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Questions and Answers
Which subunit composition defines the embryonic haemoglobin known as Gower I?
Which subunit composition defines the embryonic haemoglobin known as Gower I?
At what stage of development is foetal haemoglobin (HbF) predominantly present?
At what stage of development is foetal haemoglobin (HbF) predominantly present?
Which type of haemoglobin appears late in foetal life?
Which type of haemoglobin appears late in foetal life?
What is the primary subunit composition of adult haemoglobin (HbA)?
What is the primary subunit composition of adult haemoglobin (HbA)?
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What percentage of HbA is typically present in adult humans?
What percentage of HbA is typically present in adult humans?
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Which embryonic haemoglobin type is detectable for only up to 8 weeks?
Which embryonic haemoglobin type is detectable for only up to 8 weeks?
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Study Notes
Haemoglobin Expression
- Haemoglobin structure is determined by subunit composition
- Embryonic haemoglobins include Gower 1 (ζ2ε2), Gower II (α2ε2), and Portland (ζ2γ2)
- Embryonic haemoglobin detectable up to 8 weeks
- Fetal haemoglobin (HbF) comprises 90-95% of haemoglobin up to 36 weeks gestation
- Adult haemoglobin (HbA) is detectable from 9 weeks, and HbA2 (α2δ2) appears later in fetal life
- In adults, HbA is approximately 95%, HbF is generally less than 2%, and HbA2 is typically 1.8-3.5%
- Globin genes are located on chromosomes 16 (α-like cluster) and 11 (β-like cluster)
Learning Objectives
- Differentiate structures of developmental haemoglobins
- Compare and contrast adult (HbA) and fetal haemoglobin (HbF)
- Explain haemoglobin activation order based on gene location
Globin Gene Clusters
- α- and β-globin genes located on chromosomes 16 and 11 respectively.
- Several other globin gene types exist, and a variety are expressed during development and in some cases throughout life
- Locations of the various globin genes on chromosomes, including embryonic types (ξ, γ, ζ, δ ) and adult types (α, β, δ)
Main Haemoglobins in Adults
- Adult haemoglobin (HbA) is α2β2, comprises 95% of adult haemoglobin, and binds 2,3-DPG
- Fetal haemoglobin (HbF) is α2γ2, comprises up to 2% of adult haemoglobin, and does not bind 2,3-DPG
- Haemoglobin A2 (HbA2) is α2δ2 and constitutes 1.8-3.5% of adult haemoglobin, and does not bind 2,3-DPG
Developmental Haemoglobins and ODC
- Different haemoglobin types have varying oxygen affinities and cooperativity
- Fetal haemoglobins (HbF) have a higher oxygen affinity than adult haemoglobin (HbA), enabling them to effectively extract oxygen from maternal blood
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Description
This quiz focuses on the structure and development of haemoglobin, including its various forms such as embryonic, fetal, and adult haemoglobin. You will learn to differentiate between the types and their compositions, as well as the significance of globin gene clusters. Test your knowledge on the activation order of these haemoglobins and their genetic foundations.
