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Biology > Patterns of inheritance and variation > Flashcards

Patterns of inheritance and variation Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is phenotypic variation?

A

Variation shown in the characteristic of an organism (phenotype)

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2
Q

Give an example of phenotypic variation

A

human blood group

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3
Q

What is polygenic variation?

A

Variation influenced by many genes

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4
Q

Give an example of polygenic variation

A

Human skin colour

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5
Q

What is monogenic variation?

A

Variation influenced by only one or a small number of genes

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6
Q

Give an example of monogenic variation

A

Violet flowers, either coloured or white

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7
Q

How can variation be categorised?

A

continuous and discontinuous

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8
Q

What are alleles?

A

different versions of genes within the same species

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9
Q

What is etiolation?

A

plants don’t get enough light so grow spindly and long

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10
Q

What is chlorosis?

A

plants don’t get enough magnesium so don’t produce enough chlorophyll and turn yellow

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11
Q

What two factors can affect variation?

A

genetic and environmental

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12
Q

Give two examples where genetic and environmental factors affect phenotype variation

A
  • body mass in humans
  • dwarf and tall pea plants
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13
Q

How is genetic variation achieved during meiosis?

A
  • crossing over of non-sister chromatids (prophase 1)
  • independent assortment of homologous chromosomes (metaphase 1)
  • independent assortment of chromatids (metaphase 2)
  • independent segregation of chromatids (anaphase 2)
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14
Q

What is monogenic inheritance?

A

the inheritance of a single gene

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15
Q

Is cystic fibrosis caused by a dominant or a recessive allele?

A

recessive

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16
Q

What did Gregor Mendel do?

A

Mendel experimented genetic crosses using pea plants. He used true breeding plants to breed together and studied the outcome.

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17
Q

What are true breeding plants?

A

plants that were homozygous for traits

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18
Q

What were the offspring of true breeding crosses called?

A

F1 generation

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19
Q

In homozygous crosses, what are the offspring?

A

They are all heterozygous

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20
Q

What is a heterozygous cross?

A

where 2 of the F1 offspring are taken and crossed

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21
Q

What are the offspring of heterozygous crosses called?

A

F2 generation

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22
Q

What is the result of a heterozygous cross?

A

3 offspring with dominant trait to 1 offspring with the recessive characteristic

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23
Q

What is codominance?

A

when 2 different alleles are equally dominant so both alleles are expressed in the phenotype

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24
Q

Give and describe an example of codominance

A

Snapdragons:
Allele for red flowers: codes for enzyme that catalyses the production of red pigment from a colourless precursor
Allele for white flowers: codes for an altered enzyme that doesn’t code for a pigment

25
Q

Give an example of a trait that has more than two different alleles

A

blood groups

26
Q

What are blood groups determined by?

A

the immunoglobulin gene (gene I) coding for antigens present on the surface of blood cells

27
Q

What does I A produce?

A

antigen A (spherical shape)

28
Q

What does I B produce?

A

antigen B (triangle shape)

29
Q

What does I O produce?

A

no antigen

30
Q

Which two alleles for blood groups are codominant?

A

I A and I B

31
Q

Which allele for blood groups is recessive to the other two alleles?

A

I O

32
Q

What two genotypes express blood group A?

A

I A I A and I A I O

33
Q

What two genotypes express blood group B?

A

I B I B and I B I O

34
Q

What genotype expresses blood group AB?

A

I A I B

35
Q

What genotype expresses blood group O?

A

I O I O

36
Q

How many chromosomes are there in a human body cell?

A

46

37
Q

What are the two chromosomes found in males?

A

XY

38
Q

What are the two chromosomes found in females?

A

XX

39
Q

Give an example of a characteristic determined by a gene linked to X and Y chromosomes

A

Haemophilia

40
Q

What is haemophilia?

A

slow blood clotting due to absence of clotting factor

41
Q

What does XH represent?

A

the dominant ‘healthy’ allele on the X chromosome

42
Q

What does Xh represent?

A

the recessive allele coding for haemophilia on the X chromosome

43
Q

What does Y represent?

A

the Y chromosome which has no allele attached to it

44
Q

What is dihybrid inheritance?

A

the inheritance of 2 genes

45
Q

What is the expected phenotypic ratio of the F2 generation of a dihybrid cross test?

A

9:3:3:1

46
Q

Why might the phenotypic dihybrid cross-ratio differ in reality?

A
  • fertilisation is random
  • sometimes the genes may be linked so always inherited together
47
Q

What is autosomal linkage?

A

It is the inheritance of linked genes on the chromosomes other than those that determine sex (XX & XY)

48
Q

How are linked genes inherited together?

A

They don’t usually undergo independent assortment but they may sometimes be separated by crossing over.

49
Q

If alleles are linked, what does this produce?

A

more gametes containing that combination of linked alleles

50
Q

What are recombinant allele combinations?

A

Allele combinations that are only produced occasionally during crossing over

51
Q

What is x^2/ chi-squared for?

A

statistical test to measure if there is a significant difference between the observed and expected results in a genetic cross

52
Q

What is the null hypothesis of genetic crosses?

A

There is no significant difference between the observed and expected and any difference is due to chance alone.

53
Q

What is the equation for chi-squared?

A

x^2 = the sum of (O - E)^2 / E

54
Q

How do you work out the critical value?

A

Usually use 0.05 and the degrees of freedom is the number of possible outcomes - 1

55
Q

Do we accept or reject the null hypothesis when x^2 is less than the critical value?

A

accept and we say there is no significant difference between the observed and expected, any difference must be due to chance

56
Q

Do we accept or reject the null hypothesis when x^2 is more than the critical value?

A

reject and we say that there is a statistically significant difference between the observed and expected so there must be a reason for this

57
Q

Which type of graph can be used to present continuous data?

A

line graph

58
Q

Which type of graph can be used to present discontinuous data?

A

bar chart

Biology (21 decks)

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