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cell and nuclear division Flashcards

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Biology 101 flashcards
1
Q

interphase

A

-cell growth and synthesis of cell materials
-DNA replication

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2
Q

nuclear division

A

-nucleus divides to form two nuclei

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3
Q

cytokinesis

A

-cell surface membrane invaginates towards cell equator
-the cleavage furrow deepens until the parent cell is pinched into two, producing two daughter cells
-cytoplasm divides evenly to form two daughter cells

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4
Q

chromatin structure

A

-is the complex of DNA and proteins
-is the less condensed form of chromosome

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5
Q

chromosome structure

A

-during nuclear division, DNA condenses into chromosomes

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6
Q

unduplicated chromosome

A

-consists of a single DNA molecule

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7
Q

duplicated/ replicated chromosome

A

-consists of two genetically identical DNA molecule
-consists of two genetically identical sister chromatids joined at the centromere, that are formed due to semi-conservative DNA replication during interphase

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8
Q

diploid chromosome number

A

-two sets of chromosomes, diploid number of chromosomes is 46
-somatic/ non-sex cells

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9
Q

haploid chromosome number

A

-gametes contain a single set of chromosomes, haploid number of chromosomes is 23
-the 23 chromosomes consists of 22 autosome and a single sex chromosome
-human egg contains 22 autosomes and X chromosome
-human sperm contains 22 autosomes and an X or a Y chromosome

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10
Q

homologous chromosomes

A

-in a diploid cell, each type of chromosome exists as a pair of homologous chromosomes, each chromosome is a homolog
-may have different alleles, alleles are alternative forms of the same gene with a slight different nucleotide sequence

homologous chromosomes have
-the same length
-the same position of centromeres
-the same genes as the same loci

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11
Q

mitosis prophase

A

-longest phase in mitosis
-DNA coils and condenses into duplicated chromosomes with two genetically identical sister chromatids joined at their centromeres
-centrosomes organise microtubules into spindle fibres and migrate to opposite poles of the cell by lengthening of spindle fibres
-nucleolus seems to disappear
-nuclear envelope fragments

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12
Q

mitosis metaphase

A

-spindle fibres attach to kinetic horse proteins at the centromeres, becoming kinetochore microtubules
-centromeres of chromosomes are aligned along the cell equator

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13
Q

mitosis anaphase

A

-shortest phase in mitosis
-centromeres separate and two genetically identical sister chromatids separate, thus becoming two unduplicated daughter chromosomes
-daughter chromosomes migrate towards opposite poles of the cell, with the centromere leading the way as kinetochore microtubules shorten

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14
Q

mitosis telophase

A

-nuclear envelopes reform to form two nuclei
-nucleolus reappears in each nucleus
-chromosomes become decondensed to form back DNA
-spindle fibres break down

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15
Q

significance of mitosis

A

-each parent cell produces two genetically identical daughter cells with same number and types of chromosomes as parent nucleus

-the genetic stability between generations of cells enables organism growth, tissue repair and asexual reproduction

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16
Q

meiosis prophase I

A

-DNA coils and condenses into duplicated chromosomes with two genetically identical sister chromatids joined at their centromeres
-centrosomes organise microtubules into spindle fibres and migrate to opposite poles of the cell by lengthening of spindle fibres
-nucleolus seems to disappear
-nuclear envelope fragments
-homologous duplicated chromosomes pair up to form bivalents

17
Q

meiosis metaphase I

A

-the bivalents align themselves at the cell equator
-each one homolog is attached to kinetochore microtubules from one of the poles of the cell

18
Q

meiosis anaphase I

A

-homologous chromosomes separate
-homologous chromosomes migrate towards opposite poles of the cell, with the centromeres leading the way as kinetochore microtubules shorten

19
Q

meiosis telophase I

A

-nuclear envelope reforms, forming two nuclei
-nucleolus reappears in each nucleus
-duplicated chromosomes become decondensed to form back DNA
-spindle fibres break down

20
Q

meiosis prophase II

A

-DNA coils and condense into duplicated chromosomes with two genetically identical sister chromatids joined at their centromeres
-nucleolus seems to disappear
-nuclear envelope fragments

21
Q

meiosis metaphase II

A

-spindle fibres from centrosome attach to kinetochore proteins at the centromere of each sister chromatid of chromosome, becoming kinetochore microtubules
-centromeres of chromosomes are aligned along the cell equator

22
Q

meiosis anaphase II

A

-centromeres separates and two genetically non-identical sister chromatids separate, thus becoming two unduplicated daughter chromosomes
-daughter chromosomes migrate toward opposite poles of the cell, with the centromere leading the way as kinetochore microtubules shorten

23
Q

meiosis telophase II

A

-nuclear envelopes reform to form two nuclei
-nucleolus reappears in each nucleus
-unduplicated chromosomes become decondensed to form back DNA
-spindle fibres break down

24
Q

significance of meiosis

A

-ensures maintenance of chromosomal number in offspring and prevent doubling of chromosomal numbers during fertilisation
-generates genetic variation in offspring by producing recombinant gametes by crossing over between non-sister chromatids of homologous chromosomes and independent assortment of homologous chromosomes

25
Q

process that contribute to genetic variation arising from sexual reproduction

A

-crossing over between non-sister chromatids of homologous chromosomes
-independent assortment of homologous chromosomes
-random fertilisation of gametes

26
Q

crossing over

A

-occurs between non-sister chromatids of homologous chromosomes resulting in chiasmata formation
-during prophase I of meiosis
-results in the exchange corresponding DNA segment of chromatids, thus separating linked genes and creating new allelic combinations

27
Q

independent assortment of homologous chromosomes

A

-random orientation of pars of homologous chromosomes along the cell equator
-during metaphase I
-in humans the number of possible chromosomal combination is 2 power 23 =8388608

28
Q

random fertilisation of gametes

A

-during fertilisation, genetic material from two different individuals is combined by random fusion of gametes’ nuclei
-in humans, the number of possible combinations is (2 power 23) (2 power 23)

29
Q

non-disjunction

A

-pair or pairs of homologous chromosomes failed to separate during anaphase I
-sister chromatids failed to separate during anaphase II
-results in extra chromosome/ lacks a chromosome
-eg. down syndrome

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