89 terms

Biology Unit 4 DNA and Cell Division

Who is Griffith and what did he do?
performed experiments on mice with different types of bacteria, injected mice with a combination of heat-killed S bacteria and live R bacteria=mice die, concluded a transforming principle passed from dead S bacteria to live R bacteria
Who is Avery and what did he do?
combined living R bacteria with extract from S bacteria, this allowed them to observe the transformation, purified extract, performed qualitative test, chemical analysis, and enzyme tests, transformation failed to occur when an enzyme that destroyed DNA was added, so identified DNA as the transforming principle
Who are Hershey and Chase and what did they do?
confirmed DNA is genetic material, used a virus called "phage" or bacteriophage which takes over a bacterium's genetic machinery and directs it to create more viruses, performed two experiments, the results showed the phages' DNA had entered the bacteria, but the protein hadn't entered, this convinced scientists that genetic material is DNA and not proteins
Who is Chargaff and what did he do?
analyzed DNA of several different organisms, found the same four bases are in the DNA of all organisms, but proportion of bases differs, A=T and G=C, Chargaff's rules
Who are Franklin and Wilkins and what did they do?
studied DNA using x-ray crystallography, discovered DNA is a helix consisting of two stands that are a regular, consistent width apart
Who are Watson and Crick and what did they do?
developed an accurate model of DNA's 3D structure, paired double-ringed nucleotides with single-ringed nucleotides, found it created a double helix, explained Chargaff's rules
How did Watson and Crick use prior work to develop the model of DNA?
by using other scientists' information and putting it together, they each built on one another
What are the monomers of DNA?
What part of the nucleotide differs from the rest?
nitrogenous bases
Explain the structure of DNA.
nucleotides are joined together in a strand of DNA by covalent bonds, the sugar of one nucleotide is covalently bonded to the phosphate group of another, alternating sugars and phosphates is what creates the twisted ladder, the double helix is held together by hydrogen bonds between the two nitrogen bases=maintaining structure of DNA
What is Chargaff's Rule?
says that the number of adenine will always equal the amount of thymine, just as the amount of guanine will equal the amount of cytosine
Explain DNA's backbone and rungs.
backbone is made up of phosphate groups which are connected by sugars, the rungs of the DNA ladder are made of complementary nitrogenous base pairs. DNA contains four different nitrogenous bases: adenine, thymine, cytosine and guanine. The nitrogenous bases are divided into the purines and the pyrimidines; each rung of the DNA molecule contains one purine and one pyrimidine bonded together.
Explain the bonding of the backbone and rungs.
the parts of the nucleotide are joined together by covalent bonds, and the nucleotides are joined by hydrogen bonds
What is DNA replication?
the process by which DNA is copied during the cell cycle
What is the role of enzymes in DNA replication?
enzymes carry out the process of replication, some unzip the double helix to separate the strands, some hold the strands apart, some bond nucleotides together
What is the importance of hydrogen bonds?
Hydrogen bonds are weak, meaning they are easily broken. This way it is easier for the enzymes to unzip the DNA.
What is the source of new nucleotides for replication?
The nucleus
What is the result of the replication?
Two identical forms of DNA, one new stand of DNA and one old strand
How can replication occur in just a few hours?
DNA replication starts at many points in eukaryotic chromosomes
How does DNA replication prevent errors in the new strands?
DNA polymerases can find and correct errors
What are somatic cells?
body cells, make up most of your body tissues and organs
What are germ cells?
cells in your reproductive organs, the ovaries and testes, can develop gametes (sex cells), form egg and sperm cells
What are gametes and how are they produced?
gametes are haploids, they each have only one copy of each chromosome, produced in meiosis- divides diploid into haploids
What is a fertilized egg called?
What are the differences between mitosis and meiosis?
Mitosis produces genetically identical cells, whereas meiosis produces genetically unique cells. Mitosis results in diploid cells, whereas meiosis results in haploid cells. Mitosis takes place throughout an organism's life, and meiosis takes place only at certain times in the life cycle of the organism. Lastly, mitosis is involved in asexual reproduction, but meiosis is involved in sexual reproduction.
