Molecular Biology and Cell Division Flashcards
Nucleotide:
The simplest subunit in DNA.
What is a nucleotide composed of?
A five-carbon sugar, a phosphate, and one of four nitrogen bases.
What are the four DNA nitrogen bases?
Adenine, thymine, cytosine and guanine.
In a strand of DNA, the backbone of the molecule alternates between _________ and ___________.
phosphate, deoxyribose
What is the shape of DNA?
A double helix.
What forms the rungs of the DNA ladder?
Nitrogenous bases.
How do nitrogenous bases from one spine of the ladder join to the nitrogenous base on the other spine of the ladder?
Hydrogen bonds.
Adenine will bond with _______.
Thymine
Thymine will bond with _______.
Adenine
Guanine will bond with ________.
Cytosine
Cytosine will bond with _______.
Guanine
What is Chargoff’s rule?
Nitrogen bases bond with their complimentary pair making up a total of 100% of the rungs.
How many hydrogen bonds are in A-T?
Two.
How many hydrogen bonds are in G-C?
Three.
Which occurs first, DNA replication or cell division?
DNA replication.
Why must DNA be able to duplicate itself?
Growth, repairing of damaged cells, and maintaining cells.
Replication:
A single strand of nucleotides acts as a template for forming a complementary strand.
What does DNA replication require?
Enzymes, nucleotides, and a DNA template.
What are the steps to DNA replication?
- Starts at the replication origin
- Helicase unzips the hydrogen bonds
- The bases attract free-floating bases, which attach through DNA polymerase
Semi-conservative strands:
The daughter strands are made up of one-half old strands and one-half new strands.
What direction does DNA polymerase move in on the new strand?
From 5’ to 3’.
What synthesizes new DNA strands together?
DNA polymerase.
RNA primer:
Attaches to templates and guides DNA polymerase enzyme to starting point.
Leading Strand:
Continuous DNA part.
DNA ligase:
Glues together sugar-phosphate backbone and DNA fragments together.
Protein synthesis:
The flow of genetic information.
Proteins are made up of a long chain of specific sequences of _____ _____.
amino acids
Transcription:
Splitting DNA and making a copy of mRNA. Occurs in the nucleus.
Translation:
Proteins are made by tRNA bringing amino acids as described by the mRNA. Occurs in the cytoplasm with ribosomes.
Which occurs first, transcription or translation?
Transcription.
How is RNA different from DNA
RNa can leave the nucleus, its backbone is made of ribose instead of deoxyribose, it uses Uracil instead of Thymine, it’s single-stranded, and it can exist in multiple different forms.
DNA:
Codes for the sequence of bases in mRNA.
mRNA:
Carries messages from DNA in the nucleus to ribosomes in the cytoplasm. The message is a blueprint for the synthesis of a protein.
Ribosomes:
Attach to a strand of mRNA and synthesizes to a protein.
tRNA:
Carries amino acids to the ribosomes.
Amino Acids:
The units that are bonded together to form a protein.
Polypeptide Chain:
A chain of many amino acids. May form a complete protein or only part of a protein molecule.
Explain the full process of transcription:
- DNA unwinds in the nucleus by RNA polymerase
- One strand of the DNA will be transcribed
- RNA polymerase adds the appropriate mRNA nucleotide to create a strand of mRNA in the direction of 5’ to 3’ on the mRNA strand
- A stop signal is reached, and transcription ends
- mRNA moves to ribosome out in the cytoplasm
Codon:
Three bases that code for one amino acid on mRNA.
Redundancy:
Several codons for each amino acid.
How many amino acids are there?
20
What are the four special codes?
AUG (start codon), UAA, UAG, UGA (stop codons).
Continuous:
No punctuation/spaces in code.
What would an insertion or deletion in the code do?
Frame shift. Leads to mutation.
Explain the universal aspect of amino acids and proteins:
They are the same codes for all organisms. This supports a common origin of life theory.
