Bio exam 4 Flashcards
During what process are parental DNA strands used as templates for the synthesis of new DNA strands?
DNA replication
Explain DNA replication
process of coping a DNA molecule, polymerization of DNA, takes ALL DNA in the cell and will copy ALL DNA (amount of DNA will be double)
explain what happens after 1 round of DNA Replication
the daughter DNA molecules are formed of one parental and one daughter strand
define semiconservative in DNA replication
one strand of old (parental) DNA and one strand of new (daughter) DNA
sketch a replication bubble and label on it the 5’ and 3’ ends, the origin of replication, replication forks, as well as the direction of the leading and lagging strands
do on paper
What is the origin of replication?
A sequence that indicates where to begin DNA replication
Explain DNA replication Bubble
2 replisomes will move right and left from the origin of replication, followed by 2 replication forks
What is a replication fork?
a Y-shaped region where new DNA symthesis is heppening.
describe the functions of helicase, topoisomerase, single-strand binding protein, primase, ligase, and DNA polymerases III and I
AHHH
What is the function of DNA helicase?
Breaks hydrogen binds between parental strands
What is the function of DNA Topisomerase?
cuts DNA, allowing DNA to unwind and then joining it
What is the function of single-strand binding protein?
Attach to a single strand DNA and prevent H=bonds from reforming
What is a finction of DNA primase?
Synthesizes a short sequence of RNA, primer for RNA
What is the function of DNA Polymerase 1
To remove the RNA primers and replace them with DNA
What is the function of DNA ligase?
Closes the Gap between Okazaki fragments, forming a phosphodiester bond.
What is the function of DNA polymerase 3?
to add nucleotide to the 3’ end of a growing DNA strand.
Explain the order that DNA replication happens in, including time
Time 1
- Helicase breaks down bonds between parental strands
- Single-stranded binding proteins attach to single stranded DNA and prevent H-bonds from reforming
- Topoisomerase cuts DNA, unwinding it
- Primase synthesizes a short, sequence of RNA
- DNA Polymerase III uses 3’ end to continue synthesis of the daughter strand
Time 2
Steps 1-3 are the same as the heading strand
- Primase sets the RNA primer down
- DNA Polymerase III extends the 2nd Okazaki fragment
- DNA polymerase I removes RNA nucleotide and replaces the RNA with DNA nucleotides
Time 3:
- Ligase closes the gap between Okazaki fragments and forms a phosphodiester bond
outline the key differences between the synthesis of the leading and lagging strands
on paper
What are characteristics of the leading strand?
synthesized 5’ to 3’, same direction of the replication fork synthesized in one continuous piece
Identify characteristics of the lagging strand?
synthesized 5’ to 3’ discontinuously, in fragments, synthesized in the opposite direction of the replication fork.
define what a chromosome is, explain the relationships between DNA, genes, chromosomes, sister chromatids, and centromeres
on paper
define chromosomes
discreate units of genetics informations, can have many linear in eukaryotes, can have 1 circular in prokaryotes
Define gene
segment of DNA that encodes for one protein
Define homologous chromosomes
maternal and paternal of the same chromosomes type: will be the same order, shape, size
maternal= egg
paternnal= sperm
What are x and y chromosomes?
sexyal chromosomes that carry info that determins biological sex of a person
XX female
XY male
explain what the “n number” of a cell is as well as explain the difference between a haploid and a diploid cell
n= the number of chromosomes in each cell (humans n=23)
a haploid cell contains a single set of chromosomes
a diploid cell contains two copies of each chromosome
Explain the difference between gametes and somatic cells
a gamete is a reproductive cell of an animal/plant
somatic cells are other cells that are not reproductive
list the phases of the eukaryotic cell cycle and explain the major events that occur in each one (Section 14.1)
The cell cycle is divided into interphase and the mitotic phase
Describe the stages/what happens in interphase
G1 phase: the cell grows physically larger and copies organelles
S Phase: the cell synthesizes a complete copy of the DNA in its nucleus and a centrosome
G2 Phase: the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis
Give a general description of Mitosis
the nuclear DNA of the cell condenses into visible chromosomes and is pulled apart by the mitotic spindle, a specialized structure made out of microtubules.
Give a general description of Cytokinesis
the cytoplasm of the cell is split in two, making two new cells. Cytokinesis usually begins just as mitosis is ending.
What is a cleavage furrow and a cell plate?
A cleavage furrow in animals is created when the contractile ring pinches the cell into 2 separate parts
Since plant cells are harder, a plant cell will build a new structure down the middle of the cell, known as the cell plate
Describe each stage of mitosis
Prophase: chromosomes condense, mitotic spindle begins to form, nucleolus disappears
Prometaphase: chromosomes are very compact, nuclear envelope breaks down, mitotic spindle grows more
Metaphase: the spindle has captured all the chromosomes and lined them up at the middle of the cell, ready to divide.
Anaphase: the sister chromatids separate from each other and are pulled towards opposite ends of the cell- driven by motor proteins
Telophase: mitotic spindle is broken down, new nuclei appear
Cytokinesis: pinching the cell in two like a coin purse with a drawstring and separating the two cells
explain the role of mitosis and meiosis processes in the life cycle of a vertebrate animal as well as label the haploid and diploid phases, the time of fertilization and formation of the zygote
on paper
outline the key events that occur during the phases of meiosis
on paper
Define and describe phases of Meiosis I
Prophase I: Crossing-over occurs (homologous chromosomes pairing up)
Metaphase I: homologue pairs line up at the metaphase plate
Anaphase I: homologues separate to opposite sides of the cell, sister chromatids stay together
Telophase I: Newly forming cells are haploid (n=2), each chromosome has two non-identical sister chromosomes
Define and describe each phase of meiosis II
prophase II: the nuclear envelope dissolves and chromosomes condense
metaphase II: chromosomes line up along the cell’s middle (metaphase plate)
anaphase II: sister chromatids separate and move to opposite ends of the cell
telophase II: the nuclear envelope reforms, and the cell splits into four new cells, each with a haploid number of chromosomes.
explain the process of crossing over (source of genetic variation)
crossing over is a reciprocal exchange between non sister chromatids within a pair of homologous chromosomes. it takes place during prophase I and happens at least one per pair of human homologs.
Define chiasma
site of crossing over
crossing over will leave 4 chromosomes, 2 being strictly paternal/maternal, called ____ and two being a combination of both, called ___
maternal/paternal : non-recombinant chromosomes
combinations of both : recombinant chromosomes
explain the role of crossing over, independent assortment, and random fertilization in increasing genetic diversity
on paper
define independent assortment
chromosomes sort at random during meiosis I between daughter cells, can be maternal or paternal
if we have a 2n=4 cell, how many different ways are possible to arrange the cell?
2^n = 2^2 = 4 different ways of arranging cells
if humans have n=23, how many different ways are possible to arrange the cell?
2^23 = 8.4 million different ways
Define fertilization and how this increases genetic diversity
fertilization is when gametes fuse at random, independent of the gametes genetic information.
the odds of a human zygote having a similar genetic are-
egg (1/8.4 mil) x sperm (1/8.4 mil) = zygote (1/70.6x10^12)
we are very genetically diverse!
