Bio exam 4

Question 1

During what process are parental DNA strands used as templates for the synthesis of new DNA strands?

Answer 1

DNA replication

Question 2

Explain DNA replication

Answer 2

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)

Question 3

explain what happens after 1 round of DNA Replication

Answer 3

the daughter DNA molecules are formed of one parental and one daughter strand

Question 4

define semiconservative in DNA replication

Answer 4

one strand of old (parental) DNA and one strand of new (daughter) DNA

Question 5

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

Answer 5

do on paper

Question 6

What is the origin of replication?

Answer 6

A sequence that indicates where to begin DNA replication

Question 7

Explain DNA replication Bubble

Answer 7

2 replisomes will move right and left from the origin of replication, followed by 2 replication forks

Question 8

What is a replication fork?

Answer 8

a Y-shaped region where new DNA symthesis is heppening.

Question 9

describe the functions of helicase, topoisomerase, single-strand binding protein, primase, ligase, and DNA polymerases III and I

Answer 9

AHHH

Question 10

What is the function of DNA helicase?

Answer 10

Breaks hydrogen binds between parental strands

Question 11

What is the function of DNA Topisomerase?

Answer 11

cuts DNA, allowing DNA to unwind and then joining it

Question 12

What is the function of single-strand binding protein?

Answer 12

Attach to a single strand DNA and prevent H=bonds from reforming

Question 13

What is a finction of DNA primase?

Answer 13

Synthesizes a short sequence of RNA, primer for RNA

Question 14

What is the function of DNA Polymerase 1

Answer 14

To remove the RNA primers and replace them with DNA

Question 15

What is the function of DNA ligase?

Answer 15

Closes the Gap between Okazaki fragments, forming a phosphodiester bond.

Question 16

What is the function of DNA polymerase 3?

Answer 16

to add nucleotide to the 3’ end of a growing DNA strand.

Question 17

Explain the order that DNA replication happens in, including time

Answer 17

Time 1

1. Helicase breaks down bonds between parental strands
2. Single-stranded binding proteins attach to single stranded DNA and prevent H-bonds from reforming
3. Topoisomerase cuts DNA, unwinding it
4. Primase synthesizes a short, sequence of RNA
5. 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

4. Primase sets the RNA primer down
5. DNA Polymerase III extends the 2nd Okazaki fragment
6. DNA polymerase I removes RNA nucleotide and replaces the RNA with DNA nucleotides

Time 3:

7. Ligase closes the gap between Okazaki fragments and forms a phosphodiester bond

Question 18

outline the key differences between the synthesis of the leading and lagging strands

Answer 18

on paper

Question 19

What are characteristics of the leading strand?

Answer 19

synthesized 5’ to 3’, same direction of the replication fork synthesized in one continuous piece

Question 20

Identify characteristics of the lagging strand?

Answer 20

synthesized 5’ to 3’ discontinuously, in fragments, synthesized in the opposite direction of the replication fork.

Question 21

define what a chromosome is, explain the relationships between DNA, genes, chromosomes, sister chromatids, and centromeres

Answer 21

on paper

Question 22

define chromosomes

Answer 22

discreate units of genetics informations, can have many linear in eukaryotes, can have 1 circular in prokaryotes

Question 23

Define gene

Answer 23

segment of DNA that encodes for one protein

Question 24

Define homologous chromosomes

Answer 24

maternal and paternal of the same chromosomes type: will be the same order, shape, size

maternal= egg
paternnal= sperm

Question 25

What are x and y chromosomes?

Answer 25

sexyal chromosomes that carry info that determins biological sex of a person XX female XY male

Question 26

explain what the “n number” of a cell is as well as explain the difference between a haploid and a diploid cell

Answer 26

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

Question 27

Explain the difference between gametes and somatic cells

Answer 27

a gamete is a reproductive cell of an animal/plant somatic cells are other cells that are not reproductive

Question 28

list the phases of the eukaryotic cell cycle and explain the major events that occur in each one (Section 14.1)

Answer 28

The cell cycle is divided into interphase and the mitotic phase

Question 29

Describe the stages/what happens in interphase

Answer 29

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

Question 30

Give a general description of Mitosis

Answer 30

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.

Question 31

Give a general description of Cytokinesis

Answer 31

the cytoplasm of the cell is split in two, making two new cells. Cytokinesis usually begins just as mitosis is ending.

Question 32

What is a cleavage furrow and a cell plate?

Answer 32

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

Question 33

Describe each stage of mitosis

Answer 33

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

Question 34

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

Answer 34

on paper

Question 35

outline the key events that occur during the phases of meiosis

Answer 35

on paper

Question 36

Define and describe phases of Meiosis I

Answer 36

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

Question 37

Define and describe each phase of meiosis II

Answer 37

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.

Question 38

explain the process of crossing over (source of genetic variation)

Answer 38

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.

Question 39

Define chiasma

Answer 39

site of crossing over

Question 40

crossing over will leave 4 chromosomes, 2 being strictly paternal/maternal, called ____ and two being a combination of both, called ___

Answer 40

maternal/paternal : non-recombinant chromosomes combinations of both : recombinant chromosomes

Question 41

explain the role of crossing over, independent assortment, and random fertilization in increasing genetic diversity

Answer 41

on paper

Question 42

define independent assortment

Answer 42

chromosomes sort at random during meiosis I between daughter cells, can be maternal or paternal

Question 43

if we have a 2n=4 cell, how many different ways are possible to arrange the cell?

Answer 43

2^n = 2^2 = 4 different ways of arranging cells

Question 44

if humans have n=23, how many different ways are possible to arrange the cell?

Answer 44

2^23 = 8.4 million different ways

Question 45

Define fertilization and how this increases genetic diversity

Answer 45

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!