Miosis Flashcards

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1
Q

Sexual reproduction

A

Producing offspring via gametes
Depends on miosis, DNA recombination
Consists of n cells

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2
Q

Fertilization

A

The nuclei of an egg and a sperm meet producing a zygote, further mixing DNA

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3
Q

Fertilization cycle

A

Fertilization (2n)– miosis(2n)–spore(n)–mitosis–gametes

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4
Q

Spores

A

Divide using mitosis

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5
Q

Animals

A

2n phase dominates miosis directly followed by gamete formation

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6
Q

Males miosis

A

Each miotic cell turns into a functional sperm

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7
Q

Females miosis

A

1/4 nuclei turn into a functional egg cell

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8
Q

Most plants, some fungi

A

Alternate n and 2n generations. Fertilization produces 2n sporophytes. Miosis occurs and n spores are produced

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9
Q

Spores in plants

A

Become n gametophytes which can mature into gametes. Identical because miosis does not occur

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10
Q

Most fungi

A

2n phase is limited to only the zygote

Immediatly after fertilization miosis produces n, where mitosis can occur

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11
Q

Fungi fertilization

A

2, n gametes (+)/(-) meet. 4, n cells produced from 1 2n cell

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12
Q

Miosis

A

Produces 2 different cells. Occurs in specialized tissues producing gametes and spores

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13
Q

Homologous chromosomes have

A

The same genes in the same order in the DNA, but might have different alleles

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14
Q

Homologous chromosomes are made of

A

1 paternal chromosome and 1 maternal chromosome

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15
Q

Roles of miosis

A

Increase variability and half the chromosome number

Each n cell carries half the genes for a homologous chromosome

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16
Q

Genetic recombination purpose

A

Have maternal and paternal genes passed on

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17
Q

Meiocytes

A

Cells that divide by miosis. S phase occurs, creating 2 daughter cell SNA for G2 phase

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18
Q

Miosis I

A

Synapsis occurs. Chromosomes pair lengthwise gene for gene and recombination occurs. 2 daughter cells with n (double) chromosomes are produced

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19
Q

Miosis II

A

Sister chromatids are separated. 4 cells with n chromosomes are created

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20
Q

Internkinesis

A

Interphase that seperates the 2 miotic cycles. No DNA replication occurs

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21
Q

Prophase I

A

Duplicated chromosomes fold and condense
pairing and synapsis occurs
recombination between homologous pairs
Spindle fibers form

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22
Q

Synapsis

A

Homologous pairs line up side by side forming tetrads

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23
Q

Tetrads

A

A make up of 4 chromatids

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24
Q

Prometaphase I

A

Nuclear membrane breaks
Spindle fibres connect
Kinetochore microtubules connect to 1 sister chromatid

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25
Q

Metaphase I

A

Spindles line chromosomes on the metaphase plate

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26
Q

Anaphase I

A

Double structured sister chromosomes are divided to the poles

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27
Q

Telophase I

A

Brief, nuclear membrane may reform

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28
Q

Interkinesis

A

Spindle fibers disassemble and become 2 spindle fibers for miosis II

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29
Q

Prophase II

A

Chromosomes condense

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30
Q

Prometaphase II

A

Nuclear membrane breaks down, spindle fibers enter and attach

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31
Q

Metaphase II

A

Spindle movement brins chromosomes to the metaphase plate

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32
Q

Anaphase II

A

Sister chromatids separate and move to the poles (now are single chromosomes)

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33
Q

Telophase II

A

Chromatids decondense, spindles disintegrate and the nuclear envelope forms

34
Q

Failure in chromosome separation miosis I

A

A whole tetrad moves to 1 pole in anaphase. Results in 2, 24 chromosome cells and 2, 22 chromosome cells

35
Q

Failure in chromosome separation miosis II

A

A chromatid doesn’t separate in anaphase. Results in 1 24 chromosome cell, 1 22 chromosome cell, and 2 23 chromosome cell

36
Q

Down syndrome

A

2 copies of chromosome 21 end up in 1 cell

37
Q

Sex chromosomes

A

Different in males and females for the same species

38
Q

XX

A

Homologous chromosomes in females

39
Q

XY

A

Males, the y is smaller, homologous throughout the shot region. Act as homologous chromosomes in division

