3. struktur dan fungsi kromosom

8/20/2019 3. Struktur Dan Fungsi Kromosom

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STRUKTUR DAN

FUNGSI KROMOSOM

Laboratorium GenetikaFakultas Biologi UGM

Dr. Budi Setiadi Daryono, M.Agr.Sc.


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1. What is a chromosome?

2. When and how can chromosomes be visualized?

3. How many chromosomes does an organism have?

4. What is accomplished during the process ofmitosis and meiosis?

5. What are the sources of genetic variation?

CONCEPT OF GENETICS


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Kromosom Eukaryotik dan

Prokaryotik


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The bacterial genome is composed of

one circular chromosome

4

-

5

Mb long

Condenses by

supercoiling and looping

into a densely packed

nucleoid body

Chromosomes replicate

inside cell and cell divides

by binary fissionFig. 14.4 b


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The process of asexual reproduction in

prokaryotes is called binary fission

The two daughter cells are identical to the

original parent cell, each with a single

chromosome

Following DNA replication, the two resulting

chromosomes separate as the cell elongates

Cell Division in Prokaryotes


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Chromosome

Each chromosome has a constriction point called the centromere,

which divides the chromosome into two sections, or arms.

The short arm of the chromosome is labeled

the p arm

. The long

arm of the chromosome is labeled

the q arm

.


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NUKLEOPROTEIN


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Chromosome structure

HISTONES are proteins with a high proportion of positively charged amino acids (lysine and arginin),

which enable them to bind firmly to the negatively

charged DNA double helix.

There are 5 types of histone molecules: H1, H2A,

H2B, H3, and H4.

Except for H1, they occur in exactly equal numbers.

in less condensed chromatin fibers, it becomes apparent

that DNA between nucleosomes is bound to H1 histones.

DNA in metaphase chromosomes must be shortened

10,000-fold by very efficient packing.

This occurs in discrete units, the NUCLEOSOMES,

Consisting of DNA and histones.


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NUKLEOSOM


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The nucleosome

the fundamental unit of chromosomal packaging

arises from DNAs association with histones

X-ray diffraction analysis – DNA does not coil

smoothly

– Base sequences dictate

preferred nucleosome

positions along DNA – Spacing and structure

affect genetic function


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Packaging DNA

Histone proteins

Histoneoctomer

B DNA Helix

2 nm


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Packaging DNA

Histone proteins

B DNA Helix

Histoneoctomer

2 nm


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Packaging DNA

Histone proteins

Histoneoctomer

Nucleosome

11 nm

B DNA Helix 2 nm


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Packaging DNA


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Packaging DNA


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Packaging DNA

Protein scaffold

11 nm“Beads on

a string”

30 nm

Tight helicalfiber

LoopedDomains200 nm


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Packaging DNA

Protein scaffold

Metaphase

Chromosome

700 nm

11 nm

30 nm200 nm

2 nm

Looped Domains

Nucleosomes

B DNA Helix

Tight helical fiber


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Models of higher level compaction seek to

explain extreme compaction of chromosomes at

mitosis

Formation of 300 A fiber through supercoiling


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Centromere structure and

function

Fig. 12.11 a

Ch Ch tid


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Replication

Chromosomes, Chromatids

and Centromeres

Centromere

Chromosome

arm

Chromosome

arm

Identicalchromatid

Chromatid

Anaphase

A packagedchromosome

Two identical

chromosomes


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Chromosome Morphology

Chromosomearm

Chromosome

arm

Centromere

Submetacentric Acrocentric TelocentricMetacentric

q arm

p armpetite

Chromosomes can be distinguished on the basis of size and the relative

location of centromeres.


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Long arm

Short arm

The location of the centromere on each chromosome gives thechromosome its characteristic shape, and can be used to help

describe the location of specific genes.

Characteristic shapes of

chromosomes


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BENTUK KROMOSOM

1. TELOSENTRIS : sentromerterletak di terminal (bagian ujung

kromosom)

2. AKROSENTRIS/SUB

TELOSENTRIS : sentromer terletak di sub terminal (mendekati

ujung kromosom)

3. SUB METASENTRIS : sentromerterletak di sub median (mendekati

bagian tengah)

4. METASENTRIS : sentromer

terletak di median (bagian tengah)

Adaempatbentukkromosomberdasarkanletaksentromer:

1 2 3 4

1 2 3 4


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Bentuk kromosom Nilai Indeks Sentromer (NIS)

p

x 100

p + q

p = panjang lengan pendek kromosomq = panjang lengan panjang kromosom

p+q = panjang absolut kromosom

Nilai Indeks Sentromer


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Posisi

Sentromer

Bentuk Kromosom Simbol

Kromosom

Rata-rata

NIS

Median Metasentris m 38 -50

Sub Median Sub Metasentris sm 26 - 37

Sub Terminal Akrosentris /

Sub Telosentris

st 13 - 25

Terminal Telosentris t 0 - 12

Nilai Indeks Sentromer


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TIPE KROMOSOM

2. KROMOSOM KELAMIN sex chromosome) :

kromosomyangadahubungannyadengan

penentuanjeniskelamin

1. AUTOSOM : kromosom yang tidak ada

hubungannya dengan penentuan jenis

kelamin


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Karyotype

A display of the paired homologues

chromosomes from a cell

Allows determination of:

sex of an individual,

abnormal chromosome number,other chromosome abnormalities,

etc.

A l l k t k t


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A closer look at karyotypes:fully compacted metaphase chromosomes have

unique, reproducible banding patterns.

Bandingpatterns help

locate genes

How many chromosomes do people have?


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How many chromosomes do people have?Banding

pattern

during

metaphase

Banding

pattern

during

prophase

In humans, each cell normally contains 23 pairs of chromosomes,

for a total of 46.

The 22 autosomes are numbered by size. The other two

chromosomes, X and Y, are the sex chromosomes.


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KARYOTYPE

Bawang Putih (Allium sativum L.) Kultivar Sangga

Formula Karyotype = 2n = 2x = 16 = 14m + 2 sm

m = metasentris ; sm = submetasentris

m m m m m sm m m


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Karyotype sapi os taurus taurus).

Ada berapa dan bagaimana formula

karyotipenya?

Karyotype manusia dengan jenis kelamin laki-laki.

Pasangan kromosom 1-22 adalah autosom.

Kromosom X dan Y adalah kromosom kelamin.

3. struktur dan fungsi kromosom

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