BIOL 190 Lecture Notes - Lecture 17: Patau Syndrome, Sister Chromatids, Edwards Syndrome

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20 Apr 2017

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Independent assortment- side by side orientation of each homologous pair of chromosomes is a matter of change. Every chromosome pair orients independently of the others during metaphase. Results in different combinations of chromosomes in gametes. Change in the structure and/ or number of chromosomes in a cell. Random errors during meiosis, usually not passed from one generation to the next. The result of nondisjunction or mistakes during crossing over. Aneuploidy - too few or too many chromosomes. Non- disjunction- error in chromosome/ chromatid separation in meiosis i or ii. Results in an incorrect number of chromosomes. Gamete ( n + 1) with 24 chromosomes (from non- disjunction event) Most autosomal trisomies are lethal; embryo/ fetus dies in utero (miscarriage) Babies usually die after a few months. Gamete (n-1) with 22 chromosomes (from non-disjunction event) Monosomies are lethal embryo/ fetus dies in uerto (miscarriage) Single exception- turner syndrome, individuals are (2n- 1) Translocation- attachment of a segment to a nonhomologous chromosome.

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-Complete the following sentences: metaphase of mitosis, prophase II of meiosis, crossing over, anaphase I of meiosis, variable, random fertilization, identical, random orientation, metaphase I of meiosis, prophase I of meiosis, metaphase II of meiosis, reduction division

Two processes that occur during meiosis produce genetically ____________ cells.

In a process called ____________ , paired homologous chromosomes align randomly at the cell equator. This occurs during this stage of cell division: ____________ .

In a process called ____________ , genetic material is exchanged between homologous chromosomes. This occurs during this stage of cell division: ____________ .

-Complete the following paragraph to describe nondisjunction and the resulting effects on chromosome number.

words: euploidy, primary nondisjunction, nomal, nondisjunction, secondary nondisjunction, homologous chromosomes, abnormal, trisomy, monosomy, sister chromatids, aneuploid

1.During meiosis I, ____________ separate and move towards opposite ends of the poles.

2.During meiosis II, ____________ separate and move towards opposite ends of the poles.

3.During meiosis I, if both members of a homologous pair go into the same daughter cell, ____________ is said to occur and no normal gametes are produced.

4.During meiosis II, if the sister chromatids fail to separate and both daughter chromosomes go into the same gamete, ____________ is said to occur. Half the gametes are aneuploid while the other half are euploid.

5.If an egg that contains 24 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

6.If an egg that contains 22 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

Which statements pertaining to genetic variability are correct? Check all that apply (note that wrong answers will be deducted from right answers)!

Crossing over is defined by the exchange of chromosome pieces during metaphase one of meiosis.

If a germ cell (i.e. parent cell before meiosis) had only two pairs of homologous chromosomes (i.e. 4 chromosomes total) there are 2 possible combinations of maternal and paternal chromosomes in gametes.

Siblings produced by sexual reproduction are different because sperms are different from one another and eggs are different from one another, and the combination of an egg and sperm is basically unique.

Random fertilization means that all possible combinations of eggs and sperm are equally likely, i.e. it is pure chance which sperm fuses with which egg.

Individual chromosomes contain thousands of genes. This means that during each crossing over event, more than one gene is exchanged between paternal and maternal chromosomes.

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23. During meiosis, one way that diversity is achieved is throughthe differential ways maternal and paternal
chromosomes line up at the equator. This phenomenon is knownas:
A. Crossing under; B. Random mating; C. Crossing over; D. Randomshuffling
24. What is the correct order of classification from the leasttraits in common to the most traits in common?
1. Order; 2. Genus; 3. Kingdom; 4. Species; 5. Phylum; 6. Family;7. Class
A. 3,5,1,7,2,6,4; B. 3,7,5,6,1,2,4; C. 3,5,7,6,1,4,2; D.3,5,7,1,6,2,4; E. None of the above 25. Humans are currentlyclassified as Homo sapiens. An earlier human ancestor was Homoerectus. Please
identify the Genus of the earlier human ancestor. A. sapiens; B.Homo; C. Human; D. erectus
26. Whales utilize which type of fertilization? A. Internal; B.External; C. Terrestrial; D. None of the above
27. During internal fertilization, sperm are deposited directlyinto the femaleâs body in order to protect the
gametes. In some female animals, after the sperm fertilizes theeggs, the eggs continue to develop inside the
female, and the developing embryos receive ALL of their nourishmentfrom the mother. These animals are
considered to be: A. Oviparous; B. Viviparous; C. Precocial; D.Ovoviviparous
28. In humans, which gender has separate openings for the urinaryand reproductive systems?
A. Men; B. Women; C. Both A and B; D. None of the above
29. An animalâs anatomical structures can be used to constructphylogenetic trees. What is the term given to the
structures of two animals whereas the structures are very similarbut have different functions? Ex: Forearm of a
human and the wing of a duck:
A. Vestigial Structures; B. Analogous Structures; C. HomologousStructures; D. None of the above
30. Humans have 46 chromosomes in every somatic cell nucleus. Thereare 23 chromosomes from mama and
23 chromosomes from papa. Chromosome #3 from mother and Chromosome#3 from father contain
information to control the same genetic traits. During meiosis 1,duplication of chromosomes results in 2 copies
of chromosome #3 from the father and 2 copies of chromosome #3 fromthe mother. The pair of chromosomes
#3 from the father are refered to as:
A. Sister chromatids; B. Centromeres; C. Homologous chromosomes; D.Spindle apparatus

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BIOL 190 Lecture Notes - Lecture 17: Patau Syndrome, Sister Chromatids, Edwards Syndrome

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