Biology Sickle Cell Chapter

Outline the life cycle of humans from a 1n gamete to a sexual mature adult.

1n sperm and 1n egg will fertilize to form a 2n zygote. The zygote will undergo mitosis to grow into a sexually mature adult. The adult is capable of producing gametes, which are 1n sex cells.

Sketch a molecule of DNA, and include the following information: a.Label the four bases, sugar, phosphate, and types of bonds found between each molecule.

4 bases: Adenine, Guanine, Cytosine, Thymine. Sugars: Deoxyribose (DNA), Ribose (RNA) Phosphate Group

An organism that has a diploid number (2n) of 40 has how many homologous chromosomes?

40 homologous chromosomes or 20 homologous pairs

Describe how genetic diseases differ from communicable diseases like the flu.

A genetic disease is one that is caused by a change (mutation) in DNA that can be passed on from one generation to the next.

Explain complimentary base-pairing and how it relates to the binding of DNA strands together.

AT and CG always pair together. Weak hydrogen bonds between the two.

How can sickle cell be classified as a systemic (entire body) disease even though it is only the RBC shape that is changed?

All cells in the body need oxygen, so other organ systems (tissues) are affected.

How can DNA samples be collected from a fetus?

Amniocentesis Chorionic villus sampling

Describe how the structure of sickle cells impacts a person's ability to breathe.

Blocking the capillaries around the alveoli can cause a condition known as acute chest syndrome (pain, shortness of breath, high fever).

Evaluate how CRISPR has the potential to treat genetic diseases.

CRISPR may be used to inactivate, remove, and even replace a section of nucleotides. This means CRISPR can replace genes that code for incorrect proteins.

What is the origin of the CRISPR Cas9 enzyme and how is it normally used by the immune system?

CRISPR was found in bacteria, using it as a form of immune defense against invading viruses. Cas9 is capable of identifying specific sequences of nucleotides in the viral DNA, and breaking both DNA strands to inactivate the virus.

Summarize how genes and chromosomes are involved in transmitting information to the next generation.

Chromosomes are basically a condensed version of DNA, allowing cells to duplicated and divide to pass that DNA to the next generation.

Conclude how events during meiosis (such as crossing-over and independent assortment of chromosomes) contribute to genetic variation in sexually reproducing organisms.

Crossing-over and independent assortment introduce randomness in order to increase genetic diversity. The goal is to have 4 genetically different daughter cells.

Give a description of how DNA coils to condense inside the nucleus?

DNA double-helix is first wrapped around proteins called histones to form nucleosomes. Nucleosomes are then further condensed to form chromosomes.

Explain what would happen to DNA in the process of DNA replication if there was a mutation in the DNA helicase gene.

DNA helicase unwraps the DNA double-helix by breaking the hydrogen bonds between complementary paired nucleotides. If there's a mutation, DNA helicase wouldn't be able to do that properly.

Are the daughter cells the same or different from the starting parent cell? Explain. [Meiosis/Sexual Reproduction/Gametes]

Different. One purpose of Meiosis is to introduce genetic variation by crossing over alleles (prophase I) and then random shuffling of homologous chromosomes (metaphase I).

Distinguish the two ways that are described in our reading that whole genomes can be studied.

Direct DNA Sequencing - determines the order of nucleotides in a given segment of DNA. It involves attaching dyes to the nucleotides and detecting the different dyes via a laser in an automated sequencing machine. DNA Microarrays - This may be used to identify a specific allele or look at patterns of gene expression between two cell types, tissues, or individuals. Uses a glass slide with each gene located at a precise location.

Define the term semiconservative and describe how it applies to DNA replication.

Each new DNA strand contains one original and one newly synthesized strand.

In what ways is gene expression related to environmental factors?

Environmental factors such as diet, temperature, humidity, light cycles, presence of mutagens can all impact which of an animal's genes are expressed.

Trace the path of red blood cells in the body. Relate how gases are exchanged in the circulatory system.

Gases are exchanged in the circulatory system at the alveoli. It is simple diffusion of gases due to differences in concentration.

Analyze how gene therapy is used to treat diseases.

