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Combined Science - Biology Paper 2 (Higher) > Combined Biology - B6 Inheritance, Variation and Evolution > Flashcards

Combined Biology - B6 Inheritance, Variation and Evolution Flashcards

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1
Q

Which type of cell division leads to identical cells being formed?

A

Mitosis

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2
Q

Name the gametes (sex cells) in animal reproduction.

A

Sperm (male) and egg (female)

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3
Q

Which type of reproduction leads to a variety in the offspring as there is mixing of genetic information?

A

Sexual reproduction

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4
Q

What is a clone?

A

Genetically identical offspring (a result of asexual reproduction)

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5
Q

Which type of cell division leads to non-identical cells being formed?

A

Meiosis

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6
Q

Name the gametes (sex cells) in plant reproduction.

A

Pollen (male) and egg cells (female)

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7
Q

Which type of reproduction leads to genetically identical offspring?

A

A-sexual reproduction

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8
Q

Before meiosis, there are 46 chromosomes in a human body cell. How many are there in each gamete after meiosis?

A

23

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9
Q

Describe the structure of DNA

A

A polymer made up of two strands forming a double helix.

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10
Q

What is the name for a specific section of DNA that codes for a particular protein?

A

A gene

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11
Q

What is the genome of an organism?

A

The entire genetic material of that organism

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12
Q

Give three reasons why understanding the human genome is important.

A
  • Genes linked to different types of disease can be searched for
  • Inherited disorders can be understood / treated
  • Migration patterns of the past can be traced
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13
Q

Before cell division, what does the DNA in the cell get stored in?

A

Chromosomes

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14
Q

What does a gene code for?

A

A particular sequence of amino acids, which make specific proteins

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15
Q

Complete the Punnett square for the % chance of having a mouse with black fur.

F = brown fur, f = black fur

A

0% chance of having a mouse with black fur

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16
Q

What is embryo screening?

A

Removing a cell from an embryo and analysing its DNA to look for genetic disorders

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17
Q

Explain what is meant by a ‘dominant allele’

A

The characteristic is expressed if one or two copies of the allele is present

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18
Q

What name is given to two of the same alleles (e.g TT or tt)?

A

homozygous

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19
Q

What does ‘genotype’ mean?

A

What alleles an organism has, e.g. Tt, TT or tt

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20
Q

What is an allele?

A

A version of a gene

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21
Q

Explain what is meant by a ‘recessive allele’

A

The characteristic is only expressed if two copies of the allele are present.

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22
Q

What name is given to two different alleles (e.g Tt)?

A

heterozygous

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23
Q

What does ‘phenotype’ mean?

A

The characteristics an organism has, e.g. ‘long hair’, ‘black fur’, ‘blue eyes’ e.t.c

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24
Q

Give an example of characteristics controlled by a single gene

A

Fur colour in mice / red-green colour blindness in humans

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25
Q

Is polydactyly caused by a dominant or recessive allele?

A

Dominant

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26
Q

Complete the Punnett square for the % chance of having a boy or girl

A

50% male, 50% female

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27
Q

What is cystic fibrosis?

A

A genetic disorder that affects cell membranes and causes mucus build up in the air passages and pancreas.

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28
Q

Is cystic fibrosis caused by a dominant or recessive allele?

A

Recessive

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29
Q

Are most characteristics determined by a single gene, or by multiple genes interacting?

A

Multiple genes interacting

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30
Q

What is polydactyly?

A

An inherited disorder that causes a person to have extra fingers or toes.

31
Q

How many pairs of chromosomes are found in ordinary human body cells?

A

23 pairs

32
Q

22 pairs of chromosomes determine an organism’s characteristics, but what does the 23rd pair determine?

A

The 23rd chromosome determines sex

(XX in female and XY in male)

33
Q

What is variation?

A

Differences in the characteristics of individuals in a population

34
Q

Which of the following is true?

a) Most mutations of DNA cause a change in phenotype
b) Most mutations of DNA do not cause a change in phenotype

A

b) Most mutations of DNA do not cause a change in phenotype

35
Q

As well as genotype, what else affects the phenotype of an organism?

A

The environment

36
Q

What causes genetic variation?

A

Mutations

37
Q

What is evolution?

A

A change in the inherited characteristics of a population over time which may result in the formation of a new species

38
Q

When are two organisms with a common ancestor considered to be two different species?

A

When they cannot interbreed and produce fertile offspring.

39
Q

Describe how selective breeding works

A
  • Choosing parents with a desired characteristic
  • Breed them
  • Select offspring with the desired characterstic
  • Breed them
  • Continue over many generations until you have a population with the desired characteristic.
40
Q

Give two examples of “desired characteristics” in the selective breeding of animals

A
  • Animals which produce more milk / meat
  • Domestic dogs of a gentle nature
41
Q

According to the theory of evolution by natural selection, what have all species of living things evolved from?

