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Genetics > Lecture 12 - Mitosis and Meiosis : Simon Whitehall > Flashcards

Lecture 12 - Mitosis and Meiosis : Simon Whitehall Flashcards

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Biology 101 flashcards
1
Q

What are the 5 stages of Mitosis?

A 
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
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2
Q

What is the G0 state?

A

A non dividing senescent state.

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3
Q

What is a kinetochore?

A

Protein structure located at the centromere that serves as attachment point for mitotic spindles.

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4
Q

What is a centriole?

A

Cytoplasmic organelle composed of 9 groups of microtubules that act as foci for creating mitotic spindle fibres.

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5
Q

What is a centrosome?

A

Region of cytoplasm containing pair of centrioles.

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6
Q

What is a centromere?

A

The centre of the chromosome, where the 2 sister chromatids join.

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7
Q

What happens in G2 of interphase?

A

Chromosomes extend

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8
Q

What happens during Prophase?

A

Chromosomes condense and the centrioles divide and move apart.

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9
Q

What happens during prometaphase?

A

Centrioles reach the opposite poles.

Spindle fibres form and attach to the kinetochore.

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10
Q

What happens during metaphase?

A

Centromeres align on the metaphase plate along the midline of the cell., nuclear envelope breaks down.

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11
Q

What happens during anaphase?

A

Centromeres split (once all have lined up on the spindle) and daughter chromosomes migrate to opposite poles as they are pulled by the mitotic spindles.

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12
Q

What happens during Telophase/Cytokinesis?

A

Daughter chromosomes arrive at poles.

Chromosome de-condenses

Nuclear envelope reforms

Cell division occurs.

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13
Q

What is a chiasma?

A

A physical connection between non sister chromatids. This leads to crossing over.

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14
Q

What are the sub-stages of Prophase I?

A 
Leptonema
Zygonema
Pachynema
Diplonema
Diakinesis
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15
Q

What happens during Leptotene?

A

Duplicated chromosomes start to condense.

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16
Q

What happens during Zygotene?

A

Synapsis begins, the chromosomes start to join (bivalent forming)

17
Q

What happens during Pachytene?

A

Synapsis is complete, and crossing over occurs.

18
Q

What happens during Diplotene?

A

Synaptonemal complex disappears, and the chiasma is visible.

19
Q

What happens during Diakinesis?

A

Nuclear envelope fragments, and the bivalent chromosomes are ready for metaphase.

20
Q

What is the synaptonemal complex?

A

A nucleoprotein zipper that forms between the paired homologous chromosomes. It looks like a backbone with lateral elements with chromatin attached to the sides.

It plays an important role in crossing over, and suggests an important role in the formation of chiasmata.

21
Q

What is the metaphase plate?

A

Where all the chromosomes line up on the horizontal axis.

22
Q

What are asters?

A

Very short microtubules.

23
Q

_______ do not act independently in Meiosis.

A

Non-Sister chromatids.

24
Q

What does Bivalent/Tetrad mean?

A

2 pairs of non sister chromatids joined together.

25
Q

What is a dyad?

A

One half of the tetrad.

26
Q

What can happen , and what will not happen between Meiosis I and Meiosis II?

A

There can be a short interphase, but no DNA replication and no chiasmata formation or crossing over.

27
Q

What is the pathway for the development of gametes in a male?

A 
Spermatogonium 
-> Growth
Primary spermatocyte
-> Meiosis I
2 secondary Spermatocytes
->Meiosis II
4 Spermatids
-> Differentiation
4 Spermatazoa
28
Q

What is the pathway for development of gametes in a female?

A 
Oogonium
-> Growth
Primary oocyte
-> Meiosis I
Secondary Oocyte + polar body
-> Meiosis II *of 2ndry oocyte*
Oootid
-> Differentiation
Ovum
29
Q

What happens during meiosis in a female?

A

During development 1st oocyte division takes place but pauses at prophase I.

Meiosis resumes many years later (prior to ovulation) and 2nd division only completed after fertilization.

30
Q

What is Aneuploidy, and how does it develop?

A

Chromosome number is not an exact multiple of the haploid number. Nondisjunction results in aneuploid gametes.

31
Q

What is Trisomy?

A

3 copies of a particular chromosome.

32
Q

Where do Meiosis and Mitosis occur?

A

Meiosis occurs in a diploid cell

Mitosis can occur in haploid and diploid cells.

33
Q

Where does meiosis take place in higher eukaryotes?

A

Testis and Ovary

34
Q

What are some human syndromes associated with trisomies?

A 
Down Syndrome
Edwards Syndrome
Warkany Syndrome 2
Patau Syndrome
Chronic Lymphocytic Leukaemia
35
Q

How do you calculate no. of variations of gametes diploid organisms can produce?

A

2^number of homologous chromosomes.

Genetics (7 decks)

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