NUCLEUS AND CHROMOSOMES
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NUCLEUS AND CHROMOSOMES
NUCLEUS AND CHROMOSOMES
Variability causes in Meiosis
1. Crossing over
3.Separation of sister Chromatides during ANAPHASE II
2.Homologous Chromosomes Separation during ANAPHASE I
NUCLEUS AND CHROMOSOMES
**The Shape ( Centromere Position.)
p
q
Centromere
Arm
Arm
Metaphasic Chromosome
The Centromere divides each Chromatid in two arms than can be equal or different.
METAPHASIC CHROMOSOME STRUCTURE
The Shape ( Centromere Position.)
Metacentric
p
q
Near the middle off Centre near one end at the endBecause the Centromere is not exactly in the centre of a Chromosome, each chromosome has a sort arm and a long arm.The short arm is designated with the letter p (for the French petite)
While the long arm is designated with q.
The Shape ( Centromere Position.)
Metacentric
p
q
Near the middle off Centre near one end at the end
In Human Beings do not exist Telocentric Chromosomes
The Shape ( Centromere Position.)
Metacentric
To classify the Human Chromosomes following the Centromeric
location we have to use The Chromosomic Indexes:
PROPORTIONAL CENTROMERIC INDEX (P.C.I).PROPORTIONAL ARM INDEX ( P.A.I).
CHROMOSOMIC STUDIES
They are used to classify human chromosomes.
PROPORTIONAL CENTROMERIC INDEX (P.C.I). short Arm
Whole Length of Chromosome
p / p+q
CHROMOSOMIC STUDIES
They are used to classify human chromosomes.
PROPORTIONAL CENTROMERIC INDEX (P.C.I). short Arm
Whole Length of Chromosome
p / p+q
p
q
CHROMOSOMIC STUDIES
PROPORTIONAL ARM INDEX (P.A.I). short Arm
p / q
Long Arm
CHROMOSOMIC STUDIES
PROPORTIONAL ARM INDEX (P.A.I). short Arm
p / q
Long Arm
p
q
Human Chromosomes.
Karyotype
IDIOGRAMA photography of the Metaphasic Chromosomes.Without order.
Ordered Chromosomes following Cytogenetic Criteria.
Karyotype
Karyotype
IDIOGRAM
* * The behavior of the Chromosomes respect several stains or Dyes. For example, Giemsa Stain.
G BANDS
* * The behavior of the Chromosomes respect several stains or Dyes. For example, Giemsa Stain.
Types of bandingG-Banding is obtained with Giemsa stain following digestion of chromosomes with trypsin. It yields a series of light and dark bands - the dark regions tend to be heterochromatic, (DNA more condensed) and AT rich. The light regions tend to be euchromatic, (Less condensed)and GC rich. This method will normally produce 300-400 bands in a normal, human genome
Dark bands.DNA MORE CONDENSED
Light bands.DNA LESS CONDENSED
EUCHROMATIN
HETEROCHROMATIN
Dark bands.DNA MORE CONDENSED
Light bands.DNA LESS CONDENSED
PAINTING CHROMOSOMES USING SPECIFIC SOFTWARE
MAKING AN IDIOGRAM
MAKING AN IDIOGRAM I GROUP
MAKING AN IDIOGRAM II GROUP
MAKING AN IDIOGRAM III GROUP
MAKING AN IDIOGRAM IV GROUP
V GROUP
MAKING AN IDIOGRAM VI GROUP
VII GROUP
VIII GROUP
Phytohemagglutinin
In medicine this protein is useful and is used as a mitogen to trigger lymphocytes cell division
BLOOD OR BONE NARROW
Colchicine to stop Mitosis
PhytohemagglutininIn medicine this protein is useful and is used as a mitogen to trigger lymphocytes cell division
Colchicine is got from Colchicum autumnale.Colchicine stops Mitosis in Metaphase.
CHROMOSOME CLASSIFICATION
To classify Chromosomes we use three main criteria: **The Shape ( Centromere Position.) ** The Size ** The behavior of the Chromosomes respect several stains or Dyes . For example, Giemsa Stain .
