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IB Biology > 3: Genetics > Flashcards

3: Genetics Flashcards

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1
Q

Define a gene

A

a heritable factor that consists of a sequence of DNA that encodes for a specific trait

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2
Q

Define a loci

A

the location/position of a gene

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3
Q

Define allele

A

an alternative form of a gene that encodes for variations of a specific trait

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4
Q

Define mutation

A

change in the DNA base sequence

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5
Q

How are alleles formed

A

through mutations

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6
Q

What are the possible effects of mutations

A
  • beneficial
  • harmful
  • neutral
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7
Q

What type of mutation is sickle cell anemia

A

single base substitution

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8
Q

How was the entire base sequence of human genes sequenced

A

the Human Genome Project

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9
Q

What were some of the outcomes of the Human Genome Project

A
  • ancestry (Comparisons with other genomes have provided insight into the origins, evolution and migratory patterns of man)
  • medicine (discovery of new proteins have lead to improved treatments)
  • screening (allowed for the production of specific gene probes to detect sufferers and carriers of genetic diseases)
  • mapping (the n°, location and size of sequence of human genes is established)
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10
Q

What is the relationship between the number of genes and the complexity of an organism

A
  • no relationship
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11
Q

Compare the number of genes of humans with a named bacteria and plant

A
  • humans: 20, 000
  • E.Coli: 4, 000
  • Rice Plant: 40, 000
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12
Q

What does homozogous mean

A

two alleles at a locus are the same

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13
Q

What does heterozygous mean

A

two alleles at a locus are different

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14
Q

Which gene does sickle cell aneamia affect

A

hemoglobin

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15
Q

Outline sickle cell anemia

A

1) adenine base in GAG is replaced by a thymine base, changing the triplet to GTG
2) transcribed into the mRNA codon GUG, instead of GAG
3) translated into the amino acid valine instead of glutamic acid

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16
Q

What are the effects of sickle cell anemia

A
  • Sickle-shaped red blood cells
  • less oxygen can be carried
  • red blood cells can block the capillaries
  • immune to malaria
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17
Q

Define genome

A

the total of all the genetic information in an organism

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18
Q

What are the features of prokarytic chromosomes

A
  • single and circular chromosome
  • not associated with any proteins
  • located in nucleoid
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19
Q

Describe the structure and function of plasmid DNA

A
  • small and circular loops of DNA
  • allow gene transfer between species
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20
Q

Describe the structure of eukaryotic chromosomes

A
  • located in nucleus
  • linear DNA
  • no plasmids
  • associated with histones
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21
Q

Describe features of haploid cells

A
  • gametes
  • 23 chromosomes
  • meiosis
  • pairs of chromosomes (homologous chromosomes)
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22
Q

Describe features of diploid cells

A
  • body cells
  • 46 chromosomes
  • mitosis
  • 1 chromosome of each pair
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23
Q

What is a karyogram

A

a photograph that shows the homologous pairs arranged in decreasing length

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24
Q

What is the function of a karyogram

A
  • detect the sex of the organism
  • diagnose diseases (down syndrome)
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25
Q

What is Autoradiography

A

he studied the DNA of E. coli to determine its length and shape
- helps measure the length of DNA

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26
Q

Define homologous chromosome

A

chromosomes that share:
- the same genes at the same loci
- the same size/shape
- they may be carrying different alleles

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27
Q

How to calculate the mitotic index

A

number of cells undergoing mitosis ÷ total number of cells

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28
Q

What are the 2 different types of chromosomes

A

autosomal: body cells
sex chromosomes: gametes

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29
Q

Describe the use of a karyogram to diagnose Down syndrome

A

it has 3 chromosomes at position 21
- it has 47 chromosomes in total

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30
Q

Explain why the typical number of chromosomes in a species is always an even number

A

This is because the diploid number (2n) must always be divisible by two to produce the haploid number (n)
The haploid number must always be a whole number

31
Q

What is the SRY gene

A
  • carried on the Y chromosome
  • involved in the development of testosterone and testes
32
Q

How to recognise if the organism in the karyogram is female or male

A

female: XX (chromosomes same size)
male: XY (chromosomes different size)

33
Q

What does meiosis give rise to

A
  • gametes
  • genetically different cells
34
Q

What does the first meiotic division consist of

A

separation of homologous chromosomes

35
Q

What does the second meiotic division consist of

A

separation of sister chromatids

36
Q

Outline prophase I

A
  • DNA supercoils and becomes visible
  • Nuclear membrane starts to break down
  • Crossing over occurs
  • Spindle microtubules start to form
37
Q

Outline metaphase I

A
  • homologous chromosomes line up at the equator
  • spindle microtubules attach themselves to the centromeres
  • the orientation of the homologous chromosomes is random
38
Q

Outline anaphase I

A
  • Spindle microtubules contract
  • pull the chromosomes to opposite poles of the cell
  • non-disjunction may occur
39
Q

