Textbook Notes (362,870)
Canada (158,081)
Biology (305)
BIOL 103 (103)
Chapter 14


5 Pages
Unlock Document

Queen's University
BIOL 103
Virginia K Walker

BOAG CHAPTER 14 (pg 327-340) MEIOSIS + SEXUAL REPRODUCTION haploid: single set of chromosomes sexual reproduction: needs fertilization in which 2 haploid gametes unite to create 1 diploid zygote -->process of meiosis: haploid ells made by a diploid cell Crossing Over: physical, reciprocal exchange b/w chromosome pieces of homologous (and nonsister) chromatids -# of crossovers controlled by cells; depends on the # and sizes of the chromo -bivalents organized along metaphase plate: each bivalent aligns on the late idependently of the other bivalents -bivalents can be randomly aligned on the plate in a variety of ways: 2^n different alignments, with n=23 for humans = 8 million + possibilities on how the bivalents can be separated -b/c homologues are genetically similar but not identical, random alignment of the homologue chromo promotes lots of genetic diversity in haploid cells -4 haploid cells are produced Diploid-dominant species: diploid species that have haploid gametes destined for fertilization Haploid-dominant species: haploid organisms have haploid cells that unite to create a diploid zygote, which then immediately proceeds through meiosis to create 4 haploid cells--> spores: creates a multicellular haploid organism Alternation of generations: alternates b/w diploid forms (sporophytes) and haploid forms (gametophytes) Formation of a bivalent and crossing over during meiosis I.At the beginning of meiosis, homologous chromosomes pair up to form a bivalent, usually with a synaptonemal complex between them. Crossing over occurs between homologous, nonsister chromatids within the bivalent. During this process homologues exchange segments of chromosomes. For simplicity the two homologous chromosomes are shown side by side, with two nonsister chromatids close and two much farther apart. In real cells, however, the homologous chromosomes actually lie on top of each other; hence, both nonsister chromatids of homologous chromosomes are equivalent distances apart. VARIATIONS IN CHROMOSOME NUMBER + STRUCTURE natural variation exists in chromo structure + number -structure within a species can vary in size, location of centromere, and banding patterns MUTATIONS CAN ALTER CHROMOSOME STRUCTURE -consequence of mutation depends on mutation size + if it includes (portions of) genes that are vital to the development of the organi
More Less

Related notes for BIOL 103

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.