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Biology > Genetics > Flashcards

Genetics Flashcards

1
Q

Define: Variation

A

All of the differences found in a population due to the differences in individuals DNA/genes/alleles

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2
Q

Define: Genetic Boidiversity

A

the number and range of types of living things seen within a community or ecosystem

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3
Q

Define: Species

A

A group of organisms that are able to breed together and produce viable and fertile offspring

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4
Q

Define: Population

A

Members of the same species living in the same area at the same time

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5
Q

Define: Allele frequencey

A

The proportion of a particular allele in a gene pool relative to other alleles of the same gene

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6
Q

Define: Gene pool

A

All the genes and alleles present in a sexually reproducing POPULATION that can be passed onto the next generation

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7
Q

Define: Mutation

A

A sudden change in the DNA of an organism, only source of new alleles

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8
Q

What do mutations do and how does it effect the gene pool?

A
  • It create new alleles that are able to be inherited and then enter the population and to be passed on
  • creates more genetic variation within a population and increases the size of the gene pool
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9
Q

What do mutations do and what is the effect on organisms?

A

Mutations can be beneficial, neutral or detrimental, they cause new proteins to be created by the DNA as the base sequence has been changed, some mutations are longer hair (can be positive depending on the climate), blue eyes (neutral) or hemophilia (detrimental)

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10
Q

How can mutations become hereditary?

A

Mutations can only become hereditary if the mutation is on the gamete producing cells, this causes all newly produced gametes to have the new genetic material

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11
Q

How do mutations enter the gene pool?

A

Mutations enter the gene pool if they mutate the DNA on the reproductive cells (male=sperm, females=eggs), mutations on somatic cells (body cells) do not alter the gametes and therefore do not enter the population

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12
Q

How do mutations happen?

A

They can occur in two ways, either spontaneously (happens for no reason) or induced (caused by mutagens such as radiation, chemicals or sudden temp changes)

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13
Q

What are Karyotypes/Karyograms?

A

A picture of the chromosomes lined up from pair 1 (the biggest) to pair 22 (the smallest) plus the sex chromosomes http://worms.zoology.wisc.edu/zooweb/Phelps/ZWK99010k.jpeg

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14
Q

What is the purpose of meiosis?

A

To produce gametes for sexual reprodution and create variation

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15
Q

How does meiosis work?

A

It involves 10 steps: -Early Prophase 1 -Mid Prophase 1 -Late Prophase 1 -Metaphase 1 -Anaphase 1 -Telophase 1 -Prophase 2 -Metaphase 2 -Anaphase 2 -Telophase 2

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16
Q

What is Early Prophase 1? (meiosis 1)

A

chromosomes unscramble themselves, shortened and thickened and duplicate themselves, they then join at the centromere to form sister chromatids creating 92 chromatids (46 chromosomes)

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17
Q

What is Mid prophase 1? (meiosis 1)

A

homologous chromosomes (chromosomes that are the same type, ie same length, alleles on the same locus etc.) pair up forming tetrads (A set of 2 homologous chromosomes

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18
Q

What is Late prophase 1? (meiosis 1)

A

Spindle fibers and heads begin to form and the homologous pair of chromosomes swap genetic material between non-sister chromatids, then forming a chiasma - this is where crossing over occurs which causes a huge increases in genetic variation as this creates parental combinations and recombinations, this creates genetic variation as each gamete in the end has a unique set of unique chromosomes (independent assortment)

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19
Q

What is Metaphase 1? (meiosis 1)

A

the homologous chromosomes line up along the equator randomally and independently orient themselves, independent assortment occurs here which is a huge source of genetic variation as there are a huge number of combinations that can be created once the spindle fibers pull the homologus chromosomes apart.

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20
Q

What is Anaphase 1? (meiosis 1)

A

The spindle fibers pull apart the tetrads taking to each side of the nuclei 46 chromosomes (23 homologous pairs)

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21
Q

What is Telophase 1? (meiosis 1)

A

A new nuclei forms around each of the 23 homologous pairs of chromosomes forming 2 new unique nuclei with 23 unique homologous pairs in each

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22
Q

What is Prophase 2? (meiosis 2)

A

Spindle fibers and heads form, there is no duplication in meiosis 2

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23
Q

What is Metaphase 2? (meiosis 2)

A

The 23 homologous chromosomes independently line up along the equator again randomly, again this is independent assortment so massive genetic variation as there is a massive number of different combinations, spindle fibers attach themselves to chromatids

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24
Q

What is anaphase 2? (meiosis 2)

A

Spindle fibers pull apart the chromosomes

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25
Q

What is Telophase 2? (meiosis 2)

A

New Nuclei forms around the four sets of 23 chromatids creating a haploid cell, these are now gametes

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26
Q

Define: Segregation

A

The separation of pairs of of alleles during the formation of reproductive cells so that the gametes contain only one allele instead of the normal two. Segregation is the result of the separating homologous chromosomes during anaphase 2

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27
Q

Define: Independent assortment

A

When the homologous chromosomes line up along the equator RANDOMALLY and INDEPENDANTLYA of each other ceating new combinations of chromosomes

