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BIOLOGY IGCSE > Inheritance, Variation and Selection > Flashcards

Inheritance, Variation and Selection Flashcards

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
What does meiosis produce?
Variation by forming new combinations of maternal and paternal chromosomes
26
Describe the difference between mitosis and meiosis
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
27
Define genotype
The genetic make-up of an organism in terms of the alleles present
28
Define phenotype
The observable features of an organism
29
Define Homozygous
Having the identical alleles of a particular gene
30
What happens when two homozygous individuals breed?
Will produce pure- breeding offspring
31
Define Heterozygous
Having two different alleles of a particular gene
32
What happens when two heterozygous breed?
They will not produce pure breeding offspring
33
Define dominant
An allele that is expressed if it present
34
Define recessive
An allele that is only expressed when there is no dominant allele for the gene present
35
What do breeders use test cross for?
To find out the genotype of an organism showing the dominant phenotype
36
Give an example of codominance
Inheritance of blood group
37
Which alleles for blood group are codominant?
IA and IB are both codominant to IO
38
What does IA produce?
Antigen A in the blood
39
What does IB produce?
Antigen B in the blood
40
What does IO produce?
No antigens
41
Which alleles give blood type A?
IAIA or IAIO
42
Which alleles give blood type AB?
IA and IB
43
Which alleles give blood type B?
IBIB or IBIO
44
Which alleles give blood type O?
IO and IO
45
Define sex-linked characteristics
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
Which chromosomes can have alleles?
X chromosome
47
Why are men more likely to have sex linked disease?
Because they only need 1 X chromosome
48
What will a female with a recessive allele be?
A carrier
49
Define variation
Differences between individuals of the same species
50
What is phenotypic variation?
The difference in features between individuals of the same species and some of these differences are caused by genes which is genetic variation
51
What is phenotypic variation caused by?
Genetic and environmental factors
52
What is continuous variation?
A quantity usually measured eg. height
53
What is discontinuous variation?
Limited number of phenotypes with no intermediates eg tongue rolling and blood group
54
Define mutation
Genetic change
55
Define gene mutation
A change in the base sequence of a DNA
56
How are new alleles found?
By mutation
57
What increases the rates of mutation?
Ionising radiation and gamma rays and certain chemicals which can cause cells to become cancerous
58
What is sickle cell anaemia?
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
Which alleles give normal haemoglobin?
HbA HbA
60
Which alleles give sickle cell anaemia?
HbS HbS
61
Which alleles produce normal and abnormal haemoglobin?
HbA HbS
62
Who are resistant to malaria?
People who are heterozygous for sickle cell anaemia HbS HbA
63
Why is there a strong correlation between the prevalence of sickle cell anaemia and in areas where malaria is more common?
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
Define Adaptive features
The inherited functional features of an organism that increase its survival
65
Define fitness
The probability of an organism surviving and reproducing in the environment in which it is found
66
What are hydrophytes?
Live in wet conditions
67
What are xerophytes?
Live in dry conditions
68
Describe the adaptations of Hydrophytes
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
Describe the adaptations of Xerophytes
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
Define the process of adaptation
The process resulting from natural selection by which populations become more suited to their environment over many generations.
71
What is evolution?
The change of adaptive features of a population over time as the result of natural selection
72
What does natural selection lead to?
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
Give an example of evolution by natural selection
Development strains of antibiotic resistant bacteria
74
What is selective breeding?
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
How does artificial selection take place?
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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