6.7 Production of haploid gametes Flashcards

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1
Q

How many chromosomes are in a somatic cell?

A

46

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2
Q

What is reduction division?

A

Production of gametes through dicision in meiosis that reduces the chromosome umber from diploid to haploid

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3
Q

What is crossing over?

A

When non-sister chromatids of homologous chromosomes exchange corresponding segments

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4
Q

What is independent assortment?

A

The formation of random chromosomes combinations during meiosis that contributed to variation

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5
Q

When does crossing over occur?

A

Prophase I

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6
Q

What is bivalent?

A

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

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7
Q

Name the stages of meiosis

A

Interphase, prophase 1, metaphase 1, anaphase 1, telophase 1, prophase 2, metaphase 2, anaphase 2, telophase 2

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8
Q

What happens before meiosis?

A

A diploid cell has 4 chromosomes (2n=4)

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9
Q

What happens during interphase?

A

DNA is replicated, results in sister chromatids

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10
Q

What happens during prophase 1?

A

Chromosomes condense and nucleur envelope degrades, crossing over occurs

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11
Q

What happens during metaphase 1?

A

Homologous chromosomes line up alongside each other down the equator of cell

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12
Q

What happens during anaphase 1?

A

Seperated from each other, centromeres are pulled to opposite poles by spindle fibres

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13
Q

What happens during telophase 1?

A

Nuclear envelope reforms around each set of chromosomes, fibres disappear, cytokenisis occurs, forms two new cells

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14
Q

What happens during prophase 2?

A

Re-condense if necessary and nuclear envelope breaks down

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15
Q

What happens during metaphase 2?

A

Chromosomes line up along the equator

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16
Q

What happens during anaphase 2?

A

Replicated chromosomes are seperated into single strands by spindle fibres, pulling sister chromatids apart

17
Q

What happens during telophase 2?

A

Nuclear envelope reforms around each set of chromosomes, cytokinesis occurs, forms 4 haploid daughter cells (n=2)

18
Q

What does meiosis produce?

A

Sex cells with infinite variation due to crossing over and independent assortment

19
Q

What is meiosis?

A

The process that produces haploid gametes from a diploid cell

20
Q

What cells are diploid?

A

Somatic cells

21
Q

What cells need to be haploid and why?

A

Egg and sperm cells because they combine so the offspring has the right amount of chromosomes

22
Q

How many divisions are there in meiosis?

A

2

23
Q

How many daughter cells result from one round of meiosis?

A

4 daughter cells

24
Q

Describe the process of crossing over

A

One arm of each homologous chromosome joins (synapses) with the same arm of the pair; mum and dad’s chromosomes are now mixed

25
Q

Describe independent assortment

A

Each sex cell with recieve one copy of each chromosome; the copy of each chromosome that ends up in each sex cell is random-they assort independently

26
Q

Why is variation important?

A

Increased genetic diversity from sexual reproduction aids with the species survival. They are better equipped to survive in changing, unstable environments. Species cannot evolve