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28
Q

Define: Crossover/Recombination

A

Exchange of genetic material between inner chromatids of tetrads, swap over genetic material to form new combinations of the same chromosome *l~l* x ^l~l^ => ^l~l* ^l~l* ~=centromere

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29
Q

Define: Chiasma

A

The point where the inner chromatids of a tetrad break off and rejoin thereby exchanging genetic material during Crossover/Recombination

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30
Q

Define: Homologous chromosomes

A

A pair of chromosomes (one from each parent) that have the same genes at the same locus but may have have different versions of the genes (different alleles)

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31
Q

Define: Chromatid, identify it on this image and the anything else about the image

A

A single strand from the chromosome (chromosomes are made of 2 chromatids) 1 - chromatid, 2 - centromere, 4 - locus (locus has a gene on it), whole picture shows chromosome

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32
Q

Define: Centromere

A

the point where 2 chromosomes are joined together to form a chromosome

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33
Q

Define: Allele

A

An alternate form of a gene ie eye colour blue, green etc.

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34
Q

Define: Locus

A

The position of an gene on a chromosome

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35
Q

Define: Haploid

A

Half the number of chromosomes in a cell (23 chromatids ie gametes) also known as n=23

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36
Q

Define: Tetrad

A

A pair of homologous chromosomes that have paired up and are lining up along the equator ie Metaphase 1 —> ^l~l^ : *l~l* l=chromosome ^=allele A *=allele a :=equator ~=centromere

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37
Q

Define: Autosome/Autosomal

A

non sex chromosomes, humans have 44 autosomal chromosomes (22 pairs)

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38
Q

Define: Sex Chromosomes

A

The X and Y chromosomes that determine gender, for humans XX = female, XY= male

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39
Q

Define: Somatic cell

A

Body cells other than the sex cells, are diploid

40
Q

Define: Incomplete Dominance

A

When two recessive alleles are expressed together to create a blend of the 2 genotypes

40
Q

Define: Complete Dominance

A

When one allele is expressed over another, eg in Aa, A will be expressed fully over a

41
Q

Define: Co-Dominance

A

When two dominant alleles are expressed in equal quantity, ie roan cows, when a pure bred white cow mates with a pure bred red cow, genotype WR, the phenotype is a cow that is 50% red and 50% white

43
Q

Define: Lethal Alleles

A

Genes that have a a lethal effect when they exist as one of the homozygous genotypes

43
Q

Define: Dihybrid Inheritance

A

Crossing over of 2 non linked genes at the same time ie AaBb

44
Q

Define: Multiple alleles

A

Genes with 3 or more alleles

45
Q

Define: Geneome

A

All of the genes of an indivisual person

46
Q

Define: Genotype

A

A description of a persons alleles, ie AaBb etc.

48
Q

Define: Phenotype

A

The physical expression of the genotype

49
Q

Define: Homozygous

A

When the allele at a give locus are the same, ie ‘AA’ (can be recessive or dominant)

50
Q

Define: Hetrozygous

A

When the alleles at a give locus are not the same ie ‘Aa’

51
Q

Define: F1/F2 generation

A

The first and second generation of offsprings, ie Parents –> F1 generations –> F2 generation –> etc.

52
Q

Define: Punnet square

A

A box used to do genetic cross, ie ‘Aa’ x ‘Aa’

53
Q

Define: Dominant allele

A

The allele that is always expressed in the genotype (only 1 copy needed)

54
Q

Define: Recessive allele

A

The allele that is only expressed if homozygous, dominant allele must be absent

55
Q

Define: Test/back cross

A

Testing an unknown genotype showing dominant phenotypes by crossing organism with known homozygous recessive organism, from this we can determine the unkown genotype by looking at the ratios of offsprings and making a logical guess

56
Q

Define: Evolution

A

Changes in the allele frequency in a POPULATION over many generations

57
Q

Define: Natural selection

A

the process where organisms with more benefical alleles are more likely to survive in a given envrionment and are therefore more likley to pass on these successful alleles ontop their offspring

58
Q

Define: Migration

A

Movement of indivisuals in or out of a population

59
Q

Define: Genetic Drift

A

RANDOM changes in the allele frequency DUE TO CHANCE, such as extreme natural events,

60
Q

Define: Founders effect

A
  • Change in allele frequencies when a new populaion arises from a few colonising indivisulas whose allele frequencies are NOT represantive of original population
  • New population is geographically isolated from original population so there is no gene flow
  • different environmental factors which cause natural selection to favour organisms with different phenotypes which can lead to speciation
61
Q

Define: Bottleneck effect

A
  • Recovery of a population after a catastrophic event where only a few organisms survive
  • These organisms build up population again, however alleles may have been lost (few remaining indivisuals are highly unlikely to have represantitive allele frequency of old population), recovered population will have reduced GENETIC DIVERSITY
62
Q

Define: Non random mating/Artifical selection

A

When every oraganism doesn’t have an equal chance of mating (fruit flies won’t mate with white eye flies) or they are artifically bred (dogs, cats etc.)

