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Biology 240 > Meiosis and Sexual Life Cycles > Flashcards

Meiosis and Sexual Life Cycles Flashcards

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1
Q

What happens during asexual reproduction?

A

A single individual passes all of its genes to its offspring without the fusion of gametes (clonal)

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2
Q

What happens during sexual reproduction?

A

Two parents give rise to offspring that have unique combinations of genes inherited from the two parents

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3
Q

What is heredity?

A

The transmission of traits from on generation to the next

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4
Q

What is genetics?

A

The study of heredity and inherited variation

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5
Q

What are genes?

A

The units of heredity and are made up of segments of DNA

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6
Q

How are genes passed to the next generation?

A

Via reproductive cells called gametes (sperm and eggs)

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7
Q

How many pairs of chromosomes do human somatic cells have?

A

23 pairs

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8
Q

What is a karyotype?

A

An ordered display of the pairs of chromosomes from a cell

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9
Q

The two chromosomes in each pair are called?

A

Homologous chromosomes, or homologs

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10
Q

What are the characteristics of chromosomes in a homologous pair?

A
  • Same length
  • Same centromere position
  • Same staining pattern
  • Carry out genes controlling the same inherited characters
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11
Q

Each pair of homologous chromosomes includes one chromosome from __ ___

A

Each parent

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12
Q

What is a diploid cell?

A

Two sets of chromosomes (2n) (Ex. in humans, the diploid number is 46)

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13
Q

What are the sex chromosomes?

A

X and Y ; determines the sex of the individual

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14
Q

What are the human females sex chromosomes?

A

XX

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15
Q

What are the human males sex chromosomes

A

XY

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16
Q

What are the remaining 22 pairs of chromosomes called?

A

Autosomes

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17
Q

What is a haploid cell?

A

A gamete containing a single set of chromosomes (n) (Ex. in humans, the haploid number is 23)

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18
Q

What is an ovum?

A

Unfertilized egg

19
Q

What is the sex chromosome in an ovum

A

Always X

20
Q

What is the sex chromosome in a sperm cell

A

X or Y

21
Q

The alternation of ___ and ___ is common to all organisms that reproduce sexually

A

meiosis ; fertilization

22
Q

Where does meiosis take place?

A

In two consecutive cell divisions called meiosis I and meiosis II

23
Q

The two cell divisions result in ___ daughter cells

A

Four

24
Q

Each daughter cell has only ___ as many chromosomes as the parent cell

A

Half

25
Q

What are the steps of meiosis I?

A
  • Prophase I
  • Metaphase I
  • Anaphase I
  • Telophase I and cytokinesis
26
Q

What three events are unique to meiosis and occur in meiosis I

A
  • Synapsis and crossing over: occurs in prophase I, homologous chromosomes physically connect and exchange genetic information
  • Alignment of homologous pairs at the metaphase
  • Separation of homologs during anaphase I
27
Q

What happens to nonsister chromatids?

A

They are broken at precisely matching points

28
Q

What does the synaptonemal complex do?

A

It is a zipper-like structure that holds the homologs together tightly

29
Q

What happens during synapsis?

A

DNA breaks are repaired, joining DNA from nonsister chromatid to the corresponding segment of another

30
Q

What are the steps of meiosis II?

A
  • Prophase II
  • Metaphase II
  • Anaphase II
  • Telephase II and Cytokinesis
31
Q

What is the purpose of meiosis I?

A

To separate homologous chromosomes

32
Q

What is the purpose of meiosis II?

A

To separate sister chromatids

33
Q

What is the original source of genetic diversity?

A

Mutations

34
Q

What do mutations do?

A

Create different versions of genes called alleles

35
Q

Reshuffling of alleles during sexual reproduction produces ___ ___

A

Genetic variation

36
Q

What is responsible for most of the variation that arises in each generation?

A

The behavior of chromosomes during meiosis and fertilization

37
Q

What three mechanisms contribute to genetic variation?

A
  • Independent assortment of chromosomes
  • Crossing over
  • Random fertilization
38
Q

What happens during independent assortment of chromosomes?

A

Each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs (2^n)

39
Q

Crossing over produced what?

A

Recombinant chromosomes which combine DNA inherited from each parent

40
Q

How does crossing over contribute to genetic variation?

A

By combining DNA from two parents into a single chromosome

41
Q

How many crossover events occur per chromosome in humans?

A

An average of one to three

42
Q

How does random fertilization add to genetic variation?

A

Any sperm can fuse with any ovum

43
Q
A

Biology 240 (20 decks)

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