Phytohemagglutinin
In medicine this protein is useful and is used as a mitogen to trigger lymphocytes cell division
ANTENATAL DIAGNOSIS
Amniocentesis
Chorionic villi Sampling
ANTENATAL DIAGNOSIS
Amniocentesis
Chorionic villi Sampling
From fifteenth to seventeenth week of pregnancy
From eighth to twelfth week of pregnancy
Risk of Spontaneous abortion 0.3%
Risk of Spontaneous abortion 0.8 %
Chorionic villi Sampling
From eighth to twelfth week of pregnancy
Risk of Spontaneous abortion 0.8 %
ANTENATAL DIAGNOSIS
ANTENATAL DIAGNOSIS
Chorionic villi Sampling
From eighth to twelfth week of pregnancy
Risk of Spontaneous abortion 0.8 %
ANTENATAL DIAGNOSIS
Amniocentesis
From fifteenth to seventeenth week of pregnancy
Risk of Spontaneous abortion 0.3%
Variation in Chromosome Number
Variations in Chromosome number can be classified in two ways:Variation in the number of sets of Chromosomes, and variation in the number of particular chromosomes within a set. The suffix “ploid” or “ploidy” refers to a complete set of Chromosomes.Organisms that are EUPLOID (the prefix Eu means True) have a chromosome number that is viewed as the normal number. In human Beings , the
Euploid condition is two sets of 23 Chromosomes each; 46 Chromosomes.The somatic cells are Diploid
Variation in Chromosome Number
Organisms with three or more sets of Chromosomes are called POLYPLOID.A Diploid organism is referred to as 2n, a Triploid organism as 3n, a Tetraploid organism as 4n, and so forth. Haploid individuals or cells are referred as n.(only a set of chromosomes).In Human beings Poliploids individuals are extremely rare and only these individuals have been got in abortions.Observe the following figures because they arecases of Triploid Human beings.
POLYPLOID FORMATION
At A the Strawberry plant is exposed to a chemical called Colchicine. At B due tho the effect of the drug, total no disjunction produced Diploid gametes(2n). As a result, at C two Diploid gametes fuse at fertilization . Finally at D a new polyploid plant is formed
Observe.........................
Julia Sáenz HurtadoServicio de Inmunología. Sección GenéticaHospital Infanta Cristina
Julia Sáenz HurtadoServicio de Inmunología. Sección GenéticaHospital Infanta Cristina
Observe again
Variation in Chromosomes Number
The second way that chromosomes number varies is a phenomenon called ANEUPLOIDY.This refers to an alteration in the number of particular Chromosomes, so that the total number of chromosomes is not an exact multiple of a set.In human beings Aneuploid individuals have a chromosome number that is not an exact multiple of the haploid number of 23.The normal condition is the DISOMY (Two chromosomes in a pair) but the abnormal condition may be:
Variation in Chromosome Number
DISOMYMONOSOMY
Normal Condition
Embryos missing a chromosome usually die; hence,monosomy of an autosome is extremely rare in living persons. About 97 % of embryos lacking a sex chromosome also die, but some survive and develop characteristics of TURNER SYNDROME or XO.
45,X
45,X
TURNER SYNDROME
45,X
TURNER SYNDROME
LINDA HUNT
Meiosis Review
1. REDUCTION OF NUMBER OF CHROMOSOMES BY HALF
2.Meiosis only occurs in germ cells.
Variability causes in Meiosis
1. Crossing over
3.Separation of sister Chromatides during ANAPHASE II
2.Homologous Chromosomes Separation during ANAPHASE I
1. Crossing over
Exchange of Genetic Material between Homologous Chromosomes
2.Homologous Chromosomes Separation during ANAPHASE I
Either
or
A B
A B
A1A2
A1 A2
A3 A4 A3A4
ANAPHASE II
3.Separation of sister Chromatides during ANAPHASE II
p
q
Centromere
Sister ChromatidsEach one is a Molecule of DNA
Arm
Arm
Metaphasic Chromosome
The Centromere divides each Chromatid in two arms than can be equal or different.
METAPHASIC CHROMOSOME STRUCTURE
The Shape ( Centromere Position.)Based on Centromere location, each chromosome is classified as:
Metacentric
p
q
Comparison of centromeric locations
Near the middle off Centre near one end at the end
CHROMOSOME CLASSIFICATION
To classify Chromosomes we use three main criteria: **The Shape ( Centromere Position.) ** The Size ** The behavior of the Chromosomes respect several stains or Dyes . For example, Giemsa Stain .
Variation in Chromosome Number
TRISOMY
If three chromosomes are present instead of the usual pair. The common cause of Trisomy is nondisjunction (no Homologous separation) during the Meiosis(special division that suffer the gametes).The result is a gamete (Ovum or Sperm) with 24 Chromosomes instead of 23 Chromosomes and, after the fertilization the result is a Zygote with 47 chromosomes.
IMPORTANT: Autosomal Trisomies occur with increasing frequency as maternal age increases.
Nondisjunction DURING MEIOSIS
DOCTOR ENRIQUE GALAN.HOSPITAL INFANTA CRISTINA BADAJOZ
DOWN TRISOMYTrisomy 21
TRANSLOCATION 21:14
Translocation Down syndrome occurs when two chromosomes, one of which must be a 21, join together at their ends. Instead of having three independent, separate number 21 chromosomes, a person with translocation Down syndrome has two independent 21 chromosomes and a 21 chromosome that is attached to another chromosome. Observe as examples the Idiograms with a Tranlocation 21:21 and a Translocation 21:14.
TRANSLOCATION 21:14
TRANSLOCATION 21:21
TRANSLOCATION 21:21
DOWN SYNDROME
DOWN SYNDROME
Epicanthus
Brushfield Spots
Simian Crease
DOWN SYNDROME
Brushfield Spots
Child with Down Syndrome showing eyes exhibiting both Brushfield spots and heterochromia
DOWN SYNDROME
Simian Crease