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BIO 202 > Meiosis + Sexual Reproduction > Flashcards

Meiosis + Sexual Reproduction Flashcards

1
Q

Heredity

A

The transmission of traits from one generation to the next

–> Also known as “inheritance”

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2
Q

Impacts of inherited variation:

A

Permits flexibility and survival of a population in a changing environment

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3
Q

Genetics

A

The study of heredity and inherited variation

–> Attempting to answer: “What accounts for similarities + variation?”

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4
Q

Transmission (of traits)

A

The passage of DNA, on chromosome, from parents to offspring

–> What makes inheritance possible

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5
Q

Genes

A

DNA segments that encodes for specific traits that emerge as we develop

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6
Q

Genes are the _________ _________ to our parents and account for family ____________

A

1) Genetic link
2) Resemblance

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7
Q

Most genes program cells to synthesize…

A

specific enzymes and proteins whose cumulative action produces an organism’s inherited traits

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8
Q

Gametes

A

Reproductive (sex) cells that transmit genes from one generation to the next

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9
Q

Somatic Cells

A

All cells of the body EXCEPT gametes (and their precursors)

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10
Q

Ploidy

A

The # of SETS of chromosomes within a given cell

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11
Q

Haploid

A

= n

–> Single set of chromosomes

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12
Q

Diploid

A

= 2n

–> Two sets of chromosomes

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13
Q

Human haploids and diploids

A

Gametes = haploid = 23 chromosomes

Somatic Cells = diploid = 46 chromosomes

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14
Q

We inherit one chromosome of each pair from…

A

Each parent = one maternal chromosome set + one paternal chromosome set

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15
Q

Even after DNA is replicated to form duplicated chromosomes, we still refer to the cells as being…

A

Haploid or diploid

–> BECAUSE the cell still only has one or two sets of info REGARDLESS of how many chromatid copies there are of that info

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16
Q

Homologous Chromosomes

A

The maternal and paternal copies of a chromosome found in diploid cells

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17
Q

Similarities Between Homologous Chromosomes

A

1) Length
2) Centromere Position
3) Type of genes/Order of genes found/gene loci

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18
Q

Differences Between Homologous Chromosomes

A

Can possibly differ in alleles

–> Same genes, different alleles

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19
Q

Homologous chromosomes carry genes that…. (1)

BUT the _______________________(2) of these genes may differ between them

A

1) Control the same inherited characteristics

2) Variants/versions of these genes

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20
Q

Homologous chromosomes ARE NOT…

A

Sister Chromatids (which are IDENTICAL copies of each other)

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21
Q

Locus

A

Location/Position of a gene in a chromosome

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22
Q

Allele

A

A variant or form of a gene

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23
Q

How many alleles of each genes do diploids have?

A

2 alleles of each gene

(One from mother, one from father)

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24
Q

Sex Chromosomes

A

Chromosome that determine sex (X + Y)

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25
Q

Sex Chromosomes ARE NOT…

A

Homologs

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26
Q

Our 46 chromosomes =

A

44 (22 pairs) autosomes + 2 sex chromosomes

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27
Q

Autosomes

A

All chromosomes EXCEPT sex chromosomes

–> Essentially, the homologous chromosomes

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28
Q

Karyotype

A

An ordered display of all human chromosomes arranged in pairs –> How we can study chromosomes

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29
Q

How does karyotype work?

A

Homologs stain similarly making it easy to pair up homologs by shared size/length and staining

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30
Q

2 different types of cell division:

A

1) Asexual Reproduction
2) Sexual Reproduction

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31
Q

Asexual Cell Division

A

A single individual (cell) is the sole parent

–> = Genetically identical offspring (clones)

1) Mitosis
2) Binary Fission

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32
Q

Sexual Cell Division

A

TWO parents contribute DNA to one offspring

–> = Genetically different (unique) offspring

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33
Q

The # of chromosomes/genetic content must…

A

remain constant from cell to cell and generation to generation

34
Q

Meiosis

A

A specialized cell division in which gametes are produced whose chromosome # is reduced to HALF

35
Q

How is diploid restored after meiosis?

A

The fusion of gametes (haploid cells) restore diploid state in daughter cell

36
Q

What must occur in all sexual life cycles?

A

An alternation of fertilization and meiosis

37
Q

Fertilization

A

The fusing of gametes resulting in the fusion of their nuclei, producing a zygote

38
Q

Zygote

A

Cell produced by gametes fusing (fertilized egg)

39
Q

Higher Eukaryote Sexual Life Cycle

A

Diploid Organism —-> (Meiosis) —-> Haploid gametes
—-> (Fertilization) —-> Diploid Zygote —-> (Mitosis) —> Diploid Organism

40
Q

Lower Eukaryote Sexual Life Cycle

A

Haploid Organisms —> (Mating) —> Diploid Zygote —> (Meiosis) —> Haploid Cells —> (Mitosis) —> Haploid Organisms

41
Q

Sexual life cycles differ between organisms BUT…

A

it always involves an alternation between haploid and diploid cells

42
Q

Ploidy of cells that can undergo mitosis and meiosis

A

Mitosis = Haploid or Diploid can undergo

Meiosis = Only diploid can undero

43
Q

Meiosis is this type of division:

A

Reductional Division –> Reduces # of chromosome sets by half

44
Q

Daughter Cells of Meiosis

A

1/2 # chromosomes BUT genetic info is equivalent (maintains same genes just in one copy)

45
Q

Germ Cells

A

The cells that undergo meiosis to produce gametes

46
Q

Components of Meiosis

A

1) Interphase (DNA rep. occurs)
2) Meiosis I –> Cell Division I
3) Meiosis II –> Cell Division II

47
Q

What does meiosis produce?

