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AP Biology: CHAPTER 13

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Section 1

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Cytokinesis 2

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Biology Science

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Cards (39)

Section 1

(39 cards)

Cytokinesis 2

Front

- division of the cytoplasm that results in four haploid daughter cells (the amount of DNA is reduced in half) and are genetically different from each other

Back

Sperm

Front

haploid male sex cells produced by meiosis - determines the sex of the zygote

Back

Y chromosome

Front

sex chromosome found only in males

Back

Meiosis 1

Front

- preceded by replication of homologous chromosomes 2n -> n + n

Back

crossing over

Front

- two non-sister chromatids in the tetrad cross over each other and exchange segments of DNA - this exchange produces recombinant chromatids - this event is the major source of genetic variations in gametes - chiasma ~~~~~~~~~~~~~~~~ - helps to preserve genetic variability within a species by allowing for virtually limitless combinations of genes in the transmission from parent to offspring - is estimated to occur approximately fifty-five times in male meiosis, and about seventy-five times in female meiosis

Back

Prophase 2

Front

- sister chromatids move toward the metaphase plate

Back

chiasma

Front

the X-shaped region where the exchange of genetic material occurs

Back

Anaphase 1

Front

- the tetrads separate and sister chromatids move to opposite poles

Back

Telophase 1

Front

- a nuclear membrane encloses each set of homologous chromosomes - each nuclei now has a haploid (n) set of chromosomes due to independent assortment and there is a loss of genetic content in each cell - the genetic content has been reduced in half (n) because only some of the maternal and paternal chromosomes exist in each nucleus

Back

the three mechanisms that are responsible for most of the variation that arise in each generation are

Front

- independent assortment - crossing over - random fertilization

Back

Homologue

Front

each of two chromosomes with identical structures

Back

Öogenesis

Front

- occurs in the ovary due to estrogen - the polar bodies are smaller than the ovum due to unequal division of the cytoplasm and cannot be fertilized by sperm - the egg gets most of the cytoplasm to ensure that the egg has a larger store of food to nourish the developing embryo after fertilization - plant polar bodies are fertilized by a sperm cell - the fertilized polar bodies will develop and give rise to the endosperm - the fertilized ovum will become the plant embryo (2n)

Back

Telophase 2

Front

- the chromosomes arrive at opposite poles - nuclei form around each set and the chromosomes unwind

Back

Meiosis is responsible for

Front

genetic variations that exists in sexually reproducing species, between the parents and offspring, and even between two offspring from the same parents

Back

testosterone

Front

male sex hormone

Back

haploid

Front

half the normal number of chromosomes

Back

Homologous Chromosomes

Front

chromosomes having the same or allelic genes with genetic loci (positions) usually arranged in the same order - one chromosome inherited from the father, paternal and one from the mother, maternal - each gene in the pair of chromosomes codes for the same trait, but each chromosome may code for a different version of that trait, so homologous chromosomes are NOT identical to each other

Back

What does each daughter cell have?

Front

half the # of chromosomes and half the # of the genetic content of the diploid parent cell

Back

sex chromosome

Front

one of two chromosomes that determines an individual's sex

Back

Metaphase 1

Front

- tetrads line up at the metaphase plate - maternal and paternal sister chromatids in the tetrad are facing opposite poles (orientation to opposite poles is random) - kinetochores of all sister chromatids are attached to the spindle microtubules

Back

Prophase 1

Front

- nuclear envelope breaks down - spindle apparatus begins to develop - replicated maternal and paternal homologous chromosome form maternal and paternal sister chromatids - synapsis occurs - crossing over takes place

Back

Meiosis 2

Front

- both daughter cells from Meiosis 1 now undergo Meiosis 2 - no chromosome replication occurs n -> n

Back

recombinant chromatids

Front

two chromatids with new combinations of genes and inherited traits

Back

autosomes

Front

Any chromosome that is not a sex chromosome - human gamete has 22 of these

Back

independent assortment

Front

the separation of the maternal and paternal sister chromatids randomly to opposite poles - maternal and paternal sister chromatids of the tetrad orient toward opposite poles randomly during metaphase 1 - the number of possible combinations due to independent assortment is 2^n , where n is the haploid number of species - for humans n=23 , so there are 2^23 possible combinations of chromosomes each time a cell undergoes meiosis - 2^23 = 8.4 million possible combinations

Back

Cytokinesis 1

Front

- division of the cytoplasm forms two haploid daughter cells

Back

gonads

Front

reproductive glands-male, testes; female, ovaries

Back

Metaphase 2

Front

- sister chromatids are at the metaphase plate - two sister chromatids are no longer genetically identical to each other because of CROSSING OVER - kinetochores of sister chromatids attach to the microtubules

Back

fertilization

Front

the joining of a sperm cell and an egg cell n+n= 2n - random event with many possible outcomes

Back

Alleles

Front

different versions of a gene

Back

estrogen

Front

female sex hormone

Back

Synapsis

Front

the union of the sister chromatids to form a tetrad of homologous chromosomes

Back

Anaphase 2

Front

- the sister chromatids separate (just like in mitosis) and move as two individual chromosomes toward opposite poles

Back

primary öocyte

Front

produces one haploid egg (ovum) and three haploid polar bodies

Back

gametes

Front

sex cells

Back

Spermatogenesis

Front

- occurs in the testes due to testosterone - one diploid germ cell, spermatogonium, will produce 4 viable haploid sperm

Back

tetrad

Front

the combination of maternal and paternal sister chromatids

Back

meiosis

Front

Cell division that produces reproductive cells in sexually reproducing organisms - the number of chromosomes and genetic content will be reduced in half (reduction division process) - in mammals, meiosis occurs in the gonads (ovaries or testes) in response to estrogen or testosterone 2n -> n

Back

X chromosome

Front

the sex chromosome that is present in both sexes: singly in males and doubly in females

Back