Chapter 11 & 13: Meiosis and Linked Genes Flashcards
Describe the independent assortment of chromosomes in Meiosis I. Explain how the independent assortment of chromosomes produces genetic recombination of unlinked genes.
The diploids line up on the meiotic plate, so they are evenly split between the two cells when they split.
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Distinguish between linked genes and sex linked genes.
Sex linked genes are genes that reside on the X-chromosome, while linked genes simply reside on the same chromosome.
Distinguish between parental and recombinant phenotypes.
Parental phenotypes are phenotypes matching those of either parent.
Recombinant phenotypes are those matching one trait from either parent.
Explain why linked genes do not assort independently. Explain how crossing over can unlink genes.
Linked genes are on the same chromosome. Thus they are bound to each other in a gamete at the end of meiosis.
Crossing over places part of a chromosome on another diploid, thus separating the linked genes from each other.
Explain how Sturtevant created linkage maps. Define a map unit.
He realized that by determining which genes were linked, he could establish a linkage map by using linked genes and intermediates to produce one possible arrangement of genes in a chromosome to fit the linkage data.
A map unit is approximately equal to one percent of recombination frequency, and is called a centimorgan.
Explain why Mendel did not find linkage between seed color and flower color, despite these genes being on the same chromosome.
Crossing over separated the genes. They were far enough from each other that their recombination factor was 50% because crossing over separated them during Prophase.
Explain how genetic maps are constructed for genes located far apart on a chromosome.
An intermediate gene is linked to both traits with recombination frequencies of less than 50 for both, even though the two traits appear unlinked to each other in direct testing.
Describe how sex is typically determined in humans.
XX and XY.
Explain why sex-linked diseases are more common in males.
Since men have only one X-chromosome, X-linked recessive traits are not masked.
Describe inheritance pattern and symptomology of color blindness, Duchenne muscular dystrophy, and hemophilia.
X-linked recessive
Describe the process of X-inactivation in female mammals. Explain how this phenomenon produces the tortoiseshell coloration in cats.
X-linked codominance.
Define trisomy, tripolidy, and polyploidy. Explain how these major chromosomal changes occur and describe possible consequences.
Downs Syndrome (Trisomy 21). Occur via non disjunction, which messes up distribution of diploids in meiosis.
Explain why extra nuclear genes are not linked in a Mendelian fashion.
They don’t make their way into gametes.
Distinguish between the following pairs of terms:
A: somatic cell and gamete
B: autosome and sex chromosome
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Explain how haploid and diploid cells differ from one another. State which cells in the human body are diploid and which are haploid.
Gametes are haploid. Somatic cells are diploid.
