BASIC HAEMATOLOGICAL GENETICS

Question 1

DNA contain only four different bases; which are:
• DNA exists as a ——- helix in which the pairings are:

Answer 1

DNA contain only four different bases Adenine (A); Guanine (G); Thymine (T) and Cytosine (C) pairing
• DNA exists as a double helix in which A is paired to T and G to C

Question 2

A linear strand of DNA has one end where the OH - group attached to the 5-carbon is free (ie — primer end or———- end) while the other end in which the OH-group attached to the 3-carbon is free (—-primer end or ———— end) the 5 prime end and the 3 prime end of each DNA strands are always ———— paired.

Answer 2

A linear strand of DNA has one end where the OH - group attached to the 5-carbon is free (ie 5 primer end or up stream end) while the other end in which the OH-group attached to the 3-carbon is free (3-primer end or down stream end) the 51 end and the 31 end of each DNA strands are always complementarily paired.

Question 3

• By convention, the strand shown at the top is the ——— or ——— strand but the strand at the bottom actually serves as ———
•Four bases are required to specify for how many commonly occurring amino acids in proteins. Therefore the genetic code has to be in ——— (known as ——)

Answer 3

• By convention, the strand shown at the top is the coding or sense strand but the strand at the bottom actually serves as template
•Four bases are required to specify for 20 commonly occurring amino acids in proteins. Therefore the genetic code has to be in triplets (codon)

Question 4

•Here each amino acid is specified by one or more sequences of codon but these sequences that specifies amino acid are interrupted by intervening sequence (known as————) that do not code for aas sequence of the proteins.

Answer 4

•Here each amino acid is specified by one or more sequences of codon but these sequences that specifies amino acid are interrupted by intervening sequence (introns) that do not code for aas sequence of the proteins.

Question 5

CHROMOSOMAL IDENTIFICATION
• Chromosome are identified at ——— under light microscope.
• They are distinguishable by the relative sizes and the position of their ——— but these features alone is not easy to use in distinguishing different chrom

Answer 5

CHROMOSOMAL IDENTIFICATION
• Chromosome are identified at mitosis under light microscope.
• They are distinguishable by the relative sizes and the position of their centromeres but these features alone is not easy to use in distinguishing different chrom

Question 6

•Cytological procedures that allows differential staining along the longitudinal axis of a mitotic chromosome is called ———— technique.

Answer 6

chromosome-banding technique.

Question 7

TYPES OF CHROMOSOME BANDING

Answer 7

C-banding technique

G-Banding

Question 8

C-banding technique: Mary Loupardue and Joe Gall:
Explain the process!!

So we can identify types of chromosome,such as:

Answer 8

C-banding technique: Mary Loupardue and Joe Gall:
- Denaturing the chromosome and heat treating with Giemsa, stains the centromeric region only. So we can identify types of chromosome
• Metacentric
• Sub-metacentric
• Accrocentric
• Telomeric

Question 9

G-Banding: Digestion of ——— with ———, followed by ——— stain will give ————— staining reaction along the length of the chromosome reflecting the ———— and ——— of the chromosome

Answer 9

G-Banding: Digestion of mitotic chromosome with TRYPSIN, followed by GIEMSA stain will give differential staining reaction along the length of the chromosome reflecting the heterogeneity and complexity of the chromosome

Question 10

In —— year; A uniform nomenclature for human chromosome banding pattern was established based on G-banding

Answer 10

1976

Question 11

Chromosomes are divided into

Answer 11

REGION,BAND AND SUB-BAND

Question 12

chromosome that are identical in size and centromere placement ( e.g chm: — and—, — and —) can be easily identified (this is known as————).

Answer 12

chromosome that are identical in size and centromere placement ( e.g chm: 4 and 5, 21 and 22) can be easily identified (Karyotyping).

Question 13

Any alteration in DNA sequence is known as

Answer 13

GENE MUTATIONS

Question 14

CLASSIFICATION OF MUTATIONS

Answer 14

• Spontaneous / induced
• Classification based on Cell type and Chromosomal location
• CLASSIFICATION BASED ON TYPE OF MOLECULAR CHANGE
• CLASSIFICATION BASED ON PHENOTYPE
• Based on number of nucleotide

Question 15

• Classification based on Cell type and Chromosomal location:

Cell type includes:

Chromosomal location includes:

Answer 15

Cell types:
. somatic mutation
• Germ line mutation

Chromosomal location
• Autosomal mutations:
• X-lined mutations

Question 16

. ——— mutation: Occurs in any cell of the body except germ cells. They are not transmissible
• ——— mutation: occur in gametes only and this is transmissible

Answer 16

. somatic mutation
• Germ line mutation

Question 17

Chromosomal location
• ——— mutations: occurs on
genes located on autosomes
• ———mutations: located on X-chromosome

Answer 17

Chromosomal location
• Autosomal mutations
• X-lined mutations

Question 18

———-mutations: A change in one base pair to another in a DNA molecule.

