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BIOLOGY IGCSE > Inheritance, Variation and Selection > Flashcards

Inheritance, Variation and Selection Flashcards

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1
Q

Define Inheritance

A

Transmission of genetic information from generation to generation

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2
Q

Define Chromosome

A

A thread like structure of DNA carrying genetic information in the form of genes

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3
Q

Define gene

A

Length of DNA that codes for a protein

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4
Q

Define Allele

A

Version of a gene

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5
Q

Which chromosomes do women have

A

XX

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6
Q

Which chromosomes do men have?

A

XY

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7
Q

Who determines the sex of the child?

A

The man

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8
Q

What is the sequence of bases in a gene responsible for?

A

It is the genetic code for putting together amino acids in the correct order to make a specific protein.

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9
Q

Give the base pairings

A

Thymine with Adenine

Guanine with Cytosine

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10
Q

What does the DNA control?

A

Controls cell functions by controlling the production of proteins, antibodies and receptors for neurotransmitters.

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11
Q

How is a protein made?

A
  1. The DNA gene coding for the protein remains in the nucleus as it is too big
  2. mRNA molecules carry a copy of the gene to the cytoplasm
  3. The mRNA passes through the ribosomes
  4. The ribosome assembles amino acids into protein molecules
  5. The specific order of amino acids is determined by the sequence of bases in the mRNA.
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12
Q

What is mRNA?

A

Messenger RNA

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13
Q

How does the ribosome read the codes on the mRNA?

A

In groups of three and each triplet of bases is called a codon.

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14
Q

What does a codon do?

A

Codes for a specific amino acid

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15
Q

Describe the genes in body cells?

A

All body cells in an organism contain the same genes but many genes in a particular cell are not expressed because the cell only makes the specific protein it needs

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16
Q

Define Haploid Nucleus

A

A nucleus containing a single set of unpaired chromosomes eg. sperm

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17
Q

How many pairs of chromosomes are there in a diploid nucleus?

A

23 pairs

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18
Q

Define Diploid Nucleus

A

A nucleus containing two sets of chromosomes eg. body cells

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19
Q

Define Mitosis

A

Nuclear division giving rise to genetically identical cells

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20
Q

What is mitosis used for?

A

It is used in growth, repair of damaged tissues, replacement of cells and asexual reproduction

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21
Q

What happens in mitosis?

A

Just before mitosis, each chromosome in the nucleus copies itself exactly. Chromosomes line up along the centre of the cell where the cell fibers pull them apart. The cell divides into two and each new cell has a copy of each of the chromosomes

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22
Q

What are stem cells?

A

Unspecialised cells that divide by mitosis to produce daughter cells that can be specialised for specific functions

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23
Q

Define meiosis

A

A reduction division in which the chromosome number in halved from diploid to haploid resulting in genetically different cells

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24
Q

When does meiosis happen?

A

It is used for the production of gametes

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25
Q

What does meiosis produce?

A

Variation by forming new combinations of maternal and paternal chromosomes

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26
Q

Describe the difference between mitosis and meiosis

A

Mitosis produces two cells; Meiosis produces four
Daughter cells are diploid; daughter cells are haploid
Daughter cells are genetically identical to each other; Daughter cells are genetically different to one another
One cell division occurs; Two cell divisions occur

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27
Q

Define genotype

A

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

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28
Q

Define phenotype

A

The observable features of an organism

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29
Q

Define Homozygous

A

Having the identical alleles of a particular gene

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30
Q

What happens when two homozygous individuals breed?

A

Will produce pure- breeding offspring

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31
Q

Define Heterozygous

A

Having two different alleles of a particular gene

32
Q

What happens when two heterozygous breed?

A

They will not produce pure breeding offspring

33
Q

Define dominant

A

An allele that is expressed if it present

34
Q

Define recessive

A

An allele that is only expressed when there is no dominant allele for the gene present

35
Q

What do breeders use test cross for?

A

To find out the genotype of an organism showing the dominant phenotype

36
Q

Give an example of codominance

A

Inheritance of blood group

37
Q

Which alleles for blood group are codominant?

A

IA and IB are both codominant to IO

38
Q

What does IA produce?

A

Antigen A in the blood

39
Q

What does IB produce?

A

Antigen B in the blood

40
Q

What does IO produce?

A

No antigens

41
Q

Which alleles give blood type A?

