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Biology > 6.2 - Patterns of inheritance > Flashcards

6.2 - Patterns of inheritance Flashcards

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1
Q

What is interspecific variation?

A

-Variation between two different species

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2
Q

What is intraspecific variation?

A

-Variation between members of the same species

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3
Q

What is discontinuous variation?

A
  • Variation controlled solely by genetics (For example: Human blood type)
  • This is caused by one gene (Monogenic)
  • Discontinuous variation is when there are two or more distinct categories in which each individual falls into only one of these categories, there are no intermediates (For example: Blood group in humans)
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4
Q

What is continuous variation?

A
  • Variation that is caused by multiple genes (Polygenic) and the environment working together (For example: Height/mass of an organism)
  • Continuous variation is when a population may vary within a range
  • There are no distinct categories (For example: Humans can be any height within a range they aren’t just tall or short so can have intermediate values)
  • The data is quantitative
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5
Q

What is etoilation?

A

-Elongation of the stem in between nodes so that plants in shaded areas can reach sunlight

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6
Q

What are three examples of environmental contributions to variation?

A
  • Diet in animals
  • Etoilation in plants
  • Chlorosis in plants
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7
Q

How does sexual reproduction lead to genetic variation within a species?

A
  • Crossing over in prophase 1
  • Independent assortment in metaphase 1 and 2
  • Random fertilisation of gametes
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8
Q

What is monogenic inheritance?

A

-The inheritance of one gene

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9
Q

What is dihybrid inheritance?

A

-The inheritance of two genes on different chromosomes which are expressed as two separate phenotypic characteristics

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10
Q

What is an allele?

A

-A different version of the same gene

For example: R and r are different alleles of the same gene which code for different characteristics

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11
Q

In which situations would you not get a 9:3:3:1 phenotypic ratio from a dihybrid cross?

A
  • If epistasis occurs

- If the homozygous recessive individual inherits a disease and doesn’t survive

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12
Q

What is multiple alleles?

A

-When more than two alleles code for a phenotype

For example: Blood groups

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13
Q

What is codominance?

A

-When neither allele in a gene is dominant so both alleles are expressed at the same time

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14
Q

What is autosomal linkage?

A
  • When genes that are close together on chromosomes are more likely to be inherited together
  • This is because they are not likely to be separated by independent assortment
  • Linkage causes the chance of a 9:3:3:1 as some allele combinations are less likely due to linkage
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15
Q

What is the predicted ration from the crossing of two double heterozygous parents?

A

9:3:3:1

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16
Q

What is epistasis?

A
  • The interaction of genes at different loci (Usually on different chromosomes
  • This prevents the expected 9:3:3:1 ration as one gene could code for a protein that inhibits or activates another gene so the ratio is affected due to the interaction between one gene that is expressed and another which may not have been expressed
17
Q

What is the purpose of a chi squared test?

A

-A chi squared test is used to test whether is a significant difference in the observed value and the predicted value

18
Q

What is stabilising selection?

A

-Where the mean phenotype is favoured in selection and extreme phenotypes would likely be eliminated
-There would be an increase in allele frequency at the mean and a decrease in allele frequency at extremes
(For example: Babies of low and high birth weights have a higher mortality rate as they are prone to birth complications. This means that, as babies of an average birth weight are less likely to have these complications they are more favoured and more likely to be selected for than the extreme conditions, low and high birth weight)

19
Q

What is positive selection?

A

-When individuals with desirable (Favoured) characteristics are selected for and then pass the alleles for this phenotype on to the next generation

20
Q

What is negative selection?

A

-Individuals with extreme phenotypes would be selected against meaning that the frequency for these alleles would decrease

21
Q

What is directional selection?

A

-When one of the extreme phenotypes is selected for and another extreme phenotype is favoured against (This selection pressure may be due to an environmental change, which causes particular adaptations to have a survival advantage)
-This would cause an increase in allele frequency at one of the extremes (The favoured phenotype) and a decreases in allele frequency in the other extreme (The phenotype that is favoured against)
(For example: Antibiotic resistance, chance mutations cause some bacteria to develop penicillin resistance. These resistant bacteria survive the selection pressure of penicillin treatment and they are then selected for to survive and pass on their alleles to the next generation. This would increase the frequency of the alleles coding for antibiotic resistance relative to the alleles that don’t give resistance)

22
Q

What is disruptive selection?

