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Unit Sev Flashcards

(78 cards)

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1
Q

What is meant by the term genotype?

A

Genetic constitution of an organism

Refers to the specific alleles an organism carries.

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2
Q

What is meant by the term phenotype?

A

The expression of this genetic constitution (genotype) and its interaction with the environment

Includes physical traits and characteristics.

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3
Q

What are alleles and how do they arise?

A

Variations of a particular gene (same locus) → arise by mutation (changes in DNA base sequence)

Alleles can lead to different traits.

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4
Q

How many alleles of a gene can be found in diploid organisms?

A

2

Diploid organisms have 2 sets of chromosomes.

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5
Q

Describe the different types of alleles.

A
  • Dominant allele: Always expressed
  • Recessive allele: Only expressed when homozygous recessive
  • Codominant alleles: Both alleles expressed

Dominant alleles mask the expression of recessive alleles.

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6
Q

What does homozygous mean?

A

Alleles at a specific locus are the same

Example: AA or aa.

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7
Q

What does heterozygous mean?

A

Alleles at a specific locus are different

Example: Aa.

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8
Q

What does a monohybrid cross show?

A

Inheritance of one phenotypic characteristic coded for by a single gene

Used to predict the outcome of a single trait.

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9
Q

What does a dihybrid cross show?

A

Inheritance of two phenotypic characteristics coded for by two different genes

Demonstrates the principle of independent assortment.

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10
Q

What is the expected phenotype ratio in a monohybrid cross?

A

1:1

Represents the ratio of dominant to recessive phenotypes.

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11
Q

What is a pedigree diagram used for?

A

To show the inheritance of a genetic disorder in a family

Helps to determine genotypes and inheritance patterns.

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12
Q

What is the probability of a male offspring having a recessive disorder if both parents are carriers?

A

¼ (or 0.25)

Requires tracking of alleles through a pedigree.

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13
Q

What is a sex-linked gene?

A

A gene with a locus on a sex-chromosome (normally X)

Generally affects males more due to their single X chromosome.

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14
Q

Why are males more likely to express a recessive X-linked allele?

A

Males (XY) have 1 allele; recessive allele always expressed

Females need two copies for expression.

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15
Q

What is the expected phenotype ratio in a dihybrid cross?

A

1:1:1:1

Represents all combinations of traits from two genes.

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16
Q

What is autosomal linkage?

A

Two genes located on the same autosome (non-sex chromosome)

Results in alleles being inherited together.

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17
Q

How does crossing over affect linkage?

A

Can create new combinations of alleles

Closer genes are less likely to be split by crossing over.

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18
Q

What is autosomal linkage?

A

Two genes located on the same autosome (non-sex chromosome)

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19
Q

How are alleles on the same chromosome inherited?

A

They are inherited together during independent segregation of homologous chromosomes during meiosis

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20
Q

What can crossing over between homologous chromosomes create?

A

New combinations of alleles

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21
Q

How does the distance between genes on an autosome affect crossing over?

A

If the genes are closer together, they are less likely to be split by crossing over

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22
Q

In the example of fruit flies, what are the dominant alleles for body color and wing development?

A

Grey body color (G) and long wings (L)

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23
Q

What were the results of the cross between grey-bodied, long-winged flies and black-bodied, short-winged flies?

A

225 offspring with grey body & long wings and 220 with black body & short wings

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24
Q

What is the expected phenotype ratio if genes are not linked?

A

9:3:3:1 (tall, normal : tall, mottled : dwarf normal : dwarf, mottled)

