Mitosis and Meiosis

Question 1

What is chromosomes?

Answer 1

Coiled DNA, also contains proteins. It is a gene-carrying structure found during mitosis

Question 2

What is chromatin?

Answer 2

The complex of DNA and proteins that make up chromosomes threadlike in the nucleus during interpahse

Question 3

What is a chromatid?

Answer 3

a single strand of a chromosome which remains joined by a centromere

Question 4

What are sister chromatids?

Answer 4

A chromosome and its duplicate are attached to one another by a centromere until separated during mitosis

Question 5

What is a centromere?

Answer 5

It is the structure that holds chromatids together. It is where the spindle fibres attach to and what holds sister chromatids.

Question 6

What is a haploid?

Answer 6

the number of chromosomes in a gamete. One-half of the full complement of chromosomes, sex cells have haploid chromosome numbers. (n)

Question 7

What is a diploid?

Answer 7

Refers to twice the number of chromosomes in a gamete. Refers to the full complement of chromosomes. Every cell of the body with the exception of sex cells contain diploid chromosome number (somatic) (2n)

Question 8

What is polyploidy?

Answer 8

Having more than 2 (2n) complete copies of the chromosomes.

Question 9

What is the significance of chromosome number in somatic and sex cells?

Answer 9

Sex cells only contain half the amount of chromosomes as the somatic body cells do, they have the complete copy.

Question 10

Haploid gametes VS diploid cells?

Answer 10

Haploid cells are sex cells that only contain 23 chromosomes through meiosis they only contain half of the full complement of chromosomes. While diploid cells are usually body cells and they contain the full complement of 46 chromosomes

Question 11

What are the events of the cell cycle?

Answer 11

The cell cycle contains G1 phase, S phase, G1 phase and finally mitosis/meiosis (nuclear division) phase. Interphase is divided into G1, S and G2 phases, and it contains 90% of the cell’s life cycle.
In the G1 phase, the cell grows to carry out its metabolic processes.
In the S phase the DNA replicates and “births sister chromatids”
The G2 phase is when synthesis is complete.
The main events that occur in interphase are
- the nuclear membrane forms, DNA becomes in the form of chromatin, DNA doubles, and centrioles double.

Question 12

What occurs in prophase?

Answer 12

• The nuclear membrane dissolves
• The chromatin thickens and becomes visible separate chromosomes,
• Centrioles go to the poles and they create spindle fibres.

Question 13

What occurs in metaphase?

Answer 13

• The spindle fibres pull the chromosomes to line up on the center of the cell called the equatorial plate.

Question 14

What occurs in anaphase?

Answer 14

The Spindle fibres pull the sister chromatids apart towards the poles, the chromatids are now called chromosomes.

Question 15

What occurs in telophase?

Answer 15

The nuclear membrane reforms, and chromosomes become chromatin and cytokinesis occurs

Question 15

What is cytokinesis?

Answer 15

The dividing of the cytoplasm

Question 16

Where and why does mitosis occur in organisms?

Answer 16

Cells generally divide for the repair and growth of new cells, so mitosis will occur anywhere in the body a new cell is required. However, the more specialized the cells the fewer divisions will occur. So the skin of humans for example is where mitosis would occur, because skin cells are not specialized and as we are constantly getting cuts and brusies the repair of cells is nessasry.

Question 17

What are the major events of mitosis?

Answer 17

Interphase, prophase, metaphase, anaphase, and telophase.

Question 18

What are the major event of meisos?

Answer 18

Meiosis 1, Interphase, Prophase 1, Metaphase, Anaphase 1, Telophase 1, Meiosis 2

Question 19

How is cancer related to mitosis?

Answer 19

Cancer is caused by the uncontrolled and abnormal cell division that can cause tumours. So bad cells keep duplicating itself killing healthy cells and destroying the body.

Question 20

What is homologous chromosomes?

Answer 20

They are chromosomes that pair together (one from paternal and one from maternal) similar in shape, size, gene arrangement, and gene information.

Question 21

What are non-homologous chromosomes?

Answer 21

Chromosomes paired together that are different in shape, size, gene arrangement, and gene information.

Question 22

What is crossing over?

Answer 22

It is the exchange of genetic material between two homologous chromosomes.

Question 23

What happens at meiosis 1?

Answer 23

reduction in chromosome number

Question 24

What happens in Interphase (meiosis)

Answer 24

Same as mitosis

Question 25

What happens in prophase 1?

Answer 25

• Homologous pairs come together in a process called synapsis, these pairs are called tetrads.
• Crossing over happens (exchange of genetic info)

Question 26

What happens in Metaphase 1

Answer 26

Pairs independently assort on the equatorial plate.

Question 27

What happens at anaphase 1?

Answer 27

Pairs are separated and go to the poles

Question 28

What happens at Telophase 1?

Answer 28

cytokinesis occurs, and we now have two cells.

Question 29

What happens at meiosis 2?

Answer 29

The two cells become 4 haploid cells and it is the same as mitosis.

Question 30

What is the necessity for the reduction of chromosome number before fertilization?

Answer 30

As normal human beings, we receive 23 chromosomes from our mother and 23 from our father so we have a total of 46 chromosomes in total, we would not survive if we had 46 from both parents.

Question 31

What is spermatogenesis?

Answer 31

The production of sperm cells, when spermatagonia divide and differentiate into mature sperm cells. 4 sperm cells are produced and they are very small.

Question 32

What is oogenesis?

Answer 32

production and maturation of mature egg cells called an ova. One egg is produced it is large along with a few polar bodies

Question 33

What are fraternal twins?

Answer 33

This is when multiple ovulation occurs during the same menstrual cycle. Each egg is fertilized differently with separate sperms. (TWO EVERYTHING - almost like being pregnant twice)

Question 34

What are identical twins?

Answer 34

This is when pre-embryonic splitting occurs - same DNA, one house.

Question 35

What is nondisjunction

Answer 35

It is the failure of a pair of homologous chromosomes to separate properly during meiosis. This can lead to monosomy, where there is a single chromosome in place of a homologous pair. OR It can lead to trisomy, where there is an extra chromosome instead of a homologous pair.

Question 36

What is cloning?

Answer 36

It is the process of forming identical offspring from a single cell or tissue, it permits the production of offspring with characteristics identical to those of the parent.

Question 37

What are stem cells?

Answer 37

A cell that can arise from a cell different from itself

Question 38

Explain down syndrome

Answer 38

It is where there is an extra chromosome in the 21st chromosome pair.