BLG 143 Study Guide - Final Guide: Mendelian Inheritance, Outcrossing, Genetic Recombination

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12.2 Consequence of Meiosis

➢ Independent shuffling of mat/pat-ernal chromosomes

➢ Crossing over during meiosis I results in 4 gametes with chromosome composition

different from parent cells

➢ During fertilization, haploid sets of chromosomes from mother and father form

diploid offspring

➢ Diploid offspring chromosomes unlike either parent

Asexual reproduction  offspring produced with no fusion of gametes, clones

Sexual reproduction  production of offspring through the fusion of gametes, chromosome

makeup from one another and either parent (results from independent assortment and

crossing over)

Independent assortment

• Separation and distribution of homologous chromosomes during meiosis I produce

many combinations of mat/pat-ernal chromosomes

• Each chromosome has genes that influence trait and alleles that’re versions of genes

• Of genes generates much genetic diversity in subsequent gametes

Crossing Over

• New combinations of alleles within a chromosome, combinations that didn’t exist in

either parent  genetic recombination (any change in the combination of alleles on

a given chromosome)

• Increases genetic variability of gametes produced by meiosis beyond that produced

by random assortment of chromosomes

Fertilization Affects Genetic Variation

• Crossing over and random mixing of mat/pat-ernal chromosomes ensure that each

gamete is genetically unique

• Even if self-fertilization, where gametes from same individual combine (some

plants), offspring are genetically different from parent

• Gametes from different individuals combine to form offspring  outcrossing

(alternative self-fertilization)

• Outcrossing increases genetic diversity of offspring because chromosomes from 2

different parents combined

12.3 Why Does Meiosis Exist?

Sexual reproduction is common among multicellular organisms, but organisms in most

lineages of Tree of Life undergo asexual reproduction (bacteria, most algae, all fungi).

Paradox of Sex

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Document Summary

Crossing over during meiosis i results in 4 gametes with chromosome composition different from parent cells. During fertilization, haploid sets of chromosomes from mother and father form diploid offspring. Asexual reproduction offspring produced with no fusion of gametes, clones. Sexual reproduction production of offspring through the fusion of gametes, chromosome makeup from one another and either parent (results from independent assortment and crossing over) Independent assortment: separation and distribution of homologous chromosomes during meiosis i produce many combinations of mat/pat-ernal chromosomes. Increases genetic variability of gametes produced by meiosis beyond that produced by random assortment of chromosomes. Sexual reproduction is common among multicellular organisms, but organisms in most lineages of tree of life undergo asexual reproduction (bacteria, most algae, all fungi). John maynard smith: asexual reproduction is faster and outcompete similar organisms that invest in sexual reproduction asexual reproduction is much more efficient because no males are produced. Sexual reproduction"s offspring isn"t doomed to inherit harmful alleles.

Related Questions

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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Question 1 (2 points)

In which phase of cell division is marked by the dissolution of the nuclear membrane, the condensation of chromosomes, and the formation of the mitotic spindle?

Question 1 options:

	prophase
	metaphase
	telophase
	anaphase

Question 2 (2 points)

The physical separation of cells during cell division is called:

Question 2 options:

	Cytokinesis
	Telophase
	Interphase
	Chromosome
	Cell plate

Question 3 (2 points)

Meiosis is necessary for sexual reproduction; the gametes formed during this process before fertilization are _______________.

Question 3 options:

	Haploid
	Diploid
	Zygote
	Homologous
	Tetrads

Question 4 (2 points)

Mitosis is the process by which a ___________ cell separates the chromosomes in its nucleus into two identical sets of nuclei.

Question 4 options:

	eukaryotic
	prokaryotic
	bacterial
	all of these are correct

Question 5 (2 points)

Which of the following statements about crossing over is INCORRECT?

Question 5 options:

	It occurs between homologous chromosomes
	It allows for two parents to produce many different types of offspring
	It contributes to genetic diversity in a population
	It occurs during prophase I of mitosis

Fill in the blank, each word can be used more than once.

word bank- crossing over, avoid predation, reproduce,independent assortment, phenotypes, frequencies, nucleotides,meiosis, protein, prophase, segregation, gene, allele, amino acids,fertilization, arrangement, chromosome.

A(n) _________ is one of multiple forms of the same gene.

These different forms of genes are in the same locus of a(n)_________, but they have slightly different sequences of________.

During ________ I of meiosis, genes of homologous chromosomesalign side-by-side.

Then in a process called _________, homologous chromosomesrandomly line up double-file at the center of the cell and thenseperate. Since alleles are randomly distributed, this processcreates variation among the gametes. After ________ with a gametefrom the other sex, variation among gametes will create variationamong the offspring.

Some offspring will have a more favorable combination of allelesthan others, and will therefore survive and ________ moresuccessfully, leading to more favorable alleles in the nextgeneration. However, sometimes conditions change, andonce-favorable phenotypes may becomes less favorable.

Scientists hope that they will soon be able to use biotechnologyto track the ________ of alleles over multiple generations, therebywatching evolution as it occurs.

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BLG 143 Study Guide - Final Guide: Mendelian Inheritance, Outcrossing, Genetic Recombination

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