Practical 3 07
-
Upload
medikcz -
Category
Technology
-
view
6.219 -
download
3
Transcript of Practical 3 07
![Page 1: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/1.jpg)
Practical 3
Meiosis
Gametogenesis
![Page 2: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/2.jpg)
Chromosomal sex determination
• Drosophila type
• Male – XY
• Female - XX
![Page 3: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/3.jpg)
Sexual reproduction
2n
2nmeiosis
meiosis
n
n
Gametes (haploid)
sperm
oocyte
fertilization 2n
n + n = 2n zygote
♂
♀Life cycle:
haploid phase (gametes)
diploid phase (somatic cells)
![Page 4: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/4.jpg)
Recommended website
• http://genetics.gsk.com/chromosomes.htm#chromo
![Page 5: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/5.jpg)
Written test
• 8 minutes
• Don't forget to put down your name, your
group and the test version.
• In multiple choice questions more than 1
statement could be correct.
• Don't write anything on the question sheet!
![Page 6: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/6.jpg)
Meiotic division
1st meiotic division
2nd meiotic division
2n
n n
n n n n
![Page 7: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/7.jpg)
First meiotic division
• Heterotypic or reduction• Prophase
– Leptotene– Zygotene– Pachytene– Diplotene– Diakinesis
• Metaphase• Anaphase• Telophase
![Page 8: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/8.jpg)
Leptotene• Beginning of prophase• Chromosomes can't be
distinguished. • Condensation of
chromosomes begins.
![Page 9: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/9.jpg)
Zygotene• Attachment of homologous
chromosomes – the chromosomes
begin to synapse.
• Assemblage of chromosomes is
enabled by synaptonemal complex.
![Page 10: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/10.jpg)
Pachytene• Bivalents or tetrades are present.
– 1 bivalent = 2 chromosomes
– 1 tetrade = 4 chromatids
– bivalent = tetrade
• Crossing-over between homologous
chromosomes is possible.
![Page 11: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/11.jpg)
Crossing-over
• Reciprocal exchange of chromatid segments
between chromosomal homologues
![Page 12: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/12.jpg)
Importance of the crossing-over• New combinations of alleles of genes that are
located on the same chromosome. • New allele combinations lead to higher variability
of the offspring (important in evolution). • This increases the potential for genetic variability
between members of the same species.
![Page 13: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/13.jpg)
Chromosomes X and Y• are attached in
pseudoautosomal regions (PAR) during the 1st meiotic prophase
X
Y
SRY – sex determining region – is located on chromosome Y in the neighborhood of PAR.X
Y
![Page 14: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/14.jpg)
Task A:
• An infertile man with azoospermia had been examined in cytogenetic lab. He has no other striking phenotypic features.
• The cytogenetic analysis revealed abnormal finding because his cells contained two X chromosomes while chromosome Y is missing.
• Explain this surprising result.
![Page 15: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/15.jpg)
Crossing-over in PAR
• Nonreciprocal crossing-over can result in translocation of the SRY gene from the chromosome Y to chromosome X
![Page 16: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/16.jpg)
Task A – result
male
female
Normal combination of gonosomes X;Y translocation
„XX-male“
„XY-female“XX
XY
![Page 17: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/17.jpg)
Hermaphroditism – possible consequence of sex chromosome
abnormalities
![Page 18: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/18.jpg)
Prophase of the 1st meiotic division
next periods
![Page 19: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/19.jpg)
Pachytene
![Page 20: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/20.jpg)
Diplotene• Condensation of chromosomes
continues
• Homologous chromosomes are divided
• Disassembling of synaptonemal complex
• At the end of diplotene homologues are connected only in crossover sites. These sites are called chiasmata (singular: chiasma).
![Page 21: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/21.jpg)
Diakinesis• Final period of the 1st meiotic
prophase. • Chiasmata are transferred to
terminal chromosomal regions.
• Under specific staining chromosomes could be well distinguished under the microscope.
• Nuclear membrane disappears.
![Page 22: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/22.jpg)
Terminal phases of meiotic division
prophase
metaphase + anaphase
2nd meiotic division
(homeotypic)
1st meiotic division
(heterotypic)
Separation of double-chromatid
homologous chromosomes
![Page 23: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/23.jpg)
Metaphase I
Metaphase I
![Page 24: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/24.jpg)
Anaphase I X Anaphase II
![Page 25: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/25.jpg)
![Page 26: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/26.jpg)
Gametogenesis
• Spermatogenesis – sperm development
• Oogenesis – oocyte development
![Page 27: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/27.jpg)
n n
1st meiotic division
2nd meiotic division
n n
primary spermatocyte
secondary spermatocyte
sperm
n n
2nSpermatogenesis
![Page 28: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/28.jpg)
n n
1st meiotic division
2nd meiotic division
n n
primary oocyte
secondary oocyte
mature oocyte
nn
2n
polar bodies
polar body
Oogenesis
![Page 29: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/29.jpg)
A schedule of oocyte development
Prophase I
fetus childhood – dictyotene mature ovary
fertilization
![Page 30: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/30.jpg)
Spermatogenesis X Oogenesis
![Page 31: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/31.jpg)
Task B: Risk of chromosomal nondisjunction defects
• Compare possible risk of chromosomal
abnormalities for two couples that visited
the genetic counselling clinic:
– Couple 1: female (21 years), male (38 years)
– Couple 2: female (36 years), male (32 years)
• Which family has higher risk of numerical
chromosomal aberrations?
