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Biology > Unit 6 - Patterns of Inheritance > Flashcards

Unit 6 - Patterns of Inheritance Flashcards

1
Q

Genotype

A

Allele combinations possessed by an organism leading to specific phenotypes

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2
Q

Discontinuous variation

A 
Qualitative differences 
Clearly distinguishable categories (categorical)
Monogenic inheritance 
One/two genes 
An allele has a large effect
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3
Q

Continuous variation

A 
Quantitative differences
Phenotypic diff have a wide range of variation in a pop. (sig affected by environment)
Each allele has a small effect 
Polygenic inheritance 
Large number of diff genes involved
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4
Q

Monogenic inheritance

A

One gene w/ 2 or more alleles

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5
Q

Monohybrid cross

A

1 gene, 2 alleles (r and d)

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6
Q

Drawing genetic crosses

A

Parental genotype
Parental phenotype
Parental gametes
F1 ratio for genotype then phenotypes

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7
Q

Codominant inheritance

A

Involves more than one dominant allele

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8
Q

Multiple alleles genetic crosses

A

1 trait
1 gene
>2 alleles

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9
Q

Example of multiple allele genetic cross

A

Blood group
I A
I B
I O

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10
Q

3 ways genetic variation arises from sexual reproduction

A

IA of homologous chromosomes (M1)
Crossing over
IA of sister chromatids (M2)

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11
Q

23rd pair of chromosomes

A

Only pair that varies in shape and size
X - v. large and doesn’t carry genes involved in sexual development
Y - V. small, no genetic info, but carries gene that causes formation of male embryos

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12
Q

Sex linked genes

A

Characteristics determined by genes carried on X and Y

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13
Q

Why do sex-linked genes affect males

A

Y is much smaller so only has one copy of the gene, if recessive allele is found on X but no D allele on Y, male will express the recessive trait (usually condition)
Most females will have a D allele present on the 2nd X chromosome so are either normal or a carrier

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14
Q

Examples of sex-linked conditions

A

Haemophilia - blood clots v. slowly due to a lack of protein blood clotting factor
Red-green colour blindness

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15
Q

Dihybrid cross

A

Used to show inheritance of 2 diff characteristics, 2 genes at diff loci, >2 alleles on each

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16
Q

Expected results of a heterozygous dihybrid cross

A

9:3:3:1

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17
Q

Why may the actual ratio vary from expected

A

Fertilisation is random

If there is no crossing over, alleles for 2 characteristics will be inherited together if on same chromosome

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18
Q

Autosome

A

Any chromosome that is not a sex chromosome

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19
Q

Autosomal linkage

A

2 separate genes are found on the same autosome
Represented by diff letters
Linked genes are inherited together so offspring usually show same combination as parents (certain gametes are more common)

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20
Q

W/ no crossing over in autosomal linkage

A

Gametes stay in parental comb. and offspring show 3:1 phenotypic ratio

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21
Q

What may prevent linked genes from being inherited together

A

If they’re separated by chiasmata

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22
Q

W/ crossing over in autosomal linkage

A

Genotypic and phenotypic ratios are variable
Parental types > cross-over type
Proportion depends on how often cross overs ocurred between two loci

