Lecture 3: Mitosis and Meiosis

Question 1

Mitosis and meiosis allow for

Answer 1

Mitosis and Meiosis allow for observation of chromosomes
Distinguish size, shape and number

Question 2

What does the cell do in preparation for meiosis and mitosis

Answer 2

In preparation for mitosis and meiosis, each chromosome is a double structure
Composed of a pair of chromatids
Sister chromatids
Held together at the centromere

Question 3

Dividing cell in mitosis in meiosis

Answer 3

Each new cell requires a copy
Prior to division each chromosome makes an exact copy of itself
Results in 2 chromatids
Sister chromatids
In early division stages the sister chromatids remain attached at the centromere
Once in separate nuclei they are again referred to as single chromosomes

Question 4

Karyotype is

Answer 4

A display of a cell’s chromosomes ordered according to size
Enables detailed analysis
Cells arrested in mid-mitosis
Autosomes
Sex chromosomes

Question 5

Chromosome numbers are

Answer 5

can vary between species

Chromosome number is constant for ‘all’ cells of a given species
#can very between species

Question 6

Homologous pairs are

Answer 6

Chromosomes can be arranged in matching pairs
Homologous pairs
Homologous pairs have same size, shape, and functions – same genes (but perhaps different alleles)
They look the exact same

Question 7

Locus is

Answer 7

chromosomal location of a specific gene
Gene address

Question 8

Diploid is

Answer 8

Cell with 2 sets of chromosomes
maternal set + paternal set
2 copies of every gene
2n (n = # of chromosomes in 1 set)

Question 9

Haploid is

Answer 9

Cell with 1 set of chromosomes
1 copy of every gene
Gametes are 1n

Question 10

Mitosis is

Answer 10

Each cell receives the same number and type of chromosomes as were present in the parental cell

Question 11

Meiosis is

Answer 11

Division resulting in cells with half the chromosome number of the parental cell
Sexual reproduction
Gametes are haploid (1n)
If not, the chromosome # would double every generation

Question 12

Cell cycle is

Answer 12

Cell cycle is a series of phases that lead to cell division
The order and regulation of these phases is vital for the process of cell division

Question 13

Phases of the cell cycle

Answer 13

G1
S
G2
M
Collectively the first 3 phrases are called interphase

Question 14

G1 step of the cell cycle is

Answer 14

the first gap phase
Cell growth

Question 15

S of the cell cycle is

Answer 15

synthesis phase
DNA replicated (single to duplicated chromosomes)

Question 16

G2 part of the cell cycle is

Answer 16

the second gap phase
Protein synthesis for division

Question 17

M in the cycle cycle is

Answer 17

mitosis and cytokinesis

Question 18

Mitotic cell division is

Answer 18

Cell divides to produce 2 new cells that are genetically identical to the original cell
Involves mitosis and cytokinesis
Mitosis – division of the nucleus into 2 nuclei
Cytokinesis – division of the cytoplasm to produce 2 daughter cells

Question 19

Biological significance of mitosis

Answer 19

Enables the growth of an organism
From unicellular zygote to multicellular organism
Repair of damaged tissues
Normal cellular replacement (skin, gut lining)
Asexual reproduction reproduction
New organism produced from one parent

Question 20

Stages of mitosis

Answer 20

Prophase
Metaphase
Anaphase
Telophase

Question 21

Prophase of mitosis

Answer 21

Duplicated chromosomes condense
Nuclear membrane dissociates
Mitotic spindle begins to form

Question 22

Metaphase of mitosis

Answer 22

Duplicated chromosomes are aligned along the metaphase plate (equator) in a single row
Metaphase plate is halfway between the 2 poles
Spindle microtubules attach to the centromeres of the duplicated chromosomes

Question 23

Anaphase of mitosis

Answer 23

Sorting process occurs
Connection between sister chromatids is broken
Single chromosomes separate

Question 24

Telophase in mitosis

Answer 24

Single chromosomes have reached poles
Nuclear membranes reform to produce 2 separate nuclei
Chromosomes decondense

Question 25

Cytokinesis in mitosis is

Answer 25

Division of cytoplasm to produce distinct daughter cells Involves cleavage area Constricts like a drawstring to separate cells At end of cytokinesis the daughter cells are in interphase

Question 26

Meiosis is the proccess in and results in

Answer 26

Process by which haploid cells are produced from a cell that was originally diploid A type of nuclear division involved in gamete production Involves one round of chromosome replication and two successive rounds of nuclear division Results in 4 haploid daughter cells

Question 27

Biological significance of meiosis

Answer 27

Ensures consistent chromosome number from generation to generation Ensures variability among offspring due to new combinations of alleles independent of chromosomes at metaphase I Swapping of pieces of homologous chromosomes New combinations of alleles on the same chromosome Random fertilization of gametes

Question 28

Cell cycle differentiats of meisosis is

Answer 28

Meiosis begins after a cell has progressed through G1, S and G2 Two rounds of division are called meiosis I and meiosis II In meiosis I homologous chromosomes are separated – halves the number of chromosomes In meiosis II sister chromatids are separated

Question 29

Synapses and crossing over in meiosis

Answer 29

Synapsis and crossing over are 2 key events that occur in meiosis but not mitosis Synapsis is the process of forming a bivalent Bivalent is formed when homologous chromosomes become very closely associated

Question 30

Crossing over is

Answer 30

Involves a physical, reciprocal exchange of DNA between homologous non-sister chromatids Allows for increased variation in genetic information Chiasma = connection at a crossover site of 2 chromosomes

Question 31

Stages of meiosis

Answer 31

Prophase I Metaphase I Anaphase I Telophase I

Question 32

Prophase I in meiosis is

Answer 32

Chromosomes condense Meiotic spindle begins to form Nuclear membrane dissociates Homologous chromosomes synapse and form bivalents Crossing over occurs

Question 33

Metaphase I in meiosis

Answer 33

Bivalents attach to microtubules of spindle apparatus Bivalents align at Metaphase I plate

Question 34

Anaphase I in meiosis

Answer 34

Homologous chromosomes separate and move to opposite poles Sister chromatids are still attached at centromere

Question 35

Telophase I in meiosis

Answer 35

Duplicated chromosomes arrive at the poles Nuclear membranes form Chromosomes begin to decondense Cytokinesis I occurs 2 cells are produced, each with the haploid number of duplicated chromosomes

Question 36

Meiosis II is

Answer 36

Meiosis II is similar to mitosis However, there is no "S" phase before meiosis II begins The chromatids of each chromosome may no longer be identical because of crossing over

Question 37

Steps in meiosis II

Answer 37

Prophase II Metaphase II Anaphase II Telophase II

Question 38

Difference between meiosis and mitosis chromosome behaviour

Answer 38

Mitosis: Homologous chromosomes independent Meiosis: Homologous chromosomes pair (synapse) forming bivalents until anaphase I

Question 39

Difference between meiosis and mitosis chromosome numbers

Answer 39

Mitosis- identical daughter cells Meiosis- daughter cells haploid

Question 40

Difference between meiosis and mitosis genetic identity of progeny

Answer 40

Mitosis: identical daughter cells Meiosis: daughter cells have new assortment of parental chromosomes Meiosis: chromatids are not identical Crossing over