1. gradba na hromozomi i citogenetika

8/17/2019 1. Gradba Na Hromozomi i Citogenetika

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Морфологија и градбана хромозоми

Цитогенетика


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Od DNK do

metafaznog

hromozoma


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Hromozomi posmatra

elektronskim mikrosk

hromatida


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Центромерен регион


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MORFOLOŠKI TIPOVI HROMOZOMA

A – telocentričan

B – akrocentričan

C – submetacentričan

D – metacentričan (p = q)

p kra

q kra


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• Chromosomes are arrang

by:

1. size

2. location of centromere

• Banding patterns also hel

identify chromosomes


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Kariotip


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Kariogram


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Полов диморфизам

• Машки

- хетерогаметни

• Женски

- хомогаметни


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Полови хромозоми


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Барово телце

• секс- хроматин

• Barr и Bertram во 1949год

• еден микрон

• хетерохроматичен хромозом

• 12-18

• Lyon-ова хипотеза


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Барово телце


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Mary Lyon

Barova tela

(pokazana strelicam


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Idiogram


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Hromozomi 4 i


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2n = 46


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A B

C

D

F

E

G

2n = 46


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A A A A

HOMOZIGOT (AA)

A A a a

HETEROZIGOT (Aa


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a a a a

HOMOZIGOT (aa )

a a

X

HEMIZIGOT (XaY)

Y

XX


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• The human genome is stored on 23 chromosome pairs and in the

small mitochondrial DNA.

• Twenty-two of the 23 chromosomes belong to autosomal chromo

pairs, while the remaining pair is sex determinative. The haploid h

genome occupies a total of just over three billion DNA base pairs.• The Human Genome Project (HGP) produced a reference seque

the euchromatic human genome, which is used worldwide in

the biomedical sciences.


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• The haploid human genome contains about 23,000 protein-

coding genes, which are far fewer than had been expected b

sequencing.

• In fact, only about 1.5% of the genome codes for proteins, w

the rest consists of non-coding RNA genes regulatorysequences, introns and non-coding DNA.


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Полови хромозоми

• X-хромозом

-субметацентичен

- C-група

• Y-хромозом

-акроцентичен

-G-група

-полиморфизам

-холандричен сектор

-генот за машка сексуал

диференцијација (SR-генот за сперматогенез

(H-Y) антигенот

-генот кој го инхибира развитокот на Милерканали


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• There are estimated to be between 20,000 and 25,000 huma

protein-coding genes.

• The estimate of the number of human genes has been repe

revised down as genome sequence quality and gene

finding methods have improved. In the late 1960s, predictionestimated that human cells had as many as 2,000,000 gene


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Human genes are

distributed unevenly

across the

chromosomes. Each

chromosome

contains various

gene-rich and gene-

poor regions, which

seem to be correlated

with chromosome

bands and GC-content.


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• Most aspects of human biology involve both genetic (inherite

non-genetic (environmental) factors.

• Some inherited variation influences aspects of our biology th

not medical in nature (height, eye color, ability to taste or sm

certain compounds, etc.).


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• some genetic disorders only cause disease in combination

appropriate environmental factors (such as diet).

• With these caveats, genetic disorders may be described as

clinically defined diseases caused by genomic DNA sequenc

variation. In the most straightforward cases, the disorder canassociated with variation in a single gene.


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• For example, cystic fibrosis is caused by mutations in the C

gene, and is the most common recessive disorder in caucas

populations with over 1,300 different mutations known.

• Disease-causing mutations in specific genes are usually sev

terms of gene function, and are fortunately rare, thus geneticdisorders are similarly individually rare.


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GENE DISEASE DOWN SYNDROME


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The human karyotype

• There are 44 autosomes and 2 sex chromosomes in the

human genome, for a total of 46. Karyotypes are pictures

of homologous chromosomes lined up together during Meta

of meiosis. The chromosome micrographs are then arranged

size and pasted onto a sheet.


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X-linked and Y-linked inheritanc

• linked genes are found on the sex X chromosome. X-linked

just like autosomal genes have both dominant and recessive

Recessive X-linked disorders are rarely seen in females and

usually only affect males. This is because males inherit their

chromosome and all X-linked genes will be inherited from th

maternal side.


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• Y-linked inheritance occurs when a gene, trait, or disorder is

transferred through the Y chromosome. Since Y chromosom

only be found in males, Y linked traits are only passed on fro

father to son.


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Genetic code

• The genetic code is the set of rules by which information enc

in genetic material (DNA or mRNA sequences)

is translated into proteins (amino acid sequences) by living c

• The code defines how sequences of three nucleotides,

called codons, specify which amino acid will be added nextduring protein synthesis.


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• Not all genetic information is stored using the genetic code. All orga

DNA contains regulatory sequences, intergenic segments, chromoso

structural areas, and other non-coding DNA that can contribute grea

to phenotype.

• Those elements operate under sets of rules that are distinct from thto-amino acid paradigm underlying the genetic code


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Non-coding DNA

M ki K


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Making a Karyotype

Amniocentesis • Performed: no earlier tha

16th week of pregnancy


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Amniocentesis 16th week of pregnancy• Fetal Cells used to make

Karyotype to check forchromosome abnormalitie

• Biochemical analysis ofamniotic fluid can detect various biochemical disorde.g. tay sachs

• - Turn around time: fetal must be cultured for at lea10 days before they can be

karyotyped!• Risks involved? Increased

(about 1%) of spontaneouabortion.

Chorionic Villi Sampling (CVS)


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Chorionic Villi Sampling (CVS)

• Performed 8 to 10 weeks inpregnancy.

• Karyotype Using villi cells

• DNA analysis

• Biochemical tests can be doon tissue

• Turn around time:

Karyotype can be produced samday CVS is performed!

Risks?:

Spontaneous apportion (slightly higthan with amnio.)

Can lead to malformation of fingertoes (in .3% of cases)


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FISH (fluorescentna

in situ hibridizacija)

Humani hr. 4 obojen fuloresecntonom bojom


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Humani hr. 4 obojen fuloresecntonom bojom

Chromosome painting primenom FISH meto


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p g p


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Sky Karyotyping


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Sky Karyotyping

This technique allows each chromosome to be identi

individually using special hardware and software.

Sk K t i


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Sky Karyotyping

Cancer Cells

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