DNA Into Chromosomes

Question 1

How is DNA arranged?

Answer 1

It is arranged into fibers called chromatin

Question 2

What does DNA wrap around to form nucleosomes

Answer 2

histone

Question 3

What do nucleosomes condense into

Answer 3

chromatin

Question 4

what do chromatin condense into

Answer 4

chromosomes

Question 5

Define genome

Answer 5

The complete DNA sequence in every cell of an organism

Question 6

Cell Theory

Answer 6

• all living things are composed of one or more cells
• cells are the smallest units of living organisms
• New cells come only from pre-existing cells by cell division

Question 7

what happens at the end of every life cycle of a somatic cell?

Answer 7

it becomes two cells

Question 8

What are the three functions of cell division?

Answer 8

• growth of organism
• repair of tissues and organs that have been damaged
• maintenance to replace dying or dead cell

Question 9

somatic cell definition

Answer 9

body cells of animals

Question 10

How long does active dividing take (range)?

Answer 10

between 12 to 24 hours

Question 11

What are the stages of the cell cycle in order?

Answer 11

Interphase
G1
S
G2
Mitosis
early prophase
late prophase (aka prometaphase)
metaphase
anaphase
telophase
cytokinesis

Question 12

What happens during interphase?

Answer 12

the stage during in which a cell carries out its normal functions. Grows and makes copies of its genetic material in preparation for the next stage of the cycle

Question 13

What happens in G1 (gap 1)?

Answer 13

major period of growth for a cell, cell synthesizes new molecules and organelles

Question 14

What happens during S phase (synthesis)?

Answer 14

cellular DNA is copied or replicated

Question 15

During the S phase, how does DNA exist?

Answer 15

DNA exists during this phase as uncondensed fibres called chromatin

Question 16

What happens during the G2 phase?

Answer 16

cell has DNA in the form of chromatin which is duplicated but not visible
- there are a pair of centrosomes
- the nucleolus is visible
- the nuclear envelope is present)

Question 17

What is mitosis?

Answer 17

the stage during which a cell’s nucleus and genetic material divide

Question 18

What are the 4 phases of mitosis?

Answer 18

early prophase, late prophase, metaphase, anaphase and telophase

Question 19

What is the result of mitosis?

Answer 19

2 daughter cells that are genetically identical

Question 20

What happens during prophase?

Answer 20

• the chromatin fibres become more tightly coiled into chromosomes which can be seen with a light microscope
• the nucleoli disappear
• the duplicated chromosomes appear as identical sister chromatids joined at the centromeres
• the centromeres move away from each other

Question 21

Are the chromatin fibers visible during early prophase?

Answer 21

Yes. They can be seen with a light microscope.

Question 22

What happens during late prophase?

Answer 22

• the nuclear envelope breaks apart
• spindle fibers made of hollow tub-like structures called microtubules extend from each centrosome and begin to attach contromere of the chromosome
• nonkinetochore microtubules extend to lengthen the cell

Question 23

What happens during metaphase?

Answer 23

• the spindle fibres guide the chromosomes to the equator of the cell
• The spindle fibers from opposite poles attach to the centromere of each chromosome
• Each pair of sister chromatids is now single chromosome as long as the chromatids remain joined at the centromere

Question 24

What happens during Anaphase?

Answer 24

During anaphase each centromere
splits apart, and the sister
chromatids separate from each
other.
* The separated sisters chromatids
are now referred to as single
chromosomes.
* The spindle fibres shorten, pulling
the chromosomes to opposite
poles of the cell

Question 25

What happens during telophase?

Answer 25

* Telophase begins when the chromosomes have reached opposite poles of the cell. * The chromosomes start to unwind into strands of less-visible chromatin. * Spindle fibres break down, the nuclear membrane forms around the new set of chromosomes and a nucleolus forms within each new nucleus.

Question 26

What happens during cytokinesis

Answer 26

- the division of the cytoplasm to create two new daughter cells. * During cytokinesis in animal cells, an indentation forms in the cell membrane along the equator of the cell - the indentation deepens until the cell is pinched in two. * The cytoplasm divides equally between the two halves of the cell. * Cytokinesis ends with the separation of the two genetically identical daughter cells.

Question 27

What happens after cytokinesis?

Answer 27

The daughter cells are now in G1 of interphase. * Other cells complete cell division in different ways. * Plant cells have a rigid cell wall covering its cell membrane. Cytokinesis occurs by the formation of a cell plate between the nuclei.

Question 28

How many chromosomes and pairs do human somatic cells have?

Answer 28

46 chromosomes and 23 pairs

Question 29

Within one pair of chromosomes, where is each chromosome from?

Answer 29

one chromosome is from the father and one is from the mother

Question 30

What are the first 22 pairs called?

Answer 30

autosomes

Question 31

How many autosome pairs are there?

Answer 31

22

Question 32

What is the last chromosome pair?

Answer 32

The sex chromosomes

Question 33

What are the two sex chromosomes?

Answer 33

the X and Y

Question 34

What sex chromosomes do human females have?

Answer 34

X and X

Question 35

What sex chromosomes do human males have?

Answer 35

one X and one Y

Question 36

What are homologous chromosomes?

Answer 36

Homologous chromosomes are pairs of chromosomes that appear similar in terms of their length, centromere location, and banding pattern when stained with certain dyes.

Question 37

Are homologous pairs identical?

Answer 37

No!

Question 38

What are genes?

Answer 38

sections of DNA on chromosomes that contain information for the inheritance of specific traits

Question 39

How are homologous chromosomes related in the information they carry?

Answer 39

They carry genes for the same traits, such as hair colour, at the same location but they carry different forms of the same gene.

Question 40

Allele definition

Answer 40

different forms of the same gene

Question 41

What does the difference in allele shape account for?

Answer 41

The differences in specific traits - brown hair vs blond hair

Question 42

Karyotype

Answer 42

an individual set of chromosomes that can be photographed

Question 43

How are karyotypes prepared?

Answer 43

by treating a cell during mitosis to stop division and staining the chromosomes

Question 44

What happens after the karyotypes are prepared?

Answer 44

They have a banding pattern clearly visible under a light microscope, they are then paired and sorted into homologs of descending size

Question 45

How are autosomes labelled?

Answer 45

By numbers 1 through 22