A

-Disruptive selection favours both the extremes in a range of phenotypes, so the intermediate phenotypes are selected against and more than one distinct phenotype is selected for, leading to more than one modal class
(For example: Male salmon size, the larger male salmons are aggressive and fight other males to fertilise the eggs while the smaller ones hide among the rocks to fertilise the eggs. This means that the intermediate sized salmon are too big to hide and to small to size so they would be favoured against
-The large and small males are successful and they pass on their alleles. The intermediate males do not pass on their alleles, resulting in a decrease in this size of male salmon

23
Q

What is genetic drift?

A
  • The random change in frequency of alleles over time
  • Each generation differs from the parental allele frequency due to the random variation caused when creating gametes (Crossing over and independent assortment)
  • Over time some alleles may be lost and others increase in frequency
  • Genetic drift impacts on smaller populations more as rare alleles are more likely to be randomly lost
  • This decreases the genetic diversity due to the genetic drift
24
Q

What is a genetic bottleneck?

A

-Genetic bottleneck comes about when there is a massive reduction in the population size
-This can be caused by a natural disasters or a human impact which causes a big reduction in the gene pool
-This reduction in the gene pool causes a decreased chance of survival from disease
-This means that the population would be more affected by genetic drift as they are an unstable population
(For example: The northern elephant seal and the cheetah have been affected by poaching which has caused a genetic bottleneck as the genetic variation in both species has been reduced so they share similar alleles within the population and are more susceptible to extinction via disease

25
Q

What is the founder effect?

A

-When a few organisms from a population start a new population and therefore, there are only a small number of different alleles from the initial gene pool
-The new population grows with reduced genetic variation, and will be more likely to be influenced by genetic drift
-There is more likely to be an increase in recessive disorders in these small populations
(For example: The Amish population had a smaller population with smaller genetic diversity so they were more influenced by recessive disorders such as a condition where the individual has more than 5 fingers)

26
Q

What are the conditions of the Hardy-Weinberg principle?

A
  • The population is large
  • Mating within the population is random
  • The population is isolated
  • There are no selection pressures
  • No mutations arise
27
Q

What is the Hardy-Weinberg principle?

A

p + q = 1
p^2 + 2pq + q^2 = 1

p = The frequency of the dominant allele
q = The frequency of the recessive allele
p^2 = The frequency of the homozygous dominant genotype
2pq = The frequency of the heterozygous genotype
q^2 = The frequency of the homozygous recessive genotype
28
Q

What is a species?

A

-A group of organisms that can breed together to produce fertile offspring

29
Q

What is speciation?

A

-The formation of new species through evolution

30
Q

How can mutation arise during speciation?

A
  • The members of a population become isolated
  • Mutation arises in a population
  • This is passed to an offspring, it then increases in allele frequency in the population
  • Different populations are no longer able to breed together
  • This occurs over many generations
31
Q

How can the isolation of members in a population occur?

A
  • Allopatric speciation, where there is a geographical barrier
  • Sympatric speciation, where there isn’t a geographical barrier
32
Q

What is allopatric speciation?

A

-When a geographical barrier separates the two populations
-The populations then evolve differently due to different selection pressures and genetic drift
-Over many generations the species have become so different that if they came into contact again, they would not be able to successfully breed (As they are now 2 distinct species)
(For example: Different species were separated due to continental drift and they adapted due to different selection pressures and they evolved into distinct, different species)

33
Q

What is sympatric speciation?

A

-Organisms become separated due to non-geographical barriers
(For example: The courtship behaviours in birds are different, as they have adapted to attract their mates in different ways. Over time different alleles emerged which has lead to the different species being distinct and not able to interbreed with each other as they are separate species, due to sympatric speciation)

34
Q

What are some examples of sympatric speciation?

A
  • Different courtship behaviours
  • Different breeding seasons
  • Different times of day for breeding
  • Incompatibility of genitalia
  • Incompatibility of gametes (Different chromosome number)
35
Q

What is artificial selection?

A

-Where the selection of a plant or animal with desirable characteristics is chosen by the farmer/breeder and the individuals with these characteristics are bred together so the offspring has the desirable traits

36
Q

What are the ethical considerations of using artificial selection?

A
  • Artificial selection decreases the gene pool
  • It can lead to more homozygous recessive disorders
  • The desired trait may be inherited with an undesired trait that could cause disease
  • Breeders may select animals/plants based upon aesthetical appearance/looks rather than the offspring’s potential health

Biology (23 decks)

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