A

4 daughter cells with ONE unreplicated copy of each chromosome

48
Q

Meiosis has ONE _________ but TWO ______________

A

1) Round of DNA replication
2) Cell Divisions

49
Q

Meiosis I

A

Homologous chromosomes pair and then are separated

–> The reductional step: Reduces chromosomes by 1/2 in each cell

50
Q

Meiosis II

A

Sister chromatids are separated (like regular mitosis)

= 4 daughter cells with 1/2 # of chromosomes

51
Q

What is the critical difference between meiosis and mitosis?

A

Meiosis I –> The pairing and separation of homologs

52
Q

Prophase I (5)

A

1) Nuclear envelope breaks down
2) Chromosomes progressively condense
3) Homologs pair (synapsis)
4) Crossing over occurs –> DNA exchanges
5) Mitotic spindle formation + attachment of MT to kinetochores

53
Q

Synapsis

A

Homologs pair up with each other by physically attaching (synapse)

54
Q

Chiasmata

A

Physical bridge between homologs: The point where crossing over occurs

55
Q

Synaptonemal Complex

A

A protein structure/complex that forms between homologous chromosomes (between non-sister chromatids) that attached them along their length

56
Q

Synaptonemal Complex Function

A

Functions primarily as a scaffold to allow interacting chromatids to complete crossing over

57
Q

Synaptonemal Complex Disassembles when…

A

when chiasmata fully form

58
Q

Non-Sister Chromatids

A

Chromatids from homologous chromosomes

–> Have the same genes but may differ in alleles

59
Q

Crossing Over

A

DNA molecules of non-sister chromatids are BROKEN and exchange equivalent bits of DNA with each other

–> Causes exchange of genetic material

60
Q

Purposes of Crossing Over:

A

1) Establishes physical connections between homologs
2) Exchange genetic info which causes INCREASE of genetic variation

61
Q

Crossing over causes

A

Recombination

62
Q

Recombination

A

The production of different combinations of alleles

–> Each gamete produced has a different combo of alleles

63
Q

Metaphase I (2)

A

Chromosomes line up by homologous pairs

1) Microtubules from spindles on opposite poles attach to each homologous chromosome

2) Pairs of the homologous chromosomes are now arranged at the metaphase plate with one chromosome of each pair facing each pole

64
Q

Kinetochore Orientation in Metaphase I

A

Same-Side Kinetochore Orientation (Kinetochores of sister chromatids align side-to-side

–> BOTH kinetochores in ONE homolog gets attached by MT of the same pole of the spindle

65
Q

Spindle Attachment to the Homologs

A

Each homolog is connected to microtubules from opposite poles (to allow for separation of homologs)

66
Q

Anaphase I (2)

A

Separation of homologs

1) Cleavage/breakdown of proteins (cohesins) that are responsible for holding homologs together

2) Microtubules pull each homolog toward opposite poles

67
Q

What persists in anaphase I?

A

Sister chromatid cohesins persist
–> Sister chromatids remain attached after anaphase I

68
Q

Telophase I (2)

+ Cytokinesis

A

Formation of 2 haploid cells

1) The separated homologs cluster at each pole of the cell

2) Nuclear membrane reforms around each daughter cell nucleus

–> Followed by cytokinesis

69
Q

What is different about the sister chromatids found in cells produced by Meiosis I?

A

They are NOT IDENTICAL –> Due to earlier crossing over

70
Q

Uniqueness of Meiosis to Mitosis (3):

A

1) Synapsis and Crossing Over –> In prophase I, homologs physically connect and exchange genetic info

2) Metaphase I –> Homologs pair up at the metaphase plate

3) Anaphase I –> Homologs separate and get pulled to opposite poles

71
Q

The greater the variation…

A

The greater the chance of survival of species in an unpredictable event

72
Q

Origins of genetic variation:

A

Comes down to the behavior of chromosomes during meiosis and fertilization

1) Independent Assortment
2) Crossing Over (Recombination)
3) Random Fertilization

73
Q

Independent Assortment

A

The different possible arrangements of homologs at Metaphase I –> Causes different variants of a chromosome ending up in the final daughter cells

74
Q

Independent Assortment: What causes it?

A

Each homolog pair can arrange in 1 of TWO ways independently of other pairs

–> How they orient themselves at metaphase determines which variants go to which pole (and which cell) they end up in

75
Q

What does independent assortment produce?

A

Different combinations of alleles of genes

76
Q

How many unique gametes are possible?

A

2^n

n = haploid # chromosomes

77
Q

Recombinant Chromosomes

A

Carry genes from 2 different parents in ONE chromosome

78
Q

How many cross overs occur per homologous pair?

A

At least 2-3

79
Q

Random Fertilization

A

During sexual reproduction, the male and female gametes that end up fusing are selected randomly from the large pool of male + female gametes

–> Which gametes fuse = matter of chance

80
Q

The chance of any one sperm fusing with any one egg (for humans):

A

(2^23) x (2^23) = ~70 trillion

–> Every person is a 1 in 70 trillion chance

–> Makes it virtually impossible for humans to produce identical offspring through separate pregnancies

BIO 202 (33 decks)

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