Exam 2 genetics portage learning 2023 complete study Guide 2023 /2024

Exam 2 genetics portage learning 2023 complete study Guide 2023 /2024 Exam 2 Genetics Chapter 7  Nondisjunction in meiosis – can cause XXX Syndrome or XYY Condition  47 XYY – famous o There’s this idea that there is an over representation of XYY of men in prison o Some people think that people with XYY are more likely to become criminals or get put in jail o Above average in height and below average in intelligence  Sex determination o At 5 or 6 weeks there is a potential for the fetus to get a Y chromosome and become a male  PAR: pseudoautosomal region  SRY: sex-determining region Y  MSY: male-specific region of the Y  Primary sex ratio: ratio of males and females conceived  Secondary sex ratio: ratio of males to females actually born  Barr Body: an inactivated X chromosome  The Lyon Hypothesis: o X inactivation: occurs at random in human cells, it will turn into a Barr Body  All females are genetic mosaics depending on what they are expressing  Methylation: if methyl groups are attached to nucleotides in DNA, that shuts down gene expression o XIC – X-inactivation center  XIST – X-Inactive Specific Transcript The Ratio of X Chromosomes to Sets of Autosomes Determines Sex in Drosophila Dosage Compensation in Drosophila  The X chromosome in males is turned up in expression o Induce higher levels of gene expression and transcription Bilateral gynandromorph – left half is male, right half is female  Right after fertilization, there were two x chromosomes, one with wild type eye color and wild type wings, the other side had normal eye color and normal wings  Everything on right side is female cause of two Xs  Everything on left is going to be male o Has the two mutant alleles Temperature Variation Controls Sex Determination in Reptiles  Different temperature profiles for different species and sexes CHAPTER 8 Variation in the Number of Chromosomes Results from Nondisjunction Monosomy and Trisomy Results in a Variety of Phenotypic Effects  Turner syndrome  Partial Monosomy in Humans o Cri-du-Chat Syndrome – karyotype can be described as 46, 5p-  There is a deletion on the p arm on chromosome 5  This can be a described as a partial monosomy  Intellectual disability, microcephaly o Not going to find true monosomy’s in humans because they cannot survive Trisomy involves the addition of a chromosome to a diploid genome  Plants can tolerate this situation better than animals  Most monosomy’s and trisomy’s are going to be lethal  A trisomy in theory and reality can be passed on  Down Syndrome: 47, 21+ o An extra copy of chromosome 21 o 47 – number of chromosomes o The severity can vary from person to person o If mom is 50 or so, the odds of giving birth to a child with down syndrome increases largely o Nondisjunction is occurring in mom o Life expectancy is lower than someone without down syndrome  Variability in Human Aneuploidy o Up to 30% of all fertilized eggs from all spontaneous abortions in humans may contain an error in chromosome number o 45,X has one of the highest incidence rates among abortuses. Also, about 80% of 45,X have the maternal X Polyploidy, in Which More Than Two Haploid Sets of Chromosomes Are Present, Is Prevalent in Plants  Two sperm can fertilize a single egg and result in a triploid organism  Tetra gametic chimerism – there can be two eggs fertilized and can fuse together but not fusion of the nuclei o You can get an embryo that is two fused embryos o They should have been twins but fused together to become one person o Two different genomes o 4 gametes – 2 eggs, 2 sperms, 2 embryos come together to form one person  Auto polyploidy – more copies of that individuals genome  Allopolyploidy – take two species and make a hybrid of them o Individual with two different genomes, but they are very closely related  Endopolyploidy – some cells are diploid and some are polyploidy Variation Occurs in the Internal Composition and Arrangement of Chromosomes  Deletion – part of the chromosome is missing  Duplication – extra copies of chromosomes  If deletion and duplication are big enough, you can see them in a karyotype  Inversions – flip around one or two chromosomes  Translocations – where pieces of nonhomologous chromosomes move from one chromosome to another o Not normal for nonhomologous chromosomes to exchange with another  Nonreciprocal translocation Alternate segregation – when two opposite chromosomes segregate Exam 2 genetics portage lea