What are autosomes?
the chromosome pairs 1-22, they are homologous, chromosome that contains genes for characteristics not directly related to sex of the organism
What are sex chromosomes?
they are the 23rd pair (only one pair), either XX (girl) or XY (boy), not homologous, directly control development of sexual characteristics
Explain why the male determines the sex of the baby?
Because he either donates a Y chromosome or a X chromosome
What are homologous chromosomes?
two chromosomes, one is inherited from mother and one from the father, they have the same length and general appearance, copies of the same genes (they may differ)
What is a chromatid?
also known as sister chromatin, each half of a chromosome is identical
What is a centromere?
It holds together the chromatids
What is a histone?
protein that organizes chromosomes and around which DNA wraps, at almost all ties during the cell cycle each of the chromosomes is associated with a histone
What is chromatin?
loose combination of DNA and proteins (loose does not mean it is loosely wrapped around the histones, it is how much the DNA folds back on itself)
What are genes?
specific region of DNA that codes for a particular protein
How do genes store genetic code?
stored within the chemical structure of the molecule DNA
What do genes do with the code?
They tell the nucleus what proteins to make, proteins are made in cytoplasm, for example if the gene says you should have blue eyes, the nucleus creates the pigment (protein)
How many genes do you have?
about 24,000 genes
What are telomeres?
structures at the ends of DNA molecules, made of repeating nucleotides that do not form genes, prevent ends of chromosomes from accidently attaching to one another, prevents loss of genes, short section of nucleotides is lost every time DNA replicates so it is important the chromosome loses them from the telomere, not from the genes themselves
What is a diploid?
a cell that has two copies of each chromosome, one from the egg and one from the sperm, can be represented as 2n, in humans the diploid chromosome number is 46
What is a haploid?
a cell that has only one copy of each chromosome, can be represented as n, each human egg or sperm cell has 22 autosomes and one sex chromosome
What is the cell cycle?
A regular pattern of growth, DNA replication, and cell division in Eukaryotic cells
What is the Gap 1 (G1) and what happens?
Cell carries out normal functions, it increases in size, organelles increase in number (duplicates cellular contents, not including chromosomes)
What is synthesis (S) and what happens?
Cell makes copy of nuclear DNA, by the end of this stage the cell contains two complete sets of DNA
What does synthesis mean?
Combining of parts makes a whole
What is Gap 2 (G2) and what happens?
Cell continues to carry out normal function, additional growth occurs, this is a critical checkpoint, this is where the cell make sure the size of the cell is good and the DNA is not damaged, it is basically making sure the cell is ready to divide
What is mitosis (M) phase in the cell cycle?
Includes two processes: mitosis and cytokinesis
What is mitosis (apart of M)
Division of cell nucleus and the cell's contents
What is cytokinesis and what happens?
Process that divides the cytoplasm, produces two identical daughter cells
What are the limits of cell size?
must be big enough to "hold" everything, upper limit due to ratio of cell surface area to the volume
Why do cells divide?
because the volume grows quicker than the surface area, this means that the cell membrane would not be able to bring in the nutrients and get rid of the waste properly
What cells undergo mitosis?
somatic cells, which make up most of your body's organs and tissues
What takes place prior to mitosis?
interphase which prepares cell to divide, duplicates organelles and replicates DNA, expands cell
What are genetically identical daughter cells and how are they produced?
identical to the parent as well as to each other and two are produced by mitosis and cytokinesis
What are the four main phases of mitosis?
(PMAT) Prophase, Metaphase, Anaphase, and Telophase
What happens during prophase?
