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1. Genes &
Chromosomes

2. Chromosomes
• structural unit of genetic
material.
• In the nucleus(eukaryotes).
• Rod shaped, 2chromatids,
centromere(cadherin).
• Each chromatid is a single,
linear double-strand DNA
molecule and associated
proteins.(+small amount
RNA).
• p arm(long one), q
arm(short).

3. Chromosomes:
• bears a particular set of • Two types of
genes. CRMS :
• Different organism = autosomal(22 pair) +
different # of CRMS*. sex(XX) or(XY).
• Half the number of • CRMS # 1= biggest
CRMS is inherited from CRMS.
the mother (maternal • CRMS # 21=
CRMS) and the other smallest one.
half from the
father(paternal CRMS).
• Homologous CRMS are
the same size and
shape.

4. Chromosomes:
• CRMS are visible
during cell division. In
between cell division
they appear thread like
“Chromatin”.
• Two types of
chromatins:
heterochromatin
highly condensed
inactive DNA
Euchromatin

5. Functions of Chromosomes
• unique structure of CRMS keeps the DNA in a
tightly wrapped position.
• control all the activities of a living cell.
• essential for the process of cell division and are
responsible for the replication, division and
creation of daughter cells.
• Chromosome functions include holding genes, the
units of heredity.

6. Genes
• The physical and functional unit of heredity.
• The human genome contains at least 26,000
genes.
• A locus on CRMS constituted of DNA nucleotide
sequence that code for certain characteristics.
• Version of the genes called alleles; their loci are
the same on the homologous chromosome pairs.

7. Genes
• In molecular terms, it is the entire DNA sequence
including exons, introns, and noncoding
transcription- control regions- necessary for
production of functional protein or RNA.
• Genes = regulatory region and transcriptional
region.
• •Exons encode a peptide or functional RNA.
• •Introns will be removed after transcription.

8. Functions of Genes
1. Carrier of traits from one generation of organism
to the next generation of organism.
2. Serve as template for copies of itself.
3. Genes are expressed, mRNA is transcribed from
the gene (template), the mRNA serves as a template
during translation for peptide (protein) synthesis.

9. Chromosomal DNA in coiled
hierarchy
• The length of the 46 DNA molecules in a single
human cell is about two meters. Can’t fit in
the nucleus without condensation.
• Condensation requires intervention of two classes of
proteins : histone proteins(H1, H2A, H 2B, H3 and
H4) and non-histone proteins.
• 1st level of condensation: nucleosome
• bead on a string (11nm)= 2 nm DNA(146 bp*) +
octamer of histones

10. • 2nd level: 30 nm fiber or solenoid.
coiling of beads in a helical structure.(+H1)
• 3rd level: loops, scaffolds and domains.
DNA condensation.mpg

11. T ha nk
yo u
Done by: Shahira M Chahrour.
To: Prof Dr. Mohamad Khalid.