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biology > genetic variation defintions > Flashcards

genetic variation defintions Flashcards

(49 cards)

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1
Q

Allele

A

an alternative form of a gene

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2
Q

Centromere

A

point where the 2 chromatids are joined together

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3
Q

Chiasma

A

the point at which chromatids break and re-join in crossing-over.

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4
Q

Chromosome

A

a structure in the nucleus made up of DNA which holds the genetic information of an organism

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5
Q

Homologous pair

A

a pair of chromosomes with the same genes but may have different alleles

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6
Q

Diploid

A

full or complete number of chromosomes 2n / 2 sets (= 46 in humans)

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7
Q

Dominant

A

an allele that is always expressed if present (only one copy needed). Masks the recessive allele.

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8
Q

F1 and F2

A

first and second generation offspring

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9
Q

Gamete

A

sex cell. Egg or sperm in humans

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10
Q

Gene

A

a section of a DNA molecule that codes for a protein/characteristic

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11
Q

Gene pool

A

the total variety of genes and alleles present in a sexually reproducing population available to be passed on to the next generation.

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12
Q

Genome

A

all of an organism’s genes.

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13
Q

Haploid

A

half the normal number of chromosomes n / 1 set ( 23 in eggs or sperm)

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14
Q

Heterozygous

A

alleles are different eg. Tt

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15
Q

Homozygous

A

both alleles are the same eg. TT, tt

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16
Q

Linked

A

Genes that are located on the same chromosome

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17
Q

Locus

A

position of a gene on a chromosome

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18
Q

Meiosis

A

type of cell division producing four daughter cells each genetically different, with half the number of chromosomes of the parent cell (produces gametes)

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19
Q

Crossing-over and recombination

A

exchange of genetic material between homologous chromosomes (the inner chromatids) during meiosis

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20
Q

Independent assortment

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A

Each homologous pair of chromosomes are lined up randomly and are sorted independently of the other pairs during meiosis putting chromosomes/alleles into new combinations increasing genetic variation

21
Q

Segregation

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A

In meiosis the two members of the pair of alleles of a gene becomes separated into different gametes (so the allele can join with a different allele of that gene at fertilisation)

22
Q

Mutation

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A

a sudden change in the genetic make up / in base order of DNA of an organism

23
Q

Phenotype

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A

how the gene is expressed/what the organism looks like. eg. tall.

24
Q

Recessive

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A

an allele that only expressed when it is present in two copies - the dominant allele must be absent

25
Somatic cells
body cells other than the sex cells.
26
Species
group of organisms which can interbreed sexually and produce fertile offspring.
27
Backcross/testcross
Finding the genotype of an individual showing dominant phenotypes by crossing them with a homozygous recessive individual and looking at the phenotypes of the offspring.
28
unlinked
genes not located on the same chromosome
29
Adaptation
a feature an organism has which helps it survive in its environment. Can be structural, behavioural or physiological
30
Allele frequency
the proportion of a particular allele in a gene pool, relative to the other alleles of the same gene
31
Evolution
changes in the frequencies of alleles in a population
32
Natural selection
The theory that, in a population the individuals with favourable combination of traits are more likely to reproduce successfully
33
Gene flow
The introduction of genes/alleles from one population to the gene pool of another
34
Gene pool
the total variety of alleles present in a sexually reproducing population available to be passed on to the next generation.
35
Genetic variation / diversity
All the genes, alleles and their combination present in a population
36
Genetic change
change to allele frequencies / base order in a gene pool / population
37
Genetic drift
random changes in allele frequencies in a population due to chance
38
Inbreeding
mating of closely related individuals of the same species
39
Migration
movement of individuals of a species into or out of a population
40
Population
members of the same species living in the same area at the same time
41
Environmental factors
factors which select for or against particular phenotypes (features) in the process of natural selection
42
Founders Effect
Change in allele frequencies when a new population arises from only a few colonising individuals. The new population will have reduced genetic diversity/smaller gene pool
43
Bottleneck Effect
Recovery of a population after a catastrophic event, the range of alleles will decrease and the frequencies of alleles will change. The recovered population will have reduced genetic diversity
44
Sexual Selection
Selection based on the choice of mating partners (usually female). This leads to evolutionary change if choices are based on differences in inherited characteristics (e.g. tail length in peacocks)
45
Complete Dominance
when one allele is completely dominant over the other and is always expressed when present
46
Incomplete Dominance
When two alleles, inherited from the parents, are neither dominant nor recessive. Heterozygous offspring have a phenotype that is a blending of the parental traits.
47
Codominance
When both alleles for a gene are fully expressed when present
48
Lethal Alleles
A mutated dominant alleles that cause an organism to die when present in homozygous condition
49
Multiple Alleles
When there are three or more alleles for a gene that codes for a single trait

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