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pmp-101 > Sexual Reproduction and Meiosis > Flashcards

Sexual Reproduction and Meiosis Flashcards

1
Q

Somatic cells: dip or hap?

A

Diploid (each contain 46 chromosomes)

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2
Q

How many cells are somatic in multicellular organism?

A

-almost all of the cells

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3
Q

Diploid cells:

A

-two copies/sets of each chromosome (2n) inherited from each parents

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4
Q

DO NOT contribute

A

to inheritance in the next generation

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5
Q

in humans each diploid cells contains 46 chromosomes

A

22 paires of homologous autosomes + 2 sex

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6
Q

Originated by mitosis so..

A

chromosome number is maintained in mitosis

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7
Q

Autosome chromosomes

A

Human diploid cells have 22 homologous autosomes and a pair of SEX CHROMOSOMES

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8
Q

Homologous autosomal chromosomes

A

Pairs of chromosomes (not sex chromosomes)

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9
Q

Homologous:

A

having the same organisation, relative position, value and structure

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10
Q

In humans: 22 copies of autosomes

A

numbered in descent based on their size

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11
Q

Homologous pairs contain…

A

The same kind of genes at specific positions (locus), but slightly different sequences (two alleles, variant versions of genes)

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12
Q

Sex chromosomes

A

Pairs of chromosomes that participate in sex/gender determination at birth

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13
Q

What are the types of sex chromosomes?

A

X and Y

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14
Q

Which pair number are the chromosomes X and Y

A

23rd pair of chromosomes

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15
Q

Females

A

XX in their cells

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16
Q

Males

A

XY in their cells

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17
Q

Similar?

A

differ from autosomes in form, size and behaviour

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18
Q

Sex cells are also called

A

GAMETES

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19
Q

Gametes

A

reproductive cells of the organisms = EGG and SPERMATOZOON involved in sex reproduction

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20
Q

Haploid or diploid: gametes

A

haploid - contain only one set of chromosomes

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21
Q

in humans…

A

23 chromosomes= 22autosomes + sex chromosome

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22
Q

originated by diploid germ line cells by meiosis

A

chromosome number is divided in half by meiosis

23
Q

contribute to inheritance to the…

A

next generation

24
Q

Sexual reproduction steps

A

3 steps

25
Q

1)

A

Spermatozoa and egg (n) are produced by meiosis from diploid germ-line cells (2n)

  • maternal and parental chromosome sets are partitioned into the single chromosome sets of the gametes
26
Q

2)

A

Fertilisation (fusion) of gametes regenerates the diploid structure of the somatic cells (zygote with homologous chromosomes from both)

27
Q

3)

A

The zygote develops into a new individual, through many rounds of mitosis

28
Q

Meiosis KEY features:

A

> used for sexual reproduction
- created gametes, carrier only a single set of chromosomes (n)
- occurs in specialised germ-line cells that reside in the ovaries or testes

29
Q

A cell that produces 4 nonidentical (genetically dissimilar)

A

Daughter cells having half the number of chromosomes of the parents cell (2n&raquo_space;> n)

30
Q

process of duplication

A

2n ? 4n > 2n + 2n > n + n + n + n

31
Q

Meiosis broken down:

A
  • one round of DNA replication
  • followed by two rounds of nuclear division (Meiosis I and Meiosis II)
32
Q
  1. Meiosis v Mitosis
A

Used only for sexual reproduction
v
Used for asexual reproduction and growth

33
Q
  1. Meiosis v Mitosis
A

Requires two nuclear divisions (Meiosis I & II)
v
Requires one nuclear division

34
Q
  1. Meiosis v Mitosis
A

Halves chromosome number (2n to n)
v
Preserves chromosome number (2n to 2n)

35
Q
  1. Meiosis v Mitosis
A

Produces four daughter nuclei
v
Produces two daughter nuclei

36
Q
  1. Meiosis v Mitosis = daughter cells
A

Produces daughter cells genetically different from parent and each other
v
Produces daughter cells genetically identical to parent and to each other

37
Q

Meiotic interphase

A

3 main events:
- interphase
- meiosis I
- meiosis II

38
Q

Interphase

A

constituting in 3 phases: G1, S , G2
In S phase, DNA is replicated (sister chromatids)

39
Q

Meiosis I

A

> (1st division), with 4 stages + cytokinesis I
Separation of the pairs of homologous chromosomes, after the process of pairing of the duplicated homologous chromosomes along their entire length
Homologous chromosomes are similar but not identical

40
Q

Meiosis II

A

> (2nd division) with four stages + cytokinesis II
Separation of the sister chromatids (copies of the same chromosome)

41
Q

Meiosis : PMAT(C) I

A
  1. Prophase I
  2. Metaphase I
  3. Anaphase I
  4. Telophase I
  5. Cytokinesis I
42
Q

Meiosis II : PMAT(C) II

A
  1. Prophase II
  2. Metaphase II
  3. Anaphase II
  4. Telophase II
  5. Cytokinesis II
43
Q

Meiosis I - reductional division. Task?

A

Separation of homologous chromosomes

44
Q

Prophase I

A
  • The longest and most peculiar stage of the whole meiotic process
  • The meiotic spindle also forms from the poles of the cell (centrosomes)

-Nuclear envelope breaks down

45
Q

Duplicated chromsomes homologs (+ sex chromosomes) are..

A

condensed and brought together (lined up) during a process called PAIRING (or synapse)

46
Q

What is the structure of pairing called?

A

BIVALENT

  • give rise to a unit of four sister chromatids stuck together (tetrad)
47
Q

Crossing over (in prophase I)

A

pairing of homologous chromosomes is coupled with homologous recombination

48
Q

What is the importance of crossing-over?

A

Genetic exchange between DNA segments of the non-sister chromatids within tetrads of homologous chromosomes

49
Q

How does crossing-over work?

A
  • the chromatids break in the same place and sections of chromosomes (alleles) are swapped (based on similar sequences)
50
Q

Can cross over happen on more than one occasion per tetrad?

A

One or more cross-over events can occur per tetrad at sites called chiasmata (s. chiasma)

51
Q

How does crossing-over contribute to genetic variation?

A

> Allele reassortment
This creates chromosomes that are unique mosaics (mixture) of the maternal and paternal homologs from which they arise
Offspring will have different set of alleles to their parents

52
Q

Does crossing-over appear in MITOSIS?

A

NO - only in meiosis

53
Q

2) Metaphase I

A

pmp-101 (53 decks)

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