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Biololgy IGCSE continued 13-21 > 17: Inheritance & 18: Variation > Flashcards

17: Inheritance & 18: Variation Flashcards

1
Q

Describe inheritance

A

The transmission of genetic information from generation to generation

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2
Q

Define a chromosone

A

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

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3
Q

Define a gene

A

A length of DNA that codes for protein

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4
Q

Define an allele

A

A version of a gene

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5
Q

Describe the inheritance of sex in humans

A

Mom has XX
Dad has XY & has the role in determining what the sex of the child is as the only has a Y chromosone

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6
Q

Explain the sequence of bases in a gene

A

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

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7
Q

Explain the role of DNA

A

It controls cell function by controlling the production of proteins (some are enzymes), antibodies and receptors for neurotransmitters

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8
Q

How is a protein made?

A
  1. gene coding for the protein remains in the nucleus
  2. mRNA molecules carry a copy of the gene to the cytoplasm
  3. mRNA passes through ribosomes
  4. ribosome assembles amino acids into protein molecules
  5. specific order of amino acids is determined by the sequence of bases in mRNA
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9
Q

Explain the role of 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 proteins it needes

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10
Q

Define a haploid nucleus

A

A nucleus containing a single set of unpaired chromosomes (e.g. in gametes)

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11
Q

Define a diploid nucleus

A

A nucleus containing two sets of chromosomes (e.g. in body cells)

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12
Q

Describe a diploid cell

A

A pair of each type of chromosomes
In a human diploid cells, there are 23 pairs

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13
Q

Define mitosis

A

A nuclear division giving rise to genetically identical cells

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14
Q

State the roll of mitosis

A

In growth, repair of damaged tissues, replacement of cells & asexual reproduction

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15
Q

When does exact duplication of chromosomes occurs?

A

BEFORE mitosis

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16
Q

What happens during mitosis?

A

Copies of chromosomes separate, maintaining the chromosome number

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17
Q

Describe stem cells

A

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

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18
Q

Define meiosis

A
  • A nuclear division giving rise to cells that are genetically different
  • A reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells
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19
Q

How does meiosis produce variation?

A

By forming new combinations of maternal and paternal chromosomes every time a gamete is made
= Gametes fuse randomly at fertilisation, each offspring will be different from any others

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20
Q

Define a genotype

A

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

21
Q

Define a phenotype

A

As the observable features of an organism

22
Q

Define homozygous

A

Having 2 identical alleles of a particular gene
- 2 identical homozygous individuals that breed together will be pure-breeding

23
Q

Define heterozygous

A

Having two different alleles of a particular gene
- A heterozygous individual will NOT be pure-breeding

24
Q

Define dominant

A

An allele that is expressed IF present

25
Q

Define recessive

A

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

26
Q

Define a sex-linked characteristic

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

27
Q

What is colour blindness?

A

An example of sex linkage

28
Q

Define variation?

A

Differences between individuals of the same specifies

29
Q

What is phenotypic variation?

A

The difference in features between individuals of the same species (e.g. dyed hair, scratches on legs)

30
Q

What is genetic variation?

A

Differences in genes, which is genetic variation (e.g. eye colour)

31
Q

What is continuous variation?

A

A range of phenotypes between 2 extremes, e.g. height in humans

32
Q

What is discontinuous variation?

A

Results in a LIMITED number of phenotypes with no intermediates, e.g. tongue rolling
- mostly called by genes alone (e.g. A, B, AB & O blood groups in humans)

33
Q

Define mutation

A

A genetic change
- the way in which new alleles are formed

34
Q

Define gene mutation

A

A change in the base sequence of DNA

35
Q

What increases the rate of mutation?

A

Ionising radiation & same chemicals

36
Q

Describe the symptoms of sickle-cell anaemia

A
  • shortness of breath
  • headache or dizziness
  • extreme tiredness.
  • weakness
  • yellowish skin color (jaundice)
37
Q

How does a change in the base sequence of the gene for haemoglobin results in abnormal haemoglobin & sickle-shaped red blood cells?

A

The mutation causes haemoglobin molecules to stick together, creating sickle-shaped red blood cells

38
Q

What do people who are heterozygous for sickle-cell allele have a resistance to ?

A
39
Q

Explain the distribution of the sickle-cell allele in human populations

A
40
Q

Define an adaptive feature

A

An inherited feature that helps an organism to survive and reproduce in its environment and increases its fitness

41
Q

Define fitness

A

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

42
Q

Explain the adaptive features of hydrophytes and xerophytes to their features

A
43
Q

Describe natural selection

A
44
Q

Describe selective breeding

A
45
Q

Describe evolution

A

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

46
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

47
Q

Describe the development of strains of antibiotic resistance bacteria

A

An example of evolution by natural selection

48
Q

State differences between natural & artificial selection

A

Biololgy IGCSE continued 13-21 (7 decks)

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