Inhertiance and Selection Flashcards

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1
Q

Genotype

A

The genetic constitution of an organism.

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2
Q

Phenotype

A

Observable characteristics of an organism.

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3
Q

Gene

A

Section of DNA that usually determines a single characteristic of an organism.

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4
Q

Locus

A

The position of a gene on a chromosome.

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5
Q

Allele

A

Alternate form of a gene.

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6
Q

Homologous chromosomes

A

Two loci that can each carry one allele of a gene.

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7
Q

Co-dominance

A

Two alleles both contribute to the phenotype.

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8
Q

Monohybrid Inheritance

A

The inheritance of a single gene.

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9
Q

Pure breeding

A

Results in two alleles that are the same for a particular gene.

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10
Q

Gene pool

A

All the alleles of all the genes of all the individuals in a population at any one time.

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11
Q

Allelic frequency

A

The number of times an allele occurs within the gene pool.

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12
Q

What are the 5 conditions of the Hardy-Weinberg principle?

A
  1. No mutations arise
  2. There is no selection, all alleles are equally likely to be passed onto the next generation
  3. Population size is large
  4. The population is isolated, there is no flow of alleles out or into the population
  5. Mating within the population is random
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13
Q

Hardy-Weinberg Equation:

A

p² + 2pq + q² = 1

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14
Q

What is a fault in the Hardy-Weinberg principle?

A

In practice not all alleles are equally likely to be passed onto the next generation. Only certain individuals will reproduce successfully to pass on their alleles.

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15
Q

Outline how the reproductive success of individuals affects allele frequency in a population

A
  1. All organisms produce more offspring than can be supported by the supply of food, light, etc.
  2. Despite this overproduction, the population size remains constant
  3. There is intra-specific competition
  4. Within any population there will be a gene pool containing a wide variety of alleles
  5. Some individuals will possess combinations of alleles that will make them better suited to the environment
  6. These individuals with advantageous alleles will reproduce and pass on their alleles to the next generation
  7. The new generation of individuals with advantageous alleles are more likely to survive
  8. Over many generations, the number of individuals with advantageous alleles will grow at the expense of individuals with less advantageous alleles
  9. The frequency of the advantageous alleles in the gene pool will increase whilst the less advantageous alleles will decrease
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16
Q

Selection

A

The process by which organisms which are better suited to their environment survive and breed, while those that are less well adapted fail to do so

17
Q

Directional selection

A

When individuals who vary in phenotype in one direction from the mean of the population are favoured. This changes the characteristics of the population.

18
Q

Stablising selection

A

Where individuals with average phenotypes are selected. This preserves the characteristics of a population.

19
Q

Speciation

A

The evolution of a new species from existing species

20
Q

Species

A

A group of individuals with similar genes and who are capable of breeding with one another to produce fertile offspring (belong to the same gene pool)

21
Q

Geographical Isolation

A

When a physical barrier prevents two population from breeding with one another.

22
Q

Outline Speciation

A
  1. Groups within a population become isolated in some way
  2. The flow of alleles between them cease
  3. The environmental factors each group encounters are different
  4. Selection will affect the two populations in different ways and so the type and frequency of alleles in each will change
  5. Each population will evolve along separate lines
  6. In time, the gene pool of the two population will become so different that even if they are reunited they would be unable to breed to produce fertile offspring, they would be separate species
23
Q

Recessive allele

A

The condition in which the effect of an allele is apparent in the phenotype of a diploid organism only in the presence of another identical allele.

24
Q

Dominant allele

A

A term applied to an allele that is always expressed in the phenotype of an organism.