Explain the process of translation:
- mRNA arrives at the ribosome
- Ribosomes form from two subunits and attach to mRNA
- Start codon (AUG) will start the translation process
- tRNA will bring the correct amino acid to the mRNA codon
- Amino acids get put together like a chain using ATP with peptide bonds
- A terminating codon will turn translation off
What are the two types of mutations?
Somatic and germ line.
Somatic mutation:
Body cell mutation.
Germline mutation:
Sex cell mutation.
Beneficial mutations:
Give organisms a selective advantage, tends to become more common over time, leads to evolutionary change.
Harmful mutations:
Reduces an individual’s fitness, tends to be selected against, occurs at low rates.
Neutral mutations:
No benefit or cost, not acted on by natural selection.
Insertion:
An extra nucleotide is inserted into the DNA, which causes a frame shift.
Deletion:
A nucleotide is deleted from the DNA, which causes a frameshift.
Substitution:
One nucleotide is substituted for another, which causes a point mutation.
Hemophilia:
An inherited bleeding disorder in which the blood does not clot properly.
Cystic fibrosis:
A disorder that damages your lungs, digestive tract and other organs. It’s an inherited disease caused by a defective gene that can be passed from generation to generation.
Genome:
Makes up all the DNA in the cell
Genes:
A finite or discrete unit of heredity that is coded by a sequence of DNA bases. It produces a polypeptide (protein) made of many amino acids.
Genetic Engineering - Recombinant DNA:
To recombine DNA. A technique to determine gene expression. Gene segments from different sources are recombined in vitro and transferred into cells (usually E. coli) to see what happens.
What was the first successful genetic engineering recombinant DNA project?
The first successful GE experiment with human DNA took place in 1980. The human gene, which codes for the protein interferon, was successfully introduced into a bacteria cell. The bacteria produced human protein. Interferon combats viral infections and may help in fighting cancer.
Explain the process of recombinant DNA:
- The desired gene is isolated and cut out of the DNA with a restriction enzyme.
- Bacterial DNA, called a plasmid, is opened using a restriction enzyme.
- The isolated desired gene is inserted into a bacterial plasmid using a ligase. The new DNA is now called recombinant DNA.
- The plasmid is absorbed by a bacterium which reproduces asexually to produce many clones containing the recombinant DNA.
- Bacterial cells produce the protein coded by the foreign gene. Desired protein can be isolated and purified from the culture.
Transgenic:
To create an organism with more than one species’ type of DNA.
Mitosis:
The process that produces two new nuclei with the same number and kinds of chromosomes as the original nucleus. This ensures that each new cell inherits a complete set of the parent cell’s genetic information. Offspring are clones, produced rapidly and leads to zero diversity.
When is mitosis used?
In asexual reproduction, growth, creation of new cells, and reparations of damaged tissue.
Cell cycle:
A sequence of stages or phases through which a cell passes from one cell division to the next. It is a continuous process.
What percentage of the cell cycle is mitosis?
10%
What are the three phases in the cell cycle?
Interphase, mitosis, and cytokinesis.
Why must cells divide?
Because the surface area to volume ratio of the cell decreases and it can no longer supply itself with nutrients and get rid of wastes.
Interphase:
The process of cell activity between cell divisions. Cells are not actively dividing and are not a part of mitosis. This is 90% of the cell cycle. Cells grow and carry out chemical activities that sustain life.
What are the three stages involved in the interphase period?
G1, synthesis, and G2.
G1 (gap 1):
DNA transcription and translation occur, which leads to the growth and replication of organelles. Genetic material consists of chromatin which appears as a single strand of DNA.
S (synthesis):
DNA replication. The genetic material is chromatin, which appears as a double strand of DNA.
G2 (gap 2):
DNA transcription and translation occurs. Structures associated with mitosis are replicated and create spindle proteins. The genetic material is chromatin, which appears as a double strand of DNA.
Chromosome/Chromatin/Chromatid:
Made of nucleic acids (DNA) and proteins
What are the two forms that chromosomes/chromatin/chromatids are found in?