40
Q

Miosis purpose

A

Create repaired chromosomes to allow organisms to grow

41
Q

Repairing chromosomes

A

Make a good chromosome if both of the parents ones are damaged

42
Q

Genetic variability comes from

A
  1. Genetic recombination of homologous chromosomes
  2. Differing maternal and paternal genes segregated during anaphase I, II)
  3. Different combos of chromatids after anaphase II
  4. Which male and female gametes mix
43
Q

Genetic recombination is miosis

A

Homologous chromosomes are similar enough to pai, but different. DNA segments are switched using enzymes

44
Q

Synaptonemal complex

A

Holds homologous chromosomes tightly together during synapsis
Disassembles at the end of prophase I

45
Q

Products of miosis

A

Unchanged parental chromatid and recombinant chromatids. 2x per division

46
Q

Cross over (chiasmata)

A

When non sister chromatids cross each other. 2/4 chromatids are altered
Pair on top of each other not side by side

47
Q

Cross over location

A

Can occur on any part, for any length of chromatid

48
Q

Random srgregation

A

In prometaphase spindles attach randomly therefore some maternal and some paternal chromatids end up in each cell

49
Q

Random segregation formula

A

2^n

50
Q

Alternative combinations at miosis II

A

A recombinant and a non recombinant in every cell

51
Q

Random fertilization

A

Egg and sperm combine fully by chance. The only exception is identical twins, triplets…

52
Q

Mobil elements (jumping genes)

A

DNA that can move and does not require homology

Move around within a genome of a given cell

53
Q

Transport elements (TEs)

A

Mechanisms of movement involving non homolgous recombination call transposition

54
Q

Types of transposition

A

Cut and past, copy and paste

55
Q

Cut and past transposition

A

TE leaves its original position and transposes to a new location

56
Q

Copy and paste transposition

A

A copy of the TE is transposed to a new location, the original stays

57
Q

TE transportation

A

DNA contact is always maintained. Starts with contact between TE and the target site

58
Q

Roles of TEs

A

Gene mutation causing and increase or decrease in gene expression, alter the function or increase genetic variability

59
Q

Bacterial TEs

A

Move between bacterial chromosomes, bacterial chromosomes and plasmids, and plasmids

60
Q

Bacterial TEs can

A

Transpose anywhere, others have hot spots for insertion

61
Q

Types of TEs

A

Insertion sequences and transposon

62
Q

Insertion sequences (IS)

A

Small, simple and contain genes for transposition and transposase
Have an inverted repeat sequence

63
Q

Transposase

A

An enzyme that catalyzed recombination reactions for TE

64
Q

Inverted repeat sequences

A

Occur on each end of the IS. Same DNA sequence running in opposite directions

65
Q

Inverted repeat sequences purpose

A

Allow transposase to identify the ends of the TE

Create the homology needed for Hfr

66
Q

Transposon

A

Inverted repeat sequence with 1 or more genes in between

67
Q

Transposon in bacteria

A

Inverted repeat sequence is the IS

68
Q

Additional genes in transposon

A

Often Often code for antibody resistance. Can be form bacterial chromosomes or plastids

69
Q

Antibiotic resistance

A

Occurs because of resistance genes. Conjugation passed this along to many cells

70
Q

TE discovery

A

Leaf and Kenal mutations of corn rapidly went away under some conditions. Allele mapping showed alleles could move in corn chromosomes

71
Q

1970 TE

A

They were accepted for eukaryotes and prokaryotes

72
Q

Types of eukaryotic TE

A

Transposons and retrotransposons

73
Q

Retrotransposons

A

Copy and paste. Transposition happens via an intermediate RNA cop of the TE

74
Q

3 steps to retrotransposon

A
  1. The retrotransposons part of the DNA is transcribed
  2. Reverse transcriptase
  3. The DNA copy is inserted into its new location. DNA backbones are broken and rejoined
75
Q

Reverse transcriptase

A

An enzyme coded by retrotransposon gene that uses RNA as a template

76
Q

Retrotransposon in gametes

A

Can be inherited and therefore exists in many generations

77
Q

TE mutations

A

Happen until the DNA is a nonmobile, residual sequence. Eukaryotes have many of these

78
Q

Retroviruses

A

Eukaryotic viruses that act the same as retrotransposon by releasing RNA into the host cells DNA after it is copied

79
Q

Proviruses

A

Similar to the prophage of bacteria

80
Q

Retroviruses can…

A

Cause DNA rearrangement (deletion or translocation)
Pick up host genes and move them to recipients
Lead to abnormal activity (often resulting in cancer