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F5 Biology > C12: Variation > Flashcards

C12: Variation Flashcards

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1
Q

3 causes of continuous variation

A

(environmental factors)

  • temperature
  • pH value
  • light
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2
Q

4 causes of discontinuous variation

A

(genetic factor)

  • crossing over
  • independent assortment of chromosomes
  • random fertilisation
  • mutation
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3
Q

why environmental factors have small effect to variation only

A
  • only involves phenotypic differences
  • change allele frequency and genotype frequency
  • not change the genotype
  • cannot be inherited
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4
Q

example of effect of temperature to variation

A
  • Siamese cat
  • produces dark pigment enzyme for fur colour
  • function at temperature less than body temperature
  • thus, lower temperature body parts are dark in colour
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5
Q

example of effect of pH to variation

A
  • hydrangea sp. plant
  • produces blue flower in acidic soil
  • pink in alkaline soil
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6
Q

example of effect of light to variation

A
  • alter skin colour
  • ultraviolet ray destroy melanin pigment of exposed skin
  • more melanin pigment produced
  • cause skin to be darker
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7
Q

how crossing over affect the variation

A
  • occurs between non-sister chromatids of homologous chromosomes during prophase 1 of meiosis
  • produce new combination of genes
  • form gametes with different genetic materials
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8
Q

how independent assortment of chromosomes affect the variation

A
  • happen in metaphase 1 of meiosis
  • homologous chromosomes pair is arranged randomly on the equatorial plane
  • show two probabilities
  • different combinations of paternal and maternal chromosomes
  • different genetic content in gametes
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9
Q

how mutation affect the variation

A
  • permanent change occur spontaneously on genes or chromosome
  • create new genotypes
  • can be inherited if happen in gametes
  • cannot be inherited if happen in somatic cell
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10
Q

define variation

A

the difference in characteristics between a same population or species

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11
Q

what is natural selection

A

an evolutionary force that selects beneficial genes and removes the non-beneficial one.

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12
Q

3 necessity of variation

A
  • enables natural environment to continue selecting beneficial characteristics and remove the non-beneficial one
  • allows cross breeding among species to form new species
  • to ensure the survival of species when environment changes
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13
Q

explain continuous variation

A
  • difference in characteristics not distinct
  • graph: normal distribution//bell-shaped curve
  • quantitative, can be measured and graded
  • influenced by environmental factors
  • control by many genes
  • height, weight, skin colour
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14
Q

explain discontinuous variation

A
  • distinct differences in characteristics
  • graph: discrete distribution
  • no intermediate characteristics
  • qualitative, cannot be measured and graded
  • due to genetic factors
  • can be inherited
  • control by one genes, can be seen easily
  • fingerprint pattern, eye colour
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15
Q

why does someone has blue eyes

A
  • low level of melanin content in outer layer of iris
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16
Q

what is mutagen

A

the substance that causes mutation or increase the mutation rate to a dangerous level

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17
Q

what is mutant

A

the new genetic material produced by mutation

18
Q

3 types of mutagen

A
  • physical agents
  • chemical agents
  • biological agents
19
Q

2 physical agents cause mutation

A
  • ultraviolet from sun

- ionising rays (X-ray, alpha ray)

20
Q

4 chemical agents cause mutation

A
  • carcinogen
  • food preservations
  • formaldehyde
  • benzene
21
Q

2 biological agents cause mutation

A
  • virus

- bacteria

22
Q

how gene mutation occurs

A
  • known as point mutation
  • change in nucleotide base sequence of a gene
  • alter the genetic code to synthesise amino acid
  • change the protein structure
  • new protein form cannot function
23
Q

3 types of gene mutations

A
  • base substitution
  • base deletion
  • base insertion
24
Q

5 genetic diseases caused by gene mutation

A
  • thalassemia
  • cystic fibrosis
  • sickle cell anaemia
  • albinisme
  • haemophilia
25
Q

what disease cause by base substitution

A
  • sickle cell anaemia
26
Q

what disease cause by base deletion

A
  • cystic fibrosis
27
Q

what disease cause by base insertion

A
  • thalassemia
28
Q

explain albinisme

A
  • mutation of gene which responsible for producing the pigment of skin, hair and eyes
  • no pigment produced
29
Q

explain sickle cell anaemia

A
  • caused by the gene which responsible for synthesising of haemoglobin
  • crescent shape red blood cell
30
Q

explain chromosomal mutation

A
  • changes of chromosomal number or structure

- causes changes in characteristics

31
Q

effect of changes in chromosomal structure

A
  • changes in gene sequence in a chromosome
  • cause the abnormality to chromosome
  • knowns as chromosomal aberration
32
Q

4 types of chromosomal aberration

A
  • deletion
  • duplication
  • inversion
  • translocation
33
Q

explain the changes in chromosomal number

A
  • normal spindle fibers fail to form
  • homologous chromosome fail to separate during anaphase 1 in meiosis //
  • sister chromatids fail to separate during anaphase 2 in meiosis
  • caused a diploid organism to lose or gain more chromosomes
  • known as nondisjunction
34
Q

what happen when YO zygote form

A
  • the zygote die
35
Q

characteristics of down syndrome

A
  • slant eyes
  • flat nose
  • protruding tongue
  • broad forehead
  • mentally retarded
36
Q

cause of Cri Du Chat syndrome

A
  • partial deletion on the short arm of chromosome 5
37
Q

characteristics of Cri Du Chat syndrome

A
  • delay development in mental
  • physically retardation
  • most patient die during childhood
38
Q

characteristic of Klinefelter syndrome

A
  • 44+XXY
  • sterile male
  • long hands and legs
  • small testis
  • fail to produce sperms
  • voice and chest similar to women
39
Q

characteristics of Jacob syndrome

A
  • 44+XYY
  • male
  • taller than normal
  • pimples on face
  • slow acquiring speech
  • learning disability
  • weak muscle (hypotonia)
40
Q

characteristics of Turner syndrome

A
  • 44+XO
  • sterile female
  • lack of secondary female characteristics
  • undeveloped breast and ovaries
  • weblike neck
  • low IQ

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