Structure of DNA. Coiling of DNA. Definitions about genetics. The Gene & The Genetic Code. Gene Mutation. Regulation of gene expression. DNA Functions. Patterns Of Inheritance

1. BASICPRINCIPLES
OFGENETICS
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7. Coiling of DNA
1ry coiling of the duplex itself.
2ry coiling around histone beads
(nucleosome).
3ry coiling of nucleosomes (chromatin
fibers).
4ry coiling forming loops.

11. Structure of DNA
Two polynucleotide strands
Two chains run in opposite direction
Sugar backbone
Bases inside helix in Complementary
base pairing (A=T & C=G)
Strands bonded by weak hydrogen
bonds

16. Definitions

17. Genome
the total number of genes
contained in one cell

18. Genotype
complete genetic constitution
of an individual

19. Phenotype
the physical appearance of
an individual that is
produced by the interaction
of his genes & environment

20. Trait
variation of an expressed
characteristic

21. Karyotype
systematic arrangement of
images of chromosomes
into homologous pairs

25. Autosomal chromosome
in humans, the 22 pairs of
chromosomes that are not
the sex chromosomes (XX or
XY)

26. Sex chromosomes
pair of chromosomes
involved in sex
determination; in males, the
XY chromosomes; in females,
the XX chromosomes

27. Allele
alternative forms of a
gene that occupy a
specific locus on a specific
gene

28. Homozygous
having two identical alleles
for a given gene

29. Heterozygous
having two different alleles
for a given gene

30. Carrier
heterozygous individual who
does not display symptoms of a
recessive genetic disorder but
can transmit the disorder to his
or her offspring

31. Dominant
describes a trait that is
expressed both in
homozygous &
heterozygous form

32. Dominant lethal
inheritance pattern in which
individuals with one or two
copies of a lethal allele do
not survive in utero or have a
shortened life span

33. Recessive
describes a trait that is only
expressed in homozygous
form and is masked in
heterozygous form

34. Recessive lethal
inheritance pattern in which
individuals with two copies
of a lethal allele do not
survive in utero or have a
shortened life span

35. Incomplete dominance
pattern of inheritance in which a
heterozygous genotype expresses
a phenotype intermediate
between dominant and recessive
phenotypes

36. X-linked
pattern of inheritance in
which an allele is carried
on the X chromosome of
the 23rd pair

37. X-linked dominant
pattern of dominant
inheritance that corresponds
to a gene on the
X chromosome of the 23rd
pair

38. X-linked recessive
pattern of recessive
inheritance that corresponds
to a gene on the
X chromosome of the 23rd
pair

39. Transcription
copying of DNA
sequences into mRNA

40. Translation
copying of mRNA
sequences into protein

42. Gene

43. Gene
the unit of heredity that
occupies a specific locus on the
chromosome. It is a DNA
sequence that directs synthesis
of a specific polypeptide chain

44. Genes
Structural
Regulatory
Operator

45. Structural Gene
directs synthesis of a
specific polypeptide chain

46. Regulatory Gene
repressor substance
secretion

47. Operator Gene
switches on structural
gene

49. The Genetic Code

50. This is the language of
mRNA

51. Based on the 4 bases of
mRNA

52. “Words” are 3 RNA
nucleotide sequences
called codons

53. Gene Mutation

55. Mutation
change in the nucleotide
sequence of DNA

56. A- Spontaneous Mutations
(molecular decay)
B- Induced Mutations (mutagens)
- Chemicals
- Radiation
- Viral

57. Types of
mutations

58. Types of Mutations
Chromosomal
mutations
involve changes in
the whole
chromosome.
Gene
mutations
result from
changes in a
single gene.

