Chapter One
Main concepts of chapter 9 Genetics 1- Methods of studying genetics: A- Bredding and crossing in which organisms with well known characters are grown and crossed and then we follow the inheritance of their characters. B- Family pedigree This is a diagram in which males are represented by squares and females by circles, the shaded squares or circles indicate to the studied character. C- Cytological and biochemical studies. 2- Mendel's first law: When two homozygous individuals different in a pair of allelomorphic characters are corssed, only the dominant character appears in F1 generation while the two characters appear in F2 by 3: 1 3- Mendel's second law: When two homozygous individuals different in two pairs of allelomorphic characters are crossed, each pair is assorted randomly and inherited independantly from the other pair, the ratio of the second generation is 9: 3: 3: 1 4- In case of lack of dominance there is no gene that completely dominates over the other, so together they produce an intermediate character. e.g. colour in Antirrhinum flowers. 5- Incase of incomplete dominance the recessive gene shows the character in certain conditions only e.g sickle-cell onemia in man. 6- Complementary genes "qualitative". This is a genetic case through which the character is controlled by 2 pairs of genes, the dominant character appears if at least one dominant gene is found in each pair. The ratio is 9: 7 in the second generation. e.g some strains of pea flowers. 7- Lethal genes are genes which cause the death of forth of the offspring when they are in a pure state 8- Multiple alleles is a case in which the genetic traits are controlled by more than one pair of allelomorphic genes but each individual carries only two genes e.g. inheritance of fur colour in rabbits and blood groups in man. 9- Blood groups in man represents three genetic cases. A- Complete dominance because both gene A and B dominate over 0. B- Lack of dominance because gene A and gene B give AB. C- Multiple alleles because there are three genes A, B, O but the share of each individual is only one pair. 10- Blood groups in man are A, B, AB, O and they are determined according to the antigens and antibodies "chemical bases" 11- Rhesus factor is an antigen, it is found in about 85% of human beings which are RH+ the other 15% are RH- , there are three pairs of genes that control the production of rhesus antigens, they are very similar in their effect. 12- Linked genes are genes that carried on the same chromosome and transferred from parents to their off spring as one unit Mendel ratio can not be applied e.g. the inheritance of wing length and body colour in drosophila fly. 13- In some cases linkage between genes is broken due to the crossing over which occurs during meiosis. 14- The chromosomal maps was done by Morgan and they represent the chromosome and the arrangement of genes on these chromosomes and the distances between genes. 15- In each somatic cell there is the total number of chromosome, they are divided into one pair called sex chromosomes and the rest are called autosomes. 16- In man there are 46 chromosomes 44 autosomes + XX for females, 44 autosomes + xy for males. 17- The reproductive cells or gametes contain half the number of chromosomes. 18- There are some abnormal cases A- Down's syndrome: male 45xy, female 45xx B- Klinefeltersyndrome: 44xxy C- Turner's syndrome: 44x D- Multiple sex genes: 44xxx or 44 xxxx 19- Barr body is a sex chromosome x which is compact and can be stained it is used to determine the sex of some players or competitors at the Olympics. 20- Sex-lined inheritance means that the trait is determined by the genes located or carried on the sex chromosome x examples: White eye colour in drosophila, colour blindness in man, hemophili. The female passes these traits to her sons and the sick man passes them to his grand sons through his daughters. 21- Sex influenced inheritance means the genes are carried on the autosomes but the action of genes is influenced by sex hormones. Examples: Sheep horns [dorset-suffolk] and premature baldness in man. 22- The environment has an effect on the genes and their characters e.g. orbanch has no genes for chlorophyll formation so it can not make photosynthesis even if it is exposed to light. 23- The appearance of any character in a living organism depends on: A- The presence of its genes B- Suitable environmental conditions. 24- The effect of heat on genetic characters is seen in the following: A- The white fur changed to black in low temp. in Himalayan rabbits. B- The drosophila wings grew curved in high temp. (25o C)
Chapter two
Molecular biology
Main
Concepts of chapter-10
Molecular Biology
1-
Genetic information control the inheritance of the characters and the
development of the fertilized egg into an individual.
2-
Genes are the units of genetic information.
3-
Chromosomes are composed of DNA and proteins.
4-
Evidences that DNA is the genetic material:
A- Bacterial
transformation.
B- Bacteriophages.
C- The quantity of DNA
in cells.
C- The base content of DNA in cells.
