exam Flashcards
What is DNA
- nucleic acid
- genetic material, dictates how and what a cell will do
- consists of polymers (the monomer is a nucleotide)
What is nucleic acid
- acid that stores and express’s genetic information (the characteristics and functions of living orgnanisms)
- eg. DNA (found in nucleus, main component of genes), RNA (makes instructions for proteins)
- consists of polymers (repeating strands), and monomers (strands that repeat)
Structure of nucleic acid
- pentose sugar (BASE, pentagon that has five sides)
DNA= deoxyribose sugar
RNA = ribose sugar - phosphate group
- Nitrogen base (adendine, thymine, guanine, cytosine)
Nitrogen bases
Thymine - Adenine
Guanine - Cytosine
****URICIL replaces thymine in RNA
(Adenine and Cytosine are smaller than thymine and guanine)
**They connect ONLY with each other because each nitrogen base has a specific amount of hydrogen bonds (ie. Guanine and cytosine both have three, Adenine and Thymine both have two)
- seperated into two groups:
Purines = LARGER, double ringed compound (Guanine, Thymine)
pyramidines = SMALLER, single ringed compounds (Cytosine, Adenine, Uracil)
HOW DO THEY FORM DNA?
the sugar phosphates create the backbone of DNA, they are stronger and harder to pull apart because they are connected by covalent bonds.
The nitrogen bases connect in the middle, are easy to pull apart because they are only held together by hydrogen bonds.
DNA vs RNA?
DNA
- nucleic acid
- deoxyribonucleic sugar
- only found in nucleous
- main compononent of genes
- stabilizes itself by bonding with a nitrogen band
RNA
- nucleic acid
- ribonucleic sugar
- can be found outside the nuceleus
- SHORT TERM MOLECULE
- does not bond, dies quickly
- read by ribosomes in order to make proteins
Heredity
The process of passing down traits from parents to offspring through genes
DNA molecule (gene, locus, allele, homologous)
DNA is genetic material that stores information
GENE = genetic information that codes for a SPECIFIC trait
LOCUS = location of genes
ALLELE = variations of genes
HOMOLOGOUS CHROMOSOMES = same TYPE of chromosome (codes for the same things, has the same loci, just different alleles)
chromosomes (diploid vs haploid vs polyploid)
DIPLOID = two sets of chromosomes (2n. We have n TYPES of chromosomes, and TWO PAIRS of them: therefore we have 2n = 46)
^^^^^^^^23 types of chromosomes, and 2 pairs of them
HAPLOID = one set of chromosomes (n. We have n TYPES of chromosomes, and NO PAIRS of them:
therefore we have n = 23)
^^^^^found in gametes or sex cells
POLYPLOID = three or more sets of chromosomes
Asexual reproduction vs sexual reproduction
asexual:
- produces exact copies of the original organism (clones)
- no genetic diversity
- A lot faster, takes a lot less energy and time than sexual reproduction
- NO USE of sex cells (reproduces only through cell division)
Sexual:
- requires two organisms (one with female gametes, one with male gametes)
- creates genetic diversity
- takes a lot longer, uses a lot more energy
Mitosis
Cell division of a SOMATIC (body) cell. Creates two genetically identical cells.
- **Interphase
- most of a cells life is spent in interphase (G1- growing, S - duplicates genetic info, G2- final prep for cell division)
PMAT
- Prophase
- chromosomes condense into shapes
- centrioles appear (only in animal cells), move to the poles of the cell
- Spindles (protein fibers) extend from the centrioles
- Nucleus, nuclear membrane disapear - Metaphase
- spindles attach to the centrometer of the chromosomes, line them up along the equator (metaphase plate)
- chromosomes condense even more - Annaphase
- spindles pull apart the sister chromatids, pull them to opposite poles
- pull sister chromatids into seperate chromosomes - Telephase
- cleavage furrow begins to form (pinch in the middle of the cell)
- plant cells form CELL PLATES
- chromosomes decondense, spindles and centrioles dissapear, nuclear membrane forms - Cytokenisis
- final stage when the cells actually split, two identical daughter cells are creates
- DNA turns into chromatins again
Why is mitosis needed
As a cell grows its surface area and volume do not grow at the same time. When the inside of a cell grows to big, the cell membrane gets stretched too much. Nothing can pass in or out (which is crucial for cellular respiration).
The cell will die, so it needs to copy itself.
Meiosis
Formation of gametes (creates 4 genetically different cells)
- **intitial cell is a body cell (germ cell)
- ** gametes are haploid
- Premeiotic interphase
- same thing as mitosis, cell duplicates its DNA, gets ready for division - Prophase I
- same as mitosis
SYNAPSIS = homologous chromosomes (maternal and paternal) pair together
CHIASMATA = the point where the two chromosomes touch
TETRAD = now that the two chromosomes are attached, they are called a tetrad
CROSSING OVER = DNA passes from the chromosomes, alleles switch
KINETOCHORe = point of intersection??? - Metaphase I
INDEPENDENT ASORTMENT = tetrads RANDOMLY line up in 2 parallel lines, (23 pairs along the equatorial plate)
^^^^^because its random, one side of the cell can have more maternal DNA than the other, and vice versa
- spindle fibers attactch to the kinetochore of the tetrads - Anaphase I
- tetrad is pulled apart, each chromosomes moves to opposite poles
^^^SISTER CHROMATIDS are still intact, although genetically different - Telophase I
- membrane reforms, pinches, etc, (still technically a diploid because the cell hasnt split yet) - Cytokenisis I
- officially splits, cytoplam divides (each daughter cell is now a haploid n)
- *** Meiosis II
- same as normal mitosis
- Prophase II
- (chromosomes condense, centrioles move to posts etc) - Metaphase II
- chromosomes move to the center - Anaphase II
- chromsomes are pulled apart - Telophase II
- chromosomes unwind, nuclear membrane forms - Cytokenisis
- cells split, creates 4 gametes that are all haploid
Spermatogenisis vs oogensiis
spermatogenisis creates 4 sperm
oogenisi creates 1 ova, 3 polar bodies
Nondisjunction
chromosomes dont split properly during MEIOSIS, results in aneuploidy (wrong number of chromosomes)
Trisomy = three chromosomes monosomy = one chromosome (more fatal)
- **if nondisjuncition occurs during meiosis I, ALL gamete cells are irregular
- **if nondisjunction occurs during meiosis II (sister chromatids fail to split properly), HALF of the gamete cells are irregular
can be diagnosed through karyotypes
Deletion (abnormal chromosome structure)
lose an allele or a section of the chromosome when crossing over
very lethal
