sex determining region of Y, pronounced sorry, single gene on the Y chromosome found in 1990 and is thought to be required for normal testes development, considered a trigger gene, TURNS ON THE Y
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Where does DNA in extranuclear genes come from?
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the mother, the DNA of the mitochondria and chloroplast in the offspring matches the mother
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linkage map
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genetic map that indicates a general sequence of genes along a chromosome
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aneuploidy
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an abnormal chromosome number, this includes trisomy and monosomy
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crossing over
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process of chromosomal segments breaking off and switching places with homologous chromosomes
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genomic imprinting
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the process of the same alleles having different effects on the individual depending if that individual received the trait from the father (sperm) or from the mother (ovum)
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What are changes in chromosome number?
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aneuploidy and polyloidy (occurs during meiosis)
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inversion
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when the fragment reattaches itself to the same chromosome but in the opposite direction, not in the right order, cannot turn the genes on
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mosiacism
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the selection of which X will form the Barr body occurs randomly and independently in each embryonic cell present at the time of X inactivation, females consists of a mosiac of two type of cells: those with the active X derived from the father and those with the active X derived from the mother
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T/F: Extranuclear DNA does not duplicate.
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FALSE
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wild type
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refers to the normal phenotype (or most common), dominant
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If a boy has a sex-linked disorder, who is it from?
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mom
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T/F: Linked genes are usually inherited together.
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true, however, the further apart they are (located on that chromosome), the greater chance they have of crossing over
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Barr Bodies
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1 X in every female is inactive, occurs during embryonic development, development is random
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Fathers can pass recessive alleles on to ____ but mothers can pass them on to ____
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daughters, either
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hemophilia
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cause: results from missing blood-clotting protein
symptoms: afflicted may bleed excessively (sometimes to death) as a result of a minor injury
8 types, depends on what factor you are missing
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duplication
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when the deleted fragment is attached to the sister chromatid (resulting in extra genes), will move through the rest of meisosis with extra information, results in a miscarriage
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sex-linked
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aka "x-linked", means that some genes are located on the sex chromosomes
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When is tetraploidy an advantage?
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in plants allows genetic variation if self-fertilized
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Changes in chromosome number is a ____.
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nondisjunction
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What does X-inactivation involve?
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a methylation - the addition of a methyl group (CH3) to cytosine
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X-inactivation
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formation of Barr Bodies
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genetic recombination
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formation of a new combination of traits from 2 parents
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monosomy
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2n-1, 1 less chromosome, 45 chromosomes in humans, you can live with 1 X
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chromosomal alterations image
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deletion
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when a piece of a chromosome breaks off (missing a lot of genes), depends on which genes are lost if they survive, no idea what causes it
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chronic myelogenous leukemia (CML)
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results from a translocation of chromosome 22 with chromosome 9 (aka Philadelphia chromosome)
when an organism receives more than 2 complete chromosome sets, includes triploidy and tetraploidy
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translocation
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when the fragment reattaches itself to a non-homologous chromosome, came from Agent Orange in Vietnam
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What is the frequency of recombination based on?
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the number of total of recombinant offspring produced
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If there is an increase in frequency, then there is...
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a greater distance between the genes loci (they are further apart)
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errors and exceptions in chromosomal inheritance image
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examples of sex-linked disorders in humans
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hemophilia
color blindness
Duchenne Muscular Dystrophy (DMD)
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sex chromosome disorders
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Klinefelter, Turner, triple-X sydromes
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tetraploidy
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4n or 2 extra sets of chromosomes, 92 chromosomes in humans instead of 46
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color blindness
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symptoms: cannot see green or red (or both), usually affects males (for females to be colorblind they must be homozygous recessive), can affect only 1 eye, not lethal
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mutant phenotype
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refers to anything but normal, aka non-wild type, recessive
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nondisjunction
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the chromosomes don't segregate the way they are supposed to in MI and MII
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T/F: If the frequency is over 50%, the gene loci can still be determined.
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FALSE...It could be due to independent assortment
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linked genes
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are genes located on the same chromosome
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trisomy
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2n+1, one extra chromosome, 47 chromosomes in humans, this comes from the egg not the sperm
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He used the frequency as ___.
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map units, 1% = 1 map unit
"centimorgan" is the term used today
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T/F: Not all DNA is located in the nucleus.
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True...mitochondrial DNA
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cytogenetic map
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actual representation of a chromosome (gene location with chromosomal features), shows the actual location of genes
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What does crossing over separate and when does it occur?
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separates linked genes, occurs during prophase I of MI
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genetic map
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sequence of genes on 1 chromosomes, based on the frequency of crossing over (recombinants)
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recombinants
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offspring with mixed or different phenotypes than parents
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extranuclear genes
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DNA located outside of the nucleus, located within the mitochondria and chloroplast