62. Effects of Gene Mutations
A- Neutral Effect (Silent mutation)
B- Harmful Effect
C- Beneficial Effect

63. Silent mutation
Another triplet for the
same AA

64. Harmful Effects
1.
Errors in protein sequence 
partly or completely non-
functioning proteins.

65. Harmful Effects
2.
Germ cell mutations 
hereditary diseases/
teratogenecity
(heterozygous/homozygous)

66. Harmful Effects
3.
Somatic cell mutations 
cancers

69. Regulationofgeneexpression

70. Not all genes are transcribed
all the time.
Controlling mechanisms in
the cell regulate the flow of
enzymes & other proteins,
determining which genes
are turned on.

71. Some genes are needed
for short periods of life
cycle, others such as those
involved in energy
production may be
operating all time.

73. DNA Functions

74. DNA functions
REPLICATION
METABOLISM

75. Replication
From one generation to
another  inheritance.
From cell to cell 
division.

76. Metabolism
gene expression & protein
synthesis (transcription &
translation)

77. Replication

78. DNA replication
it is the process by which
genetic information is
transmitted from one cell to
another

79. DNA replication
it starts by separation of the
2 strands. Each acts as a
template for a new strand
(semi-conservative)

80. DNA replication
DNA polymerase proceeds in
only one direction along the
helix (from the 5’ to 3’ end of
DNA) but starts in many sites.

83. Transcription

84. Transcription
the process whereby genetic
information is transmitted from
DNA to mRNA by RNA
polymerase into
complementary single-stranded
copies of RNA

86. mRNA
are the processed
transcripts of genes that
code for polypeptides

87. Codon
a triplet of adjacent
nucleotides in the mRNA
chain that codes for a
specific AA in the synthesis of
a protein molecule

88. Exons
nucleotide sequences that is
found in a gene, code
information for protein
synthesis, & is transcribed to
mRNA

89. Introns
segments of a gene situated
between exons that is removed
before translation of mRNA &
does not function in coding for
protein synthesis

90. Promoter
the place where RNA
polymerase 1st attaches. They
vary from gene to another but
contain sequences in common
of 7 base sequence of all T’s &
A’s

91. Termination
certain sequence that
terminates gene
transcription (downstream
beyond the 5’ end)

92. Sense strand
the strand that is actually
transcribed is the one with
specific promoter sequence.
The other non-sense strand
is not used in transcription

93. Processing
CAPPING: addition of a chemical cap to
the 5’ end (attach RNA to the
ribosome).
SPLICING: excision of introns.
POLYTAIL: addition of poly A tail
(AAAA) to the 3’ end (it aids in
transporting RNA molecule into the
cytoplasm).

94. Translation

95. Translation
it is the process by which
mRNA is translated into
protein synthesis. It
involves tRNA & rRNA

98. tRNA
one end binds a particular
AA (all are 20), the other end
has a 3-base sequence, the
anticodon, that pairs with a
particular codon on mRNA

99. rRNA
structural elements of
ribosomes. They are the
benches on which protein
synthesis occurs

100. Steps of translation
mRNA moves along ribosomes
tRNA adapts
Starting codon= ATG
Stop codon= UGA, UAG, UAA

101. Summary
DNA  transcription at
chromosomes  mRNA 
movement across NM
rRNA translation at
ribosomes  protein

103. Patterns Of Inheritance

104. Patterns of inheritance
Autosomal Recessive Inheritance
Autosomal Dominant Inheritance
X-Linked Recessive Inheritance
X-Linked Dominant Inheritance

105. AutosomalRecessiveInheritance

106. Autosomal recessive
pattern of recessive
inheritance that corresponds
to a gene on one of the 22
autosomal chromosomes

113. AutosomalDominantInheritance

115. Autosomal dominant
pattern of dominant
inheritance that corresponds
to a gene on one of the 22
autosomal chromosomes

118. X-LinkedRecessiveInheritance

122. X-LinkedDominantInheritance

126. References
cnx.org
Basics Of Human Genetics Prof. Dr. Randa
Youssef Kasr El Aini (Presentation)
All about genes. Maha Adel Shaheen, MD
Professor of Dermatology & Venereology Ain
Shams University (Presentation)
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127. YOU
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