G12║ Biology T1 Final

As a cell becomes larger
a)it does not need molecules for cell growth
b)it is less efficient at moving waste materials across the cell membrane.
c)it places fewer demands on its DNA.
d)it is more efficient at moving nutrients across the cell membrane.

b

As a cell's size increases, what happens to the ratio of its surface area to its volume?
a)The surface area increases as the volume increases.
b)The surface area does not increase as fast as the volume increases.
c)The ratio of surface area to volume does not matter.
d)The ratio stays the same.

b

Which statement about sexual and asexual reproduction is true?
a)There is no difference in the level of genetic variation produced by the two types of reproduction.
b)There is a lot of genetic variation in organisms that reproduce only asexually.
c)There is more genetic variation in organisms that reproduce sexually than those that reproduce only asexually.
d) Only yeast and bacteria reproduce asexually.

c

What is an advantage of asexual reproduction that is not an advantage of sexual reproduction?
a)Asexual reproduction produces a great deal of genetic diversity.
b) Populations of asexual organisms produce viable offspring.
c)Populations of asexual organisms can increase in number very quickly.
d)Asexual organisms can evolve new genetic defenses against diseases.

c

When during the cell cycle are chromosomes visible?
a) only during interphase
b) only when they are being replicated
c) only during cell division
d) only during the G1 phase

c

Which pair includes a phase of the cell cycle and a cellular process that occurs during that phase?
a) G1 phase, DNA replication
b) G2 phase, preparation for mitosis
c) S phase, cell division
d) M phase, cell growth

b

During which phase of mitosis do the chromosomes line up along the middle of the dividing cell?
a) prophase
b) telophase
c) metaphase
d) anaphase

c

One difference between cell division in plant cells and in animal cells is that plant cells have
a) centrioles.
b) centromeres.
c) a cell plate.
d) chromatin.

c

What is the role of the spindle fibers during mitosis?
a) They help separate the chromosomes.
b) They break down the nuclear membrane.
c) They duplicate the DNA.
d) They make the chromosomes visible.

a

What are some of the difficulties a cell faces as it increases in size?

The larger a cell becomes, the more demands the cell places on its DNA. In addition, a larger cell is less efficient in moving nutrients and waste materials across the cell membrane.

How do asexual and sexual reproduction compare?

The production of genetically identical offspring from a single parent is known as asexual reproduction. Offspring produced by sexual reproduction inherit some of their genetic information from each parent.

cell division

process by which a cell divides into two new daughter cells

asexual reproduction

process of reproduction involving a single parent that results in offspring that are genetically identical to the parent

sexual reproduction

type of reproduction in which cells from two parents unite to form the first cell of a new organism

What is the role of chromosomes in cell division?

to separate DNA precisely during cell division

What are the main events of the cell cycle?

During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells.

What events occur during each of the four phases of mitosis?

- Prophase: the genetic material inside the nucleus condenses and the duplicated chromosomes become visible. Outside the nucleus, a spindle starts to form.
- Metaphase: the centromeres of the duplicated chromosomes line up across the center of the cell. Spindle fibers connect the centromere of each chromosome to the two poles of the spindle.
- Anaphase: the chromosomes separate and move along spindle fibers to opposite ends of the cell
- Telophase: the chromosomes, which were distinct and condensed, begin to spread out into a tangle of chromatin.

How do daughter cells split apart after mitosis?

Cytokinesis completes the process of cell division—it splits one cell into two

chromosome

threadlike structure of DNA and protein that contains genetic information; in eukaryotes, chromosomes are found in the nucleus; in prokaryotes, they are found in the cytoplasm

chromatin

substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones

cell cycle

series of events in which a cell grows, prepares for division, and divides to form two daughter cells

interphase

- G1 + S + G2
- period of the cell cycle between cell divisions
- cell functions normally
- duplication of organelles
- replication of DNA
- cell size becomes larger

mitosis

part of eukaryotic cell division during which the cell nucleus divides; asexual reproduction

cytokinesis

- division of the cytoplasm to form two separate daughter cells
- in animal cells, the cell membrane pinches in the center to form two daughter cells
- in plant cells, cell plate divides the cell into two daughter cells because the tough cell wall doesn't allow the cell membrane to pinch in

prophase

- first and longest phase of mitosis in which the genetic material inside the nucleus condenses and the chromosomes become visible
- nuclear membrane starts to disappear
- centrioles move towards the pole
- chromatid appears
- duplicated chromosomes attached at centromere

centromere

region of a chromosome where the two sister chromatids attach

chromatid

one of two identical "sister" parts of a duplicated chromosome

centriole

structure in an animal cell that helps to organize cell division

metaphase

- phase of mitosis in which the chromosomes line up across the center of the cell
- spindle fibers radiate out from centriole
- duplicated chromosomes arranged in the center
- spindles attached at centromere

anaphase

- phase of mitosis in which the chromosomes separate and move to opposite ends of the cell
- spindle fibers contact, pulling the chromosomes toward opposite poles

telophase

- phase of mitosis in which the distinct individual chromosomes begin to spread out into a tangle of chromatin
- spindle fibers disappear
- chromosomes gather at poles
- nuclear membrane appears
- cell develops 2 nuclei

How is the cell cycle regulated?

by regulatory proteins both inside and outside the cell

How do cancer cells differ from other cells?

