Lec 3 - SAQ Genetics Quiz

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What are the genotypes for the ABO blood group antigens?

Homozygous AA - Group A BB - Group B OO - Group O Heterozygous AO - Group A BO - Group B AB - Group AB (co-dominant expression)

What is the function of Haemoglobin?

Carry O2

How many pairs of chromosomes do humans have?

23

What is the biallelic expression of Hb genes?

Both paternal and maternal alleles are expressed (αβ)2 (Haemoglobin A) Signup and view all the answers

What is the name of the haemoglobin found in foetuses?

Hb F (α2γ2) - Foetal Haemoglobin (HbFF) Signup and view all the answers

What is the concentration of haemoglobin in red blood cells?

320-350g/L of cytoplasm Signup and view all the answers

What are the two major types of abnormalities of Hb?

Haemoglobinopathies and Thalassaemias Signup and view all the answers

What causes sickle cell anaemia?

Mutation in β globin gene sequence Signup and view all the answers

What is codominance?

Codominance is when two alleles of the same gene which code for proteins with different specific functions are co-expressed in heterozygote individuals. Signup and view all the answers

What is the function of the H antigen?

The H antigen is responsible for the synthesis of a sequence of monomers on the surface of red blood cells. Signup and view all the answers

Where is the H locus located?

The H locus is located on chromosome 19. Signup and view all the answers

Which locus determines the ABO blood group?

The ABO locus on chromosome 9 determines the ABO blood group. Signup and view all the answers

What is the difference between codominance and incomplete dominance?

Codominance is when both alleles are expressed completely, while incomplete dominance is a blending of traits. Signup and view all the answers

What is an example of codominance in the ABO blood group?

The AB blood group is an example of codominance. Signup and view all the answers

What is the basic genetics of hemoglobin biosynthesis?

Hemoglobin biosynthesis is the process of producing hemoglobin and it changes during development and is regulated. Signup and view all the answers

What happens when mutations disrupt the balanced biosynthesis of globin production?

Mutations that disrupt the balanced biosynthesis of globin production lead to thalassemias. Signup and view all the answers

What is the gene responsible for β-globulin?

HBB Signup and view all the answers

How many copies of the β-globulin gene are expressed?

2 Signup and view all the answers

Which chromosome is the β-globulin gene located on?

Chromosome 11 Signup and view all the answers

What are the two types of β-thalassaemia?

Minor and Major Signup and view all the answers

What is the difference between minor and major β-thalassaemia?

Minor: heterozygous mutation, one defective gene copy. Major: homozygous/compound heterozygous mutations, both gene copies defective Signup and view all the answers

What are the problems that can occur in β-thalassaemia?

Transcription (promoter), Processing of mRNA, Translation of mature mRNA, Post translation integrity of β globin Signup and view all the answers

What are the genotypes for β-thalassaemia minor?

β/β0 or β/β+ Signup and view all the answers

What are the genotypes for β-thalassaemia major?

β0/β0, β+/β+, or β0/β+ Signup and view all the answers

What are the symptoms of β-thalassaemia minor?

Clinically asymptomatic or mild symptoms (mild microcytic anaemia) Signup and view all the answers

What category of mutation best describes the Glutamic acid > Valine mutation that converts HbA to HbS, with respect to O2 carrying function?

Antimorph (dominant negative) Signup and view all the answers

What category of mutation best describes the PML-RARα fusion protein in APML?

Neomorph Signup and view all the answers

How would you perform prenatal diagnosis for sickle cell disease?

Chorionic Villous Sampling (9-10 weeks) PCR Amplify Fragment of β-globin Gene Oligonucleotide Probe Hybridization/Sequencing Signup and view all the answers

Is newborn screening for sickle cell disease available in Ireland?

Not specified in the text Signup and view all the answers

What is the allele frequency of the sickle cell gene in parts of Africa?

16% Signup and view all the answers

What is the allele frequency of the sickle cell gene in US African Americans?

