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| What is sickle cell disease? | Individuals who are homozygous for the gene controlling hemoglobin S. The disease is characterized by the destruction of red blood cells and by episodic blocking of blood vessels by the adherence of sickle cells to the vascular endothelium. |
| Why does the sickling of red blood cells cause health problems? | The fragile, sickle-shaped cells deliver less oxygen to the body's tissues. They can also get stuck more easily in small blood vessels or can break into pieces that can interrupt healthy blood flow. These problems decrease the amount of oxygen flowing to body tissues even more.Individuals with sickle cell disease are more prone to blood clots which can lead to strokes, pulmonary embolisms, and heart attacks. Another complication of the disease is an increased susceptibility to bacterial and viral infections. |
| What is sickle cell anemia? | Sickle cell anemia is a disease passed down through families in which red blood cells form an abnormal sickle or crescent shape. Red blood cells carry oxygen to the body and are normally shaped like a disc. Sickle cell anemia is caused by an abnormal type of hemoglobin called hemoglobin S which causes red blood cells to become shaped like crescents or sickles. |
| How is anemia diagnosed? | A blood test called a hematocrit. A blood sample is taken, the red blood cells are separated from the rest (through centrifugation), and the % is measured. |
| How does sickle cell disease affect daily life? | Sickle cell crises could cause missed school/work, treatments (take a long time, involve needles), dealing with pain, missed events, etc. Lots of hospitalizations. Can become depressed. Some treatments can cause problems (i.e. medicine that can cause birth defects, so not able to have own children). Etc. |
| What is the DNA code? | DNA is made of 4 different nucleotides (A, T, G, and C). The sequence of the nucleotides determines the proteins that are made, which in turn, determines our traits. |
| What is the connection between genes and proteins? | Genes are segments of DNA. Genes code for an mRNA codon (3 nucleotides). The tRNA brings an amino acid to the ribosome based on the mRNA. The amino acids bond together to form a protein. So, if there is a change in the DNA, the wrong amino acid could be brought to the ribosome, changing the protein. |
| How are proteins produced in a cell? | Proteins are produced through the process called protein synthesis, which has two steps: transcription and translation. During transcription, an mRNA strand is made based on the DNA sequence. The mRNA strand leaves the nucleus and goes to the ribosome/cytoplasm. Translation then occurs. tRNA brings amino acids to the ribosome. These amino acids are put into sequence based on the mRNA strand. The amino acids bond together using peptide bond to form a protein. |
| How does the sequence of nucleotides in DNA determine the sequence of amino acids in a protein? | The sequence in DNA determines the sequence of amino acids in a protein because mRNA is made from the DNA sequence. The mRNA codon specifies a particular amino acid. (The tRNA--anticodon--identifies the amino acid carried and binds to a complementary codon in mRNA. |
| What is a mutation? | A rare change in the DNA of a gene, ultimately creating genetic diversity. It can be a nucleotide is changed (substitution), deletion (nucleotide is removed), or insertion (nucleotide is added). Deletions and insertions typically have the most harmful effects as it can change the entire amino acid sequence. If a substitution occurs, it is possible for the same amino acid to be coded for. |
| What determines the shape of a protein? | The sequence of amino acids determines the shape of the protein. The amino acids' properties can affect the shape (whether amino acids are hydrophilic or hydrophobic, their charges), as well as the environment that they are in can affect the protein's shape. |
| Is the shape of a protein affected by its surrounding environment? | Yes. Temperature changes and pH changes can affect the protein's shape (which would change its ability to function properly) as well as whether it is in an oil or water (hydrophilic or hydrophobic). |
| How does a change in the DNA code affect the shape of a protein? | A change in the DNA code affects the shape of the protein because a different amino acid to be in the amino acid sequence (which is the protein). The amino acid could be hydrophilic instead of hydrophobic (or the reverse) so it folds differently in water. |
| Can changing just one nucleotide in a gene affect the shape of a protein? | A change in just one nucleotide in a gene CAN change the shape of a protein. A different amino acid could be coded for, which could changing how it folds/reacts in water. |
| How is DNA passed to new cells during cell division? | MITOSIS *Makes two duplicate body cells *Used for growth and repair *Before the cell divides the DNA in the chromosomes will replicate so each cell has the same DNA and same amount of chromosomes MEIOSIS *Makes 4 different sex cells (gametes) *Used to divide chromosome number in half so sex cells can combine during fertilization and produce a zygote with the same amount of chromosomes as the parent. Similar process as mitosis, but cells divide twice after DNA replicates to produce 4 cells with half as many chromosomes. |
| What is a chromosome? | *Structures in the nucleus that are composed of the DNA wrapped around a protein *Humans have 46 chromosomes in their body cells (only 23 in sex cells) -There are 22 pairs of homologous chromosomes (chromosomes that contain the same alleles in the same location) -Alleles – are one type of a gene. There are dominant and recessive alleles. |
| How are traits passed through the generations? | Parents pass on their genes to their offspring. The genotype (genes) that child receives determines their phenotype (appearance) *If a dominant allele is present then the person will have the dominant phenotype (Bb or BB) *If only recessive alleles are present then the person will have the recessive phenotype (bb) *Some individuals can be carriers (Bb) and pass on the recessive allele even though they have the dominant phenotype |
| How are pedigrees used to track diseases? | We label the individuals as affected, carriers (if the trait is recessive), or unaffected by coloring. DOMINANT TRAITS: *Every affected individual has at least one affected parent *Affected individuals who mate with unaffected individuals have a 50% chance of transmitting the trait to each child *Two affected individuals may have unaffected children RECESSIVE TRAITS: *An individual who is affected may have parents who are not affected *All children of two affected individuals are affected |
| Why does sickle cell disease run in families, yet it is not present in every generation? | This happens if the trait is recessive. In the pedigree below the two people in the first generation would be carriers. Carriers have the recessive allele, but do not have the trait because of the dominant allele. Both parents can pass on the recessive allele to their child and they can have the trait. |
| How can doctors and genetic counselors calculate the probability of a child inheriting a disease? | They can use punnett squares. Once the genotypes of the parents are determined, they can calculate the %chance of the baby having a particular trait. |
