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alevel biology ocr > chapter 20- patterns of inheritance and variation > Flashcards

chapter 20- patterns of inheritance and variation Flashcards

1
Q

describe in words how this phenotypic ratio might be different if the 2 genes were autosomally linked (1)

A

higher proportion of heterozygous/like parents

alleles not completely remixed

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2
Q

what does F1 generation mean

A

first filiel generation and it is the first set of offspring produced by a set of parents

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3
Q

what is F2 generation

A

result of a cross between 2 F1 individuals

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4
Q

Agammaglobulinemia and Vici syndrome are both genetic diseases.
Agammaglobulinemia results in a lack of mature B lymphocytes in a person’s blood.
i. Suggest and explain one symptom of agammaglobulinemia. (2)

A

greater susceptibility to infection/pathogens

no or fewer antibodies /effector/plasma cells

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5
Q

A ratio that is different from the expected 9 : 3 : 3 : 1, in a cross such as this, can be the result of
epistasis.
Suggest and explain one reason, other than epistasis, why the phenotype ratio might not be 9 :
3 : 3 : 1. (3)

A

autosomal linkage

both genes/alleles occur on the same chromosome

no independent assortment

so alleles are inherited together and end up in the same gamete

unless crossing over occurs

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6
Q

what is epistasis

A

when one gene modifies the allele of another gene eg suppress to control one phenotypic trait

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7
Q

which chromosome is the recessive allele for haemophilia carried on

A

the X chromosome

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8
Q

crude oil contains hydrocarbons, the oils dont breakdown easily and harm sealife. some bacteria can breakdown the hydrocarbons, they ahave been used by conservationists at oil spill sites

the bacteria are more common is places where oil spills are common
suggest an explanation for this observation (1)

A

adapted to occupy the niche oil spill environment

outcompete other bacteria

oil is acting as a selective agent, selection of bacteria that were able to digest the oil

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9
Q

suggest one way in which genetic diversity can be measured (1)

A

genetic polymorphism
proportion of heterozygotes/gene variants

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10
Q

explain why a genetic bottleneck can lead to low genetic diversity

A

many alleles lost when population dropped

modern pop descended from few survivors

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11
Q

what is intraspecific variation

A

Intraspecific variation is when organisms of the same species have different characteristics.

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12
Q

what are the 2 types of intraspecific variation and what is each of them caused by

A

genetic variation and phenotypic variation

genetic- genetic factors

phenotypic- genetic and environmental factors

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13
Q

what is genetic variation

A

Genetic variation is the difference in DNA between organisms of the same species.

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14
Q

which 2 events lead to genetic variation

A

meiosis during which different combinations of gamete alleles are produced.

sexual reproduction, where two gametes randomly fuse at fertilisation.

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15
Q

When a fruit fly is given its regular food, it is black in colour.

However, if it is fed silver salts, it becomes yellow in colour.

This is an example of how ….. can cause …

A

environmental factors can cause phenotypic variation

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16
Q

What is monogenic inheritance?

A

Monogenic inheritance is the inheritance of one gene.

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17
Q

What is a dominant allele?

A dominant allele is an allele that, when present, is…

A

always expressed in the phenotype

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18
Q

Define phenotype.

A

The phenotype is the expression of the genotype and its interaction with the environment.

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19
Q

Two heterozygous pea plants are crossed.

The genotypes of the parents are Pp.
so the … of the parents are P and p

A

gametes

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20
Q

what is the expected ratio for a monohybrid cross and give an example

A

3:1

3 pea plants had purple flowers and 1 had white

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21
Q

What is dihybrid inheritance?

A

Dihybrid inheritance is the inheritance of two genes.

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22
Q

In pea plants, one gene codes for ….. colour, and another gene codes for the …. of the pea plant. The two genes are found on ….

The dominant allele of the first gene (P) produces ….. flowers, while the recessive allele (p) produces …… flowers.

The dominant allele gene of the second gene (T) produces …… plants, while the recessive allele (t) produces …. plants.

A

flower
height
on two different chromosomes.

purple
white
tall
short

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23
Q

Two pea plants that are heterozygous for both genes (flower colour and height of plant) are crossed.

What is the genotype of the parent pea plants?

and what are the gametes

A

PpTt

PT
Pt
pT
pt

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24
Q

The phenotypic ratio of offspring that are tall with purple flowers : tall with white flowers : short with purple flowers : short with white flowers is ..