5- DNA is
a polymer which consists of four monomers called nucleotides.
6-
Each nucleotide consists of :
A- Nitrogenous base [purines or
prymidines]
B- Ribose or deoxyribose sugar.
C- Phosphate
group.
7- Adenine pairs to thymine and guanine pairs to
cytosin through hydrogen bonds.
8- The replication of DNA
needs a number of enzymes and proteins:
A- DNA helicase which
moves along the double helix, separating the two strands
B- DNA
polymerase which works only on the 3 to 5 template and it adds new
nucleotides.
C- DNA ligase which joins pieces of DNA together.
9- All Biological polymers are damaged by :
A- The
body heat.
B- The aqueous state inside the cell.
C-
Various chemicals and radiations.
10- DNA in prokaryote
is circular , its two ends are joined, it is attached to the plasma
membrane at a point or more where douplication starts, it is not
complexed with proteins, 100% coding sequences, there are some
additional small circular DNA called plasmids.
11- DNA of
Eukaryotes is organized into several chromosomes, each one contains a
single DNA molecule which is associated with various protein
(chromatin) these proteins may be:
A: histone proteins
B:
Non- histone proteins.
12- Genome is the total of all the
genes (DNA) in any body cell.
13- Any gene is a sequence
of nucleotides.
14- DNA can be divided into:
A-
Coding DNA which is responsible for the production of RNA and protein
synthesis.
B- Non-coding DNA.
15- Transcription is
to change the sequence of nitrogenous bases in a DNA strand into a
sequence of nitrogenous bases in m-RNA strand.
16- There
are three types of RNA:
A- Messenger RNA
B- Ribosomal RNA
C- Transfer RNA
17- Most of genes are present in
only one copy or few copies in the genome, but sometimes some
sequences of nucleotides are repeated which we call repetitive DNA or
satellite DNA.
18- In 1960 it was discovered that the
genes that make bacterial resistant against drugs transfer from one
bacterium to another by plasmids.
19- Proteins are
divided into two main groups:
A- Structural proteins
Fibrous
proteins - collagens - keratins
B- Regulatory proteins -
Enzymes - Antibodies - Hormones
20- Proteins are formed
of un branched linear chains join between amino acids.
21-
There are 20 different amino acids, which have the same basic
structure
22-
Amino acids are joined together by peptide bonds through dehydration
reaction.
23- RNA is formed of a single strand, the sugar
is ribose and pyrimidines bases are uracil and cytosine.
24-
M.RNA has the following main parts:
A- Ribosome binding site (5
end)
B- Start codon [AUG]
C- Polyadenine tail (3 end)
D-
Stop codon [UAA - UAG - UGA]
25- Ribosomes consists of 4 types
of rRNA and about 70 kinds of polypeptides.
26- The
production of ribosomes takes place in the nucleolus.
27-
T.RNA carries amino acids from the cytoplasm to the ribosomes.
28-
For each kind of amino acids there is a specific kind of t.RNA
molecule that can recognize and transport it.
29- There
are 2 sites on T.RNA:
A- The amino acid attachement site
B-
The anti-codon.
30- The genetic code is the triplet
sequence of nucleotides in DNA and it is transcribed into a
complementary sequence in m-RNA which goes to the ribosome where it
is translated into a sequence of amino acids in a poly-peptide
(protein)
31- Protein synthesis passes through three main
stages:
A- Initiation
B- Elongation
C- Termination
32- Nucleic acid hybridization :
- If DNA is heated
to 100 o
C the hydrogen bonds between base pairs are broken down and the two
strands of DNA molecule are separated producing single stranded DNA.
- Hybridization technique is used in producing hybrid or mixed
double helices, to tell if a particular gene is present in a genome,
and also to determine the degree of relationship between two
different species of living organisms.
33- Bacterial
restriction enzymes are secreted by some strains of E-coli, they
attack specific sequences of nucleotides in the viral DNA and break
it down into useless fragments, the bacteria protect themselves from
these enzymes with the help of modification enzymes which add or bind
methyl groups to the recognition sites.
34- Several
copies of a desired gene can be produced by splicing it to a molecule
that carry it into bacterial cells, this carrier may be a phage or
plasmid in case of prokaryotes and jumping genes in case of
eukaryotes.
35- Recombinant DNA technology is the
introducing of DNA from one organism into cells of another living
organism.
36- Interferons are proteins that interfere
with replication of viruses specially viruses with RNA genomes such
as influenza and poliomyelities.