definitions and imp points

Question 1

nucleosome

Answer 1

it is a core of eight histone molecules with double DNA strands around fit

Question 2

nucleotide

Answer 2

it is the unit of DNA comprising of i) sugar ii) nitrogenous base and phosphate

Question 3

gene

Answer 3

sequence of nucleotides on a chromosome that encodes a specific protein to express a particular physical feature of the body

Question 3

chromosome

Answer 3

it is a condensed form which is visible during the start of cell devision which consists of two sister chromatids joined at some point along the length an d the point of attachment is called centromere

Question 4

components of chromatin / chromosome

Answer 4

histone and DNA

Question 5

nitrogenous bases in RNA

Answer 5

adenine, guanine, cytosine, uracil

Question 6

nitrogenous bases in DNA

Answer 6

adenine, guanine, cytosine, thymine

Question 7

components of nucleotide

Answer 7

nitrogenous base, phosphate, pentose sugar

Question 8

the element (type of bond) joining nitrogenous bases

Answer 8

hydrogenous bonds

Question 9

between adenine and thymine the bond there are __ Hydrogen bonds

Answer 9

double hydrogen bond

Question 10

Between Guanine and Cytosine there are __ Hydrogen bonds

Answer 10

triple hydrogen bond

Question 11

shape of DNA

Answer 11

stranded helix

Question 12

need for new cells

Answer 12

replacement repair reproduction and growth

Question 13

deifne cell cycle

Answer 13

is series of evens that take place in a cell leading to the duplication of its DNA and the subsequent division of the cell tom produce the 2 daughter cells

Question 14

Mitosis:

Answer 14

Produces two genetically identical daughter cells.

sed for growth and repair in somatic cells

Question 15

Meiosis:

Answer 15

Produces four genetically unique daughter cells.

Reduces chromosome number by half, crucial for sexual reproduction.

Question 16

Interphase:

Answer 16

Key Event: Preparation phase. DNA replication occurs.

Sub-phases:G1: Cell growth.S: DNA synthesis.G2: Preparation for mitosis.

Question 17

Prophase:

Answer 17

Chromosomes condense.

Nuclear membrane starts disintegrating.

Spindle fibers form.

Question 18

Metaphase:

Answer 18

Chromosomes align at the metaphase plate.

Question 19

Anaphase:

Answer 19

Sister chromatids are pulled apart to opposite poles.

Question 20

Telophase:

Answer 20

Chromosomes decondense.

Nuclear envelope reforms.

Question 21

Cytokinesis:

Answer 21

Cytoplasm divides, resulting in two daughter cells.

Question 22

Longest Phase:

Answer 22

Interphase (in both mitosis and meiosis):

Reason: It is the preparation phase where the cell grows, replicates DNA, and prepares for division. It can take up to 90% of the total cell cycle time.

Key Processes:G1: Cell growth and preparation.S: DNA replication.G2: Final preparation for division.

Question 23

Shortest Phase:

Answer 23

Anaphase (in mitosis and meiosis):

Reason: It involves a quick separation of chromatids (in mitosis) or homologous chromosomes (in meiosis) to opposite poles.

Key Process: The spindle fibers rapidly pull the chromatids or chromosomes apart, ensuring equal distribution.

Question 24

significant of meiosis

Answer 24

chromosome number is halved

provides missing of genes (maternal and paternal chromosomes get mixed up)

Question 25

what is chiasma

Answer 25

x shaped framed due to the crossing over between the non sister chromatids of the pared homologous chromosomes