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25
What is epistasis?
Interaction of non-linked genes where one gene masks or suppresses the expression of another
26
What does a chi-squared (X2) test determine?
If observed results are significantly different from expected results
27
What type of data is required for a chi-squared test?
Categorical data that can be divided into groups (e.g., phenotypes)
28
What are some reasons observed phenotypic ratios may differ from expected ratios?
* Random fusion of gametes * Autosomal linkage * Epistasis * Small sample size * Lethal genotypes
29
How is a chi-squared value calculated?
O = frequencies observed, E = frequencies expected (total n multiplied by each expected ratio)
30
How is the number of degrees of freedom calculated in a chi-squared test?
Number of categories - 1
31
What is a population?
A group of organisms of the same species in one area at one time that can interbreed
32
What is a gene pool?
All the alleles of all the genes in a population at any one time
33
What is allele frequency?
Proportion of an allele of a gene in a gene pool (decimal or percentage)
34
What does the Hardy-Weinberg principle state?
Allele frequencies will not change from generation to generation under certain conditions
35
What are the conditions for the Hardy-Weinberg principle to apply?
* Population is large * No immigration/emigration * No mutations * No selection for/against alleles * Mating is random
36
What is the Hardy-Weinberg equation?
p² + 2pq + q² = 1
37
What does 'p' represent in the Hardy-Weinberg equation?
Frequency of one (usually dominant) allele of the gene
38
What does 'q' represent in the Hardy-Weinberg equation?
Frequency of the other (usually recessive) allele of the gene
39
How can you find the percentage of heterozygous individuals using the Hardy-Weinberg equation?
Calculate 2pq
40
What is genetic variation?
Differences in phenotypes within a population due to genetic factors and environmental factors
41
What drives natural selection?
Predation, disease, and competition for survival
42
What is the first step in the principles of natural selection?
Mutations create new alleles
43
What is stabilizing selection?
Selection favoring average variations of a trait
44
What is directional selection?
Selection favoring one extreme variation of a trait
45
What is disruptive selection?
Selection favoring both extreme variations of a trait
46
What is speciation?
The process by which new species arise from existing species
47
What is allopatric speciation?
Speciation due to geographical isolation
48
What is sympatric speciation?
Speciation occurring without geographical isolation
49
What is genetic drift?
A mechanism of evolution where allele frequencies change due to chance
50
How does genetic drift affect small populations?
It has a stronger effect as chance influences allele frequencies more in small gene pools
51
What is genetic drift?
A mechanism of evolution in which allele frequencies in a population change over generations due to chance ## Footnote Genetic drift is particularly significant in small populations.
52
How does genetic drift affect small populations?
It has stronger effects due to a smaller gene pool, making chance a greater influence ## Footnote Examples include the bottleneck effect and founder effect.
53
What is the bottleneck effect?
A sharp reduction in population size that can lead to a decrease in genetic diversity.
54
What is the founder effect?
When a small, new colony forms from a main population, leading to reduced genetic diversity.
55
What can genetic drift lead to in terms of alleles?
Some alleles can become fixed or lost entirely.
56
True or False: Speciation and natural selection cause genetic variation.
False ## Footnote They act on existing genetic variation but do not cause it.
57
What is a community in ecological terms?
All the populations of different species living in the same place (habitat) at the same time.
58
Define an ecosystem.
A community and the non-living (abiotic) components of its environment.
59
What is a niche?
The specific role of a species within its habitat, including what it eats and where it feeds.
60
List advantages of species occupying different niches.
* Less competition for food/resources * One species can outcompete another if they occupy the same niche.
61
What is carrying capacity?
The maximum (stable) population size of a species that an ecosystem can support.
62
List factors that influence carrying capacity.
* Abiotic factors (e.g., light intensity, temperature, soil pH) * Interspecific competition * Intraspecific competition * Predation
63
How do abiotic factors affect population size?
Favorable conditions increase survival and reproduction, thereby increasing carrying capacity.
64
Explain interspecific competition.
Competition between organisms of different species that can reduce resource availability, limiting survival and reproduction.
65
Explain intraspecific competition.
Competition between organisms of the same species that affects population size based on resource availability.
66
Describe the predator-prey population cycle.
Populations fluctuate in cycles, with predator populations peaking after prey populations due to lag time.
67
How can the size of a population of slow-moving organisms be estimated?
Using quadrats and calculating the mean number per quadrat, then scaling up based on total area.
68
What is the mark-release-recapture method?
A technique to estimate population size of motile organisms by marking and releasing a sample, then recapturing.
69
List assumptions of the mark-release-recapture method.
* Sufficient time for marked individuals to mix * Marking does not affect survival * Limited immigration/emigration * No significant births/deaths
70
Describe primary succession.
The change in a community over time, starting with pioneer species that modify abiotic conditions.
71
What characterizes a climax community?
* Same species present over time * Fairly constant abiotic factors * Fairly stable populations around carrying capacity
72
How does conservation of habitats involve management of succession?
Preventing further succession to maintain a current stage of succession (plagioclimax) and preserving species.
73
Describe the conflict between human needs and conservation.
Human demand for resources leads to habitat destruction, necessitating conservation to protect biodiversity.
74
What is the importance of managing the conflict between human needs and conservation?
To ensure sustainability of natural resources for future generations.
75
Why might percentage cover be used instead of frequency?
Counting individual organisms may be too difficult or impractical.
76
Why is random sampling used in ecological studies?
To avoid sampling bias.
77
Explain the importance of a large sample size.
Minimizes the effect of anomalies and ensures the sample is representative.
78
What statistical test is used to determine the relationship between abundance and an environmental factor?
Correlation coefficient, e.g., Spearman’s rank.

Biology (8 decks)

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