Exam III Chapter 11 1 How does hemoglobin change over time a Fetal hemoglobin 2 epsilon and 2 zeta chains b Embryo hemoglobin 2 gamma and 2 alpha chains c Adult hemoglobin 2 beta and 2 alpha chains 2 What is chromatin a DNA and its associated histones 3 What are the ways I which chromatin is remodeled and how do they effect gene expression a Chromatin is remodeled by adding or removing chemical groups from the histones b Acetylation signal attracts enhanceosomes and attract acetylase this adds acetyl groups to the histone tails histones change shape and transcription occurs c Methylation addition of methyl group to histones Prevents transcription 4 What is RNA interference a A natural process that destroys specific mRNA molecules using small interfering RNAs that result from transcribing short sequences on both DNA strands It happens after transcription and before translation 5 How much of the human genome actually codes for proteins a 1 5 6 What are some of the explanations for the difference between the number of genes and the number of proteins present in humans a 25 00 genes specify for 200 000 proteins b Alternative splicing and cutting proteins translated from a single gene c d Inrons may function as exons Larger proteins edited into smaller proteins 7 What kinds of DNA sequences make up the non coding DNA found in the human genome a 98 5 b Viral DNA c Non coding RNAs d Introns e Promoters f Other controls g Repeats transposons telomeres centromeres pseudogenes Chapter 12 8 What is a mutation a A change in the nucleotide sequence of a gene b If present in more than one of the population polymorphism multiple forms 9 What are the two basic classes of mutations a Somatic mutations occur in any cell of the body except the germline cells Affects subsequent somatic cell descendants Not transmitted to offspring b Germline mutations occur in germline cells possible transmission to offspring 10 Sickle cell anemia a encodes valine instead of glutamic acid b Phenotype is associated with homozygotes autosomal recessive Creates altered hemoglobin surface and becomes sticky c Hemoglobins link in low oxygen conditions Sickling causes anemia joint pain organ damage d Homozygous dominant normal e Heterozygous carrier f Homozygous recessive disease 11 Thalessemia a Caused by another beta hemoglobin mutation b Too few beta hemoglobin molecules c Excess of alpha hemoglobin leads to iron release which destroys RBCs and damages the heart liver and endocrine glands d Thalassemia minor heterozygous with mild symptoms e Thalassemia major homozygous recessive more severe 12 Spontaneous mutation a Caused by errors in DNA replication b Not caused by exposure to known mutagens c DNA bases have slight chemical instability and exist in altering forms called tautomers d As replication fork unzipping encounters unstable tautomers mispairings can occur A G 13 Induced mutation a Caused by mutagens and carcinogens i Alkylating agents remove a base ii Acridine dyes add or remove base iii X rays breaks chromosomes delete a few nucleotides iv UV radiation creates thymidine dimmers kinks in DNA 14 Point Mutation a A change of a single nucleotide b Two types C T C G 15 Missense mutation i Transition purine replaces purine A G or pyrimidine replaces pyrimidine ii Transversion purine replaces pyrimidine A T pyrimidine replaces purine a A point mutation that changes the codon b Causes amino acid substitution and may affect protein function c Examples hemoglobin mutations sickle cell anemia 16 Nonsense mutation a point mutation changing a codon fro an amino acid into a stop codon a b Creates truncated proteins that are nonfuctional c d Example factor XI hemophilia C Some have dominant effects interference with normal functions 17 Splice site mutation Intron translated left in a Alters a site where introns are normally removed b c Exon skipped cut out d Example cystic fibrosis BRCA1 breat cancer 18 Insertions or deletions a A normal genetic code is read in triplet nucleotides b Addition or subtraction of nucleotides NOT in multiples of three leads to a change in the reading frame c Causes a framshift and alters amino acids after mutation d Addition or subtraction of entire amino acids 19 Expanding repeats a Insertion of triplet repeats leads to extra amino acids b Some genes are particularly prone to expansion or repeats c Number of repeats correlated with early onset of the disease and severity of the d Anticipation expansion of triplet repeat with increased phenotype severity as the phenotype generations pass 20 DNA repair carcinogens radicals 21 Mismatch repair a Excision repair damaged DNA is removed by excision of the bases and the bases are replaced by DNA polymerase i Nucleotide Excision Repair replaces up to 30 bases used in repair of UVB and ii Base Excision Repair replaces 1 5 bases used in oxidative damage O2 free a Enzymes detect nucleotides that do not base pair in newly replicated DNA b c Incorrect base pair is removed and replaces proofreading is the detection of mismatches Chapter 13 22 Centromere a The largest constriction in the chromosome b Attaches to the spindle fibers 23 Telomere a The chromosome tips a The chromosome region between the centromere and telomere but closest to the b TAGGG repeats c 24 Subtelomers Shorten with each cell division telomere b 8 00 300 000 bases c 500 protein encoding genes d Includes muteigenes and pseudogenes 25 Heterochromatin a Dark staining b Most repetitive c Densely compacted d Very few genes Light staining 26 Euchromatin a b Protein encoding genes Less densely packed c d More genes 27 The p arm a Short arm 28 The Q arm a Long arm 29 Karyotype a A size ordered chromosome chart b 1 22 homologous chromosomes c 23 sex chromosomes 30 Centromere position a At the tip telocentric b Close to end acrocentric c Displaced from center submetacentric d At midpoint metacentric 31 Polyploidy a 17 of all spontaneous abortions b 3 of still births and newborn deaths haploid sperm and a diploid egg 32 Aneuploidy a Subset of being polyploidy b Calls have an extra or missing chromosome c Caused by nondisjunction 33 Nondisjunction a A cause of aneuploidy i Triploid 3 copies of each chromosome produced by 2 sperm and 1 egg or a It s a failure of chromosomes to split up during cell division b c Gametes produced with one extra chromosome an another with one missing chromosome i Meiosis I Nondisjunction 2 monosome and 2 trisome zygotes ii Meirosis II Nondisjunction 2 euploid normal 1