Cancer cells do not respond to the signals that regulate the growth of most cells. As a result, the cells divide uncontrollably.

cyclin

one of a family of proteins that regulates the cell cycle in eukaryotic cells

growth factor

one of a group of external regulatory proteins that stimulate the growth and division of cells

apoptosis

- process of programmed cell death
- imp. role in structuring tissues during growth and development
- cell undergoes a series of controlled steps for self-destruction

cancer

disorder in which some of the body's cells lose the ability to respond to growth regulators and to control growth

tumor

mass of rapidly dividing cells that can damage surrounding tissue

cell

smallest structure and functional unit

types of cells

body cells and gamete cells

characteristics of mitosis

- identical cells
- asexual
- diploid

characteristics of meiosis

- non identical
- sexual
- haploid

characteristics of asexual reproduction

- produce many offspring in short period
- one parent involved
- genetically identical offspring that thrive in stable environments
- if conditions change, offspring not well adapted
- unicellular organism
- mitosis

characteristics of sexual reproduction

- relatively fewer offspring; growth takes more time
- two parents involved
- in changing environments, genetic diversity may be beneficial
- offspring may be less adapted to current conditions
- multicellular organism
- meiosis

need of cell division for multicellular growth and repair (body cells)

mitosis

need of cell division for multicellular reproduction (gamete cells)

meiosis

DNA + histone =

chromatin

centromere connects the sister chromatids because it ________________

carries the same allele

G1 phase

- cell preform normal function
- cell becomes mature
- prepare for cell division (make new proteins, duplication of organelles, cell size becomes larger)

S (synthesis) phase

- replication of DNA
- processes from G1 will continue

G2 (checkpoint) phase

self assessment to check all organelles & DNA are duplicated

M phase

- mitosis: division of nucleus
- cytokinesis: division of cytoplasm

treatment of cancer

- surgical removal: for localized tumors
- chemotherapy: they slow the growth of cancer cells
- radiotherapy: affects the DNA of cancer cells to stop their growth

causes of cancer

- uncontrolled cell cycle
- gene mutations
- carcinogenic agents (ex. radiation, UV rays, drugs, environmental pollution)

cancer formation

- a cell begins to divide abnormally
- cells produce a tumor and start to displace normal cells and tissues
- cancer cells move to other parts of the body

internal regulatory factors

- to check events (ex. chromosome duplication before the start of mitosis)
- to check alignment of chromosomes in metaphase before proceeding to anaphase

external regulatory factors

- to regulate the speed of cell division (to speed up --> repair; to slow --> when not needed)
- growth factors: controlled by growth hormone from brain, balancing the generalized growth of the body

How many sets of genes are found in most adult organisms?

The diploid cells of most adult organisms contain two complete sets of inherited chromosomes and two complete sets of genes.

What events occur during each phase of meiosis?

prophase I: each replicated chromosome pairs with its corresponding homologous chromosome
metaphase I: paired homologous chromosomes line up across the center of the cell
anaphase I: spindle fibers pull each homologous chromosome pair toward opposite ends of the cell
telophase I: a nuclear membrane forms around each cluster of chromosome
cytokinesis: forms two new cells
prophase II: chromosomes—each consisting of two chromatids—become visible
The final four phases of meiosis II are similar to those in meiosis I. However, the result is four haploid daughter cells.

How is meiosis different from mitosis?

- mitosis: when the two sets of genetic material separate, each daughter cell receives one complete set of chromosomes. meiosis: homologous chromosomes line up and then move to separate daughter cells.
- Mitosis: doesn't normally change the chromosome number of the original cell. but meiosis reduces the chromosome number by half.
- Mitosis results in the production of two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells.

How can two alleles from different genes be inherited together?

Alleles of different genes tend to be inherited together from one generation to the next when those genes are located on the same chromosome.

homologous

term used to refer to chromosomes in which one set comes from the male parent and one set comes from the female parent

diploid

term used to refer to a cell that contains two sets of homologous chromosomes

haploid

term used to refer to a cell that contains only a single set of genes

meiosis

process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell

tetrad

structure containing four chromatids that forms during meiosis

crossing-over

process in which homologous chromosomes exchange portions of their chromatids during meiosis

zygote

fertilized egg

(mitosis/meiosis):
- results in 2 in identical diploid daughter cells
- no genetic exchange
- occurs in body cells for growth and repairs and for reproduction only in unicellular organisms

mitosis

(mitosis/meiosis):
- results in 4 haploid daughter cells with genetic diversity
- crossing over among tetrads in Prophase I
- occurs in germ cells to produce gametes for reproduction

meiosis

What clues did bacterial transformation yield about the gene?

By observing bacterial transformation, Avery and other scientists discovered that the nucleic acid DNA stores and transmits genetic information from one generation of bacteria to the next.

