BIOL 1020 Lecture Notes - Lecture 23: Chromosome, Autosome, Somatic Cell

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blushseal731

2 Nov 2017

School

University of Manitoba

Department

Biological Sciences

Course

BIOL 1020

Professor

Michael P.Shaw

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BIOL 1020 Full Course Notes

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The behaviour of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation. Independent assortment of chromosomes: crossing over, random fertilization. Ho(cid:373)ologous pai(cid:396)s of ch(cid:396)o(cid:373)oso(cid:373)e"s o(cid:396)ie(cid:374)t (cid:396)a(cid:374)do(cid:373)l(cid:455) at (cid:373)etaphase 1 of (cid:373)eiosis. In independent assortment, each pair of chromosomes sorts maternal and paternal homologues into daughter cells independently of the other pairs. Crossing over produces recombinant chromosomes, which combine genes inherited from each parent. Crossing over begins very early in prophase 1, as homologous chromosomes pair up gene by gene. In crossing over homologous portions of two non-sister chromatids trade places. Crossing over contributes to genetic variation by combining dna from two parents into a single chromosome. Point where crossing over is the chiasma (where they break) Random fertilization adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg) Each zygote has a unique genetic identity. Mendel used the scientific approach to identify two laws of inheritance.

Related Questions

3)During Metaphase I of meiosis, microtubules called spindle fibers attach to the

	homologous pairs of each chromosome
	non-homologous pairs of each chromosome
	non-sister chromatids of each chromosome
	chiasmata of each chromosome
	centrosome of each chromosome

4)Which meiotic process generates genetic diversity?

	Independent assortment
	Transcription
	Mitosis
	Translation

5)Crossing over:

	Occurs between two homologous chromosomes in Meiosis
	Occurs only in Mitosis
	Can occur in Mitosis and Meiosis
	Involves the exchange of DNA between two chromosomes
	Involvs the exchange of centromeres between two chromosomes

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.

limedonkey586

1). Explain the significance of the fact that gametes contain half of the chromosome complement of somatic cells. Tell me something about variation, if you have a sibling (if you don't imagine you do) - how is your sibling's genetic make-up similar and/or different from yours? What about your mom and dad?

2). Explain the terms reductional division and equational division. What is reduced or kept equal? To which nuclear divisions do these terms refer?

3). What is the diploid number (2n = ?) of an organism if it has
a) 12 chromosomes at Anaphase of Mitosis?
b) 12 chromosomes at Anaphase I of Meiosis?
c) 12 chromosomes at Anaphase II of Meiosis?

4). Compare/contrast Metaphase I of Meiosis with Metaphase of Mitosis.

5). What are the two mechanisms of variation in Meiosis, and during which stage(s) does each occur?

6). Draw a diagram of a bivalent and label the following parts: centromere, sister chromatids, non-sister chromatids, homologous chromosomes, chiasma.

7). A diploid cell has 1 pair of acrocentric chromosomes (Chromosome 1) and 1 pair of submetacentric chromosomes (Chromosome 2).
Â· Gene X is on Chromosome 1. Gene Y is on the short arm of Chromosome 2 and Gene Z is on the long arm of Chromosome 2.
Â· The maternal chromosomes have the X, y, z alleles, whereas the paternal chromosomes have the x, Y, Z alleles.
Draw these chromosomes, labeling ALL alleles, as they might appear in Metaphase I of Meiosis.

BIOL 1020 Lecture Notes - Lecture 23: Chromosome, Autosome, Somatic Cell

BIOL 1020 Full Course Notes

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