BIO 1201 Chapter 8 Cell Reproduction

How does meiosis produce such genetic variation?

1) Independent Assortment of Chromosomes -When aligned during metaphase I of meiosis, the side-by-side orientation of each homologous pair of chromosomes is a matter of chance. -For a species with more than two pairs of chromosomes, such as humans, every chromosome pair orients independently of all the others at metaphase I. 2) Crossing over is the exchange of corresponding segments between nonsister chromatids of homologous chromosomes, which occurs during prophase I of meiosis. -gametes arise with chromosomes (Recombinant) that are partly from the mother and partly from the father.

What is the chromosome number found in humans cells after meiosis I is completed?

22 autosomes and a sex chromosome

Humans have ________ chromosomes

46

Comparing Mitosis and Meiosis

All the events unique to meiosis occur during meiosis I. Meiosis II is virtually identical to mitosis in that it separates sister chromatids. But unlike mitosis, meiosis II yields daughter cells with a haploid set of chromosomes.

In terms of drugs that help to fight cancer cells, there are several categories that are used. What is the category of anti-cancer drugs that have been shown to act against tumors in human trials?

Anti-cancer

Duplicating Chromosomes

Before a cell begins the division process, the DNA molecule of each chromosome is copied through the process of DNA replication The result is that each chromosome consists of two copies called sister chromatids, which contain identical genes Two sister chromatids are joined together tightly at a narrow "waist" called the centromere Once separated from its sister, each chromatid -is considered a full-fledged chromosome and -is identical to the original chromosome

cancer

Cancer is a disease of the cell cycle. Cancer cells -do not respond normally to the cell cycle control system, -divide excessively, and -may invade other tissues of the body. can form tumors, abnormally growing masses of body cells.

Which of the following occurs during the S-phase of interphase?

DNA synthesis

Chromosomes are always coiled in a tight "X" shape.

False

Genetic variability is a result of asexual reproduction.

False

diploid cell

Humans are said to be diploid organisms because all body cells contain pairs of homologous chromosomes.

benign tumor.

If the abnormal cells remain at the original site

This diagram is showing the probability of chromosomes and how they align during meiosis. What is this probability know as?

Independent assortment of chromosomes

Immunomodulators

Medicines that stimulate the immune system to fight against cancer cells.

metastasis

The spread of cancer cells beyond their original site

Chromosomes are too thin to be seen with a light microscope before they prepare for division.

True

Tumors can start for many reasons in all parts of a human body. In terms of cancer growth on the genetic level, there are two major genes that can contribute to a cell becoming cancerous. This major gene group has a normal function of promoting apoptosis and inhibiting cell division.

Tumor suppressor genes

Amanda's parents realized that her body was not developing properly about the time she was 12 years old. She was shorter than most of her friends and was not going through changes normally associated with female puberty. They took her to a doctor who initially diagnosed Amanda with Turner Syndrome because of her physical features. He ordered a karyotype that confirmed his diagnosis. Amanda was born with only one X chromosome. Although there is no specific cure, the doctor was able to treat her and correct some of the problems associated with the condition. For example, she received growth hormone to improve her growth and estrogen to help her develop the physical changes of puberty. Fill in the blank: With respect to her sex chromosomes, Amanda would be designated as ________.

XO

interphase

a cell -performs its normal functions, -doubles everything in its cytoplasm, and -grows in size. The period when this occurs is called the S phase (for DNA synthesis).

Anti-tumor

acting against tumors in animals

Anti-cancer

acting against tumors in human trials

Cytotoxic

acting against tumors in vitro (lab culture)

During the G2 phase

after DNA duplication during the S phase), each chromosome in the cell consists of two identical sister chromatids, and the cell prepares to divide.

How does cytokinesis differ between plant and animal cells?

animal cells are separated by cleavage while plant cells form a cell plate

The production of genetically identical offspring from a single parent refers to ___________.

asexual reproduction

What are the chromosomes that do NOT determine genetic sex of an individual called?

autosomes

cytokinesis in plant cells

begins when vesicles containing cell wall material collect at the middle of the cell and then fuse, forming a membranous disk called the cell plate.

Malignant tumors

can spread into neighboring tissues and other parts of the body, forming new tumors, and can interrupt organ function. An individual with a malignant tumor is said to have cancer

Where are Sister chromatids joined together?

centromere

Tumor suppressor genes

code for proteins that inhibit the cell cycle and promote apoptosis. When tumor suppressor genes mutate, their products no longer inhibit the cell cycle or promote apoptosis

Proto-oncogenes

code for proteins that promote the cell cycle and inhibit apoptosis. They are often likened to the gas pedal of a car because they accelerate the cell cycle. When proto-oncogenes mutate, they become cancer-causing genes called oncogenes.

cell cycle control system

consists of specialized proteins within the cell. These proteins -integrate information from the environment and from other body cells and -send "stop" and "go-ahead" signals at certain key points during the cell cycle

Sexual reproduction

depends on the cellular processes of meiosis and fertilization

During the G1 phase

each chromosome is single, and the cell performs its normal functions. Most variable in length of time of all phases

Mitosis

for growth and maintenance most genes are located on chromosomes in the cell nucleus involves one division of the nucleus and cytoplasm (duplication, then division in half), producing two diploid cells.

Meiosis

for reproduction number of chromosomes during meiosis is cut in half. a cell that has duplicated its chromosomes undergoes two consecutive divisions, called meiosis I and meiosis II an exchange of genetic material—pieces of chromosomes—between homologous chromosomes. -crossing over entails two nuclear and cytoplasmic divisions (duplication, division in half, then division in half again), yielding four haploid cells.

fertilization

haploid sperm cell from the father fuses with a haploid egg cell from the mother The resulting fertilized egg, called a zygote, is diploid, with two sets of chromosomes, one set from each parent.

haploid cell

has only one member of each pair of homologous chromosomes. Producing haploid gametes by meiosis keeps the chromosome number from doubling in every generation.

A human somatic cell

is a typical body cell has 46 chromosomes.

Cytokinesis in animal cells

is known as cleavage begins with the appearance of a cleavage furrow, an indentation at the equator of the cell.

At least 90% of the cell cycle is spent in interphase. What occurs in the cell during interphase?

performs normal functions, doubles everything within the cytoplasm, and grows in size

Ordinary cell division produces two daughter cells that are genetically identical. This type of cell division is important for all of the following functions EXCEPT ________.

production of sperm and eggs

Homologous chromosomes

resemble each other in length and centromere position carry genes controlling the same inherited characteristics.

Cytokinesis typically begins during the end of ________ during mitosis

telophase

nondisjunction

the members of a chromosome pair fail to separate at anaphase, producing gametes with abnormal numbers of chromosomes. can occur during meiosis I or II. occurrence increases with age down syndrome

It is a common fallacy that reproduction most commonly results in the birth of new organisms. In fact, reproduction more commonly involves ___________.

the production of new cells

Upon completion of telophase I and cytokinesis, there is (are) ________ cell(s).

two haploid

mitotic spindle

what chromosomes and their movements depend on

mitotic (M) phase

​​mitosis, in which the nucleus and its contents divide evenly into two daughter nuclei ​​cytokinesis, in which the cytoplasm (along with all the organelles) is divided in two