What role did bacterial viruses play in identifying genetic material?

Hershey and Chase's experiment with bacteriophages confirmed Avery's results, convincing many scientists that DNA was the genetic material found in genes—not just in viruses and bacteria, but in all living cells.

What is the role of DNA in heredity?

The DNA that makes up genes must be capable of storing, copying, and transmitting the genetic information in a cell.

transformation

process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria

bacteriophage

kind of virus that infects bacteria

Frederic Griffith discovered transformation in his experiments on mice and Pneumococcus bacteria. He injected the mice with combinations of harmless, R-strain bacteria and disease-causing S-strain bacteria. Which combination of bacteria killed the mice and showed that transformation occurred?
a. heat-killed R-strain and live S-strain
b. heat-killed S-strain and live R-strain
c. heat-killed bacteria of both strains
d. live bacteria of both strains

b

To learn more about Griffith's experiment, scientists extracted a mixture of various molecules from the heat-killed bacteria. They found that (transformation / translation / transcription) no longer occurred when they treated the mixture with enzymes that destroyed (lipids / proteins / DNA / RNA / carbohydrates). This experiment supports the hypothesis that (lipids / proteins / DNA / RNA / carbohydrates) is the genetic material.

transformation, DNA, DNA

Which statements describe a bacteriophage? Select all that apply.
a. It is a type of virus that infects bacteria.
b. It is a type of bacteria that infects viruses.
c. It is a virus consisting of a protein coat and a DNA core.
d. It is a bacterial strain consisting of protein and a DNA core.

a, c

What was the purpose of marking the bacteriophages with phosphorus-32 and sulfur-35?
a. to track the movements of DNA and sugars
b. to track the movements of DNA and proteins
c. to remove DNA and sugars from the bacteriophages
d. to combine DNA and proteins into a single molecule

b

What are three tasks that DNA must be able to perform in all organisms? Select three answer choices.
a. It must store genetic information.
b. It must discard foreign genes.
c. It must instruct cells to produce needed molecules.
d. It must copy itself.
e. It must move to locations throughout the cell.

a, d, e

When does transformation occur?
a. when an organism receives foreign RNA that is transformed into DNA
b. when DNA is transformed into RNA
c. when bacteria are killed with heat
d. when a cell receives foreign DNA that is expressed as a new characteristic

d

conclusion of Griffith's experiment

by mixing the two types of bacteria allowed a chemical factor to transfer from the heat-killed s-type cells into the living r-type harmless bacteria that changed its composition and the mouse caught the disease and died (he named this transformation)

Avery's conclusion

- He continued Griffith's experiment to figure out the cause of transformation and he used enzymes that can dissolve DNA
- from that he concluded that those who were treated with enzymes do not show transformation and others do, indicating that DNA is the cause of transformation

What are the chemical components of DNA?

DNA is a nucleic acid made up of nucleotides joined into long strands or chains by covalent bonds.

What clues helped scientists solve the structure of DNA?

The clues in Franklin's X-ray pattern enabled Watson and Crick to build a model that explained the specific structure and properties of DNA.

What does the double-helix model tell us about DNA?

The double-helix model explains Chargaff 's rule of base pairing and how the two strands of DNA are held together.

base pairing

principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine

DNA composition

phosphate group, deoxyribose sugar, nitrogen base (adenine, guanine, cytosine, thymine)

purines

Adenine and Guanine

Pyrimidine bases

Cytosine and Thymine

What role does DNA polymerase play in copying DNA?

DNA polymerase is an enzyme that joins individual nucleotides to produce a new strand of DNA.

How does DNA replication differ in prokaryotic cells and eukaryotic cells?

prokaryotic cells: starts from a single point and proceeds in two directions until the entire chromosome is copied.
eukaryotic cells: may begin at dozens or even hundreds of places on the DNA molecule, proceeding in both directions until each chromosome is completely copied.

replication

process of copying DNA prior to cell division

DNA polymerase

principal enzyme involved in DNA replication

telomere

tip of chromosomes; their replication is controlled by telomerase; repetitive DNA at the end of a eukaryotic chromosome

steps of DNA replication

1) unzipping of DNA helix into DNA fork
2) attachment of complementary base pairs, they are checked by DNA polymerase
3) twisting of newly formed DNA into double helix

As a cell becomes larger, its
a. volume increases faster than its surface area.
b. surface area increases faster than its volume.
c. volume increases, but its surface area stays the same.
d. surface area stays the same, but its volume increases.

a

If the surface area of a cell that is shaped like a cube increases 100 times, its volume increases about
a. 5 times.
b. 10 times.
c. 100 times.
d. 1000 times.

d

The rate at which wastes are produced by a cell partially depends on the cell's
a. ratio of surface area to volume.
b. type of membrane.
c. volume.
d. surface area.

c

All of the following are problems that growth causes for cells EXCEPT
a. more demands on DNA.
b. excess oxygen.
c. obtaining enough food.
d. expelling wastes.

b