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Life Science > Meisos > Flashcards

Meisos Flashcards

1
Q

Chromosome

A

Rod shaped filamentous bodies present in nucleas & cytoplasm of prokaryotic cell which carries genes

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2
Q

Difference between somatic & gamete

A

Somatic cells are human body cells with:
46 chromosomes, diploid number

Gametes are sex cells with 23 chromosomes and only n

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3
Q

Zygote

A

Fusion of female gamete and male gamete

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4
Q

Chromosome components

A

Centromere : holds 2 chromostids
Gene: segment of DNA that codes for a trait
Chromotids : identical copies making up a chromosome

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5
Q

Homologous chromosomes

A

Chromosomes that are identical in shape, size & which code genes for same set of characteristics

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6
Q

Karyotype

A

Image which depicts an organisms chromosomes which determines gender & whether a person has down syndrome

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7
Q

Loci

A

Genes in same position

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8
Q

Importance of mitosis

A

Growth (allows zygote to produce more cell in order to grow)
Repair & replacement : allow multicellular organism maintain its tissues.

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9
Q

Cytokinesis definition

A

Process of cytoplasmic division to form two daughter cells

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10
Q

Karyokinesis

A

Division of nucleas

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11
Q

Meisos definition

A

Cell division whereby a diploid cell undergoes 2 cell divisions & divides to form 4 dissimilar haploid cells (sex)

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12
Q

Prophase 1

A

Homologous Chromosomes shorten, visible
Nuclear membrane & Nucleolus dissappear
Spindle starts to form
Chiasma from pairing of homologous pairs

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13
Q

Metaphase 1

A

Homologous chromosomes line up at equator
Centromere of chromosome attaches to extended spindle fibres
Random arrangement at equator

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14
Q

Anaphase 1

A

Spindles contract, shorten & pull chromosomes to opp sides of cell
Creating random assortment

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15
Q

Telophase 1

A

Nuclear membrane and Nucleolus reform
Each pole has half no. of chromosomes present in original cell
Invagination of cleavage furrow deepens till cytokinesis & karyokinesis occurs to form 2 different daughter cells

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16
Q

Meiosis significance

A

Process reduces diploid to haploid
Produces Gametes for fertilisation
Ensures no. of chromosomes in species stays constant over generations
Genetic variation

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17
Q

Autosomes

A

22 pairs of Chromosomes which aren’t sex cells in diploid cell

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18
Q

Bivalent

A

Homologous chromosomes held together by DNA cross over

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19
Q

Centriole

A

Organelle in cytoplasm giving rise to spindle fibres during mitosis and meisos

20
Q

Chiasma

A

Point where crossing over takes place between chromatids of homologous pair during prophase 1

21
Q

Mitosis

A

Process of cell division where resulting daughter cells have same diploid chromosomal no. as original parent cell

22
Q

Non disjunction

A

Failure of homologous chromosome to divide leading to extra chromosome or one less chromosome in another gamete

23
Q

Spindle fibres

A

Micros tubules that form during cell division

24
Q

Gonosomes

A

Last Single pair of sex chromosomes (XX or XY)

25
Q

Significance of meoisis

A

Genetic variation
Reduced genetic content by half
Gametes produced for fertilisation
Ensures no. of chromosomes in species remains constant

26
Q

How Genetic variation occurs

A

Crossing over
Random arrangement at equator
(metaphase 1 & 2)
Random fertilisation

27
Q

Where does Meiosis in animals occur

A

Female: ovary
Male: testis

28
Q

Where does Meiosis occur in cell

A

In animal cell:
Centrosome consisting of centriole form spindle fibres that attach to chromosome during meiosis

29
Q

Fertilisation

A

Fusion of a sperm and ovum to form a diploid zygote

30
Q

Interphase

A

Phase in cell cycle where DNA replicates

31
Q

Importance of DNA replication

A

Helps double genetic material to be shared equally during cell division

32
Q

Tetrads

A

Homologous pairs carrying genes controlling same inherited traits

33
Q

Prophase 2

A

Centriole move to opp sides
Nuclear membrane & Nucleolus disintegrate.
Spindle fibre forms

34
Q

Metaphase 2

A

Centromeres attach to spindle fibres
Single chromosomes now like Up at equator
Random arrangement

35
Q

Anaphase 2

A

Centromeres split up
Chromatids move to opp sides
Random arrangement
Spindle fibres shorten & contract & pull chromotids to opp poles

36
Q

Telophase 2

A

Nuclear membrane & Nucleolus reforms
Cytokinesis occurs.
4 haploid daughter cells produced.
Genetically different

37
Q

Difference in prophase 1 & 2

A

No crossing over ring prophase 2, no bivalent
Chromosome have a patched appearance in prophase 2

38
Q

Metaphase 1 & 2 differences

A

1: pairs of chromosomes align at equator but 2: single pairs align

39
Q

Anaphase 1 & 2 differences

A

2: split centromeres

40
Q

Telophase 1 & 2 differences

A

2: unreplicated chromosome / single stranded
2: 4 haploid daughter cells that are genetically different but 1: 2 identical daughter cells

41
Q

Difference between meiosis and mitosis

A

Mitosis is for somatic cells and meiosis is for gametes (site)
Mitosis is for growth meiosis is for formation of haploid Gametes
Mitosis makes 2 identical cells and meiosis makes 4 genetically different haploid cells
Mitosis have 1 division and meiosis has 2

42
Q

Variation importance

A

Forms raw material for natural selection
Increases survival chance
Creates favorable features and conditions

43
Q

Causes & consequences of non - dysjunction

A

Spindle fibres fail to separate during meiosis
One pair of homologous chromosome fail to separate in anaphase 1 or replicated chromosome does not separate & move into different cells in anaphase 3
2 of 4 gametes receive extra copy of affected dna
2 of 4 chromosomes lack dna

44
Q

Trisomy

A

Non dysjunction in meiosis 1 resulting in 21 down syndrome

45
Q

Characteristics of someone with down syndrome

A

Small eyes
Flattened nasal bridge
Protuding tongue
Broad neck
Epicanthic fold

46
Q

Cause of abnormal chromosome count

A

Homologous pairs fail to separate in meiosis 1
Or replicated chromosomes fail to separate in meiosis 2

47
Q

Types of nondisjunction

A

Trisomy (3 chromosomes on set 21)
Monomy 23 (has 1 chromosome in set 23)

Life Science (4 decks)

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