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A2 Biology > Inheritance, selection and speciation > Flashcards

Inheritance, selection and speciation Flashcards

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1
Q

What is a gene?

A

A sequence of bases on a DNA molecule that codes for a polypeptide which results in a characteristic

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2
Q

What is an allele?

A

Different version of the same gene

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3
Q

What is meant by genotype?

A

The genetic composition of an organism

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4
Q

What is meant by phenotype?

A

The expression of genotype in an organism and it’s interaction with the environment

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5
Q

What is meant by a dominant allele?

A

It is always expressed in the phenotype of an organism

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6
Q

What is meant by a recessive allele?

A

An alleles whose characteristic will only appear in the phenotype if two copies are present- homozygous recessive

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7
Q

What are co-dominant alleles?

A

Alleles that are both expressed in the phenotype and neither one is recessive

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8
Q

What is meant by homozygous?

A

Two copies of the same allele , either dominant or recessive

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9
Q

What is meant by heterozygous?

A

When an organism carries two different alleles, usually one dominant and one recessive and can often be described as a “carrier”

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10
Q

What are gametes?

A

Sex cells i.e. egg and sperm. They only contain one allele for each gene

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11
Q

What is monohybrid inheritance?

A

The inheritance of a single characteristic/gene controlled by different alleles

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12
Q

What sex chromosomes do female mammals have?

A

XX

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13
Q

What sex chromosomes do male mammals have?

A

XY

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14
Q

How many pairs of chromosomes do humans have?

A

23

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15
Q

What is the name given to genes/ alleles found on either the X or Y chromosome?

A

Sex linked

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16
Q

What is meant by a species?

A

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

17
Q

What is meant by the gene pool?

A

The range of alleles present within a population of a species

18
Q

What is meant by allele frequency?

A

How often an allele occurs in a population

19
Q

What are the equations of the Hardy Weinburg equations?

A

p² + 2pq + q² = 1

P + q = 1

20
Q

What can the Hardy Weinburg equations

A

Allele and genotype frequency , percentage of population with a certain genotype

21
Q

What does each part of the Hardy Weinburg principle mean?

A 
P = frequency of dominant allele
Q = frequency of recessive allele
2PQ = frequency of heterozygous genotype 
p² = frequency of homozygous dominant genotype 
q² = frequency of homozygous recessive genotype
22
Q

What does the Hardy Weinburg principal predict?

A

The proportion of dominant and recessive alleles of any gene in a population remains the same from one generation to the next, provided certain conditions are met

23
Q

What conditions does the Hardy Weinburg equations need to meet?

A
  • No mutations
  • population is isolated
  • no selection of any sort
  • population is large
  • random mating occurs
24
Q

What is meant by selection?

A

Process that results in the best-adapted organisms in a population to survive, breed and pass on their favourable alleles to the next generation

25
Q

What is a selection pressure?

A

The environmental force altering the frequency of alleles in a populations gene pool

26
Q

What is a major cause in changes of allele frequencies in a population?

A

Gene mutations

27
Q

What are the different types of selection?

A

Natural , stabilising and directional

28
Q

What is stabilising selection?

A

The individuals with alleles for characteristics towards the middle of the range are more like to breed and produce ( peak part of a graph)

29
Q

What is directional selection?

A

Individuals with alleles for characteristics of an extreme phenotype are more likely to survive and reproduce, can be in response to an environmental change ( graph shifts to left or right)

30
Q

When does stabilising selection occur?

A

When environmental conditions remain constant

31
Q

What is speciation and when does it occur?

A

Formation of new species from an existing species, occurs when populations of the same species become isolated in some way I.e. Reproductively or geographically

A2 Biology (12 decks)

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