Gene Therapy introduces or fixes cells with the correctly functioning DNA in order to work correctly or make the proper proteins.

Describe the function of a gene and what type of information genes store.

Gene is a segment of DNA that code for characteristics of a trait or produces a product (proteins or RNA molecules).

Differentiate between the terms gene and allele.

Genes are the basic unit of inheritance. Allele is simply a variation of a gene.

Evaluate this statement—"All homologous chromosomes have the same genes, but not always the same alleles."

Homologous chromosomes carry the same genes, one from each parental source. They can have variation though.

Identify the chromosomes human males and females have in common and which are different (ie, autosomes and the specific sex chromosomes)

Humans have 23 sets of chromosomes. 22 Autosomes and 1 sex chromosome.

Why must gametes contain half (n) the number of chromosomes as body cells?

In order to combine with another gamete to achieve fertilization and become a zygote.

Describe the forms of non-Mendelian inheritance (incomplete dominance and codominance) and explain the results of crosses with these forms of inheritance.

Incomplete dominance - dominant allele does not completely mask the recessive allele. Codominance - many dominant alleles, many alleles expressed. (Blood type for example).

Using the definition of inheritance, explain how certain characteristics appear in closely-related family members.

Inheritance is based on the passing of genes to the next generation. Certain characteristics appear in closely-related family members because they share parents or close ancestry.

Evaluate how the environment can influence trait expression.

Interactions of the environment with genotypes can produce variation in the phenotype.

Identify the characteristics of a genetic disease.

It can be passed from one generation to the next. It is due to changes in the DNA of an individual

Make some conclusions about why having multiple alleles influencing a trait that is also impacted by the environment is advantageous?

It is advantageous because of the increase in genetic diversity. Having multiple alleles makes a species more versatile.

Identify the process of inserting human genes into other organisms.

It is possible to use bacteria to make many copies of a gene or make specific gene products (like insulin). The process involves cutting bacterial DNA with a restriction enzyme, and fusing it with human DNA to become recombinant DNA. The recombinant DNA is then duplicated whenever the bacteria reproduces.

Describe what is shown on a karyotype and how it can be used to detect chromosomal abnormalities.

Karyotype shows un-replicated chromosomes. It helps identify the chromosomes and any changes or abnormalities. A tagged piece of DNA can be developed for a specific gene, which helps researchers identify the chromosomal location of a gene of interest.

Construct and analyze a pedigree to determine the inheritance pattern of a trait—recessive, dominant, X-linked. [Pedigree Notation]

Males = Squares Females = Circles Line between = Union Vertical Line = Children of that union Shaded = Affected

In what way is diffusion related to the function of red blood cells?

Oxygen diffuses from the alveoli of the lungs into the RBCs, where it binds to hemoglobin. One molecule of hemoglobin can bind 4 moles of oxygen.

Compare and contrast the process of DNA replication and PCR.

PCR (Polymerase Chain Reaction) can make millions of copies of a single gene. It involves a variation of DNA polymerase (enzyme used to build complimentary DNA strands) that is able to withstand higher temperature. PCR does not use the helicase enzyme, using heat to denature the strand. PCR uses primers to target specific segments of the DNA molecule.

Explain methods and techniques used to test for genetic disorders?

Pedigree - Old way amniocentesis - Obtains a sample of amniotic fluid from the uterus of a pregnant woman by passing a long needle through the abdominal and uterine walls to collect fetal cells. chorionic villus sampling - Obtains a sample of fetal cells in the region where the placenta will develop. An ultrasound is used to place a thin suction tube through the vagina into the uterus.

Distinguish between recessive and dominant forms of inheritance.

Recessive inheritance, need two recessive alleles in order to show trait. Dominant inheritance, need only one dominant allele in order to show trait.

Describe how restriction enzymes are used to identify unique sequences of DNA.

Restriction enzymes can break the DNA molecule at particular based sequences. This is related to genetic markers (variation in the pattern of nucleotides). Sometimes it is possible to know that susceptibilities for a certain disease may be associated with the inheritance of a genetic marker.

Describe one strategy scientists are using with CRISPR and stem cell therapy to treat Sickle Cell Disease.

