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Biology Higher GCSE Edexcel > Chapter Three: > Flashcards

Chapter Three: Flashcards

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1
Q

What are the three advantages of Asexual Reproduction?

A

+Rapid Populating
+No mates required
+Emergency option

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2
Q

What are the three disadvantages of Asexual Reproduction?

A
  • No diversity
  • Prone to extinction
  • Cannot adapt
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3
Q

Why is rapid populating an advantage of asexual reproduction?

A

Asexual reproduction gives the ability to produce large quantities of offspring

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4
Q

Why is not having a mate an advantage of asexual reproduction?

A

Finding a mate can be difficult for organisms in desolate environments

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5
Q

Why is asexual reproduction a good emergency option?

A

In dire situations, plants and organisms can keep themselves alive and produce others to help them.

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6
Q

Why does asexual reproduction produce offspring with no diversity?

A

Traits are only passed on from one parent, so there is no genetic mixing meaning all offspring produced are identical.

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7
Q

Why are offspring of asexual reproduction prone to extinction?

A

Same traits mean same weaknesses. Predators that have evolved to kill a single organism can wipe out an entire population.

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8
Q

Why can the offspring of asexual reproduction not adapt?

A

An organism has established reactions to certain things which are passed down in asexual reproduction, making it almost impossible for them to adapt to any environment changes.

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9
Q

What is the purpose of sexual reproduction?

A

To produce offspring that resemble the parents, but are not identical.

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10
Q

What are the sex cells called in organisms?

A

Gametes

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11
Q

Name the advantages of sexual reproduction:(2)

A

More variation - more chance of survival

Bad genes can become extinct through meiosis and natural selection

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12
Q

Name the disadvantages of sexual reproduction:(4)

A

Requires two parents
Takes time and energy
Favorable genes can also become extinct through meiosis
Produces less offspring than asexual reproduction

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13
Q

What is Meiosis?

A

A type of cell division that produces gametes

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14
Q

How many chromosomes does a human body cell contain?

A

46 (23 pairs)

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15
Q

How many chromosomes does a gamete contain?

A

23

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16
Q

How does Meiosis differ to Mitosis?

A

They produce four daughter cells

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17
Q

What does Meiosis produce?

A

Four genetically haploid daughter cells

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18
Q

What is the Genome?

A

The haploid set of chromosomes

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19
Q

What is formed at fertilization?

A

A Zygote

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20
Q

What does a zygote contain?

A

23 pairs of chromosomes - 23 single chromosomes from each parent

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21
Q

What do chromosomes contain?

A

Genes

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22
Q

What are Genes?

A

A distinct sequence of nucleotides forming part of a chromosome

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23
Q

What does DNA stand for?

A

Deoxyribose Nucleic Acid

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24
Q

What is DNA?

A

The complex chemical that carries genetic information

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25
Q

What are chromosomes?

A

A thread-like structure of nucleic acids and proteins. Carries genetic information in the form of genes.

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26
Q

What are the function of the bases in DNA?

A

To carry different codes needed for different amino acids

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27
Q

What is the code for an amino acid made of?

A

Three bases in a particular order

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28
Q

What are the four different bases of DNA?

A

Thymine, T
Adenine, A
Guanine, G
Cytosine, C

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29
Q

What does Thymine pair with?

A

Adenine

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30
Q

What does Guanine pair with?

A

Cytosine

31
Q

What bonds hold the bases of DNA together?

A

Hydrogen Bonds

32
Q

What bases form three hydrogen bonds?

A

Guanine and Cytosine

33
Q

What bases form two hydrogen bonds?

A

Adenine and Thymine

34
Q

What are Proteins made up of?

A

Large numbers of amino acid molecules

35
Q

What is a Mutation?

A

A change that occurs in a gene

36
Q

What causes a Mutation?

A

They can be random or caused by radiation or chemicals.`

37
Q

What do Mutations cause? (Terms of genetic code)

A

Alteration to the base pair sequence

38
Q

What’s the difference between DNA mutations in normal body cells and sex cells?

