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Biology > DNA Into Chromosomes > Flashcards

DNA Into Chromosomes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

How is DNA arranged?

A

It is arranged into fibers called chromatin

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2
Q

What does DNA wrap around to form nucleosomes

A

histone

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3
Q

What do nucleosomes condense into

A

chromatin

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4
Q

what do chromatin condense into

A

chromosomes

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5
Q

Define genome

A

The complete DNA sequence in every cell of an organism

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6
Q

Cell Theory

A
  • 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
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7
Q

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

A

it becomes two cells

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8
Q

What are the three functions of cell division?

A
  • growth of organism
  • repair of tissues and organs that have been damaged
  • maintenance to replace dying or dead cell
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9
Q

somatic cell definition

A

body cells of animals

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10
Q

How long does active dividing take (range)?

A

between 12 to 24 hours

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11
Q

What are the stages of the cell cycle in order?

A

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

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12
Q

What happens during interphase?

A

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

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13
Q

What happens in G1 (gap 1)?

A

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

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14
Q

What happens during S phase (synthesis)?

A

cellular DNA is copied or replicated

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15
Q

During the S phase, how does DNA exist?

A

DNA exists during this phase as uncondensed fibres called chromatin

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16
Q

What happens during the G2 phase?

A

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)

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17
Q

What is mitosis?

A

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

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18
Q

What are the 4 phases of mitosis?

A

early prophase, late prophase, metaphase, anaphase and telophase

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19
Q

What is the result of mitosis?

A

2 daughter cells that are genetically identical

20
Q

What happens during prophase?

A
  • 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
21
Q

Are the chromatin fibers visible during early prophase?

A

Yes. They can be seen with a light microscope.

22
Q

What happens during late prophase?

A
  • 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
23
Q

What happens during metaphase?

A
  • 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
24
Q

What happens during Anaphase?

A

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

25
Q

What happens during telophase?

A
  • 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.
26
Q

What happens during cytokinesis

A
  • 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.
27
Q

What happens after cytokinesis?

A

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.

28
Q

How many chromosomes and pairs do human somatic cells have?

A

46 chromosomes and 23 pairs

29
Q

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

A

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

30
Q

What are the first 22 pairs called?

A

autosomes

31
Q

How many autosome pairs are there?

A

22

32
Q

What is the last chromosome pair?

A

The sex chromosomes

33
Q

What are the two sex chromosomes?

A

the X and Y

34
Q

What sex chromosomes do human females have?

A

X and X

35
Q

What sex chromosomes do human males have?

A

one X and one Y

36
Q

What are homologous chromosomes?

A

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

37
Q

Are homologous pairs identical?

A

No!

38
Q

What are genes?

A

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

39
Q

How are homologous chromosomes related in the information they carry?

A

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

40
Q

Allele definition

A

different forms of the same gene

41
Q

What does the difference in allele shape account for?

A

The differences in specific traits - brown hair vs blond hair

42
Q

Karyotype

A

an individual set of chromosomes that can be photographed

43
Q

How are karyotypes prepared?

A

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

44
Q

What happens after the karyotypes are prepared?

A

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

45
Q

How are autosomes labelled?

A

By numbers 1 through 22

Biology (22 decks)

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