DNA condenses into chromosomes, nuclear envelope breaks down, and centrioles move to opposite ends of the cell (or pole) and release spindle fibers
What happens during metaphase?
spindle fibers attach to chromosomes and line up in the MIDDLE (equator) of the cell
What occurs during anaphase?
sister chromatids separate to opposite sides of the cell
What happens during telophase?
nuclear membrane begins to form, chromosomes begin to uncoil and turn into chromatid, and the spindle fibers fall apart, however the cell is not split yet
Explain the regulation of the cell cycle.
internal and external factors regulate cell division, this includes chemical factors, once a cell touches another cell it stops growing, external factors trigger internal factors
What is apoptosis?
programmed cell death, signals active genes producing self-destructive enzymes, example of tadpole to frog
What is cancer?
common name for class or diseases characterized by uncontrolled cell division, form disorganized clumps called tumors, come from normal cells that have suffered damage from genes that make the proteins involved in cell division
Explain the two types of cancer.
benign- cancer cells typically remain clustered together, usually doesn't spread, malignant- some cells break away (or metastasize which means to spread) from the tumor and spread throughout body
How do cancer cells spread through the body?
cancer cells make their way into the blood stream, which carries them around the body
What are the causes for cancer?
damage from radiation, inherited, chemicals, or ultraviolet radiation, carcinogens are substances known to cause cancer
How does someone get skin cancer?
a UV light could have damaged one of the strands of DNA
How can cancer be treated?
radiation or chemotherapy, kill both cancerous and healthy cells
What is asexual reproduction?
the creation of offspring from a single parent, offspring is normally genetically identical (mutations),
What is binary fission?
asexual reproduction of single-celled organisms, normally occurs in bacteria or prokaryotes, mitosis and binary fission have similar results
What are the advantages of asexual and sexual reproduction?
Asexual- can produce twice as many, does not require fertilization, quickly forms groups
Sexual- more genetic variation, ability to reproduce more offspring because of mate, children differ from their parents, raises chances of survival
What are the disadvantages of asexual and sexual reproduction?
Asexual- reproduction based on amount of food, very little variation which creates a higher probability of extinction
Sexual- slower reproduction rate, less reliable production, takes time as well as energy to find a mate
What is the product of meiosis?
four haploid cells from one diploid cell, haploid cells are genetically unique
Where does meiosis take place?
germ cells
What are the stages of meiosis?
Meiosis I and Meiosis II
What is the difference between homologous chromosomes and sister chromatids?
homologous chromosomes are two separate chromosomes, similar in length to each other and carry same genes, however they are not copies of each other. Each half of a duplicated chromosome is a chromatid, and together the two form a sister chromatid
When does Meiosis I occur and what happens?
occurs after DNA is replicated, it divides homologous chromosomes in the four phases: Prophase I, Metaphase I, Anaphase I, and Telophase I
What happens during Meiosis II?
divides sister chromatids in four phases: Prophase II, Metaphase II, Anaphase II, and Telophase II, DNA is not replicated between meiosis I and meiosis II, haploids have half the number of chromosomes that were in the diploid
What is gametogenesis?
production of mature gametes
What are the two gametes in humans?
Male- sperm, Female- egg
What are the levels of organization in multicellular life?
cells, tissues, organs, organ systems
What do cells do?
communicate and work together in groups
What do tissues do?
group of cells that work together to do a certain function
What do organs do?
group of tissues that work together to perform either a specific function of related functions
What do organ systems do?
organs that carry our similar functions, work to maintain homeostasis
What is cell differentiation?
process by which unspecialized cells develop into their mature forms and functions
What is a stem cell?
unique type of body cell, can divide and renew themselves for a long period of time, they remain identical in form, and develop into a variety of specialized cells
How is a stem cell categorized?
by it's ability or potential to develop into different cell types and different tissues
What are the types of stem cells?
adult stem cells which are partially identical cells located by the specialized cells of many organs and tissues, and the embryonic stem cells that come from donated embryos grown in a clinic
What are the importance of stem cells?
used to treat leukemia and lymphoma, sometimes used to repair damaged organs, and used to cure diseases
What are the rates of cell division in human cells?
usually about 12 hours, however, the length of G1 stage differs for most cell types. Also, the rate of cell division in embryos and children is greater