Meiosis and Sexual Life Cycles

Question 1

What happens during asexual reproduction?

Answer 1

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

Question 2

What happens during sexual reproduction?

Answer 2

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

Question 3

What is heredity?

Answer 3

The transmission of traits from on generation to the next

Question 4

What is genetics?

Answer 4

The study of heredity and inherited variation

Question 5

What are genes?

Answer 5

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

Question 6

How are genes passed to the next generation?

Answer 6

Via reproductive cells called gametes (sperm and eggs)

Question 7

How many pairs of chromosomes do human somatic cells have?

Answer 7

23 pairs

Question 8

What is a karyotype?

Answer 8

An ordered display of the pairs of chromosomes from a cell

Question 9

The two chromosomes in each pair are called?

Answer 9

Homologous chromosomes, or homologs

Question 10

What are the characteristics of chromosomes in a homologous pair?

Answer 10

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

Question 11

Each pair of homologous chromosomes includes one chromosome from __ ___

Answer 11

Each parent

Question 12

What is a diploid cell?

Answer 12

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

Question 13

What are the sex chromosomes?

Answer 13

X and Y ; determines the sex of the individual

Question 14

What are the human females sex chromosomes?

Answer 14

XX

Question 15

What are the human males sex chromosomes

Answer 15

XY

Question 16

What are the remaining 22 pairs of chromosomes called?

Answer 16

Autosomes

Question 17

What is a haploid cell?

Answer 17

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

Question 18

What is an ovum?

Answer 18

Unfertilized egg

Question 19

What is the sex chromosome in an ovum

Answer 19

Always X

Question 20

What is the sex chromosome in a sperm cell

Answer 20

X or Y

Question 21

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

Answer 21

meiosis ; fertilization

Question 22

Where does meiosis take place?

Answer 22

In two consecutive cell divisions called meiosis I and meiosis II

Question 23

The two cell divisions result in ___ daughter cells

Answer 23

Four

Question 24

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

Answer 24

Half

Question 25

What are the steps of meiosis I?

Answer 25

- Prophase I - Metaphase I - Anaphase I - Telophase I and cytokinesis

Question 26

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

Answer 26

- 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

Question 27

What happens to nonsister chromatids?

Answer 27

They are broken at precisely matching points

Question 28

What does the synaptonemal complex do?

Answer 28

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

Question 29

What happens during synapsis?

Answer 29

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

Question 30

What are the steps of meiosis II?

Answer 30

- Prophase II - Metaphase II - Anaphase II - Telephase II and Cytokinesis

Question 31

What is the purpose of meiosis I?

Answer 31

To separate homologous chromosomes

Question 32

What is the purpose of meiosis II?

Answer 32

To separate sister chromatids

Question 33

What is the original source of genetic diversity?

Answer 33

Mutations

Question 34

What do mutations do?

Answer 34

Create different versions of genes called alleles

Question 35

Reshuffling of alleles during sexual reproduction produces ___ ___

Answer 35

Genetic variation

Question 36

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

Answer 36

The behavior of chromosomes during meiosis and fertilization

Question 37

What three mechanisms contribute to genetic variation?

Answer 37

- Independent assortment of chromosomes - Crossing over - Random fertilization

Question 38

What happens during independent assortment of chromosomes?

Answer 38

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

Question 39

Crossing over produced what?

Answer 39

Recombinant chromosomes which combine DNA inherited from each parent

Question 40

How does crossing over contribute to genetic variation?

Answer 40

By combining DNA from two parents into a single chromosome

Question 41

How many crossover events occur per chromosome in humans?

Answer 41

An average of one to three

Question 42

How does random fertilization add to genetic variation?

Answer 42

Any sperm can fuse with any ovum