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biology > genetics and meiosis > Flashcards

genetics and meiosis Flashcards

1
Q

meiosis

A

nuclear division that produces 4 haploid cells from a diploid cell. The gametes are used in sexual reproduction.

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2
Q

4 things in prophase I

A

1 Chromosomes condense and become visible
2 crossing over occurs
3 centrioles migrate to opposite poles forming spindle fibre
4 nuclear envelope breaks down and nucleolus disappears

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3
Q

chromosomes of bivalents are joined at the

A

chiasmata

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4
Q

2 things in metaphase I

A
  1. homologous pairs chromosomes are arranged randomly on equator
    2 homologous chromosomes are still attached at chiasmata
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5
Q

1 thing in anaphase I

A

spindle fibres attached at centromeres contract and pull homologous chromosomes apart- one pair to each pole

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6
Q

telophase I

A

1 spindle fibres break down
2 chromsones uncoil
3 in animals nuclear envelope and nucleolus reform

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7
Q

what is the division after anaphase I called

A

reduction division

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8
Q

cytokinesis is animals

A

organelles distributed
cell surface membrane pinches inwards creating cleavage furrow which contracts

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9
Q

cytokinesis in plants

A

organelles distributed
vesicles form Golgi apparatus gather along the equator of spindle and merge to create new cell membrane

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10
Q

prophase II

A

nucleolus and nuclear envelop disappear, centriole move to opposite poles, chromosomes condense

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11
Q

metaphase II

A

chromosomes arrange themselves on equator. Spindle fibres attach to centromere of each chromosome

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12
Q

crossing over

A

the exchange of alleles between non sister chromatids of homologous chromosomes

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12
Q

anaphase II

A

centromeres divide and are pulled by spindle fibre to opposite poles carrying chromatids with them. Chromatids are separated

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13
Q

locus

A

position of gene on chromosome

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14
Q

gene 3 marks

A

a specific sequence of DNA occupying a position on a chromosome that codes for a specific protein, Each gene consists. of 2 or more alleles

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15
Q

phenotype

A

observable features of an organisms determined by its genes and environment

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16
Q

genotype

A

alleles an organism has

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17
Q

homozygous

A

having 2 identical alleles of a gene BB/bb

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18
Q

dominant allele

A

has the same effect on a phenotype whether or not another allele is present

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19
Q

co dominance

A

co dominant alleles each effect phenotype when both are present

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20
Q

multiple allele

A

the existence of 3 or more alleles of a gene eg blood groups

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21
Q

sex linkage

A

genes or alleles present in sex chromosomes are inherited together

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22
Q

sources of genetic mutation meiosis

A

crossing over-new combination of alleles on the 2 chromosomes
independent assortment- different combination of alleles in daughter cells due to random alignment of homologous Paris along the equator of the spindle
fusion of gametes- at fertilisation there is a random fusion of gametes creating variation between zygotes

23
Q

crossing over is more likely to occur

A

further down the chromosomes away from the centromere

24
Q

work out the number of possible chromosomes combinations

A

2^n where n is the number of chromosomes in a haploid cell 23 in humans

25
Q

chi squared is used to

A

find the difference between expected and observed results

26
Q

if chi squared value is bigger than critical value then

A

differences are due to chance otherwise differences are significant and caused by something else

27
Q

haploid

A

containing one complete set of chromosomes

28
Q

diploid

A

containing two complete set of chromosomes

29
Q

need for reductive division

A

reduces number of chromosomes to half original number diploid to haploid so when gametes fuse cell with have correct number of chromosomes

30
Q

homologous pair of chromosomes

A

2 chromosomes with similar gene loci but different alleles- one inherited form each parent

31
Q

allele

A

alternative form of a gene

32
Q

F1

A

first generation of offspring from a genetic cross

33
Q

F2

A

the offspring produced when F1 individuals reproduce with one another

34
Q

autosomal linkage

A

the presence of 2 genes on the same autosome, tend to b’e inherited together and do not assort independently

35
Q

why is haemophilia only found in men

A

factor vII is a gene found on t a non-homologous region of the x chromosome, Males (xy) only have one copy of the allele to be diseasedwhereas females (xx) have 2.

36
Q

epistasis

A

interaction of 2 different genes at different loci- one gene may effect expression of another

37
Q

continuous variation

A

variation within a range eg- mass and height

38
Q

what is variation

A

differences amongst individuals of the same species

39
Q

what is variation caused by

A

genes and environment

40
Q

what is genetic variation caused by (5)

A

1 independent assortment of chromosomes during mitosis
2 crossing over between non sister chromatids of homologous chromosomes during meiosis
3 random mating between organisms within species
4 random fertilisation of gametes
5 mutation

41
Q

discontinuous variation

A

can only take particular values eg gender and shoe size

42
Q

monogenic

A

characteristics influenced by only one gene

43
Q

natural selection

A

process in which fitter individuals who are better adapted to the environment survive and pass on the advantageous genes to future generations

44
Q

evolution

A

process by which the frequency of alleles in the gene pool change over time

45
Q

genetic drift

A

small change in alleles frequency occurs as a result of the fact not all the individuals in a population reproduce. effect amplified in very small groups isolated forms eh rest of the population

46
Q

genetic bottleneck effect

A

rapid reduction of population size which has an effect on genetic variation in future generations

47
Q

founder effect

A

decrease in genetic diversity which occurs when the population descends from a small number of ancestors

48
Q

selection

A

process by which organisms that are better adapted to the environment survive and breed while those less well adapted do not

49
Q

speciation

A

process by which new species arise after a population becomes seperated and cannot interbreed

50
Q

antibiotic resistance

A

1 random mutation occurs in bacteria
2 mutation bacteria can survive and reproduce
3 they pass mutant allele over many generations

51
Q

3 ways natural selection can act on a population

A

directional selection against an extremes
stabilising selection against both extremes
disruptive selection against the mean

52
Q

species

A

populations of similar organisms with similar morphological and physical features occupying the same niche and can reproduce to make fertile offspring. Reproductively isolated from other populations

53
Q

allele frequency

A

relative proportions of alleles of a gene present in a population

54
Q

3 causes of allele frequency change in a population

A

mutation, migration, natural selection

55
Q

hardy Wienberg principle in words

A

in a large randomly mating population there is a fixed relationship between gene and genotype frequency. Frequencies remain constant unless there is mutation, migration or natural selection

56
Q
A

biology (19 decks)

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