4% Signup and view all the answers

Why is the incidence of sickle cell disease lower in African Americans compared to parts of Africa?

Not specified in the text Signup and view all the answers

What are the common types of mutation?

Deletions, Insertions, Substitutions, Frameshifts, Dynamic mutation (tandem repeats e.g. HD) Signup and view all the answers

What are the different functional consequences of mutations?

Loss of function (inactivating) and Gain-of-function (activating) Signup and view all the answers

What is the concept of balanced genetic polymorphism?

It refers to the coexistence of two or more alleles in a population, maintained at a relatively stable frequency due to selective advantage Signup and view all the answers

What is the relationship between sickle cell trait and sickle cell anaemia?

Sickle cell trait refers to individuals who inherit one copy of the sickle cell gene and do not usually experience symptoms, while sickle cell anaemia occurs in individuals who inherit two copies of the sickle cell gene and experience severe symptoms Signup and view all the answers

How can mutations distant from structural genes cause disease?

Mutations distant from structural genes can affect gene regulation and disrupt normal protein production, leading to disease. An example is thalassaemia Signup and view all the answers

What is the central dogma of biology?

DNA Transcription Pre mRNA Splicing mRNA Translation peptide Post –Translation Folding Protein Then multimer assembly Signup and view all the answers

What is the definition of mutation?

A permanent heritable change in the nucleotide sequence of a gene or chromosome Signup and view all the answers

What does the mutation G > A mean?

Guanine is replaced by Adenine Signup and view all the answers

What is balanced polymorphism?

Balanced polymorphism refers to the persistence of multiple alleles in a stable equilibrium in a population, with one allele being disadvantageous in the homozygous state. Signup and view all the answers

How does the sickle cell allele relate to malaria?

The sickle cell allele is particularly associated with populations that originated from areas with a high incidence of malaria. Natural selection favors the HbAS sickle cell trait as it provides protection against malaria. Signup and view all the answers

What is the difference between sickle cell anaemia and sickle cell trait?

Sickle cell anaemia (HbSS) is a recessive inherited disorder characterized by a clinically manifest phenotype, while sickle cell trait (HbAS) is a dominant inherited trait with a cryptic phenotype. Signup and view all the answers

What is the pattern of inheritance for sickle cell anaemia?

Sickle cell anaemia (HbSS) follows an autosomal recessive pattern of inheritance. Signup and view all the answers

What are thalassaemias?

Thalassaemias are inherited disorders of balanced haemoglobin biosynthesis, characterized by an imbalance in the production of structurally normal globin chains. Signup and view all the answers

What is the role of gene expression in β-thalassaemias?

In β-thalassaemias, the regulation of gene expression is critical to function. Mutations in the β-globin gene promoter, such as the A to G mutation at position -34, can disrupt binding of the transcription machinery and result in reduced or no transcription of the gene. Signup and view all the answers

What is the recommended approach for prenatal diagnosis of β-thalassaemia?

First, the blood of both parents should be checked by Hb electrophoresis. If both parents have the β-thalassaemia trait, more invasive tests such as chorionic villus sampling (CVS) or amniocentesis can be performed to obtain fetal DNA for PCR/sequencing analysis. Signup and view all the answers

Why is the face an abnormal shape in β-thalassaemia?

The abnormal shape of the face in β-thalassaemia is related to the physiological response to compensate for the physiological deficit associated with the inherited mutation. Hypoxia leads to increased production of erythropoietin (EPO), which causes bone marrow hyperplasia and distorts the bones. Signup and view all the answers

What are the key features of sickle cell anaemia?

Sickle cell anaemia is mainly seen in people of African descent and is characterized by an autosomal recessive pattern of disease. It is caused by the presence of abnormal haemoglobin (HbS) that distorts red blood cells into a sickle shape, leading to various complications such as pain crises, organ damage, and increased susceptibility to infections. Signup and view all the answers