![Page 32: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/32.jpg)
Task B – result
• Oogenesis lasts much longer
than spermatogenesis – risk of
chromosomal nondisjunction
defects is age-related.
• The second couple has higher
risk due to 36 years old female.
• In pregnant females older than
35 years prenatal examination
of the fetus is recommended.
35 years … risk 1/365
Age-related risk of the Down syndrome child
Mother´s age
![Page 33: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/33.jpg)
Practical tasks
![Page 34: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/34.jpg)
Task 1: Observation of meiosis in the grasshopper testis
• The slide was prepared from the testis of the grasshopper. After removing from the individual the tissue was fixed with methanol + glacial acetic acid (3 : 1) and stained with the Giemsa-Romanowski solution. After dehydration the tissue was mounted in the Canada balsam.
• Find the spermatocytes on the slide using 10x objective lens.
• Change the objective magnification into 40 or 45x and observe different phases of meiosis. For their determination use adjacent photos.
![Page 35: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/35.jpg)
Task 2: Disjunction of the sex chromosomes during meiosis
• Redraw the scheme of disjunction of the sex chromosomes during meiosis of the male to your materials and fill it.
• In the first scheme (A) distinguish the chromosomes according to their shape and number of chromatids.
• In the second scheme (B) designate the chromosomes using letters X or Y no matter of the number of chromatids.
XYA B
![Page 36: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/36.jpg)
Task 3: Changes of nuclear DNA concentration during the cell cycle
• Contrast the two types of cell division (mitosis X meiosis) by completing the following graphs below.
• Redraw the picture to your materials and fill curves demonstrating changes in the DNA content per one cell:– during the cell cycle followed with mitosis– during the cell cycle followed with meiosis.
• (Value „C“ on y-axis represents DNA content per one cell in G1 phase.)
![Page 37: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/37.jpg)
G1 G2S M G1
C
2C
G1 G2S M1 M2 G1
Cell cycle + mitosis Cell cycle + meiosis
Nuclear DNA content
Task 3: Changes of nuclear DNA concentration during the cell cycle
![Page 38: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/38.jpg)
Results
![Page 39: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/39.jpg)
Task 3: Observation of meiosis in the grasshopper testis
![Page 40: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/40.jpg)
Task 4: Disjunction of the sex chromosomes during meiosis
XY
X Y
XX YY
Scheme A Scheme B
![Page 41: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/41.jpg)
Task 5: Changes of nuclear DNA concentration during the cell cycle
G1 G2S M G1
C
2C
G1 G2S M1 M2 G1
Cell cycle + mitosis Cell cycle + meiosisNuclear DNA
![Page 42: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/42.jpg)
Assisted reproduction
• A group of methods that allows reproduction of
infertile couple that can't be therapeuted by
common medical treatment (e.g. using drugs of by
psychological intervention)
• The assisted reproduction could be also used for
prevention of genetic defects in families with
normal fertility but with increased risk of genetically
conditioned disorder for the offspring.
![Page 43: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/43.jpg)
Assisted reproduction methods
• Intrauterine artificial insemination
– application of sperm to the uterus of the
female.
• In vitro fertilization and embryo transfer
– fertilization is performed outside the organism
of the mother
![Page 44: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/44.jpg)
Artificial insemination
• homologous – the
female is fertilized with
sperm of her husband;
• sperm of anonymous
donor are applied – the
donor and the couple
remain unknown to
each other
![Page 45: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/45.jpg)
In vitro fertilization
• Application of gonadotropins (= fertility drugs) induce maturation of numerous oocytes.
• The oocytes are removed from ovaries by biopsy. In a special dish they are mixed with sperms of the husband.
• After short term cultivation in medium with nutrients 3 embryos are transferred to the female's uterus.
![Page 46: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/46.jpg)
ICSI (intracytoplasmatic sperm injection)
![Page 47: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/47.jpg)
ICSI protocol
![Page 48: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/48.jpg)
Preimplantation diagnostics• Genetic or other examinations of oocytes or
embryo before transfer to the mother's • We use
– Polar body– 1 – 2 cells from 8-cell embryo– More cells from blastocyst
![Page 49: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/49.jpg)
Presentation
Ethical issues of assisted
reproduction
![Page 50: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/50.jpg)
Next seminar
• In vitro cell cultivation
• Recommended websites:
– http://www.research.umbc.edu/~jwolf/method5.htm
– http://homepages.gac.edu/~cellab/chpts/chpt12/intro12.html
• Be careful when handling cell cultures!
• Test: previous topics (only seminars)
![Page 51: Practical 3 07](https://reader033.fdocuments.us/reader033/viewer/2022060110/5560e183d8b42a016e8b4b4f/html5/thumbnails/51.jpg)
See you next week!