DNA and basic genetics

Question 1

Chromatin and Chromosome:

Answer 1

During the life of the cell, the 𝐷𝑁𝐴 is found as a chromatic fibre called chromatin. This is the open form of 𝐷𝑁𝐴 with associated proteins around it that help it stay untangled.

During cell division, we can witness the 𝐷𝑁𝐴 in its condensed from. That form is called chromosome.

Question 2

Chromosomes in the human body:

Answer 2

The human cell includes 46 chromosomes that are made of two sets:

• One originated from its mother (one set of 23 chromosomes).
• One originated from its father (another set of 23 chromosomes).

Each chromosome in each set has its own coding for type of characteristics. Because we have two sets,
there are two chromosomes with different coding for the same type of characteristics that form a pair.
Such pair is called “Homologous Chromosomes”. In short, Homologous chromosomes Is a term to describe
each pair of chromosomes that are coding for the same characteristics.

Question 3

What does choromosomes contain:

Answer 3

The 46 chromosomes can be divided to:

• 22 (44 chromosomes in total) pairs of autosomal chromosomes coding to all body functions.
• 1 (two chromosomes) pair of sex chromosomes coding for sexually characteristics.

Diploid cell (symbolized as 2𝑛) is any cell that contains two sets of chromosomes. Haploid (symbolized as 1𝑛) cells are cells that contain one set only. 
Haploid are found only as sperm cells (in males) and oocyte cells (in females).

Question 4

Chromatin:

Answer 4

𝐷𝑁𝐴 double helix around histones.

Question 5

Histones:

Answer 5

Packing proteins.

Question 6

Chromosomes:

Answer 6

Chromatin’s condensed form that only apparent when the cell divides.

Question 7

Homologous Chromatid (homologs)

Answer 7

Every somatic cell has 46 chromosomes or 23 homologous pairs. Meaning: 1 maternal chromosome and 1 paternal chromosome (a set). They are similar but
not identical; they carry the same genetic material but in different traits/coding.

Question 8

Chromatid

Answer 8

1 identical copy of a replicated chromosome creating Sister Chromatids.

Question 9

Sister Chromatids

Answer 9

2 identical copies joined together at a region known as the Centromere.

Question 10

Diploid cell

Answer 10

A cell that contains 2 sets of chromosomes. Each set inherited by each parent.

Question 11

Haploid cell

Answer 11

A cell that contains only one set of chromosome (after meiosis ΙΙ).

Question 12

Somatic cells

Answer 12

All cell except Gametes. These cell contain 46 chromosomes (23 homologs). Their
division forms two identical daughter cells throw mitosis.

Question 13

Gametes

Answer 13

Sperm and oocyte cells (sex cells) that contain only on set of chromosomes.

Question 14

Germ cells

Answer 14

Diploid cell that give rise to Gametes. They generate four non-identical daughter cells through meiosis ΙΙ.

Question 15

Crossing

Answer 15

The part is meiosis Ι where the homolog chromosomes in the tetrad are exchanging
genetic material

Question 16

Chiasma

Answer 16

A place where a genetic material was exchanged in meiosis Ι.

Question 17

Centromere

Answer 17

A region in the sister chromatids where they are attached to one another.

Question 18

Kinetochore

Answer 18

A protein structure in eukaryotes which assembles on the centromere and links the
chromosome to microtubules polymer from the mitotic spindle during division.

Question 19

Telomere

Answer 19

A region of a 𝐷𝑁𝐴 at the start and end of each chromosome. It protects it from
deterioration and from fusing with neighbour chromosomes. Without it the genomes would
progressively lose information during division.

Question 20

Mitotic spindle

Answer 20

A structure that separates Sister Chromatids or Humongous Chromosome into
daughter cells during division. It is made out of microtubules.

Question 21

Centriole

Answer 21

Microtubules that are involved in the organization of the mitotic spindle and the
completion of cytokinesis.