A

Simple life forms that first developed more than three billions years ago.

42
Q

Describe how speciation occurs

A
  • Isolation of two populations.
  • Differences in environmental conditions or food availability in the two areas.
  • Natural variation in populations.
  • Mutations occur.
  • Individuals that are better adapted to their environment…
  • …survive, reproduce and produce offspring.
  • Populations become so genetically different that they can’t interbreed and produce fertile offspring.
43
Q

Give two examples of “desired characteristics” in the selective breeding of plants

A
  • Disease resistance in food crops
  • Large / unusual flowers
44
Q

What are the negative consequences of selective breeding?

A
  • Inbreeding causes a reduction in gene pool.
  • Reduced variation in genes means the population is less resistant to disease
  • Inbreeding can cause populations to have genetic defects.
45
Q

What is genetic engineering?

A

Taking a gene from one organism and inserting it into the genome of another.

46
Q

Which organisms have been genetically engineered to produce insulin?

A

Bacteria

47
Q

What are genetically modified (GM) crops?

A

Crops that have been genetically engineered (had genes from other organisms inserted into them)

48
Q

What is gene therapy?

A

The use of genetic engineering to treat inherited diseases caused by faulty genes.

49
Q

Give two reasons for genetic engineering plants

A

Examples include:

  • Disease resistance
  • Pest resistance
  • Drought resistance
  • Produce bigger fruits
50
Q

What are the two main concerns about GM crops?

A
  • The effect on populations of wild flowers and insects
  • Human health (not being fully explored)
51
Q

Higher Q. Describe how genetic engineering works

A
  • Enzymes are used to cut the desired gene out of an organism.
  • The gene is inserted into a vector (using enzymes).
  • The vector is inserted into the target organism.
  • The desired gene is transferred from the vector into the target organism.
52
Q

Higher Q. What two things are often used as vectors in genetic engineering?

A
  • Bacterial plasmid
  • Virus
53
Q

Higher Q. Why are genes transferred at an early stage of the organism’s development during genetic engineering?

A

So the organism develops with the desired characteristic

54
Q

What happens during fertilisation?

A

The nuclei of the gametes fuse together

55
Q

How many cells are produced in meiosis?

A

4 cells (all genetically different)

56
Q

What is a gamete?

A

A sex cell (e.g. sperm or egg)

57
Q

Describe the process of meiosis

A
  1. Copies of the genetic information are made (to make chromosomes with two identical arms)
  2. Chromosomes line up as pairs and mixing of genetic information occurs.
  3. The first cell division takes place and the chromosome pairs are pulled apart. This results in two cells.
  4. The chromosomes line up again.
  5. A second cell division pulls the arms of the chromosomes apart. This results in four genetically different cells.
58
Q

What are the three main types of fossils?

A
  • Parts of organisms that have not decayed because one or more the conditions for decay was absent.
  • Parts of the organism are replaced by minerals as they decay.
  • Preserved traces (footprints / burrows etc…)
59
Q

Why are there very few traces of early life forms?

A

They were soft-bodied (fossil record incomplete)

60
Q

What is extinction?

A

When there are no remaining individuals of a species still alive

61
Q

Why can bacteria evolve rapidly?

A

They reproduce at a fast rate

62
Q

What is MRSA resistant to?

A

Antibiotics

63
Q

What do fossils show?

A

How organisms evolved as life developed on Earth

64
Q

Give three causes of the extinction of a species

A

Any three from:

  • Environmental changes
  • New predators
  • New diseases
  • Catastrophic events
  • Can’t compete for food
65
Q

How do new strains of bacteria occur that are resistance to antibiotics?

A

Random mutations that cause antibiotic resistance

66
Q

Give three ways antibiotic resistance can be reduced?

A
  • Reduce prescription of antibiotics, especially when inappropriate (e.g. for a viral infection)
  • Patients should complete course of antibiotics so all bacteria are killed
  • Restriction of agricultural antibiotic use
67
Q

Who developed the three-domain system of classification?

A

Carl Woese

68
Q

What are the categories for the Linnaean system of Classification?

K………

P………

C………

O………

F………

G………

S………

A
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
69
Q

What caused new models of classification to be proposed?

A

Evidence of internal structures (using microscopes) and biochemical processes were better understood

70
Q

In an evolutionary tree, which organisms are most closely related?

A

The species that are connected by the shorted paths on the evolutionary tree.

71
Q

Who developed the Linnaean system of classification?

A

Carl Linnaeus

72
Q

What two categories of the Linnaean system make up the binomial system for naming organisms?

A

Genus and species

73
Q

What are the three-domains in the ‘three-domain’ system?

A
  • Archaea (primitive bacteria)
  • Bacteria (true bacteria)
  • Eukaryota (protists, fungi, plants and animals)

Combined Science - Biology Paper 2 (Higher) (3 decks)

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