63
Q

Define: Disruptive selection

A
  • When indivisuals with variations on either side of the mean are selected for while indivisuals with variations closest to the mean are selected aganist
  • This causes a population to develop 2 mean peaks going in different directions, over time this leads to speciation
64
Q

Define: Directional Selection

A

When a feature of a population on extreme side of the mean is more selected for while the other extreme side is selected aganist causing the mean of the population to move, ie peppered moths, during industrial revolution the moths that survived were darker so the darker the moth, the more likely it was to survive

65
Q

Define: Stabilising selection

A

When a feature of indivisuals on either side of the mean is selected aganist, this causes a very narrow and high mean with very little variation, ie Coelacanth fish have remained unchanged for millions of years as they have a very stablilising selecting

66
Q

Define: Autosome

A

Non sex-linked, not inherited

67
Q

What is meiosis?

A

Type of cell division producing 4 daughter cells each genetically different and with the haploid number of chromosomes

68
Q

Define: pedigree

A

An organism that is homozygous for all alleles

69
Q

Define: chromosome

A
  • A thread like structure that contains DNA
  • found in the nucleus of all living cells
  • it contains genetic the genetic code necessary for the production of proteins (FYI humans have 23 pairs of chromosomes, 22 autosomal pairs (non sex linked) and 1 pair of sex chromosomes (X and/or Y) giving a total of 46 chromosomes)
70
Q

Define: Linked genes

A

Genes that are located on the same chromosome

71
Q

Define: Dihybrid cross

A

When 2 different characteristics controlled by 2 NONLINKED genes are being crossed at the same time

72
Q

Define: Monohybrid cross

A

When 1 characteristic controlled by a gene or linked genes are being crossed over at the same time

73
Q

Describe a dihybrid cross

A

Phenotype ratio=9:3:3:1

74
Q

How do you cross linked genes?

A

You do a monohybrid cross but instead of just 1 genotype, you cross both

75
Q

How does the distance between genes on a chromosome affect it’s chance of recombination?

A

The further apart the genes are the more likely they will be split apart due to recombination as there is a higher chance that the chiasma will form between them

76
Q

What is the phenotype ratio of a cross between an AaBb x aabb if the genes are on the same chromosome?

A

1:1 (AaBb and aabb), this is because these genes are linked, however this ratio may not be exact and hetrozygous genotypes may be produced (Aabb or aaBb) in very small numbers due to random formation of chiasma during recombination causing the alleles to form recombinants

77
Q

What are the types of inheritance?

A

Co-dominance

Complete dominance

Incomplete dominance

Lethal allele

78
Q

What is complete dominance?

A

It is when a dominant allele is expressed over a recessive allele, dominant allele is expressed as either homozygous dominant or hetrozygous, a recessive allele can only be expressed as homozygous recessive ie eye colour where if a brown eyed person (BB) is crossed with a blue eyed person (bb) their offspring will be hetrozygous and all offspring will have brown eyes (Bb)

79
Q

What is codominance?

A

It is when 2 dominant alleles are crossed and they are equally expressed in the organism

80
Q

What is incomplete dominance?

A

It is when 2 recessive alleles are in a genotype and neither is expressed fully, instead they find a mid way point, ie snap dragons, white flower crossed with red flower produces pink flower as red and white alleles are recessive and pink is midway point

81
Q

What process of meiosis produces the most genetic variation? Why?

A

Independent assortment, this is beecause there are 2^23 different combinations that the homologus chromosomes can make when lining up on the equator, this process occurs twice. Also, unlike recombination, it effects both chromatids in the homologous choromosomes which means that more genetic material is being shuffled creating MORE VARIATION, recombination only swaps genetic material between the inside chromatids and only occurs once

82
Q

What is sexual reproduction?

A

It is the process of an egg and sperm cell fusing, each containing genetic material from either the mother or father. The fusion of these gametes produces a genetically different offspring from the mother and father

83
Q

Define Centromere

A

The point where 2 chromatids join to make a homologous pair

84
Q
A
85
Q

Define Chromosome

A

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

86
Q

Define Diploid

A

Full or complete number of chromosomes (somatic cells)

87
Q

Define Gamete

A

A sex cell (egg or sperm), it contains the haploid number of chromosomes

88
Q

Define Gene

A

A section of DNA on a chromosome that codes for a protein/characteristic

89
Q

Define geneome

A

all of an organisms genes

90
Q
A
91
Q

Define adaptation

A

A feature of an organism that helps it survive in its environment, can be structural, physiological or behaivoural

92
Q

Define gene flow

A

The introduction of genes/alleles from one population to the gene pool of another population (immigration and emmigration)

93
Q

Define Environmental factors

A

Factors which select for or aganist particular phenotypes in the process of natural selection

94
Q

Define sexual selection

A

Selection based on choice of mating partners, leads to evolutionary change if choices are based on differences in INHERITED characteristics

95
Q

Define Sex linked genes

A

Genes found on the sex chromosomes

96
Q

What are the types of inheritance?

A

Complete dominance, Incomplete dominance, Co-dominance, Lethal alleles, Multiple alleles

Biology (7 decks)

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