A

9:3:3:1

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25
Q

what is incomplete dominance

A

incomplete: when neither allele is dominant and hence both alleles are expressed and contribute equally to the phenotype. a heterozygote has an intermediate phenotype as there is partial influence from both alleles

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26
Q

when writing genes and alleles in codominance/incomp how are they written

A

with the gene expressed as a captial letter and the alleles as superscripts

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27
Q

give an example of a phenotypic ratio that indicates codominance

A

1:2:1 eg in the colour of snapdragon flowers

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28
Q

in an example of codominance in a monohybrid cross the parents are pure breeds red (CrCr) and white (CwCw)

what are the gametes and what is the genotype of all the offspring (F1)

snapdragon example

A

all gametes for red are Cr and for white all Cw

the offspring are all CrCw which means that they are all pink

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29
Q

Define codominance

A

Alleles are codominant when both alleles for a single gene contribute to the phenotype.

both alleles are expressed equally and contribute to the phenotype, with there
either being a blend of the two characteristic or both characteristics being seen together.

when both alleles are dominant and therefore both expressed in the phenotype, these alleles are independent and so there is no blending of characteristics, instead the phenotype is as a result of the full expression of both alleles.

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30
Q

blood groups is an example of …

and what are the 4 blood groups

A

codominance

group:
A
B
O
AB

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31
Q

what are the 3 alleles for blood type in humans

A

I^A
I^B
I^O

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32
Q

which alleles for blood type are codominant and which is recessive

A

I^A and I^B are dom
I^O is rec

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33
Q

When neither A nor B alleles are present, the blood type is ..

A

O

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34
Q

What is the blood type of a person with the genotype I^A I^A

A

group A

35
Q

What is the blood type of a person with the genotype I^A I^O and why is this

A

group A

o is recessive

36
Q

What is the blood type of a person with the genotype I^B I^B

A

group B

37
Q

What is the blood type of a person with the genotype I^B I^O

A

group B

38
Q

What is the blood type of a person with the genotype I^A I^B and why is this

A

group AB

both alleles are codominant and so are both expressed

39
Q

What is the blood type of a person with the genotype I^O I^O

A

group O

40
Q

group O means that that person is a …. and why

A

universal donor because the rbcs will have no antigens and therefore cannot detect any other type of rbc as non self??

41
Q

group AB means that that person is a …. and why

A

universal recipient because they have both A and B antigens and so they cant detect any of the rbcs as nonself?

42
Q

with parents gametes I^A and I^B and parent 2 as I^O and I^O what is the phenotypic ratio of offspring with type A to type B

A

1:1

43
Q

what does the allele I^A and allele I^B code for

A

a is for antigen A on the surface of rbcs and b is for antigen B

the antigens are used for recognising self and foreign blood groups

I^O doesnt code for any antigen

44
Q

individuals are either rhesus positive or negative depending on the presence/absence of ….

and which is which

A

antigen D

positive has antigen D and negative doesnt

allele Rh+ is dom to -

45
Q

what is the probability of having blood group AB+, B+, A+, O+

and AB-, B-, A-, O-

A

3/16

1/16

46
Q

what is sex linkage

A

Sex linkage is when genes are located on the sex chromosome. This means that allele expression depends on the sex of the individual.

47
Q

which chromosome is the gene that causes haemophilia located on and is the allele dominant or recessive

A

on the X chromosome
it is recessive (h)

haeomophilia is controlled by a single gene

48
Q

eye colour is also controlled by a single gene but it isnt located on a sex chromosome.

are the alleles for brown and blue eyes dominant or recessive

A

brown is dom
blue is rec

49
Q

Why are cats with tortoiseshell fur almost exclusively female?
(context may be needed)

A

males only have one X chromosome and so more likely to occur in females than males

50
Q

what was good about mendel using pea plants

A

they are easy to grow

have a short life cycle and produce lots of offspring

have easily observable characteristics

51
Q

why was mendel not getting a perfect 3:1

A

because some plants died/did not germinate
weather
herbivores eat the plant

52
Q

what is a locus/loci

A

the specific position on a chromosome that a gene occupies

53
Q

what are alleles

A

alternative forms of a the same gene which occupy the same locus on a pair of a homologous chromosomes

54
Q

how do alternatives forms of a gene usually arise and what could this mean

A

by spontaneous mutation and may alter the way in which a particular characteristic is expressed

frameshift
deletion

55
Q

what is a gene

A

a specific segment of DNA whose nucleotide sequence codes for a specific protein

sequence of bases/nucleotides in dna coding for a sequence of aas/protein

56
Q

what is a genotype

A

the genetic constitution of an organism comprising all the genes possessed by an individual

