Chromosome n DNA rearrangement Fatch

(1)

04/21/19 fatchiyah, JB UB 1

Fatchiyah, Ph.D.

(2)

Chromosome & DNA?

• Chromosomes, threadlike structures, first

observed by Nageli in 1842.

• Walter Flemming was the first to follow the

process of mitosis and replication of

chromosomes.

• Thomas Morgan, in his experiments with fruit

flies, described genetic recombination, and

demonstrated that traits were to inherited

together to varying degrees.

• Alfred Sturtevant extended Morgan’s ideas,

used observed recombination rates to

(3)

• Surrounded by a nuclear envelope

•

Perinuclear space

•

Communicates with cytoplasm

through nuclear pores

(4)

The Nucleus

Figure 3.13

Content of nucleus:

•A supportive nuclear matrix •One or more nuclei

•Chromosomes •Chromatin

(5)

What Are Chromosomes?

•

Cytogenetics is the study of

chromosomes and the related disease

states caused by abnormal chromosome

number and/or structure.

•

Chromosomes are complex structures

located in the cell nucleus, they are

composed of DNA, histone and

non-histone proteins, RNA , and

polysaccharides.

(6)

•

Normally chromosomes can't be seen with a

light microscope but during cell division they

become condensed enough to be easily

analyzed at 1000X.

•

To collect cells with their chromosomes in

this condensed state they are exposed to a

mitotic inhibitor which blocks formation of

the spindle and arrests cell division at the

metaphase stage

(7)

Type of chromosome structure

Metacentric Chrom. 1 Acrocentric Chrom. 14 Submetacentric Chrom. 9

1. The short arm is

designated as

p

and

the long arm as

q

.

2. The centromere is the

location of spindle

attachment and is an

integral part of the

chromosome

.

3. It is essential for the

normal movement and

segregation of

chromosomes during

cell division.

(8)

Figure 3.14 Chromosome

Structure

(9)

(10)

(11)

Structural Organization of the

(12)

Structural Organization of the

(13)

Nucleosome Disruption

(14)

(15)

(16)

(17)

Chromosome Facts

• number of chromosomes: 22 pairs + 1 pair

sex-determining chromosomes = 46

– one chromosome of each pair donated from

each parent’s egg or sperm

– sex chromosomes: X,Y for males; X,X for

females

– largest chromosome #1 = ~263 million base

pairs (bp)

(18)

Chromosomes can be “painted” for easy

identification.

By technique of multiplex

(19)

Mitotic

(20)

Gene Facts

• size of human genome: 3.4 billion base

pairs (bp)

• number of human genes: ~100,000

• genes vary in length and can cover

thousands of bases

– avg. size: ~3,000 bp

• only about 5% of the human genome

contains genes

(21)

Chromosomes come in pairs

• Humans have 23 pairs of

chromosomes

–Total of 46 chromosomes

• Fruit flies have 4 pairs of

chromosomes

(22)

Normal Chromosomes



Normal human somatic cells have 46 chromosomes: 22

pairs, or

homologs

, of autosomes (chromosomes 1-22)

and two sex chromosomes. This is called the

diploid

number. Females carry two X chromosomes (46,XX)

while males have an X and a Y (46,XY).



Germ cells (egg and sperm) have 23 chromosomes: one

copy of each autosome plus a single sex chromosome.

This is referred to as the

haploid

number.



One chromosome from each autosomal pair plus one

sex chromosome is inherited from each parent.



Mothers can contribute only an X chromosome to

(23)

Chromosomes of human

Male

Female

(24)

Members of a chromosome pair

• Cells with PAIRS of chromosomes are

diploid

–

di –

means “two”, “double”, “twice”

–

oid

– “appearance”

• The two members of any chromosome pair are

called

homologues, or a homologous pair

• Ex:

– The two “number 1” chromosomes are homologues

– The two “number 21” chromosomes are

(25)

In sexual reproduction

• new organisms (zygotes) are

formed by the joining together of

two sex cells (gametes):

– a sperm cell from a male

and

(26)

What would happen if…….

• a human egg cell had 46 chromosomes

AND

• a human sperm cell had 46 chromosomes?

46 chromosomes

+ 46 chromosomes

92 chromosomes

(27)

Diploid organisms need….

• A way to produce sex cells (eggs and

sperm) that only have ONE member of

each chromosome pair

• In humans, sex cells each have 23

chromosomes

– ONE member of each homologous pair

– Half of amount of chromosome is named

(28)

23 chromosomes

+23 chromosomes

46 chromosomes

(29)

The different possibilities of the way chromosomes will

separate into gametes helps create genetic diversity

(30)

Effect of Crossing Over

Crossing over occurs when homologous

chromosomes pair with each other before the first meiotic division

(31)

Chromosomes

Figure 4-14. Two closely related species of deer with very different

chromosome numbers. In the evolution of the Indian muntjac, initially separate chromosomes fused, without having a major effect on the animal. These two

(32)

The emphasis in the human

genome

Human

26,588 genes

• The nervous system

• The immune system

• The blood system

• Signaling and cell-cell

communication

• Programmed cell

death

Arabidopsis

25, 498 genes

Missing

Different

(33)

Structure of Chromosome - NORs

Interphase nucleus of onion

root tip through light

microscope

(34)

Structure of Chromosome - NORs

electron micrograph of interphase cell from bat pancreas

(35)

(36)

Phase-contrast image of

Drosophila

melanogaster

polytene cromosomes.

A. The end of the X-chromosome is marked with

an arrow. Chromocentre is in the upper right

corner.

B. Shows a magnification of chromomere and

interchromomere bands

(37)

W-chromosome

(38)

Bacterial Artificial Chromosome Manipulation

by Homologous Recombinant

(39)

(40)

Antibodies of a person with an

autoimmune disease stain