Chapter 2 - Meiosis Flashcards

1
Q

What is sexual reproduction?

A

Combines genetic material from 2 parents to form a gentically unique individual

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2
Q

What is one advantage of sexual reproduction

A

Increases genetic diversity
Increases survival chances

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3
Q

What are the two disadvantages of sexual reproduction?

A

Takes time and energy to find a mate
Lower rate of offspring production

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4
Q

What are body cells/somatic cells called?

A

Diploid cells (2n)

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5
Q

What are haploid cells?

A

Haploid cells are our gametes/sex cells and only contain one copy of a chromosome (n)

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6
Q

What is the total number of chromosome is one somatic cell?

A

46
(22 pairs of autosomes - non sex chromosome)
(1 pair of sex chromosomes)

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7
Q

What is a homolog/homologous pair?

A

A pair of chromosomes which contain the genetic code for the same features

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8
Q

What is Meiosis?

A

Producing four haploid gametes from a single parent cell

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9
Q

Where does Meiosis occur?

A

Gonads

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10
Q

What differentiates Meiosis from Mitosis?

A

Meiosis has two deparate division events rather than one because they are producing four haploid gametes.

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11
Q

What happens before meiosis begins?

A

DNA replication occurs during the S phase to produce identical sister chromatids

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12
Q

What does Meiosis 1 involve?

A

Separation of homologous chromosome from 2n to n

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13
Q

How many stages are there in total for Meiosis?

A

8 (Meiosis stage 1 = 4 phases. Meiosis stage 2 = 4 phases)

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14
Q

What is a parent cell called?

A

Germline cell - diploid (2n)

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15
Q

Describe the events at prophase 1

A
  • replicated DNA condenses
  • centrioles start to produce spindle fibres
  • Nuclear envelope breaks down
  • Spindle fibres attach at centromeres and move to opposite ends
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16
Q

What occurs at prophase 1?

A

Synapsis

17
Q

What is synapsis?

A

The homologous chromosome will pair up

18
Q

What is crossing over?

A

The sister chromatids closest to each other cross over
Two chromatids can swap equivalent genetic material

19
Q

What is a Chiasma?

A

The point at which crossing over occurs

20
Q

Describe the events at Metaphase 1

A

Chromosomes line up in homologous pair at centre

21
Q

Describe the events at Anaphase 1

A

Spindle fibres are pulled back
Homologous pair are separated
Sister chromatid remains together

22
Q

Describe the events at Telophase 1 and cytokineses

A

Often occur at the same time
Cleavage furrow or cell plate forms and separates the cytoplasm into two separate cells

23
Q

What does Meiosis 2 involve?

A

Separates sister chromatids

24
Q

Which stage of Meiosis is similar to Mitosis?

A

Meiosis stage 2

25
Q

Describe the events at prophase 2

A

Spindle reforms and attaches to centromeres of condensed chromosomes

26
Q

Describe the events at metaphase 2

A

Chromosomes line up down the equator of the cell

27
Q

Describe the events at anaphase 2

A

Spindle fibres pull back towards centrioles
Sister chromatids are separated

28
Q

Describe the events at telophase 2 and cytokineses

A
  • Groups of chromosomes reach the poles of the cell
  • Nuclear envelope starts to form around the group of chromosomes
  • Spindle fibres break down and chromosomes start to unwind
  • Cleavage furrow forms
29
Q

How does meiosis produce genetically different offspring? (3 ways)

A
  • The chromosomes are arranged randomly
  • Process of crossing over
  • Random fertilisation of haploid gametes
29
Q

What is the product of Meiosis 2?

A

Four non-identical haploid gametes