57
Q

what is a phenotype

A

the observable or measurable trait displayed by an organism as a consequence of its genotype

could be visible trait, experimentally determined trait eg blood group, or possession of eg enzyme

58
Q

what are homologous chromosomes

A

pairs of chromosomes of the same size and shape that carry genes for the same traits,

59
Q

explain how a change of one amino acid could lead to a change in the structure and properties of the haemoglobin protein (4)

A

different sequence of aas/primary structure

so a different aa will have a different r group

therefore secondary/tertiary/quaternary structure will change

due to a change in hydrogen, ionic bonds, disulphide bridges

Hb may not bond to oxygen

60
Q

explain what is meant by the term polygenetic inheritance (2)

A

idea of more than one gene for a single characteristic

at different loci

idea of giving rise to continuous variation

61
Q

some scientists have suggested that diet may affect the growth of a child

explain how the height of an adult human demonstrates how environmental factors with genotype (3)

A

malnutrition/lack of nutrition eg protein, calcium

nutrient is needed for specified growth eg protein for muscle

other relevant environmental factor that affect expression of genotype for height eg health/disease

environmental factor determining achievement of genetic potential

62
Q

colour blindness in humans is an example of a sex linked condition

which of the following is another example of a sex linked condition in humans

atherosclerosis
cystic fibrosis
haemophilia
lung cancer

A

haemophilia

63
Q

explain why colour blindness is more common in males than females (2)

A

it is caused by a recessive allele on the x chromosome

males only need one recessive allele and females need two recessive alleles to be colour blind

64
Q

what does variation rely upon and what is it acted upon by

A

relies on mutations within species

acted upon by selection pressures

the way that evolution via natural selection operates

65
Q

what is variation

A

the existence of variety and differences within and between species

66
Q

what is intraspecific variation

A

members of the same species differ

67
Q

what is interspecific variation

A

one species differs from another species

68
Q

what are the 2 main causes of variation

A

genetic differences and environmental differences influences

69
Q

what are the 2 FORMS of variation (not intra/inter)

A

continuous and discontinuous

70
Q

what is continuous variation, what is it controlled by, inc egs

A

complete range of measurements from one extreme to another

it is quantitative (can be given a measurement)

result of combined effect of many genes (polygenic inheritance)

significantly affected by environmental influences

eg height, mass, milk yield in litres in cows

71
Q

how can continuous data be displayed

A

can have a central mean, commonly displayed on an inverted U, and its a discrete measurement

use a tally chart and plot results on a histogram (NO GAPS BETWEEN BARS)

72
Q

what is discontinuous variation, what is it controlled by, inc egs

A

when individuals fall into a number of distinct classes or categories

controlled by alleles of a single or small number of genes, environment has little/limited effect

it is qualitative- cannot be given a measurement

eg male or female, blood groups, earlobes (attached or detached)

73
Q

how should discontinuous data be displayed

A

on a bar chart that has each distinct category as bars, THAT HAVE EQUAL GAPS BETWEEN THEM

74
Q

what environmental factors could influence plants

A

amount of sunlight, rainfall, mineral availability, soil pH, temp, soil conditions

75
Q

suggest an explanation for the changes in mean height of these two groups of adult males (2)

one northern european and one southern

A

there is a change in diet or difference in diets between N and S

eg the one has more protein

improved healthcare or better sanitation

less effects of disease on growth

differences due to migration and these changes the gene pool as a result of migration

76
Q

what is a pedigree analysis diagram? they show…

A

Pedigree analysis diagrams show the inheritance of a particular phenotype over several generations.

77
Q

on a pedigree analysis diagram, what does a half shaded shape mean

A

the person is a carrier and carry the recessive allele associated with the phenotype but don’t show the phenotype themselves.

and so is heterozygous

78
Q

if the allele coding for the phenotype is dominant X-linked

what is the frequency in males/females and what is the child parent links

A

equal/slightly more females

father-daughter

79
Q

if the allele coding for the phenotype is dominant Y-linked

what is the frequency in males/females and what is the child parent links

A

males only

father-son

80
Q

if the allele coding for the phenotype is recessive X-linked

what is the frequency in males/females and what is the child parent links

A

more males
mother-son
father-daughter

81
Q

what is mendels first law: in a cross between plants bearing contrasting characteristics these ….

A

characteristics segregate in the second filial generation

during monohybrid cross characteristics do not blend together. they retain distinct individuality and separate unchanged in the f2 generation

82
Q

what is mendels second law: law of independent assortment

A

mendel argued that when plants make pollen grains and ova (gametes) the factor pairs separate so that each gametes

83
Q
A

alevel biology ocr (29 decks)

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