Outline telophase I

A
  • chromosomes uncoil
  • The nuclear membrane starts to reform
  • the cell divides into 2 daughter cells
  • Spindle microtubules break down
40
Q

What is crossing over

A

the exchange of genetic material between non-sister chromatids at the chiasma
- occurs during Prophase I
- promotes genetic variation

41
Q

How does random orientation promote genetic variation

A
  • occurs during Metaphase I
  • results in the production of different allele combinations in the haploid cells
42
Q

How does random fertilisation promote genetic variation

A

The random fertilisation of an egg and a sperm will generate different zygotes

43
Q

What is non-disjunction

A

When the spindle microtubules fail to separate the chromosomes correctly, which either results in the gametes having an extra or missing chromosome. This occurs in either Anaphase I or Anaphase II

44
Q

What factor increases the risks of having a kid with Down syndrome

A

older a parent gets the higher the risks of non-disjunction happening because the spindle microtubules may not function properly

45
Q

Outline prophase II

A
  • nuclear membrane breaks down
  • DNA supercoils
  • the spindle microtubules start to form
46
Q

Outline metaphase II

A
  • chromosomes line up at the equator
  • the spindle microtubules attach themselves to the centromeres
47
Q

Outline anaphase II

A
  • the spindle microtubules contract and pull the sister chromatids to opposite sides of the pole
  • non-disjunction could occur
48
Q

Outline telophase II

A
  • the nuclear membrane reforms
  • the chromosomes uncoil
  • the spindle microtubules break down
  • the cell divides into 4 haploid cells
49
Q

Difference between sexual and asexual reproduction

A
  • sexual: offsprings are genetically different to the parent
  • asexual: offsprings are genetically identical to the parent
50
Q

Why is the halving of chromosomes important during meiosis

A

allows for the fusion of gametes (fertilisation)

51
Q

List the factors that promote genetic variation

A
  • crossing over
  • fertilisation
  • random orientation
52
Q

How many chromosomes do gametes have

A

23 chromosomes

53
Q

Define dominant allele

A

it masks the effects of recessive alleles

54
Q

Outline sexual reproduction/what a zygote is

A

a process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote (fertilized egg cell) and the production of offspring that are genetically different from each other

55
Q

Define recessive allele

A

needs to be inherited from both parents in order for the characteristic to be expressed in the phenotype

56
Q

example of co-dominant genes

A

blood groups

57
Q

Define sex linkage

A

sex-linked diseases are on the X chromosome

58
Q

What causes genetic diseases

A
  • new alleles are formed form other alleles by gene mutation
  • radiation
  • mutagenic chemicals
59
Q

What are examples of sex-linked diseases

A

hemophilia and colour-blindness

60
Q

What are examples of genetic diseases caused by dominant alleles

A

Huntington

61
Q

What are examples of genetic diseases caused by recessive alleles

A

cystic fibrosis and albinism

62
Q

What is the function of gel electrophoresis

A

separate proteins or fragments of DNA according to size and charge

63
Q

Outline gel electrophoresis

A
  • DNA is negatively charged it will go to the anode
  • smaller molecules travel further away
64
Q

What is the function of PCR

A

amplify fragments of DNA

65
Q

Outline PCR

A

1) the DNA is heated breaking the hydrogen bonds that bond the two DNA strands together (denaturation)
2) the temperature is decreased so that primers can anneal to the ends of the single strands of DNA (annealing)
3) the temperature is increased for Taq polymerase to build the complementary strands of DNA to produce the new identical DNA

66
Q

What is the function of DNA profiling

A
  • paternity investigations
  • identify crime suspects
67
Q

Why is genetic modification through gene transfer possible

A

genetic code is universal
- same codons code for the same proteins in all organisms

68
Q

Outline gene transfer

A

COMPLETE

69
Q

Benefits of genetic modification of crops

A
  • less use of chemicals
  • more resistant to harsh weather and pests
  • higher crop yield
  • crop-shelf life is improved
  • less keep up of plants, less machinery used more efficient that traditional methods
70
Q

Risks of genetic modification of crops

A
  • the long-term effects are unknown
  • reduces genetic variation (more vulnerable to extinction)
  • reduction of biodiversity
  • mutations may occur in the inserted genes that cause them to have unwanted effects on organisms
  • contaminate nearby non-GM crops
71
Q

Gene transfer

A

COMPLETE

72
Q

Examples of natural cloning

A
  • plants reproduce by asexual reproduction
  • identical twins
73
Q

Outline the production of cloned embryos produced by somatic cell nuclear transfer

A

1) animal to be cloned donates a somatic (body) cell
2) egg cell is extracted from the egg donor and enucleated
3) nucleus to be cloned is injected into the enucleated egg cell
4) cell divides forming an embryo
5) embryo is implanted into the surrogate mother

IB Biology (11 decks)

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