A

IAIA or IAIO

42
Q

Which alleles give blood type AB?

A

IA and IB

43
Q

Which alleles give blood type B?

A

IBIB or IBIO

44
Q

Which alleles give blood type O?

A

IO and IO

45
Q

Define sex-linked characteristics

A

A characteristic in which the gene responsible is located on a sex chromosome and that this makes it more common in one sex than in the other

46
Q

Which chromosomes can have alleles?

A

X chromosome

47
Q

Why are men more likely to have sex linked disease?

A

Because they only need 1 X chromosome

48
Q

What will a female with a recessive allele be?

A

A carrier

49
Q

Define variation

A

Differences between individuals of the same species

50
Q

What is phenotypic variation?

A

The difference in features between individuals of the same species and some of these differences are caused by genes which is genetic variation

51
Q

What is phenotypic variation caused by?

A

Genetic and environmental factors

52
Q

What is continuous variation?

A

A quantity usually measured eg. height

53
Q

What is discontinuous variation?

A

Limited number of phenotypes with no intermediates eg tongue rolling and blood group

54
Q

Define mutation

A

Genetic change

55
Q

Define gene mutation

A

A change in the base sequence of a DNA

56
Q

How are new alleles found?

A

By mutation

57
Q

What increases the rates of mutation?

A

Ionising radiation and gamma rays and certain chemicals which can cause cells to become cancerous

58
Q

What is sickle cell anaemia?

A

A mutation that changes the molecule haemoglobin causing the RBC’s to become stiff and sometimes sickle shaped when they release oxygen and these tend to get stuck in narrow blood vessels blocking the flow of blood. They may suffer strokes, blindness or damage to the heart, lungs and kidneys.

59
Q

Which alleles give normal haemoglobin?

A

HbA HbA

60
Q

Which alleles give sickle cell anaemia?

A

HbS HbS

61
Q

Which alleles produce normal and abnormal haemoglobin?

A

HbA HbS

62
Q

Who are resistant to malaria?

A

People who are heterozygous for sickle cell anaemia HbS HbA

63
Q

Why is there a strong correlation between the prevalence of sickle cell anaemia and in areas where malaria is more common?

A

If a heterozygous individual is protected from malaria and the negative effects of sickle cell are only present in the small proportion of people who are homozygous for the affected allele then the affected allele could be more common.

64
Q

Define Adaptive features

A

The inherited functional features of an organism that increase its survival

65
Q

Define fitness

A

The probability of an organism surviving and reproducing in the environment in which it is found

66
Q

What are hydrophytes?

A

Live in wet conditions

67
Q

What are xerophytes?

A

Live in dry conditions

68
Q

Describe the adaptations of Hydrophytes

A
  1. Have large air spaces to keep them close to the surface to get more light
  2. Small roots so that can also extract nutrients from the surrounding water
  3. Stomata found in the upper epidermis in order to exchange gases more easily with the air
69
Q

Describe the adaptations of Xerophytes

A
  1. Thick cuticle to prevent water loss as it acts as a barrier to evaporation and the shiny surface reflects gear so temperature goes down
  2. Thickened leaves contain cells that store water
  3. Extensive shallow roots allow for quick absorption of large quantities of water
  4. Sunken stomata trap moist air and lengthens diffusion pathways and reduces evaporation rate
  5. Small leaves reduce SA therefore the evaporating surface
70
Q

Define the process of adaptation

A

The process resulting from natural selection by which populations become more suited to their environment over many generations.

71
Q

What is evolution?

A

The change of adaptive features of a population over time as the result of natural selection

72
Q

What does natural selection lead to?

A

Competition for food
Competition for survival as the individuals with characteristics most suited to the environment have a higher rate of survival and more chances to reproduce therefore these alleles are passed to their offspring at a higher rate.

73
Q

Give an example of evolution by natural selection

A

Development strains of antibiotic resistant bacteria

74
Q

What is selective breeding?

A

It is done by humans of individuals with desirable features. They cross these individuals to produce the next generation until the new breed will reliably show those characteristics in all offspring

75
Q

How does artificial selection take place?

A
  1. Individuals with the characteristics you want are bred together
  2. Offspring that show the desired characteristic are selected and bred together
  3. This process is REPEATED FOR MANY SUCCESSIVE GENERATIONS before you have a new breed

BIOLOGY IGCSE (16 decks)

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