A

If changes occur in normal body cells, the changes are lost when we die. If changes occur in sex cells, there is a possibility they will be passed on to the next generation.

39
Q

How is a new species produced?

A

Through the combined effect of mutations, environmental changes and natural selection

40
Q

What is transcription?

A

The copying of DNA in the process of creating a protein.

41
Q

Where does transcription occur?

A

In the cell nucleus

42
Q

What is the first stage of Transcription?

A

The DNA in a gene unzips so both strands are separate

43
Q

What is the second stage of Transcription?

A

Complementary bases attach to the strand being copied.

44
Q

What is the third stage of Transcription?

A

Thymine is not present so a different base (U) joins with Adenine

45
Q

What is the fourth stage of Transcription?

A

Messenger RNA is formed

46
Q

What is the difference between DNA and mRNA? (In terms of exiting/entering the nucleus)

A

mRNA is small enough to leave the nucleus and travel to the ribosomes in the cytoplasm.

47
Q

What is translation?

A

The process of mRNA being interpreted and new proteins forming

48
Q

Where does translation take place?

A

In the Ribosomes

49
Q

What is the first step of Translation?

A

The mRNA attaches to a ribosome which ‘reads’ the mRNA

50
Q

What is the second step of Translation?

A

The ribosome decodes the mRNA in groups of three (base triplets or codons) which are complementary in transfer RNA

51
Q

What is the third step of Translation?

A

The tRNA collects its specific amino acids and returns to the mRNA

52
Q

What is the fourth step of Translation?

A

The amino acids are lined up in order of the instructions of the mRNA

53
Q

What is the fifth step of Translation?

A

Bonds form between the amino acids and a polypeptide chain is formed

54
Q

What is the sixth step of Translation?

A

The polypeptide chain folds and becomes a specific shape forming a protein

55
Q

What is an allele?

A

each of two or more alternative forms of a gene that arise by mutation

56
Q

What does dominant mean in the terms of genetics?

A

an allele or a gene that is expressed in an organism’s phenotype, masking the effect of the recessive allele or gene when present

57
Q

What does recessive mean in the terms of genetics?

A

an allele or gene in which the effect is masked by the effects of a dominant gene or allele

58
Q

What does Homozygous mean?

A

When an individual has two of the same allele

59
Q

What does Heterozygous mean?

A

When an individual has two alleles that are different

60
Q

What is a genotype?

A

the genetic constitution of an individual organism

61
Q

What is a phenotype?

A

A set of observable characteristics of an individual

62
Q

What is cystic fibrosis caused by? (In the terms of alleles)

A

Recessive Allele

63
Q

What does Cystic Fibrosis cause?

A

The individual to produce abnormally thick and sticky mucus in their lungs and airways

64
Q

If a person has one copy of the allele causing CF but one not carrying CF, what are they referred to as?

A

A carrier

65
Q

What is an example of multiple alleles for one gene?

A

The ABO blood group

66
Q

What is codominance?

A

When two or more alleles are expressed in the same phenotype

67
Q

Which is more domination? I^A or I^B?

A

Neither, none are dominant over each other

68
Q

True or False? Both I^A and I^B are dominant over I^O.

A

True

69
Q

If a person has the genotype I^A I^O, what phenotype are they?

A

A

70
Q

What sex chromosomes code for a male?

A

XY

71
Q

Why does the sperm determine the sex of the fetus?

A

The Sperm carries the alternating sex chromosome, the ovum always contains the X chromosome but the sperm can contain either the X or Y.

72
Q

What are the effects of Haemophilia?

A

People with it have a problem forming blood clots

73
Q

What causes Haemophilia?

A

A recessive gene on the X chromosome

74
Q

What environmental factors can affect our phenotype?(5)

A
  • climate
  • diet
  • physical accidents
  • culture
  • lifestyle

Biology Higher GCSE Edexcel (4 decks)

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