BIOL1012 Exam 4

Chromosomes become visible during ________, when the _________ _______ become discrete chromosomes.

prophase; chromatin fibers

If an organism has two non-identical versions of a gene, the one that is not expressed in the organism is called the _______ allele.

recessive

Most human genes come in alternate versions called ______

alleles

The cell plate, which divides the cytoplasm in two, forms during telophase of mitosis in a _______ cell.

plant

Spindle fibers attach to kinetochores during ______________

prometaphase

At the end of telophase I of meiosis, as cytokinesis occurs, how many haploid cells are there?

2

___________ is the division of the cytoplasm that occurs in conjunction with __________, the last phase in mitosis.

Cytokinesis; telophase

__________ of the __________ to produce sister chromatids occurs in both mitosis and meiosis

Duplication of the chromosomes

Cells will usually divide if they receive the proper signal at a checkpoint in the ___ phase of the cell cycle. If a cell receives a go-ahead signal, it will usually enter the S phase, eventually going on to complete its cycle and divide. If such a signal never arrives, the cell will switch to a permanently nondividing state called the ___ phase.

G1; G0

________ is the first phase of mitosis, when the centrosomes begin moving toward ________ ______ and the ________ ________ breaks up.

Prophase; opposite poles; nuclear envelope

__________ is the final phase of mitosis, when the chromosomes have arrived at the _____ and the nuclear envelopes of the ____ _____ ____ form.

Telophase; poles; two new cells

sister chromatids separate and start their migration toward opposite poles during __________.

anaphase

During _____ sister chromatids separate

anaphase II

Centromeres divide and sister chromatids become full-fledged chromosomes during ________. sister chromatids separate and migrate to _________ _______.

anaphase; opposite poles

A cell replicates its entire chromosomal DNA only when? This ensures that genetic material can be appropriately distributed to each of the __________ ______

before it is about to divide; daughter cells.

A _______ _______ is a lump of abnormal cells that, although growing out of control, remains at its original site.

benign tumor

A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates what?

both parents are heterozygous for both genes

An individual with a malignant tumor is said to have ________

cancer

The most common type of cancer is a __________; this type always originates in tissues that line organs.

carcinoma

A ________ is an inherited feature that varies from individual to individual.

character

Metaphase occurs in the middle of mitosis when the ___________ line up in the _______ of the cell.

chromosomes; middle

What processes lead to most genetic variation in sexually reproducing organisms?

crossing over, independent orientation of chromosomes in meiosis, random fertilization

A cross between two individuals with black eyes and green skin which results in an individual with orange eyes and white skin is an example of a _____ cross.

dihybrid

Somatic cells are _______ and have two homologous copies of each chromosome.

diploid

If an organism has two non-identical versions of a gene, the one that is expressed in the organism is called the _______ allele.

dominant

Before mitosis can begin, the chromosomes, or genetic material, must be ___________, which occurs during _________.

duplicated; interphase

During meiosis II, sister chromatids separate into what?

four different gametes

Meiosis II typically produces _____ cells, each of which is _____.

four; haploid

Different versions of a _____ could encode different eye colors. Alternately, they could encode different coat colors.

gene

The _______ is the genetic makeup of an organism.

genotype

Fertilization joins _____ ______ to produce a ______ _____.

haploid gametes; diploid zygote

The relationship between the sequence of bases in DNA of one sister chromatid compared to the other is that the sequences are ________. Both sister chromatids come from replication of a single DNA molecule, which is present in the one chromatid before replication.

identical

Nucleoli are present during which phase of mitosis?

interphase

A fragment of chromosome 21 reattaches to chromosome 21, but in the reverse direction. What is the name given to this change?

inversion

Synapsis, the pairing of homologous chromosomes, occurs during ___________

prophase I

During _____ a spindle forms in a haploid cell.

prophase II

A _________ _______ is an abnormally growing mass of cells that is actively spreading through the body.

malignant tumor

A hybrid chromosome that has crossed over will contain pieces of both the ________ and ________ _____________.

maternal and paternal chromosomes

If it weren't for _____, chromosome number would double with every generation of sexual reproduction.

meiosis

chromosomes line up on the equatorial plane during which phase?

metaphase

During _____ chromosomes align single file along the equator of a haploid cell.

metaphase II

__________ is the spread of cancer cells from their site of origin to other sites in the body.

metastasis

A genetic cross involving parents that differ in a single character is called a ________ _______

monohybrid cross

The physical traits of an organism are called its ________

phenotype

During anaphase I, what do homologous chromosomes do?

separate and migrate toward opposite poles

if a version of a gene is dominant, then a ______ ______ of it will produce its trait

single copy

During anaphase II, ______ _________ separate and migrate toward opposite poles

sister chromatids

Mitosis occurs in _____ or _____ cells and meiosis occurs in _____ cells in the _______ or ________

somatic or body; germ; testes or ovaries

Cytokinesis often, but not always, accompanies ___________

telophase

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids

telophase I

At the end of _____ and cytokinesis there are four haploid cells.

telophase II

During binary fission, each copy of the duplicating chromosome moves to opposite ends of the cell. This ensures what?

that each daughter cell receives one copy of the chromosome.

During prophase I of meiosis I, what happens to homologous paternal and maternal chromosomes?

they pair up and undergo crossing over

Skin color is known to be affected by at least ______ genes, possibly more.

three

a ______ is one particular variation of a character.

trait

During prophase a homologous pair of chromosomes consists of what?

two chromosomes and four chromatids

Meiosis I produces _____ cells, each of which is _____

two; haploid