Structure of Chromosome, Cell Cycle and Cell division - Biology

Chromatin fibre is made up of DNA and __

Histones

The two sister chromatids of a chromosome are attached to each other at __

Centromere

The structure of DNA was first discovered by __

Rosalind Franklin

DNA strand wound around a histone octamer forms a complex called a __

Nucleosome

A specific sequence of nucleotides on a chromosome constitutes a __

Gene

The chromatin material is formed of

DNA and Histones

The term “chromosomes” literally means

Coloured bodies

The number of chromosomes is halved in

Both ovary and testis (Meiosis)

Synthesis phase in the cell cycle is called so for synthesis of

DNA

Correct sequence of mitosis is

Prophase → Metaphase → Anaphase → Telophase

Chromosomes are duplicated in

S phase

Triple hydrogen bonds are present between

Guanine and Cytosine

In the cells of a human male body the number of autosomes is

22 pairs

The basis of genetic variation in organisms occurs due to

Crossing over

After a mitotic cell division a human female cell will have

44 + XX chromosomes

The correct sequence of phases in interphase is

G1 → S → G2

The phase of karyokinesis almost reverse of prophase is

Telophase

The lengthwise arrangement of DNA consists of a phosphate group attached with

Pentose sugar

The number of histone proteins in a nucleosome is

8

The pyrimidine bases of DNA are

Thymine and Cytosine

The female gamete/egg cell of a human will have

22 + X chromosomes

The repeating components of each DNA strand lengthwise are

Nucleotides

The complex structure of DNA strand and a core of histones is

Nucleosome

The type of bond joining complementary nitrogenous bases is

Hydrogen bond

Cell A (mitosis) produces

2 cells

Cell B (meiosis) produces

4 cells

DNA replicates in the __ phase

Synthesis phase

Mitosis occurs in our __ cells

Somatic (body)/ vegetative

Meiosis occurs only in __ cells

Reproductive

Sperms and eggs of humans will have - how many chromosomes each

23 chromosomes each

During meiosis __ chromosomes come to lie side by side

Homologous chromosomes

Non-sister chromatids of a paired chromosome attach at

Chiasma

Two main constituents of chromatin are

DNA and Histones

Two kinds of nucleic acids are

DNA and RNA

Three components of a nucleotide are

Phosphate, sugar, nitrogenous base

Four nitrogenous bases are

Adenine, Guanine, Thymine, Cytosine

Two kinds of nitrogenous bases are

Purine and Pyrimidine

Two components of nucleosome are

DNA and Histone

Two kinds of cell division are

Mitosis and Meiosis

Four phases of karyokinesis are

Prophase, Metaphase, Anaphase, Telophase

Two steps of mitosis are

Karyokinesis and Cytokinesis

Two haploid cells in humans are

Male gamete (22+Y), Female gamete (22+X)

Rungs of DNA ladder are made of

Adenine, Thymine, Guanine, Cytosine

nitrogenous bases in DNA are

Adenine, Thymine, Guanine, Cytosine

Genes are specific sequences of

Nucleotides

A nucleotide is composed of

Phosphate, sugar, nitrogenous base

Nucleosomes are groups of

Histones + DNA strands

If a cell has 46 chromosomes, chromatin fibres inside during interphase are,

46

Assertion: Both centromere and centrosome are parts of chromosome
Reason: The centromere is the region where spindle fibres attach while the centrosome helps in formation of spindle fibres

False
True

Assertion: The basic structural unit of DNA is nucleotide
Reason: DNA is composed of repeating nucleosome made of nucleotide and histone proteins

True
False

Assertion: Centrosome is the point of attachment of two chromatids of a chromosome
Reason: Centrosome initiates and regulates cell division as it helps in spindle fibre formation

False
True

Assertion: Meiosis occurs during gamete formation in gonads
Reason: During meiosis chromosome number remains the same in parent and daughter cells

True
False

DNA replicates in the

S phase

Mitosis occurs in

Somatic/vegetative (body) cells

Where does meiosis occur

Reproductive cells

Human sperms and eggs will have how many chromosomes

23 chromosomes each

In meiosis, __________ chromosomes come to lie side by side

Homologous

Non-sister chromatids attach at - where

Chiasma

Chromosomes at equator - when

Metaphase

Daughter chromosomes move to poles - when

Anaphase

Chromosomes become visible as threads - when

Prophase

Chromosomes lose distinctness into chromatin network - when

Telophase

Define Chromosome

Highly coiled chromatin fibres (DNA + histones) carrying genetic information

Define Gene

Specific sequence of nucleotides on chromosome coding for a protein/trait

Define Cell Division

Process where a cell divides and distributes chromosomes to daughter cells

define Chromatid

One of the identical strands of a duplicated chromosome

Define Aster

Star-like structure of centrioles + rays formed in animal cell mitosis

Gametes must be produced by meiosis - why

To halve chromosome number and restore diploid state at fertilisation

Meiosis is called reductional division - why

Because it reduces chromosome number by half (diploid → haploid)

Children of same parents differ - why

Due to recombination and genetic variation in meiosis

full form - DNA

Deoxyribonucleic acid

full form - RNA

Ribonucleic acid

Adenine, Guanine, Adrenaline, Thymine → Odd:

Adrenaline; Remaining: Nitrogenous bases

Pentose sugar, Histones, Phosphate group, Nitrogenous bases →

Odd: Histones; Remaining: Nucleotide components

Metaphase, Anaphase, Interphase, Telophase →

Odd: Interphase; Remaining: Phases of mitosis

G1 phase, M phase, G2 phase, S phase → Odd:

M phase; Remaining: Phases of interphase

Chromoplast, Chromosome, Chloroplast, Leucoplast → Odd:

Chromosome. Remaining: Plastids;