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Pathophysiology

Ch 4 - Genes and Genetic Diseases

QuestionAnswer
What is genetics? The study of biologic heredity
What is a gene? The basic unit of heredity
What is a genome? DNA representing all of the genes for a given species
What are the components of DNA? A pentose sugar (deoxyribose), a phosphate molecule, and four types of nitrogenous bases.
What are nitrogenous bases? nucleoproteins created from amino acids
What are the four nitrogenous bases? Adenine, Guanine, Cytosine, Thymine
Which of the nitrogenous bases are purines? Adenine and Guanine
Which of the nitrogenous bases are pyramidines? Cytosine and Thymine
Which of the nitrogenous bases have a double ring structure? Purines (A and G)
Which of the nitrogenous bases have a single ring structure? Pyramidines (C and T)
DNA has what type of structure? An antiparallel structure
Which nitrogenous bases pair with each other and how many hydrogen bonds are involved in each pair? A pairs with T (2 hydrogen bonds) C pairs with G (3 hydrogen bonds)
What are proteins made of? Amino acids
How many amino acids are there? 20
How does DNA replication work? DNA strand untwists and unzips. A single strand acts as a template. DNA polymerase adds the matching base pair to the template strand and proof reads.
Describe the process of transcription, what it results in and where it occurs. RNA is synthesized from the DNA template by RNA polymerase. Results in the formation of mRNA. Occurs in the nucleus. mRNA then leaves the nucleus and moves into the cytoplasm.
What is translation? Process by which RNA directs the synthesis of a polypeptide via interaction with transfer RNA
Where is the site of protein sythesis? The Ribosome
How does tRNA interact with mRNA? tRNA contains a sequence of nucleotides (anticodons)complementary to the triad of nucleotides on the mRNA strand (codons). Codons paired with anticodons by the ribosome which moves along the RNA strand translating it into a polypeptide chain
What is a chromosome and what is it composed of? A chromosome is a temporary but consistent state of DNA. It is composed of two sister chromatids.
How many chromosomes do somatic cells contain and what kind of cells are they. 46 chromosomes (23 pairs). diploid cells
How many chromosomes do gametes contain and what kind of cells are they? 23 chromosomes. haploid cells
What is meiosis? Formation of a haploid cell from a diploid cell.
What are autosomes? The first 22 of the 23 pairs of chromosomes. The two members are virtually identical and are thus said to be homologous.
What are sex chromosomes? The remaining pair of chromosomes. In females it is a homologous pair (xx) and in mails it is a nonhomologous pair (xy)
What are the pieces of the chomosome structure? Short arm Long arm Centromere- regioun of attachment for sister chromatids Telomere- region containing multiple base pairs. shortens with each cell division.
What is a karyotype? An ordered display of chromosomes.
What is a mutation? Any inherited alteration of genetic material
Are mutations in somatic cells transmitted to offspring? No
Are mutations in gametes transmitted to offspring? Yes
What is a point mutation? A single nucleotide base-pair change in DNA
What is a mutagen? An agent known to increase the frequency of mutations
What are some examples of a mutagen? radiation and chemicals
What is a silent muation? A change in DNA sequence that does not change the amino acid sequence of a gene.
What is a missense mutation? A type of mutation that results in a single amino acid change in the translated gene product.
What is a nonsense mutation. A type of mutation in which an mRNA stop codon is produced or removed.
What happens in a nonsense mutation if a stop codon is produced? The protein sequence is terminated prematurely
What happens in a nonsense mutation is a stop codon is removed? An elonged protein sequence is created
What is a frameshift mutation? An alteration of DNA in which an addition or deletion of a base pair occurs. Results in a change in the entire reading frame.
What are gain of function mutations associated with? Autosomal dominant disorders. Cause production of new protein product or overexpression/inappropriate expression of protein product.
What are loss of function mutation associated with? Associated with recessive disorders. Loss of 50% of the protein product. This may or may not be adequate for normal function.
What are euploid cells? Cells that have a multiple of the normal number of chromosomes.
What is a polyploid cell? A euploid cell that has more than the diploid number. examples= triploidy and tetraploidy
What is disjunction? Normla separation of chromosomes during cell division
What is nondisjunction? Failure of homologous chromosomes or sister chromatids to separate normally during meiosis or mitosis. Usually the cause of aneuploidy.
What is aneuploidy? A somatic cell that does not contain a multiple of 23 chromosomes.
Is it better to have more genetic informaiton or less? More. Mutations with less often do not survive although there are still consequences to having more genetic material.
What are some physical characteristics of down's syndrome? mental retardation, low nasal bridge, epicanthal folds, protrouding tonge, poor muscle tone.
What is partial trisomy? Only an extra portion of a chromosome is present in each cell.
What is a chromosome mosaic? Trisomies occuring only in some cells of the body.
What is trisomy x? A female that has three x chromosomes. termed "metafemale". Symptoms may include sterility, menstrual irregularity, and/or mental retardation.
What is turner syndrome? Females having only one x chromosome. Characteristics include absence of ovaries, shor stature, webbing of neck, underdeveloped breasts.
What is Klinefelter syndrome? Individuals wtih at least two x's and one y chromosome. Characteristics include male appearance, development of female like breasts, long limbs, small testes, and sparse body hair.
What is a deletion? Loss of a sequence of DNA from a chromosome
What is an inversion? Chromosomal rearrangement in which a segment of a chromosome is reversed end to end.
What is a translocation? Transfer of one chromosome segment to another
What is a ring chromosome? Telomere of each chromosome arm has been deleted and the broken arms have joined
What causes Cri du chat sydrome Deletion of short arm on chromosome 5.
Created by: MEPN 2013