Exam #2 Flashcards
Why does Mitosis happen?
Growth, repair, asexual reproduction. Cells become too big and the volume too where the cells need to divide
How many times can a cell divide?
Till its no longer able to divide, which results to a programmed cell death called apoptosis
How many stages are there of Mitosis?
2; Interphase and Mitotic Phase
Interphase
growth and replication of DNA; G1, S, G2
Mitotic Phase
division of cell into 2 daughter cells: mitosis
How many phases does interphase have?
3
G1
small cell is trying to obtain nutrients and growing at the same time
S; synthesis
cell is still growing and duplicating its DNA
G2
cells keeps growing and doing whatever cell job it has
S phase
Where DNA is copied and created, created in 2 sets of chromosomes where they are connected together in the middle by a centromere
what is a single copy of chromosome is called?
chromatid
How many stages are in the Mitotic Phase?
4, PMAT and cytokinesis
What happens in the Prophase phase?
Chromatids will condense, The nuclear enveloped will dissolve, centrioles will appear and migrate to the opposite sides, spindle fibers will the form
What happens in the Metaphase phase?
Chromosomes will line up on the metaphase plate, centromeres are attached to the spindle fibers
what happens in the anaphase phase?
Spindle fibers will contract, then the centromeres will divide, sister chromatids are pulled away from each other towards the pole
what happens in the telophase phase?
Chromosomes will now have reached the poles and new nuclear membranes will form around 2 new nuclei
What happens in the cytokinesis phase?
The cytoplasm will distribute equally between the 2 new cells
what happens post mitosis?
the cells return to interphase and go through G1,S and G2. Chromosomes will not unpack back to chromatin
Meiosis
haploid (n). Split into two stages meiosis 1 and 11
Fertilization
The sperm and egg fuse together to form a zygote 2n=46 (n=23)
Interphase 1
similar to mitosis interphase, chromosomes replicate during S phase, two identical sister chromatids, centriole pairs also replicate
Meiosis 1
P1 M1 A1 T1
Meiosis 1: Prophase 1
Chromosomes will condense, synapsis occurs(where homologous chromosomes come together to form tetrad),
Crossing Over
segment of non site chromatids break and r attach to the other chromatid
Where does crossing over occur?
chiasmata
Metaphase 1
tetrads align, orientation if homologous pairs to pole is random
Anaphase 1
homologous chromosomes separate and move towards the poles, sister chromatids remain attached at their centromeres
Telophase 1
Each pole now has haploid set of chromosomes, cytokinesis occurs and two haploid daughter are formed
Meisosis II
No interphase ll, similar to mitosis
Prophase II
Nucleus and nucleolus disappear, chromosomes condense, spindle forms
Metaphase II
chromosome line up at the equator
Anaphase II
sister chromatids separate
Telophase II
nuclei and nucleoli reform, spindle fibers disappear, Cytokinesis occurs and four haploid daughters are produced
Genome
the complete complement of an organism’s DNA
heredity
the way of transferring genetic information to offspring
homologues
are two pieces of DNA within a diploid that carry the same genes that are both from a parental source
karyotype Down syndrome
trisomy 21
A,T,C,G
A=30.3 T=30.3 G=19.5 C=19.9
Chargaff’s rule
A=T. G=C
Nucleotides are made up of
Phosphate group, 5 carbon sugar, nitrogenous base
Direction of DNA
5’ to 3’ 3’ to 5’
Pyrimidines
Cytosine and Thymine
Purines
Guanine and Adenine
Guanine and Cytosine are stronger because?
They have three hydrogen bonds
Transcription
the flow of information from DNA to RNA
Translation
the flow of information from RNA to protein
Stop codons are
UGA, UAA, UAG
Start Condon
AUG
Transcription proceeds through
Initiation, Elongation and termination
initiation
RNA polymerase identifies where tow begin transcription
elongation
RNA nucleotides are added to the 3’ end of the new RNA
Termination
RNA polymerase stops transcription when it encounters terminators in the DNA sequence
Messenger RNA
carries the information from DNA that encode proteins
Ribosomal RNA
is a structural component of the ribosome
Transfer RNA
carries amino acids to the ribosome for translation
Core polymerase
capable of RNA elongation but not initiation
Holoenzyme
composed of the core enzyme and the sigma factor which is needed for transcription initiation
APE site
where ribosomes has multiple tRNA binding sites
A site
binds the tRNA carrying the next amino acid
P site
binds the tRNA attached to the growing peptide chain
E-site
the tRNA that carried the last amino acid
Enzyme in DNA replication
-Helicase unwinds parental double helix
-Binding proteins stabilize separate strands
-Primase adds short primer to template strand
-DNA polymerase binds nucleotides to form new strands
-Ligase joins Okazaki fragments and sealed other nicks in sugar phosphate backbone
Activities at the Replication Fork
1.Helicase binds to origin and separates strands
2.Binding proteins keep strands apart
3.Primase makes a short stretch of RNA on the DNA template
4.DNA polymerase adds DNA nucleotides to the RNA primer
5.DNA polymerase proofreading activity checks and replaces incorrect
6.Continuous strand synthesis continues in a 5’ to 3’’ direction
7.Discontinuous synthesis produces Okazaki fragments on the 5’ to 3’ template
8.Enzymes remove RNA primers. Ligase seals sugar-phosphate backbone
