Biology > Inheritance > Flashcards

Inheritance Flashcards

(54 cards)

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1
Q

Monogenetic inheritance

A

A trait is determined by the expression of a single gene or allele

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2
Q

Dominant allele

A

Version of a gene that will always be expressed if present in an organism

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3
Q

Reccessive allele

A

Only expressed if 2 copies are present

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4
Q

Homozygous

A

Organism has 2 identical alleles for a characteristic

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5
Q

Heterozygous

A

Have 2 different alleles for a characteristic

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6
Q

Phenotype

A

Observable characteristic which results from genotype/ environment

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7
Q

Genotype

A

All the genetic material in an organism

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8
Q

Codominance

A

When genotype for a feature is 2 dominant genes, both are expressed in phenotype

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9
Q

Sex linkage

A

A gene controlling a characteristic which is on a sex chromosome

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10
Q

Name 2 sex linked diseases

A

Colour blindness
Haemophilia

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11
Q

What is dihybrid inheritance?

A

Inheritance of two different genes at the same time

Alleles assorting independently if the genes are on separate chromosomes or far apart on the same chromosome

Each gamete carries 1 allele of each gene

4 possible genotypes

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12
Q

What is the usual ratio of a dihybrid cross?

A

9:3:3:1

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13
Q

Reasons for unexpected ratios

A

Random fertilisation

Autosomal linkage + crossing over

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14
Q

Autosome

A

Non-sex chromosome

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15
Q

Autosomal linkage + crossing over

A

Linked genes are inherited together

No independent assortment during meiosis unless alleles are separated by a chiasma

Crossing over more likely to occur if genes are spread out on chromosome (the closer together=behave more like monogenic)

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16
Q

Chi squared test purpose

A

To measure the significance of a difference between the expected and observed ratio of offspring

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17
Q

Chi squared outcome meanings

A

Chiasma value bigger than critical value, linkage/epistasis has occurred

Chiasma value less than critical value, linkage/epistasis has not occurred

Critical value= 95% or 0.5

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18
Q

Mendels law of independant assortment

A

Alleles of different genes assort independently during gamete formation.

So, allele inherited for one gene does not affect which allele is inherited for another gene.

As they’re on different chromosomes or far apart on the same chromosome.

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19
Q

Recombinant offspring

A

Offspring that have a different combination of alleles from their parents, due to crossing over during meiosis.

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20
Q

Dominant epistasis

A

A dominant allele at one locus masks the expression of alleles at a second locus.

E.g Aa AA

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21
Q

Epistasis

A

When one gene masks or modifies the expression of another gene at a different locus.

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22
Q

Reccessive epistasis

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A

A recessive allele at one locus masks the expression of alleles at a second locus.

E.g aa

23
Q

What 5 factors effect evoloution?

Study These Flashcards
A
  1. Mutation
  2. Sexual selection
  3. Gene flow
  4. Genetic drift
  5. Natural selection
24
Q

What is sexual selection?

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A

Alleles coding for characteristics that improve mating success and frequency

25
What is gene flow
Movement of alleles between populations, immigration and emigration contribute to fluctuations of these Smaller change to population
26
What is genetic drift?
Occurs in small populations. Change in allele frequency due to random mutations
27
What is natural selection?
Animals with favourable characteristics survive, alleles coding for these characteristics therefore are inherited.
28
Epistatic gene
Gene that masks the expression of another gene.
29
Hypostatic gene
Gene whose expression is masked by the epistatic gene
30
What does the Hardy Weinberg principle state?
In a stable, non-evolving population, allele frequencies stay constant.
31
What is the formula for Weinbergs principle?
P^2 + 2pq + Q^2 = 1 (Descries the genotypes of individuals alleles) P+Q=1 (Describes the gene pool of all the alleles in a population)
32
What are the 4 factors that effect evolution?
1. Mutation 2. Change in population size 3. Genetic drift 4. Selection of favourable variables
33
What factors do we assume stay the same to use Winbergs principle?
Large population size No mutations No selection pressures/evolution Random mating
34
What does each letter represent in Weinberg's formula?
P=Dominant allele PQ= Heterozygous Q=Recessive allele
35
Why does mutation effect evoloution?
Causes genetic variation, favourable alleles remain in the population, disadvantageous alleles won’t
36
What is a density dependent factor?
Effect the population due to its size. E.g competition
37
Density independent factors?
Effect the population regardless of its size. E.g natural disasters
38
What are density independent factors?
Effect the population regardless of its size. E.g natural disasters
39
What is a genetic bottleneck?
An event that drastically reduces the size of a population and its gene pool (Natural disaster)
40
What is the founder effect?
A few, originally ‘rare’ alleles are favoured and form new population
41
What is sexual selection?
Increase in alleles that promote mating success
42
What is natural selection?
Increase in alleles that promote survival success
43
What is stabilising selection?
When there are less individuals with extreme phenotypes, more with the average phenotype
44
What is disruptive selection?
When 2 extremes are favourable
45
What is directional selection?
More individuals in one particular extreme
46
What is allopatric speciation and why does it cause speciation?
When a physical barrier separates a population Populations exposed to different selection pressures Different alleles selected for survival due to different conditions Change in allele frequency in gene pool Characteristics are accumulated until a new species is formed
47
What is sympatric speciation?
The population lives in the same area, but splits into two groups with no gene flow between them
48
What are the 2 types of symatric speciation?
Ecological, behavioural
49
What is ecological seperation?
Groups live in different environments within the same area
50
What is behavioural seperation?
Groups develop different behaviours which prevent mating
51
What is reproductive isolation?
Changes in alleles or phenotypes prevent certain individuals from breeding successfully with others in the same population
52
What is seasonal isolation?
Individuals reproduce at different times of year
53
What is behavioural isolation?
Changes in courtship behaviour prevents the attraction of mates
54
What is mechanical seperation?
Changes in genitalia prevent successful mating
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