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23
Q

Recombinant offspring

A

Offspring w/ a diff combination of alleles to either parent

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24
Q

Closer genes are located on a chromosome …

A

Less likely to be separated during crossing over –> fewer recombinant offspring

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25
Recombination frequency
Measure of amont of crossing over occured in meoisis - indicating level of linkage Also used to map genes loci ; 1% = distance of 1 map unit on chromosome
26
Calculating recombinant frequency
No of recombinant offspring/ total no. of offspring
27
50% recombination frequency
No linkage, separate chromosomes
28
<50% recombination frequency
Gene linkage and IA has been hindered Signifies autosomal linkage Linked genes are inherited together Crossing over produces few recombinant offspring
29
Homozygous
Has identical alleles on both chromosome
30
H0 in chi squared
There is no sig. difference between expected and observed values
31
Degrees of freedom in chi squared
No. of categories - 1
32
Epistasis
Interaction of genes at diff loci Genes masking the expression of other genes (not alleles) Gene regulaion is a example w. reg . genes controlling structural genes
33
When can epistasis be seen
Multistep reactions
34
Hypostatic
Gene affected by another gene | Cause the phenotype
35
Epistatic gene
Gene that affects the expression of another gene; can happen as a result of dominant or recessive alleles
36
Epistatic alleles
Another pair of alleles found at diff loci
37
Antagonistic epistasis
Dominant and recessive epistasis
38
Dominant epistasis
If there are ANY dominant alleles present in the epistatic alleles, masks expression of hypostatic alleles
39
Phenotypic ratio in a heterozygous dihybid cross w/ dominant epistasis
12:3:1
40
Recessive epistasis
Occurs when a pair of homozygous recessive alleles at one gene locus masks the expression of the hypostatic allele at a 2nd locus
41
Phenotypic ratio in a heterozygous dihybrid cross w/ recessive epistasis
9:3:4
42
Bivalent
Homologous pair of chromosomes
43
Chiasmata
Point representing where homologous touch and exchange genetic info
44
Gene pool
Total no.of genes and their alleles in a particular population
45
Assumptions of the Hardy-Weinberg Principle
Pop is v. large (reduced effect of genetic drift) Mating within pop. is random - no selective breeding No selective advantage for any genotype coded for by that allele No mutation No migration Gene pool is stable
46
Hardy Weinberg principle
A is dominant, p = freq. of A a is recessive, q = freq. of a p + q = 1 p^2 + 2pq + q^2 = 1
47
When to use p + q = 1
When given allele frequency
48
When to use p^2 + 2pq +q^2
When given phenotypes
49
Evolution
Changes in allele frequencies over time leading to changes in species
50
What can affect allele frequencies
Mutations - new advantageous alleles will remain in pop Natural selection Effects of small population Genetic drift Artificial selection and selective breeding
51
Selection
Increase in allele frequency
52
Stabilising selection
Selection pressure toward the centre increases no. of individuals at the modal values Extreme values are selected against and lost
53
Types of selection
Stabilising Directional Disruptive
54
Directional selection
Selection pressure towards one extreme moves the mode in this direction Extreme value is advantageous; more likely to survive and reproduce
55
Disruptive selection
Selection pressure toward the extremes creates two modal values Intermediae values selcted against - lose those alleles Creates two distnct populations e.g. Darwin's finches
56
Genetic drift
Random events causing changes in allele frequencies Effects are greatly increased in small pop or small gene pools Alleles in new generation will therefore be the genes of the 'lucky' individuals and not necessarily healthier individuals
57
Polymorphic
Genes w/ > 1 allele
58
Effects of small populations
Founder effect and genetic bottleneck reduce genetic diversity by creating small populations
59
Founder effect
Occurs when a small group of migrants that aren't genetically representative of the pop. from which they came from, establish in a new area New population is v. small w/ an increase in inbreeding and relatively low genetic variation
60
Why does inbreeding cause genetic diseases
Increases impact of recessive alleles and most genetic diseases are caused by recessive alleles
61
Genetic Bottleneck
Big events that cause drastic reduction in a parent pop leaving a surviving pop w/ v. low genetic diversity (unless they mutate)
62
Events that may cause genetic bottleneck
Overhunting to the point of extinction Habitat destruction Natural disasters
63
Process leading to Genetic Bottleneck
``` Orig population Large no. die Reduced population (some alleles lost) Reproduction New population w/ low genetic diversity ```
64
Order of conservation
Habitat Population Genes
65
Artifical selection and selective breeding
Humans use animal and plant breding to selectively develop particular phenotypic ratios by choosing spp individuals Occurs over several generations
66
Agent of selection in natural selection
Environment
67
Agent of selection in artifiicial selection
Human
68
Effect of allele frequencies in selection
Changes for both natural and artificial
69
Effect of evolution due to natural selection
Drives it
70
Effect of evolution due to artificial selection
Drives it then slows it down
71
Speed of natural selection
Slow
72
Speed of artifical selection
Fast
73
Ethical considerations w artificial selection and selective breeding
Health problems; certain traits may be exaggerated Reduction of genetic diversity - more susceptible to genetic diseases caused by r alleles, potentially useful alleles for the future lost
74
Speciation
Formation of new and distinct species through the course of evolution
75
Factors that may cause directional selection
Predation Habitat changes Competition
76
Environments that cause directional selection
Slowly changing environmental conditions in one direction
77
'Ingredients' for speciation
``` Existing genetically varying poulation Isolation: geographical or reproductive Time Different selective pressures Large change in allele frequencies ```
78
Why do you need diff selective pressures for speciation
Changes allele frequencies in diff directions
79
Allopatric speciation
Geographically isolated | Gene pool is physically separated so the sep pop can then evolve independently of each other
80
What causes changes in allele frequency in allopatric speciation
Accumulation of diff mutations forms separate gene pools Different biotic/ abiotic factors Differential reproductive successes
81
Sympatric speciation
Reproductively isolated Organisms inhabiting same area separated into 2 or more groups due to changes in alelles and phenotypes preventing them from successfully breeeding together
82
Examples of things causing reproductive isolation
``` Seasonal changes (Different flowering seasons) Mechanical changes (Changes in genitalia) Behavioural changes (Diff courtship rituals) ```
83
How does the presence of epistatic alleles inhibit the expression of the hypostatic allele
Epistatic allele codes for repressor protein/ TF Product of epistatic allele binds to promoter of hypostatic allele Product stops transcription or inhibits enzyme action of enzyme encoded by A
84
Causes of variation in continuous variables e.g. height
Environment Age Polygenic
85
Result of speciation
Gene flow restricted | Leads to diff specialisation

Biology (27 decks)

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