Answer 18

Point mutations/substitutions.

Question 19

Depending on type and location, mutation can have a wide range of phenotypic effect from non to severe;which are:

Answer 19

Depending on type and location, mutation can have a wide range of phenotypic effect from non to severe
1.Loss of function mutation
2. Gain of function mutation
3. Lethal mutations

Question 20

Depending on type and location, mutation can have a wide range of phenotypic effect from non to severe
1.———— mutation: reduces or eliminate the function of the gene product (null mutations)

2. ———— mutation: Mutation resulting in a gene product with enhanced or new function and may result from mutation in regulating region of the gene resulting in expression at a higher level
3. ——— mutations: mutations interrupting a process that is essential to the survival of the organism

Answer 20

1.Loss of function mutation:
2. Gain of function mutation
3. Lethal mutations

Question 21

Based on number of nucleotides
1.————-: when an additional nucleotide is introduced into a gene sequence
2. ————: when one or more nucleotide sequence are removed these mutation can affect the whole sequence (ie ———-) all these may result in fusion ——— and ——— protein.

Answer 21

Based on number of nucleotides
1.Insertion(Ins): when an additional nucleotide is introduced into a gene sequence
2. Deletion(Del): when one or more nucleotide sequence are removed these mutation can affect the whole sequence (ie frame shift) all these may result in fusion mRNA and chimeric protein.

Question 22

Implication of a mutation
i. A single base change may result in creation of a new triplet codon that codes for a different amino acid in protein product (————mutation)
ii. A triplet codon due to base substitution may be changed to a stop codon in resulting in premature termination (———— mutation)
iii. The base substitution may still lead to production of the same amino acid at that position (———- mutation)
Note:A transition is said to occur when a ———- replaces another ———, or ——— to ———
A transversion occurs when a ———— replaces a ——— or vice versa

Answer 22

Implication of a mutation
i. A single base change may result in creation of a new triplet codon that codes for a different amino acid in protein product (Mis-sense mutation)
ii. A triplet codon due to base substitution may be changed to a stop codon in resulting in premature termination (Nonsense mutation)

iii. The base substitution may still lead to production of the same amino acid at that position (Silent mutation)
Note:A transition is said to occur when a pyrimdine replaces another pyrimdine, or purine to purine
A transversion occurs when a pyrimdine replaces a purine or vice versa

Question 23

:A ———— is said to occur when a pyrimdine replaces another pyrimdine, or purine to purine
A ———- occurs when a pyrimdine replaces a purine or vice versa

Answer 23

A transition
A transversion

Question 24

ABO blood group
I gene encodes ——— which modifies ———
. 3 alleles are known —,— and —.
DNA sequence IA and IB when compared show four consistent single nucleotide substitution these changes result in different glycosyltransferase functions → diff H-substance modification. DNA of IO show deletion of a single nucleotide early in the code coding sequence(loss of ——— in position —— of exon—) thus resulting in a ——— mutation at the point of the deletion. This then causes a —— codon to arise after about how many? nucleotide sequence thus leading to chain termination of the enzyme product → non-functional product. -gain of function is seen in ——

Answer 24

ABO blood group
I gene encodes glycosyltransferase which modifies substance H. 3 alleles are known IA,IB and IO.
DNA sequence IA and IB when compared show four consistent single nucleotide substitution these changes result in different glycosyltransferase functions → diff H-substance modification. DNA of IO show deletion of a single nucleotide early in the code coding sequence(loss of guanine in position 261 of exon6) thus resulting in a frame shift mutation at the point of the deletion. This then causes a stop codon to arise after about 100 nucleotide sequence thus leading to chain termination of the enzyme product → non-functional product. -gain of function is seen in CML

Question 25

CHROMOSOMAL ANOMALIES
Can be:

Answer 25

CHROMOSOMAL ANOMALIES
Can be:
1. Quantitative (numerical)
2. Qualitative

Question 26

Quantitative Chromosomal abberations:
Can be addition or loss of one or more chromosome (called——-) or even addition of one or more complete set of chromosomal (called———)

Answer 26

Quantitative Chromosomal abberations:
Can be addition or loss of one or more chromosome (aneuploidy) or even addition of one or more complete set of chromosomal (Euploidy)