin cancer.
  2. Chemicals.
    - Cigarette smoke contains a number of cancer-causing chemicals collectively known as tar. Tar causes lung cancer.
  3. Viruses.
    - Some cancers can be caused by viruses, including the human papilloma virus (HPV). There are a number of types of HPV virus and they are linked to various human cancers including cervical cancer.
  4. Genetic factors.
33
Q

What are some of the ways to prevent skin cancer, caused by UV radiation?

A
  1. Reducing the time spent in strong sun.
  2. Covering up.
  3. Using sun lotion (sun cream).
34
Q

What are the two different types of cancerous tumours/growths, and how are they different?

A

Benign - Remain in one place and do not spread throughout the body. They may be surrounded by a distinct boundary or capsule (encapsulated).

Malignant - In malignant tumours groups of cancer cells may break off from the main (primary) tumour and spread around the body, where they can grow into other (secondary) tumours. Malignant tumours are less likely to have a distinct boundary or capsule around them. Malignant tumours are usually much more dangerous.

35
Q

What is the aim of screening programmes for cancer?

A

Screening programmes are designed to detect cancer early. If the cancer is detected earlier, the tumour will be smaller and will therefore have caused less damage to the body.

36
Q

Describe the three treatments of cancer?

A
  1. Surgery
    - This involves removing the cancer cells from the body. Surgery will be less effective if the cancer has spread throughout the body or the tumour is in an inaccessible part of the body.
  2. Radiotherapy
    - X-Rays or other forms of radiation can be used to kill the cancer cells. Sometimes other (normal) cells can be affected as well.
  3. Chemotherapy
    - Chemotherapy involves using a drug or a range of drugs to kill the cancer cells. There are a range of side-effects with chemotherapy, including other (normal) cells being affected, and hair loss.
37
Q

Where does mitosis occur?

A

Everywhere in the body, excluding the sex organs (testes and ovaries).

38
Q

Where does meiosis occur?

A

In the sex organs, testes and ovaries.

39
Q

How many daughter cells are produced by mitosis?

A

2

40
Q

How many daughter cells are produced by meiosis?

A

4

41
Q

What are the three different types of tissue cloning?

A
  1. Natural
  2. Cuttings
  3. Tissue culture
42
Q

Name three substances present in the agar used in tissue culture.

A

Water
Hormones
Magnesium

43
Q

Meiosis is also described as …

A

Reduction division

44
Q

Why does genetic variation arise through meiosis?

A

Independent assortment
Crossing over
Random mutations

45
Q

What is the order of stages in meiosis?

A
  1. Chromosomes become shorter and thicker (chromosome condensation).
  2. Homologous chromosomes pair up in the center of the cell.
  3. Spindle fibres separate homologous chromosomes.
  4. The cell divides into two daughter cells.
  5. Chromosomes align in the centre of each cell.
  6. Spindle fibres separate chromosomes into chromatids.
  7. Each cell divides into two daughter cells, producing four genetically variant daughter cells.
46
Q

What is the diploid number?

A

46

47
Q

What is the haploid number?

A

23

48
Q

Name two gamete cells.

A

Sperm cells

Ova (egg cells)

49
Q

What is the purpose of meiosis?

A
  1. To produce haploid gametes.

2. To give rise to genetic variation.

50
Q

Who is described as the ‘father of genetics’?

A

Gregor Mendel

51
Q

Gregor Mendel described genes as …

A

Factors

52
Q

What is pure breeding?

A

Pure breeding is when homozygous individuals are bred together.

53
Q

What is a monohybrid cross?

A

When only one factor/characteristic is considered (e.g. height) which is controlled by a single gene with two different alleles.

54
Q

When completing genetic diagrams it is helpful to use a small grid called a …

A

Punnett square.

55
Q

What is a pedigree diagram?

A

A pedigree diagram shows the way in which a genetic condition is inherited in a family or group of biologically related people.

56
Q

A complete set of chromosome is known as a …

A

Karotype

57
Q

Give an example of a recessive hereditary disease.

A

Cystic fibrosis

58
Q

How is sex determined in humans?

A

The female gamete (ovum, egg cell) contains an X chromosome and the male gamete (sperm cell) contains either an X or Y chromosome. This will determine whether the child is a boy (XY) or a girl (XX).

59
Q

Name two sex linked genetic disorders.

A

Haemophilia

Red/green colour blindness

60
Q

Why is the X chromosome larger than the Y chromosome?

A

As it carries more genes.

61
Q

What is haemophilia?

A

Haemophilia is a condition where individuals who are only carrying the recessive allele are unable to make all the products required to clot their blood.

62
Q

What is red-green colour blindness?

A

Individuals with red-green colour blindness are unable to distinguish between the colours red and green.

63
Q

Why do males suffer from genetic disorders more than females?

A

Many genetic disorders are sex linked to the X chromosome. If males inherit the recessive allele present on the X chromosome, there is no other dominant X chromosome to mask the condition.

XHY (Normal male)
XhY (Male with genetic condition)

XHXH (Normal female)
XHXh (Carrier female)
XhXh (Female with genetic condition)

64
Q

What are mutagens?

A

Mutation causing factors.

S2 GCSE Biology Unit 2 (8 decks)

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