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Genetics block 2 > meiosis > Flashcards

meiosis Flashcards

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Biology 101 flashcards
1
Q

p arm

A

short arm

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2
Q

Q arm

A

Long arm

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3
Q

centromere

A

location establishes appearance of cromosome

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4
Q

Types of chromosomes

A

Metacentric
Submetacentric
acrocentric
Telocentric

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5
Q

Metacentric

A

Centromere is at middle

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6
Q

Submetacentric

A

Centromere is between middle and end

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7
Q

Acrocentric

A

Centromere is close to end

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8
Q

Telocentric

A

Centromere is at end

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9
Q

general features of chromosomes

A

-Chromosomes appear most condensed during mitosis.
-Diploid number is 2n
-Chromosomes exist in pairs
-For each chromosome with specific length and centromere placement, there is another with identical features.
-Bacteria and viruses have just one chromosome

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10
Q

karyotype

A

-Shows human mitotic chromosomes at metaphase
-Chromosomes are photographed, cut out and matched
-All chromosomes are homologous pairs except X and Y

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11
Q

Haploid set

A

Half of number of chromosomes of diploid number
genetic informatiomin in haploid set constitutes the genome of the species
Different organisms have different haploid number

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12
Q

Homologous chromosomes

A

Includes copies of all genes and non-coding DNA
One haploid set- one paternal, the other paternal

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13
Q

Biparental inheritance

A

Inheritance from two parents

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14
Q

Meiosis

A

-Meiosis produces two daughter cells with full diploid complements
-Meiosis produces gametes/spores- one haploid set of chromosomes
-During sexual reproduction- haploid gametes fuse to constitute a diploid set
-NB: Maintains genetic continuity from generation to generation

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15
Q

Meiotic variation

A

-First meiosis- Produces gametes with unique combinations due to crossing over
-Reshuffles genetic material to produce diverse offspring

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16
Q

Basis of Mendel’s principles

A
17
Q

Crossing over

A

Genetic exchange between members of each homologous pair of chromosomes
-Creates chromosome-mosaics of maternal and paternal homologs

18
Q

Prophase 1

A

-Meiosis begins with diploid cell duplicating its DNA during interphase- like mitosis
-Homologous chromosomes pair up (undergo synapsis) to form bivalents
-Bivalents give rise to tetrads
-Tetrads remain intertwined in some areas ( chiasmata)
-Nonsister chromatids undergo exchange
-Tetrads attach to spindle fibres

19
Q

Bivalent

A

A pair of homologous chromosomes that are physically held together by at least one DNA crossover

20
Q

Tetrad

A

two pairs of sister chromatids joined at centromere.

21
Q

Metaphase I

A

-Chromosomes shortened and thickened
-Terminal chiasmata visible
-Tetrads interact with spindle fibres
-alignment of tetrads are random prior to anaphase I (increases variation)
-One dyad (half of tetrad) pulled by spindle fibres to one or other pole
-single centromeric region holds sister chromatids together by cohesin protein

22
Q

Anaphase I

A

-Cohesin degraded between sister chromatids, except at centromere
-Dyad pulled to each polle
-Reductional division- no. of centromeres halved
-seperation (disjunction)
-At completion- series of dyads at each pole equals the haploid number
-Crossing over results in mosaic chromatids of mixed paternal and maternal origin

23
Q

Non-disjunction

A

Error where total seperation is not achieved

24
Q

Telophase I

A

-some organisms, nuclear membrane forms around dyads and enter short interphase period but chromosomes do not replicate
-Other organisms- cells go directly from anaphase I to meiosis II
-Meiotic telophase- much shorter than mitosis

25
Q

Meiosis II

A

Essential for gametes to have a single chromatid from original tetrad

26
Q

Prophase II

A

Each dyad has a pair of sister chromatids attached by centromere

27
Q

Metaphase II

A

Centromeres positioned on equatorial plate and shugoshin complex is degraded

28
Q

Anaphase II

A

Iniated and sister chromatids are pulled to opposite poles

29
Q

Telophase II

A

One member of each pair of homologous chromosomes present at each pole
-Each chromosome is now a monad
-Number of centromeres in resulting daughter cells is not reduced during this division (equatorial division)

30
Q

Following cytokinesis in Meiosis II

A

Four haploid gametes are formed, crossing over has occured, monads are a combination of maternal and paternal genetic information, genetic variation increased

Genetics block 2 (9 decks)

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