Chapter 7 Exam 2 Flashcards
(44 cards)
What is a mutation?
Mutations are heritable changes in the sequence of the bases in DNA. Mutations can occur in any cell. Mutations in somatic cells in the body can cause detectable changes to phenotypes and are an important cause of many types of cancer. Only mutations in germ cells that form sperm and eggs can be passed on to future generations
How does a mutation differ from damaged DNA?
Mutations can (but not always) result from Damaged DNA
What is a point mutation?
a mutation affecting only one or very few nucleotides in a gene sequence
What is a frameshift mutation?
caused by pesticides with large flat ring structures insert themselves between base pairs in the DNA helix
What are heritable changes and mutations in germ cells?
can be passed on to future generations
Cancer and mutations in somatic cells:
mutations in somatic cells in the body can cause detectable changes to phenotypes and are an important cause of many types of cancer (uncontrolled cell division)
What are silent mutations?
a change to the DNA sequence that can have no effect if they are located outside of the coding regions of genes or don’t change the protein sequence. Because of the exons in genes make up about 1-1.5% of human DNA, most mutations actually do not change the phenotype
What is the connection between DNA polymerase and mutation?
DNA polymerase and other replication proteins can repair most of the errors that they have made- they can proofread- and remove the incorrect nucleotide if it is the last one of the 3’ end
What is a mutagen?
otherwise known as chemical agents in the environment that can damage DNA. If the damage is not repaired then the altered DNA structure can lead to mutation when it is replicated
What are some types of radiation that cause damage
ultraviolet light, decay of radioactive elements (particularly radon), cosmic radiation, medical x-rays and nuclear medicine, consumer products
What are free radicals?
radiation causes direct damage to the bases in DNA or the formation of highly reactive chemical structures called free radicals that can damage DNA
What are oxygen radicals?
Oxygen radicals are very reactive and quickly form new covalent bonds with adjacent DNA, RNA, or protein molecules
What are chemical mutagens?
chemical mutagens include compounds in tobacco products, industrial chemicals, food and water, vehicle exhaust
How do geneticists identify that a new mutation has occurred?
A pedigree analysis should show that a new mutation may have occurred. DNA based genetic testing can confirm diagnosis. Phenotypes for many genetic disorders can overlap the effects of teratogens; teratogenic effects must be considered
What are X-linked recessive mutations?
a mode of inheritance in which a mutation in gene on the X chromosome causes the phenotype to be expressed either in males or in females who are homozygous for the mutation
Paternal vs. Maternal mutation:
more mutations arise in the father than in the mother and paternal age was a significant factor. Increasing paternal age increased the number of mutations
What are the human mutation rates?
about 1 error in 100 million base pairs or about 6-70 new mutations in each child. Estimated 60 new mutations per generation
What is the connection between fragile-x syndrome and trinucleotide repeats?
some genes have nucleotide repeats that can easily increase (or decrease) in number each generation
What is fragile-X syndrome?
the most common form of severe inherited mental disability in humans. 1/2000 males
What is apoptosis?
cell death in response to DNA damage
What is the epigenome?
the epigenome and the pattern of gene expression can change during a lifespan, depending on environmental conditions
What is the role of histone modifications and DNA methylation in epigenetics?
DNA is wound around clusters of histones proteins to form nucleotides and nucleosomes are in turn coiled to form chromosomes, if a chemical modification to the histones takes place at the gene promoter, then transcription can either be shut off or turned on at a higher rate. DNA methylation of promoter bases usually turns off genes
What is genetic imprinting?
genetic imprinting involves selective use of only one of the paternal or the paternal copies of a gene and the silencing of the second copy. Imprinting is reset during gamete formation
What is Beckwith-Wiedemann Syndrome?
A growth disorder involving enlarged organs, high birth weight, and a predisposition to cancer. It’s caused by abnormal patterns of imprinting to genes located on chromosome 11. Involves failed silencing of maternal copies of the genes in the affected region of chromosome 11
