Principles of Biology I - Exam 4 (Ch. 13 - 15)

Chapter 13

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Heredity is __

the transmission of traits from one generation to the next

Offspring are __ copies of their parents or siblings

not identical

Along with inherited similarity, there is __

variation

Genetics is __

the study of heredity and variation

Genes are __

units of heredity

Genes are made up of segments of __

DNA

Genes are passed to the next generation via __

gametes

Cells that are not gametes are called __

somatic cells

In asexual reproduction, how many individuals pass genes to offspring?

a single individual

In asexual reproduction, offspring are considered __

clones

In sexual reproduction, how many parents contribute genes?

two parents

In sexual reproduction, offspring have __

a unique combination of genes

A karyotype is __

an ordered display of the pairs of chromosomes from a cell

Homologous chromosomes are __

two chromosomes from the same pair

Homologous chromosomes carry the same __ at the same __

genes; loci

Sex chromosomes function to __

determine sex

Human sex chromosomes are represented as __ or __

XX; XY

Chromosomes that are not sex chromosomes are called __

autosomes

A life cycle is __

the generation-to-generation sequence of stages in the reproductive history of an organism

A gamete contains __ set of chromosomes

a single

A cell with a single set of chromosomes is called __

haploid

Fertilization is __

the union of two gametes

A zygote is __

a fertilized egg

A zygote has __ sets of chromosomes

two

A zygote receives one set of chromosomes from __

each parent

A cell with two sets of chromosomes is called __

diploid

Meiosis allows the passage from __ to __

diploid; haploid

Fertilization allows the passage from __ to __

haploid; diploid

The purpose of meiosis and fertilization alternating during life cycle is to __

maintain the number of chromosomes specific for a given species

In diploid life cycles, which cells are haploid?

only gametes

In diploid life cycles, gametes are produced by __

meiosis

In diploid life cycles, do cells divide after reaching the haploid stage?

no

In diploid life cycles, gametes fuse to form a __

diploid zygote

In diploid life cycles, how does the zygote develop into a multicellular organism?

by mitosis

Animals have what type of life cycle?

diploid

Plants and some algae exhibit what type of life cycle?

haplo-diploid (alternation of generations)

In haplo-diploid life cycles, both __ and __ stages undergo mitosis

haploid; diploid

In haplo-diploid life cycles, both haploid and diploid stages are __

multicellular

In haplo-diploid life cycles, the diploid organism is called the __

sporophyte

The sporophyte produces __ through the process of __

haploid spores; meiosis

A spore grows by __ into a haploid organism

mitosis

The haploid organism in a haplo-diploid life cycle is called the __

gametophyte

The gametophyte produces __ through the process of __

gametes; mitosis

In haploid life cycles, which organisms are typically haploid?

most fungi and some protists

In haploid life cycles, which stage is diploid?

only the zygote

In haploid life cycles, the zygote produces __ cells through __

haploid; meiosis

In haploid life cycles, haploid cells grow by __

mitosis

In haploid life cycles, gametes are produced by __

mitosis

Prior to meiosis, chromosomes undergo __

replication

Meiosis consists of __ consecutive divisions

two

The two divisions in meiosis are called __ and __

meiosis I; meiosis II

Between meiosis I and meiosis II, do chromosomes replicate?

no

The result of meiosis is __ daughter cells

four

Meiosis reduces the chromosome number by __

half

During prophase I, centrosomes migrate to __

opposite directions

During prophase I, what forms from polymerized microtubules?

the spindle

During prophase I, what happens to the nuclear envelope?

it breaks

During prophase I, chromosomes undergo __

condensation

During prophase I, what genetic exchange occurs?

crossing over

During crossing over, each chromosome pairs with its __

homolog

During crossing over, DNA from __ is exchanged

non-sister chromatids

Crossing overs occur __ along chromosomes

randomly

The result of crossing over is __ chromatids

four different

During metaphase I, pairs of chromosomes align at the __

metaphase plate

During metaphase I, both chromatids of a chromosome attach to kinetochore microtubules from __

one pole

During metaphase I, the homolog attaches to microtubules from the __ pole

other

During metaphase I, each chromosome pair lines up __ of other pairs

independently

The independent alignment of chromosome pairs is called __

independent assortment

During anaphase I, what structures migrate toward opposite poles?

homologous chromosomes

During anaphase I, sister-chromatid cohesion remains at the __

centromere

During anaphase I, do sister chromatids separate?

no, they stay together

During telophase I, each pole receives __ set of chromosomes

a complete haploid

During telophase I, are sister chromatids identical?

no, they're different due to crossovers

During telophase I, the cytoplasm __

divides

During telophase I, may a nuclear envelope form in some species?

yes

Meiosis II is similar to what other cell division process?

mitosis

During prophase II, what forms to move chromosomes?

the spindle

During prophase II, chromosomes move toward the __

metaphase plate

During metaphase II, chromosomes align at the __

metaphase plate

During metaphase II, sister chromatid kinetochores attach to microtubules from __

both poles

During anaphase II, what proteins break?

those holding sister chromatids at the centromere

During anaphase II, sister chromatids migrate to __

opposite poles

During telophase II, what forms around the chromosomes?

nuclear envelope

During telophase II, chromosomes begin to __

decondense

During telophase II, what cell division process occurs?

cytokinesis

Meiosis creates __ haploid cells

four

Are the four cells produced by meiosis genetically identical?

no, they are genetically distinct

How many events are unique to meiosis I?

three

What unique event occurs during prophase I?

crossing over

What unique event occurs during metaphase I?

alignment of homologous pairs at the metaphase plate

What unique event occurs during anaphase I?

separation of homologs

Mutations are changes in an organism's __

DNA

Mutations are the original source of __

genetic diversity

Different versions of genes are called __

alleles

What process reshuffles alleles during sexual reproduction?

genetic recombination

What are the main sources of variation occurring in each generation?

behavior of chromosomes and fertilization

How many mechanisms contribute to genetic variation?

three

Name one mechanism that contributes to genetic variation

independent assortment of chromosomes

Name a second mechanism that contributes to genetic variation

crossing over