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Sickle Cell Genetics PowerPoint Presentation

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Description : Check out this medical titled "Sickle Cell Genetics”.

This medical is about sickle cell disease, an inherited blood disorder caused by a mutation in the HBB gene, which provides instructions for making a protein called hemoglobin that carries oxygen in the blood. The mutation causes the hemoglobin molecules to form abnormal shapes, leading to the characteristic sickle-shaped red blood cells.

Sickle cell disease is inherited in an autosomal recessive pattern, which means that a person must inherit two copies of the mutated HBB gene (one from each parent) to develop the condition. If a person inherits only one copy of the mutated gene, they are said to have sickle cell trait, which is usually asymptomatic.

The HBB gene is located on chromosome 11, and there are several different versions, or alleles, of the gene. The most common allele that causes sickle cell disease is called HBB*S, which results from a specific mutation in the HBB gene. There are also other less common mutations that can lead to sickle cell disease.

Because sickle cell disease is inherited in an autosomal recessive pattern, it is more common in certain populations where the HBB*S allele is more prevalent, such as people of African descent, people from parts of the Middle East, and people of Hispanic descent. However, sickle cell disease can occur in anyone, regardless of their ethnicity.

Tags : Sickle Cell Genetics, sickle cell disease, inherited blood disorder, mutation in the HBB gene, hemoglobin molecules, Medical Genetics, Medical Genetics

Published on : Jun 01, 2023 | Views : 1926 | Downloads : 6

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Slide 1-

Sickle Cell Genetics @miniPCR fb.com/miniPCR Using gel electrophoresis to investigate molecular genetics, inheritance and disease. @miniPCR
Slide 2-

Our goals for today Review the genetics and biology of sickle cell anemia. Analyze DNA sequences to diagnose sickle cell anemia in a family. Welcome!
Slide 3-

Engaging story-based content Modern molecular techniques Rich curriculum that can be adapted to your use Use as an introduction to DNA or use extensions to probe AP level topics One Lab, many concepts Today’s lab Genes and disease Genotype/phenotype Mendelian genetics Protein Structure Natural Selection Biotechnology
Slide 4-

The Robinson Family: Jaqueline: Mom – 32 years old Cory: Dad – 32 years old Samuel: Son – 4 years old Marie: Daughter – 2 months Marie’s routine infant screening was inconclusive. The entire family has been referred for genetic testing and counseling. Today’s lab
Slide 5-

We will test this family using gel electrophoresis Gel electrophoresis separates molecules based on 2 basic factors, size and charge-to-mass ratio. For DNA, because all DNA has the same charge to mass ratio, only size matters. © 2019 by Amplyus LLC
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Larger molecules migrate more slowly +
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GelGreen® Agarose Tabs Add water. Melt. Pour. Pre-weighed agarose tabs contain: Agarose Buffer DNA stain One tab makes one 2% agarose gel
Slide 10-

Hemoglobin is a tetramer. Two alpha-globin and two beta-globin subunits Sickle-cell is due to a mutation that affects the beta-globin subunit. Hemoglobin – what makes your blood red. Image by David S. Goodsell CC-BY-4.0
Slide 11-

The first ten amino acids in the beta-globin subunit. The sickle cell mutation
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The protein dissolves easily in the cytoplasm. All hemoglobin proteins can move freely. Normal hemoglobin
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The valines (represented here by blue triangles), clump together, as they are repelled by the water. Sickle Cell Disease
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These long chains of hemoglobin cause the cell to “sickle” in shape and lead to many serious health concerns. Sickle cell disease Illustration courtesy Diana Grib under Creative Commons license
Slide 15-

Some hemoglobin molecules will clump together, but it is unlikely that long chains will form. Heterozygotes Sickle cell trait
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A recessive disease The beta-globin (HBB) gene has 2 alleles A (HbA) = normal beta-globin S (HbS) = sickle cell beta-globin Chromosome 11
Slide 17-

A recessive disease AA – unaffected – homozygote SS – sickle cell disease – homozygote AS – sickle cell trait – heterozygote
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Two parents who are carriers can have children with or without the disease. A (HbA) = normal beta-globin S (HbS) = sickle cell beta-globin AA – unaffected AS – sickle cell trait SS – sickle cell disease A recessive disease AA AS AS SS
Slide 19-

This lab looks at results Electrophoresis is the final step in the experimental chain. DNA extraction Gel electrophoresis PCR Restriction Digest
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ppt slide no 20 content not found
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Sickle cell is by far most common in people who are from, or who’s ancestors are from, central West Africa. Therefore, the single largest risk factor is family history and by extension, ancestry. Sickle cell risk factors From: Sickle Cell Disease in Africa, Grosse et al. 2011
Slide 22-

If sickle cell disease is so dangerous, why has it not been removed from the population by natural selection? Link to evolution- heterozygote advantage Wikimedia Commons AA homozygotes: Fully susceptible to malaria AS heterozygotes: Reduced malaria susceptibility SS homozygotes: Full sickle cell anemia
Slide 23-

Sickle cell and malaria From: https://map.ox.ac.uk/explorer/#/explorer From: Sickle Cell Disease in Africa, Grosse et al. 2011 Prevalence of sickle cell allele in Africa Prevalence of malaria in Africa
Slide 24-

One SNP (single nucleotide polymorphism) Sickle-cell allele Normal allele
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Exponential Amplification
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The change in DNA sequence that causes sickle cell is a change from and adenine (A) to a thymine (T) in position 20 of the beta-globin coding sequence. A genetic test for sickle cell We can test for this mutation using a restriction enzyme.
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PCR-RFLP Normal allele - HbA ctcctgTggag gaggacAcctc 5’…CTNAG…3’ 3’…GANTC…5’ Sickle cell allele - HbS Restriction fragment length polymorphism ctcc gaggacT DdeI tgAggag cctc
Slide 29-

Larger molecules migrate more slowly +
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Jacqueline: 32-year-old female who was born in Port-au-Prince, Haiti No abnormal medical history other than occasional migraine headaches Older brother died from pneumonia as a 1-year-old She is of primarily African descent. Medical histories Cory: 32-year-old male who was born and raised in the United States No abnormal in his medical history Two siblings also have nothing abnormal in their medical histories He is of primarily African descent. Risk Factors?
Slide 32-

Samuel: 4-year-old healthy boy Normal pregnancy with he has had no major illnesses No abnormalities in his routine infant screenings Marie: 2 months old girl Normal pregnancy and no significant illness since birth Screening program found low levels of normal hemoglobin A second blood test was inconclusive Medical histories continued Risk Factors?
Slide 33-

Experimental design
Slide 34-

Which lane represents a sickle cell beta-globin homozygote? Which lane represents a normal beta-globin homozygote? Which lane represents a heterozygote? How to interpret the gel
Slide 35-

Can you diagnose: Jacqueline? Cory? Samuel? Marie? What is you diagnosis?
Slide 36-

Living with sickle cell Antibiotics given regularly up to age 5 Medications that can reduce the regularity and severity of pain crises Bone marrow transplant
Slide 37-

CRISPR gene therapy Sickle Cell Anemia www.npr.org Victoria Gray: a human GMO
Slide 38-

Engaging story-based content Electrophoresis and RFLP One lab, many concepts Adaptable to many classroom levels Summary
Slide 39-

Questions Why do sickle cell patients only have occasional crises? Why don’t they happen all the time? Other hemoglobinopathies? Is this the same as the test normally done by doctors and clinics?