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Genetic Variation Flashcards

1
Q

Allele

A

Different forms of a gene due to slightly different order of bases e.g. brown eyes and blue eyes

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2
Q

Allele frequency

A

A measure of the relative frequency of an allele on a genetic locus in a population

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3
Q

Asexual reproduction

A

Reproduction involving only one parent. Doesn’t produce genetic variation

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4
Q

Biological Population

A

All the members of one species that live in a defined area

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5
Q

Bottleneck effect

A

Where the population size is dramatically reduced by a random catastrophic event e.g. earthquake, storm. the population rebuilds without the diversity in the gene pool it once had.

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6
Q

Centromere

A

The part of a chromosome that attaches to the spindle during cell division, also holds two sister chromatids together at the start of meiosis

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7
Q

Chiasma

A

The point where two homologous non-sister chromatids exchange genetic material during meiosis. Plural is chiasmata

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8
Q

Chromatid

A

A threadlike strand made of DNA formed from a chromosome during the stages of cell division

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9
Q

Chromosome

A

A threadlike structure made of DNA on which the genetic information of an individual is stored

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10
Q

Cloning

A

Artificial production of genetically identical individuals

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11
Q

Co-dominance

A

When both alleles in a heterozygous genotype are dominant and are equally and independently expressed – e.g. the human blood type AB

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12
Q

Complete dominance

A

Complete dominance occurs when one allele is dominant and the other is recessive. Dominant alleles are completely dominant over the recessive allele and will always be expressed when present. If present that will be the phenotype. Recessive alleles are only expressed (in the phenotype) when both alleles inherited are recessive and there is no dominant alleles

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13
Q

Crossing over

A

Occurs during meiosis, when the homologous chromosomes line up at the equator, they may tangle, snap and exchange genetic information

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14
Q

Di-hybrid cross

A

A cross that studies the inheritance pattern of two genes

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15
Q

Diploid

A

A cell or organism with two copies of each chromosome, twice the haploid number of chromosomes, e.g. human body cells have 46 chromosomes (2 x 23)

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16
Q

DNA

A

Deoxyribonucleic acid. The genetic material of most living organisms. It plays a central role in the determination of hereditary characteristics by controlling protein synthesis in cells. It has a double helix shape

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17
Q

Dominant allele

A

The allele that is expressed when two different alleles of a gene are present in the cells in an organism, represented by a capital letter

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18
Q

Emigration

A

When an individual leaves a gene pool. As a result, some genes/alleles may be lost. This is one aspect of gene flow

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19
Q

Evolution

A

Is the change in the characteristics of a species over several generations. It relies on the process of natural selection, and gradual and cumulative changes in allele frequencies amongst the members of the population.

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20
Q

F1 generation

A

The first generation of offspring resulting from an arranged cross between selected parents in breeding experiments

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21
Q

F2 generation

A

The second generation of offspring in breeding experiments, obtained by crossing individuals of the F1 generation

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22
Q

Fertilisation

A

Fusing of egg and sperm

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23
Q

Founder effect

A

Random changes to a gene pool due to a few individuals establishing a new population. E.g. blown or drift to a separate island.

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24
Q

Gametes

A

Sex cells, these fuse together to form a zygote e.g. egg and sperm

25
Gene
A length of DNA that codes for a particular protein/enzyme
26
Gene flow
Genes are exchanged with other gene pools as individuals move between them (immigration and emigration). This provides sources of genetic variation and reduces genetic differences between populations.
27
Gene Pool
Refers to the total number of genes of every individual in a population
28
Genetic code
The genetic information in DNA which controls the manufacture of specific proteins by the cell , see cells def.
29
Genetic drift
Chance events can cause the allele frequencies of small populations to “drift” (change) randomly from generation to generation. This plays a significant role in very small populations such as those caused by the bottleneck and founder effects
30
Genome
An organisms’ complete set of DNA, including all of its genes. In humans, each body cell with a nucleus contains a copy of the entire genome
31
Genotype
The specific combination of alleles possessed by an organism e.g. AA
32
Haploid
A cell or organism with one copy of each chromosome, half the diploid number of chromosomes, e.g. human sex cells have 23 chromosomes
33
Heterozygous
This describes an organism that possesses two different alleles for a particular gene, one inherited from each parent e.g. Aa
34
Homozygous
This describes an organism that possesses two identical alleles of a particular gene, one inherited from each parent e.g. aa, AA
35
Homologous pair
Matching pair of chromosomes with the same genes but not necessarily the same versions of the gene (alleles). In diploid cells, each parent contributes one chromosome to the pair. These pair up and separate during meiosis
36
Immigration
When individuals enter a population, introducing new alleles to the gene pool. This is one aspect of gene flow
37
Incomplete dominance
Incomplete dominance refers to the inability for any allele to mask another allele. This Results in a blended phenotype.
38
Independent assortment
The random orientation of homologous chromosome pairs during metaphase I allow for the production of gametes with many different assortments of homologous chromosomes
39
Law of segregation
During meiosis, the two members of any pair of alleles segregate (separate) unchanged and are passed into different gametes
40
Lethal allele
A combination of alleles [you are told the combo] that are lethal.
41
Linked genes
Genes that are found on the same chromosome that also tend to be inherited together. This reduced genetic variation in the offspring
42
Locus
Position of a gene on a chromosome
43
Mate choice
Non-random mating, individuals may seek out particular phenotypes, increasing the frequency of these “favoured” alleles in the population (tends to reduce genetic variation). E.g. peacock
44
Meiosis
Cell division that results in four non-identical gametes each with half the chromosome number of the parent cell (haploid)
45
Mitosis
Cell division that results in two daughter cells, each having a nucleus containing the same number and kind of chromosomes as the mother cell
46
Monohybrid
A cross that studies the inheritance pattern of one particular gene
47
Multiple alleles
Multiple alleles are the many different versions of a trait that exist within a population. This results in more than 2 different phenotypes.This is where there are more than 2 different alleles, although individuals will only inherit 2 of all the possibilities (one from each parent)
48
Mutation
A change in the base sequence of DNA. Can occur randomly or as a result of a mutagen
49
Natural Selection
A process that leads to changes in gene frequencies in populations over time. Certain allele combinations produce phenotypes that may be advantageous in the current environment and increase reproductive success (individuals more likely to survive and reproduce), in this way favourable genotypes are maintained in a population. It tends to reduce genetic diversity within the gene pool and increase differences between populations
50
Phenotype
The observable characteristics of an organism
51
Recessive allele
An allele which will only be expressed when the dominant allele is not present, shown by a lower case letter
52
Recombination
The exchange of alleles between homologous chromosomes as a result of crossing over
53
Species
A group of similar populations with individuals which can potentially interbreed and produce fertile offspring
54
Somatic cells
All the cells in the body except for the sex cells
55
Test-cross
When an organism with a dominant phenotype is crossed with an organism with the recessive phenotype. The pattern of traits seen in the offspring can determine whether the organism with the dominant phenotype is homozygous or heterozygous for that trait.
56
Traits
Features that are determined by genes (inherited)
57
True breeding
An individual that is homozygous for the gene involved (also known as pure-breeding).
58
Variation
Differences within and between species created by their different genetic make-up, may arise from changes to the DNA (mutation), through sexual reproduction (new combinations) or as a result of the effects of the environment (genes interact with environment to influence phenotype).

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