Uncondensed or condensed.
Uncondensed:
Long, thin, bumpy strands that cannot be seen under a light microscope. This is called chromatin.
Condensed:
Bar-like bodies that can be seen under a light microscope. This is called a chromosome.
Chromatid:
Replication of the DNA results in each thread becoming a doubled molecule of DNA and protein held together by a centromere.
{
Uncondensed chromatin made of one chromatid, unreplicated, and is a single strand of DNA.
}{
Uncondensed chromatin made of two chromatids, replicated and made of a double strand of DNA.
[]
Condensed chromosome made of one chromatid.
[]-[]
Condensed chromosome; made of two chromatids/a pair of sister chromatids.
}}}}
How many chromatins?
4
}{ }{ }{
How many chromosomes?
3
}{ }{ }{
How many chromotids?
6
}{ }{ }{
How many pairs of sister chromatids?
3
Mitosis:
Nuclear division characterized by the formation of two identical daughter nuclei.
The four phases of mitosis:
Prophase, metaphase, anaphase, telophase.
What occurs after mitosis?
Cytokinesis.
Prophase:
Chromatin condenses to form visible chromosomes, centrioles separate and move to the poles of the cell, spindle fibres form, and the nuclear membrane and nucleolus disappear.
Metaphase:
Chromatid pairs align together on the equatorial plane of the cell manoeuvred by the spindle fibres (called metaphase plates in plants), chromosomes appear dark, thick, and attached to spindle fibres, visible but difficult to count because they are intertwined.
Anaphase:
Centromeres divide, and sister chromatids separate and move to opposite cell poles. There should be the same number of single-stranded chromosomes at each pole.
Telophase:
Chromosomes uncondense to become chromatin, and spindle fibres dissolve. The nuclear membrane begins to reform.
Cytokinesis:
The visible process during telophase that divides the cell into equal parts. A cleavage furrow forms near the equator in animal cells and it then separates. In plant cells, a cell plate forms and separates it, creating new cell walls.
Cancer:
A broad group of diseases characterized by rapid uncontrollable growth of cells.
Why do cancer cells divide rapidly?
These cells don’t care about space to grow, nutrients available, or communication with other cells. They also don’t have to differentiate.
Why do cancer cells spread so easily?
Cancer cells do not adhere to other cancer cells or normal cells very well.
Metastasis:
When cancer cells dislodge from a tumor and move to another area.
Tumor:
A mass of cancerous cells within an otherwise normal tissue.
Benign tumour:
When cells remain at a site and do not usually cause serious problems. They can be removed with surgery.
Malignant tumor:
Impairs function of one or more organs through cancer. They posses an unusual number of chromosomes, lose attachment to neighbouring cells, and may enter blood and lymph vessels and invade other parts of the body.
What factors contribute to cancer?
X-rays, chemical poisons, asbestos, fungi, oncoviruses, diet, age, and inherited mutations.
What technologies are used to identify cancer?
Cell biopsies, x-rays, CT scans, and MRI’s.
What technologies are used to treat cancer?
Surgery, chemotherapy, radiation, and hormone therapy.
A normal human body cell contains __ chromosomes or __ pairs of chromosomes.
46, 23
Where do sex chromosomes come from in the parents?
23 from the egg and 23 from the sperm.
Haploid (n):
The number of chromosomes in a gamete.
Diploid (2n):
The normal body cell which holds twice as many chromosomes as a haploid.
Asexual Reproduction:
Reproduction in single celled organisms which takes place in successive cell divisions. This leads to new individuals through mitosis.
Mitosis produces only genetically __________ offspring.
identical
Meiosis:
The production of sex cells or gametes. Converts diploid cells to haploid gametes and causes a change in genetic information to increase diversity in the offspring.
