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BIOLOGY > CHROMOSOMES > Flashcards

CHROMOSOMES Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define the term chromosome

A

Chromosomes are highly coiled, ribbon like structures formed by the condensation of chromatin fibres during cell divison

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2
Q

Who discovered chromosomes?

A

Walther Flemming

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3
Q

Who first studies the structure of chromosomes?

A

Rosalind Franklin

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4
Q

Who proposed the double helical structure of DNA?

A

Watson and Crick

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5
Q

What is the composition of chromatin fibre?

A

DNA - 40%
Histones - 60%

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6
Q

What is the structure of DNA?

A

Double helical macromolecule

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7
Q

What are nucleotides?

A

Nucleotide is the structural and functional unit of DNA.
DNA is composed of repeating nucleotides.

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8
Q

What are nucleotides made up of?

A

pentose sugars, nitrogenous bases, phosphate and hydrogen bonds

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9
Q

What are the 4 types of nitrogenous bases in DNA?

A

Adenine, guanine, thymine and cytosine

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10
Q

What are the different types of nitrogenous bases in RNA?

A

Adenine, guanine, cytosine and uracil

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11
Q

Define the term histone

A

Histones are proteins which help in the coiling and packaging of DNA into structural units called nucleosome

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12
Q

What are nucleosomes?

A

1 strand of DNA winds around a core of 8 histone proteins and is called histone octamer or nucleosomes

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13
Q

What are the structural and functional units of chromosomes?

A

Nucleosomes

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14
Q

What are the 2 types of nucleic acids?

A

DNA & RNA

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15
Q

Define centromere

A

Centromere is the point of attachment of 2 sister chromatids that appears as a small constricted region

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16
Q

What are the functions of centromere?

A
  1. Centromere helps in attaching the sister chromatids to the spindle fibres
  2. they help in the detaching of the sister chromatids during the anaphase stage
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17
Q

What is the structure of a chromosome?

A

A chromosome is composed of 2 sister chromatids that are joined at the centromere

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18
Q

Define the term chromatid

A

Chromatid is one vertical half of a duplicated chromosome

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19
Q

What are sister chromatids?

A

Sister chromatids are two identical chromatids joined at the centromere

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20
Q

What are genes?

A

Genes are specific sequences of nucleotides on a chromosome that encode particular proteins and are expressed in the form of some particular feature on the body

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21
Q

What is the need for new cells?

A
  1. growth
  2. repair
  3. replacement
  4. reproduction
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22
Q

Define cell cycle

A

Cell cycle is a series of events leading to the duplication of DNA and division of the cell to produce two daughter cells

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23
Q

What are the 2 phases of the cell cycle?

A
  1. interphase
  2. mitosis
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24
Q

What is the interphase?

A

The interphase is a non dividing phase of the cell where the relatively small daughter cells prepare for the next cell division and grow to the same size as the mother cell

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25
Q

What are the 3 phases of the interphase?

A
  1. Growth phase 1
  2. Synthesis phase
  3. Growth phase 2
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26
Q

What are the 2 paths that a cell may follow in Growth phase 1?

A

The cell may withdraw from the cell cycle during Growth phase 1 and enter into a Resting phase or continue to the Synthesis phase

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27
Q

What are the changes in the cell during Growth phase 1?

A
  1. RNA and proteins are synthesized
  2. Chloroplasts or mitochondria duplicate
  3. Cytoplasm increases
28
Q

What is synthesized in the Synthesis phase?

A

DNA is synthesized
chromosomes are duplicated

29
Q

What is synthesized during Growth phase 2?

A

RNA and proteins

30
Q

How does DNA duplicate?

A

The DNA opens at one end, making the 2 strands free, to which new strands form

31
Q

What are the 2 types of cell division?

A
  1. Mitosis
  2. Meiosis
32
Q

What is mitosis?

A

Mitosis is the cell division leading to the production of diploid cells
- one parent cell divides into 2 identical daughter cells

33
Q

What are the 2 phases of mitosis?

A
  1. Karyokinesis
  2. Cytokinesis
34
Q

What is karyokinesis?

A

Karyokinesis is the division of the nucleus of the cell
All the nuclear changes that take place in the cell during cell division can be called karyokinesis

35
Q

What are the 4 phases of karyokinesis?

