basic consideration of human genetics , modes of cell devision , definitions of human genetics , cell cycle , gametogenesis

1. Mohamed Abu-Bakr Mohamed
M.B.B.CH
M.SC.DEGREE IN PAEDIATRICS
Assistant lecturer of pediatric , AUCH
Clinical geneticist & metabolic diseases
specialist
2016

3. Human body
Different systems
Different organs
Millions of cells

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6. Definitions

7. Genome:-
the total number of genes contained in one cell.
Genotype:-
complete genetic structure of an individual.
Phenotype:-
the physical appearance of an individual that is produced by the
interaction of his genes & environment.
Allele:-
alternative forms of a gene that occupy a specific locus on a
specific gene

8. • Karyotype:-
systematic arrangement of chromosomes into homologous pairs
• Autosomal chromosome
in humans, the 22 pairs of chromosomes that are not the sex
chromosomes (XX or XY)
• Sex chromosomes :-
pair of chromosomes involved in sex determination; in males, the
XY chromosomes; in females, the XX chromosomes

10. Cell cycle & Cell divison

11. Diploid (2N) – cell that contains
both chromosomes
of a homologous pair
human body
cells 46

13. Homologous Chromosomes
pair of chromosomes that
have same size and shape
• human body
cells have
23 homologous
pairs

17. Haploid (N) – cell that has
only one
chromosome
of each
homologous
pair
ovum &
sperm
human sex
cells
23

18. Cell cycle

19. Cell Cycle
• The cell cycle is a sequence of cell growth and division.
• The cell cycle is the period from the beginning of one
division to the beginning of the next.
• The time it takes to complete one cell cycle is the generation
time.
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20. Cells divide when they reach a certain size.
NO (nerve and red blood cells)
Stages in eukaryotic cell cycle
Interphase
1-First gap phase
2-Synthesis phase
3-Second gap phase
M phase
1-cell divison
2-Cytokinesis
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21. Cell Cycle

22.  Interphase
G1 phase
cell grows to mature size
S phase
Cell’s DNA copies
G2 phase
Cell prepares for cell division

23. Interphase

24.  Why cells divide?
Replace old, damaged or dead cells
Growth of organism (multicellular)
Or organs

25. Eukaryotic Cell Division
2 kinds of cell division
Mitosis- Process in which 2 new cells with
identical genetic material are made from the
parent cell (1 diploid cell divides to produce 2 new
diploid cells)
Meiosis- Process in which gametes (sex cells) are
made in which they recieve half of the genetic
information

26. Mitosis divison

27. Mitosis division of chromosomes
4 Events
Prophase
Metaphase
Anaphase
Telophase

28. 1st step in Mitosis:
Prophase (preparation phase)
The DNA recoils,
the chromosomes condense
the nuclear membrane
disappears
Two pairs of centrioles migrate
to each pole of the cell and
release spindle fibers that
radiate throughout the cell and
attach to the centromere of
each chromosome

29. 2nd step in Mitosis:
metaphase (organizational phase)
The chromosomes line up
the middle of the cell
with the help of spindle
fibers attached to the
centromere of each
replicated chromosome.

30. 3rd step in Mitosis:
Anaphase (separation phase)
 Chromatids of each
chromosome split and
are pulled apart to
opposite poles of the
cell

31. 4th step in Mitosis:
Telophase
The chromosomes,
along with the
cytoplasm and its
organelles and
membranes are divided
into 2 portions. This
diagram shows the end
of telophase.

32. After Mitosis:
Cytokinesis
The actual splitting of
the daughter cells into
two separate cells is
called cytokinesis and
occurs differently in
both plant and animal
Cells.

34. Cell Cycle

35. Meiosis divison

37. Meiosis Interphase
Meiosis is preceded by
interphase.
The chromosomes have
not yet condensed.

38. Meiosis Prophase I
 The chromosomes are
completely condensed.
In meiosis (unlike mitosis), the
homologous chromosomes pair with
one another
 crossing over may occur

39. Crossing Over
Between Homologous Chromosomes

40. Meiosis Metaphase I
The nuclear membrane
dissolves
the homologous chromosomes
attach to the spindle fibers.
They are preparing to go to
opposite poles.

41. Meiosis Anaphase I
The chromosomes move to
opposite ends of the cell.

42. Meiosis Telophase I & Cytokinesis
The cell begins to divide into
two daughter cells.

43. Meiosis Prophase II
The cell has divided into two
daughter cells.

44. Meiosis Metaphase II
As in Meiosis I, the
chromosomes line up on the
spindle fibers.

45. Meiosis Anaphase II
The two cells each begin to
divide. As in Meiosis I, the
chromosomes move to opposite
ends of each cell.

46. Telophase II & Cytokinesis
With the formation of four cells,
meiosis is over.
Each of these germ cells carries
half the number of
chromosomes of somatic cells.

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49. Why we study cell division?!!!

50. Gametogensis

51. Male Spermatogenesis
1- spermatogenesis occur in
seminiferous tubules.
2- process started at puberty.
3-continuos process without
any pauses till end of life.
4- mitosis primary
spermatocyte.
5-1st meiotic secondary
spermocyte.
6-2nd meiotic spermatid.
7- duration of process69-75
days.

52. Female oogenesis
1- process occur in ovary.
2-mitosis start during intra-uterine life
 primary oocyte
3-then 1st meiotic start after birth and
arrested at prophase I then resumed at
puberty when ovulation occurred
4- 2nd meiotic occur after ovulation and
arrested at metaphase II until
fertilization occur with formation of
mature ovum
5- duration of process12-45 years

53. Gametes
sex cells (sperm and egg)
human sperm cells
human egg cell

54. cell that results from
the fusion of gametes
• forms when
sperm
fertilizes the
egg
Zygote

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