BIOB 272 1st Edition Lecture 13Outline of Last Lecture LinkageI. Linkage in Sweet Peas ExampleII. Test CrossesIII. Crossing OverIV. Recombination RateV. Linkage TermsVI. Gene Order DeterminationVII. Double-Stranded RecombinationVIII. 3 Types of Genome Maps Outline of Current Lecture Chromosome Structure and VariationI. Species and Individual’s Chromosomes may differ by:a. Chromosome Number (ploidy)- Karyotype- Aneuploidy- Euploidy- PolyploidyThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. Chromosome StructureII. Genome Instability (Aneuploidy)III. Aneuploidy most common in females-why?IV. Down Syndrome: Trisomy-21V. Why Sex Chromosome abnormalities are more common than autosomal abnormalities:VI. Somatic MosaicCurrent LectureChromosome Structure and VariationI. Species and Individual’s Chromosomes may differ by:a. Chromosome Number (ploidy): number of chromosome present in somatic cell- Aneuploidy: loss or gain of an entire chromosome- Euploidy: “true” ploidy- individual has balanced set (equal numbers) of all chromosomes- Polyploidy: when # set of chromosomes >2Nb. Chromosome Structure- Change in the amount of genetic infoo Deletionso Duplications- Change in gene positiono Inversionso TranslocationsII. Genome Instability (Aneuploidy):- Aneuploidy produces imbalances in the amount of gene products (abnormal number or chromosomes)- Arises from non-disjunction (don’t split into 2 chromosomes correctly) during Meiosis I or II- sometimes instead will split into 3 or not split at all- most are lethal very early in development- If anything goes wrong during division during Meiosis I or II- This non-disjunction at Meiosis I or II causes many human diseases- i.e. Down Syndrome- Trisomys (aneuploidies) on larger chromosomes= more lethal in early developmentIII. Aneuploidy most common in female meiosis I or II- Why?o Females – Meiosis I begins in 3rd month of fetal life and arrests prior to birth. This “arrest” of the eggs do not allow them to age very well. Ovulation occurs once per month between 12 and 50 years of age. Ovulation stimulates completion of Meiosis Io Females have one copy of their X-chromosomes that in inactivatedo Males- constantly restarting Meiosis to generate new spermIV. Down Syndrome: Trisomy-21- 1/700 births- Can detect before birth- 3 copies of chromosome 21- caused from a non-disjunction during Meiosis I or II V. Why Sex Chromosome abnormalities are more common than autosomal abnormalities:- Aneuploidy of sex chromosomes is not as harmful- mutations aren’t as extreme- humans can still live fairly normal lifeVI. Somatic Mosaic- Random X-inactivation in some mammals can be observed in progeny if phenotype is X-linked- Females have one of their X-chromosomes in inactive form-the other stays active= results in tissue level mosaics- In given cell only express one X but in a gien tissue has two X chromosomes (some parts of cell with X1 and some with X2) to form a mosaic- Why Calico cats are colored the way they
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