Scientists target cells that divide to produce red blood cells (called progenitor cells), being able to use CRISPR in order to repair up to 40% of the progenitor cells.

Summarize how we know that DNA is the genetic material.

Series of experiments Frederick Griffith using injected bacteria mice. Alfred Hershey and Martha Chase using radioactively labeled DNA into viruses that infected bacteria to reproduce.

In addition to the Respiratory system, identify the other systems that are impacted by sickle cell.

Sickle-cell anemia affects the whole body, including immune and lymphatic systems.

List the genetic and physical characteristics of sickle-cell disease.

Sickle-cell disease is caused by a single change(nucleotide) in a gene. It causes a different shape for the hemoglobin protein, which leads to a sickle cell shape instead of the normal circular concave shape.

Why don't all DNA mutations result in misshapen or malfunctioning proteins?

Sometimes the mutation doesn't change the amino acid because multiple codons can code for the same amino acid.

Identify what makes up the backbone or external side of the DNA molecule.

Sugar-Phosphate backbone

Summarize how does the shape of the sickle-cell RBCs cause problems within the circulatory system.

The altered hemoglobin becomes sticky and clumps together to form the sickle shape. In the capillaries, the sickle shape of the RBC can block the capillary and restrict blood flow to organs and tissues. Can result in anemia.

Using the hemoglobin molecule as an example, relate how the structure of a protein is linked to its function.

The changed structure of hemoglobin make it ineffective at transporting oxygen.

What is the function of red blood cells in the body? Include how hemoglobin allows for that function.

The function of RBCs is to transport oxygen to the cells in the body. Also carries back carbon dioxide.

Explain where in the body meiosis occurs and how the cells produced are different from skin cells.

The sex organs (testes and ovaries). The cells produced are called gametes which are 1n and are genetically different than the parent cells. Spermatogenesis Oogenesis

Summarize the process of transcription.

Transcription (DNA -> mRNA) RNA polymerase binds to spot and unwraps the DNA, and make a complementary RNA strand (mRNA)

Summarize how the information in DNA is transmitted to a functional protein in gene expression.

Transcription (DNA -> mRNA) Translation (mRNA -> Protein)

Summarize the process of translation; be sure to include RNA types, enzymes, organelles, and products.

Translation (mRNA -> Protein) mRNA is the input, complimentary RNA. tRNA is used to put the right amino acid in the chain. happens in the ribosomes.

Relate how a change in the DNA code can result in a misshapen or malfunctioning protein.

can lead to a different amino acid in the polypeptide chain, which can change the shape and function of the protein.

Explain how gene therapy is being developed for sickle cell disease.

ex vivo gene therapy seems promising. Scientists work on correcting the gene outside of the body and inserting the corrected gene into the bone marrow of those with sickle-cell disease. The goal is to produce new cells that lack the sickle-cell trait and can produce normal hemoglobin. Experiments involving mice seem promising. Some trials show that mice had normal hemoglobin production.

Can you predict why ex vivo techniques are used for SCID treatment and in vivo techniques are used for CF?

ex vivo techniques is better for SCID because the cells used are bone marrow cells. in vivo techniques are better for CF (cystic fibrosis) because it results in potentially deadly infections in the respiratory tract. The virus with the functioning gene can be sprayed into the nose or injected directly into the lower respiratory tract.

Compare the techniques of ex vivo and in vivo therapy and what are typically used as vectors to deliver DNA to cells.

ex vivo therapy - occurs outside the body. in vivo therapy - occurs inside the body. Two most common vectors are genetically modified viruses that are used to transport normal genes to target cells. Many viruses are specific in the types of cells they target, so this method allows for more specific means of targeting a cell type in the body. Liposomes - engineered fat transport vesicles that enclose copies of a gene of interest, very general vector.

Compare and contrast the physical appearance of normal Red Blood Cells (RBCs) to sickle-cell RBCs.

normal RBCs have a concave circular shape (no nucleus) sickle-cell RBCs have a sickle-cell shape.

Determine the inheritance pattern of sickle-cell disease.

sickle-cell disease is an autosomal recessive inherited disease. Individuals who have sickle-cell disease are (aa) genotype.