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Biology 111A Exam 2 > Meiosis > Flashcards

Flashcards in Meiosis Deck (47):
1

What is being made in meiosis?

gametes/sex cells

2

What are the two goals of meiosis?

Cut chromosomes in half (1N)
Shuffle genes

3

Why do we want to shuffle genes in meiosis?

To increase genetic variation for adaptation

4

What are homologous chromosomes?

Gene #1 from Mom, Gene #1 from Dad, same size and shape, they code for the same things but the traits might be different

5

What are alleles?

Versions of genes (blue, brown, green eyes)

6

What are autosomes?

every other chromosome besides sex chromosomes

7

What are sex chromosomes?

Last chromosome set in a karyotype, codes for whether the zygote will develop to be male or female

8

What is ploid?

Number of chromosomes

9

The only haploid cells we have are what?

Gametes

10

In meiosis, one mother cell (2N) is converted into what?

4 daughter cells (1N)

11

How many total phases are in meiosis?

8

12

What is special about prophase I of meiosis?

tetrads form at synapsis
crossing over

13

What is a tetrad?

When chromosomes come together (synapse) to form 4 legs (tetrads)

14

What is crossing over?

legs of non-sister chromatids cross over for genetic diversity

15

In metaphase I, what happens to the tetrads?

They line up at the equator

16

In anaphase I, what happens to the tetrads?

tetrads separate into dyads

17

What is a dyad?

One crossed over homologous chromosome

18

What are the 2 basic aspects of meiosis?

Maintains chromosome number
Generates diversity

19

Fertilization does what two things after meiosis?

Re-establishes diploid status
Produces new genetic combinations

20

How many genetically different zygotes are there?

2^23

21

What happens during prophase I?

Chromosomes condense
Spindle forms
Tetrads form
Synapsis
Crossing-over occurs (only here)
Nuclear envelope fragments

22

What happens during metaphase I?

Tetrads line up randomly at spindle equator
Spindle fibers attach to chromosomes or reach across equator

23

What happens during anaphase I?

Tetrads separate randomly
Homologous chromosomes separate and move to poles

24

What happens during telophase I?

2 daughter nuclei form
Chromosomes de-condense
Spindle disintegrates
Haploid (2 sister chromatids from homologous pair)

25

What are the accomplishments of meiosis I?

genes shuffled through crossing over
haploid cells were generated

26

What happens during prophase II?

Chromosomes condense
Spindle fibers form
Daughter cell nuclei disappear

27

What happens during metaphase II?

Chromosomes line up at spindle equator randomly
Spindle fibers either attach to chromosomes or reach across equator

28

What happens during anaphase II?

Sister chromatids separate randomly
Daughter chromosomes move to poles

29

What happens during telophase II?

4 daughter nuclei form
chromosomes de-condense
spindle disintegrates
haploid

30

At the end of telophase, what is different about the daughter cells?

They are genetically different from each other and the parent cell

31

What are the accomplishments of meiosis II?

Chromosomes were randomly sorted into daughter cells
Haploid conclusion

32

The occurrence of meiosis is dependent on what?

Species and gender

33

Explain why deer hunting season is in the fall.

The rut. Buck can sense doe pheromones, which are only released during meiosis, which occurrs randomly

34

Males form how many gametes from one mother cell?

4

35

Females form how many gametes from one mother cell?

1

36

What happens during a female's meiotic process?

The cells divide unequally, and the larger daughter cell proceeds to absorb the smaller polar bodies produced

37

When does a human male undergo meiosis?

It starts at puberty and never ends

38

When does a human female undergo meiosis?

It starts in utero by doing meiosis I, pauses until puberty, completes meiosis II once a month until menopause

39

Explain fertilization

Happy, healthy fertilization happens at the fallopian tubes
Takes 6 days to reach the uterus
Large egg cleaves to about 64 cells to survive the trip

40

What is nondisjunction?

Chromosomes fail to separate
Meiosis I- tetrads don't separate
Meiosis II- sister chromatids don't separate

41

What is trisomy?

Three instances of a particular chromosome, rather than just 2

42

What is monosomy?

Absence of one member of a pair of chromosomes

43

What is down syndrome?

Trisomy 21

44

What are some recognizable characteristics of down syndrome?

short stature
eyelid fold
stubby fingers
mental disabilities

45

The chance of a woman having a Down syndrome child increases with what?

Age, starting at 40

46

What are the aspects of abnormal sex chromosome numbers?

too few or too many X or Y chromosomes
greater chance of survival (fewer genes, barr bodies)

47

What are two examples of abnormal sex chromosome number syndromes?

Turner (45, XO)
Klinefelter (XXY)