A
  1. prophase
  2. metaphase
  3. anaphase
  4. telophase
36
Q

What is cytokinesis?

A

The division of cytoplasm is called cytokinesis

37
Q

What changes take place during prophase?

A
  1. The nuclear membrane disappears
  2. nucleolus dissapears
  3. centrioles move towards opposite poles (animal cell)
  4. spindle fibres are formed
  5. chromosomes become distinct
38
Q

What is an Aster?

A

Centrioles are surrounded by radiating rays and are termed as aster

39
Q

What changes take place in the cell during metaphase?

A
  1. chromosomes line up in one plane on the equator
  2. chromosomes attach to the spindle fibres with the help of their centromeres
40
Q

What changes take place in the cell during anaphase?

A
  1. centromere splits
  2. sister chromatids separate
  3. sister chromatids move to opposite poles
  4. a furrow starts developing ( animal cell )
41
Q

What changes take place in the cell during telophase?

A
  1. 2 nucleus form
  2. spindle fibres disappear
  3. nuclear membrane forms
  4. chromatids thin out to become chromatin fibres
  5. furrow deepens ( animal cell )
    cell plate is laid down ( plant cell )
42
Q

Asters are formed in which cell?
(a) animal cell
(b) plant cell

A

(a) animal cell

43
Q

How are spindle fibres formed in animal cells?

A

with the help of centrioles and asters

44
Q

How are spindle fibres formed in plant cells?

A

with the help of microtubules

45
Q

How does cytokinesis occur in animal cell?

A

By furrowing of cytoplasm

46
Q

How does cytokinesis occur in plant cell?

A

By formation of cell plate

47
Q

What is the significance of mitosis?

A
  1. growth
  2. repair
  3. replacement
  4. asexual reproduction
  5. same number of chromosomes is maintained in the daughter cells
48
Q

Why do mitochondria and chloroplasts divide on their own?

A

Mitochondria and chloroplasts have their own DNA and ribosomes which help them produce particular proteins. They divide by simple fission.

49
Q

What is meiosis?

A

Meiosis is the cell division leading to the production of haploid cells or gametes - sperms and eggs

50
Q

What is the significance of meiosis?

A
  1. number of chromosomes are halved - haploid
  2. mixing up of genes occurs
51
Q

How does mixing up of genes take place during meiosis?

A
  1. during the first reduction division, due to the separation of the chromosomes from the homologous pairs
  2. by crossing over
  3. random assortment of chromosomes between the gametes
52
Q

Why is the chromosome number halved during meiosis?

A

As the diploid (2n) number of chromosomes will be restored on fertilization

53
Q

What is crossing over?

A

The exchange of genetic material during meiosis between a pair of non sister chromatids from a homologous pair of chromosomes

54
Q

What is chiasma?

A

The point of attachment between 2 non sister chromatids of a pair of homologous chromosomes during meiosis

55
Q

Where does mitosis occur?

A

Vegetative or somatic parts of the plant

56
Q

Where does meiosis occur?

A

In the reproductive cells

57
Q

Why does meiosis occur?

A

To form gametes

58
Q

How many daughter cells are formed in mitosis?

A

2 daughter cells

59
Q

How many daughter cells are formed in meiosis?

A

4 daughter cells

60
Q

How many divisions occur in
a) mitosis
b) meiosis

A

a) 1 division
b) 2 divisions

61
Q

How many chromosomes are passed on in
a) mitosis
b) meiosis

A

a) 2n - diploid
b) n - haploid

62
Q

When does it occur?
a) mitosis
b) meiosis

A

a) throughout life
b) only during reproductively active age

63
Q

How are the daughter cells with respect to their parent cells after mitosis?

A

daughter cells are identical to parent cells

64
Q

What are homologous chromosomes?

A

Homologous chromosomes are chromosomes that are of the same length and centromere positioning.
One chromosome is inherited from each parent

65
Q

How many hydrogen bonds is adenine paired with thymine with?

A

2 hydrogen bonds

66
Q

How many hydrogen bonds is guanine paired with cytosine with?

A

3 hydrogen bonds

BIOLOGY (7 decks)

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