Unit 3 lecture 1 part 2 10/12/22

Question 1

Prophase I typically occupies more than __________ of the time required for meiosis

Answer 1

90%

Question 2

In 1.__________, homologous chromosomes loosely pair up, aligned gene by gene forming structures called 2.__________

Answer 2

1.Synapsis
2.Tertrads

Question 3

In __________, nonsister chromatids exchange DNA segments

Answer 3

crossing over

Question 4

Each homologous pair has one or more X-shaped regions called __________

Answer 4

Chiasmata

Question 5

__________ exist at points where crossing over has occurred. AND THIS STEP IS RESPONSIBLE FOR GENETIC VARIATION IN THE NEXT GENERATION

Answer 5

Chiasmata

Question 6

In __________, tetrads line up at the metaphase plate, with one chromosome facing each pole and Microtubules from one pole are attached to the kinetochore of one chromosome of each tetrad

Answer 6

Metaphase 1

Question 7

In __________, pairs of homologous chromosomes separate from tetrads

Answer 7

anaphase 1

Question 8

In the beginning of 1.__________, each half of the cell has a 2.__________ of chromosomes; each chromosome still consists of two sister chromatids

Answer 8

1.telophase 1
2.haploid cell

Question 9

In __________, a spindle apparatus forms

Answer 9

Prophase 2

Question 10

In __________, the sister chromatids are arranged at the metaphase plate

Answer 10

Metaphase 2

Question 11

In metaphase 2 because of crossing over in meiosis I, the two sister chromatids of each chromosome are ____________________

Answer 11

no longer genetically identical

Question 12

In __________, the sister chromatids separate

Answer 12

Anaphase 2

Question 13

In __________, the chromosomes arrive at opposite poles

Answer 13

Telophase 2

Question 14

Three events are unique to meiosis, and all three occur in __________

Answer 14

Meiosis 1

Question 15

1.__________ and 2.__________ in 3.__________ : Homologous chromosomes physically connect and exchange genetic information

Answer 15

1.Synapsis
2.Crossing over
3.prophase 1

Question 16

__________ at the metaphase plate: Homologous pairs of chromosomes are positioned there in metaphase I

Answer 16

homologous pairs

Question 17

Separation of homologs during __________

Answer 17

anaphase 1

Question 18

Protein complexes called __________ are responsible for this cohesion

Answer 18

cohesins

Question 19

In mitosis, 1.__________ are cleaved at the end of 2.__________

Answer 19

1. Cohesins
2. Metaphase

Question 20

In meiosis, __________ are cleaved along the chromosome arms in __________(separation of homologs) and at the centromeres in __________

Answer 20

chesins
anaphase 1
anaphase 2

Question 21

Meiosis I is called the __________ because it halves the number of chromosome sets per cell from diploid (2n) to haploid (n)

Answer 21

reductional division

Question 22

Meiosis II is called the __________ because the haploid cells divide to produce haploid daughter cells

Answer 22

equational division

Question 23

__________(changes in an organism’s DNA) are the original source of genetic diversity

Answer 23

Mutations

Question 24

Mutations create different versions of genes called __________

Answer 24

alleles

Question 25

Reshuffling of alleles during sexual reproduction produces __________

Answer 25

genetic variation

Question 26

Three mechanisms contribute to genetic variation

Answer 26

1.independent assortment of chromosomes
2.Crossing over
3.random fertilization

Question 27

In __________, each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs

Answer 27

independent assortment

Question 28

Crossing over produces __________, which combine DNA inherited from each parent

Answer 28

recombinant chromosomes

Question 29

Crossing over begins very early in __________, as homologous chromosomes pair up gene by gene

Answer 29

prophase 1

Question 30

In __________, homologous portions of two nonsister chromatids trade places

Answer 30

Crossing over

Question 31

__________ adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg)

Answer 31

Random fertilization

Question 32

__________ results in the accumulation of genetic variations favored by the environment

Answer 32

Natural selection

Question 33

Asexual reproduction is __________ expensive than sexual reproduction

Answer 33

less

Question 34

Overall, genetic variation is evolutionarily __________