The products of meiosis are called ______.
zygotes
Sex cells are (haploids/diploids).
haploids
Haploids have ___ set(s) of chromosomes.
one
Diploids have ___ set(s) of chromosomes.
two
Most plant and animal adults are __ploids.
di
Eggs and sperm are __ploids.
ha
In mitosis, the chromosomes are duplicated ____, and the cell divides ____.
once, once
In meiosis, the chromosomes are duplicated ____, and the cell divides _____.
once, twice
Complete meiosis involves ___ successive divisions, which result in ____ new haploid daughter cells.
two, four
The first meiosis division produces ___ _______ cells with _______________ chromosomes.
two haploid, double-stranded
The second meiosis division produces ___ _______ cells with _______________ chromosomes.
four haploid, single-stranded
Prophase 1:
Chromatin condenses into chromosomes which are double-stranded. The nuclear membrane disappears. Homologous chromosomes move together and lie side by side. Synapsis occurs.
Crossing over:
When homologous chromosome pairs synapse and intermix genetic material.
Chiasma:
The place where two chromosome arms overlap.
Meiosis 1:
Homologous pairs reach the equator and attach to spindle fibres at centromeres. Homologous pairs line up independently of each other.
Anaphase 1:
Double-stranded chromosomes move apart to opposite poles. The centromeres have not separated.
Telophase 1:
Chromosomes arrive at the poles and decondense. A nuclear envelope and nucleolus reform and cytokinesis produce two daughter cells. Interphase may occur prior to this decision but biologically, nothing happens.
Meiosis 2:
No further genetic reassortment occurs. Four haploid cells form.
Prophase 2:
The nuclear envelope and nucleolus disappear. Chromatin condenses into chromosomes.
Metaphase 2:
Spindle fibres form and attach to centromeres. Chromosomes, each consisting of two sister chromatids, line up with centromeres on the metaphase plate (equator).
Anaphase 2:
Centromeres separate. Daughter chromosomes move towards poles, and sister chromatids separate.
Telophase 2:
Chromosomes decondense and nuclear envelopes and nucleolus reform. Cytokinesis produces four daughter cells.
Chromosome behaviour in mitosis:
Homologous chromosomes are independent.
Chromosome behaviour in meiosis:
Homologous chromosomes are paired.
What are the two ways meiosis behaves abnormally?
When two homologous chromosomes move to the same pole in meiosis 1 or when sister chromatids fail to separate in meiosis 2.
Karyotype:
A picture of chromosomes arranged in homologous pairs according to size and structure.
What chromosome pair do females have?
XX
What chromosome pair do males have?
XY
Downs Syndrome:
When a person has three copies of chromosomes on 21, totalling 47 chromosomes.
Turners Syndrome:
When there is only one X chromosome totalling only 45 chromosomes in the body cells.
Klinefelter’s Syndrome:
An extra X chromosome which causes men to appear male at birth but excrete high levels of female sex hormones during puberty. They are sterile. (XXY)
Binary Fission:
Many unicellular organisms reproduce asexually by dividing into two smaller identical cells.
Vegetative Propagation:
A form of asexual reproduction where the new plant grows from a fragment of the parent plant.
Budding:
A form of asexual reproduction where a smaller individual detaches from the parent by budding off
Parthenogenesis:
A form of asexual reproduction in which the growth and development of embryos occur without fertilization.
Advantages of asexual reproduction:
- Only one parent required
- Efficient in terms of energy required by the parent
- Offspring are large in comparison to parents and have a good chance of survival
What is the advantage of internal fertilization?
Fewer gametes are lost.
What is the disadvantage of internal fertilization?
A lot of energy is spent on courtship and mating/production of flowers.
Advantages of sexual reproduction:
Leads to greater variation and an increased chance of survival throughout time.
2n -> n
meiosis
n + n -> 2n
fertilization
2n ->2n
mitosis
n -> n
mitosis
Which of these processes produces genetically identical offspring?
1. 2n -> n
2. n + n = 2n
3. 2n -> 2n
4. Budding
5. Internal fertilization
6. Parthenogenesis
7. Binary Fission
8. Sexual Reproduction
9. Vegetative Propagation
3, 4, 6, 7, 9
