case 2

Question 1

Does crossing-over happen in mitosis or meiosis and what about independent assortment?

Answer 1

In meiosis crossing-over and independent assortment happens. In mitosis crossing-over and independent assortment does not happen.

Question 2

Production/function of mitosis and meiosis?

Answer 2

Production of mitosis is asexual and from meiosis is sexual and the function of mitosis is growth. Embryo development, tissue repair. The function of meiosis is gamete formation.

Question 3

(in meiosis) What happens in the interphase?

Answer 3

Three phases; G1 (first gap) The S phase and the G2 (secund gap). During al the phases of interphase, actually a cell grows by producing proteins and cytoplasmic organelles such as mitochondria and endoplasmic reticulum. During the s phase only Duplication of the chromosomes occurs, crucial for eventual division of the cell. in G2 it also completes preparations for cell division.

Question 4

(in meiosis) What happens in the first prophase?

Answer 4

This is where the chromosomes are going to condense and thicken. They are going to line up with their homologous pairs. Crossing over appears here. Mitotic spindles start to form. Nuclear envelope breakdown occurs.

Question 5

(in meisosis) what happens in the first metaphase?

Answer 5

(tip m= for middle the chromosomes are now going to be in the middle of the cell (on the metaphase plate)) the chromosomes are going to be in pairs in the middle. Each pair is lined up independently of other pairs( this is called independent assortment) both chromatids of one homolog are attached to kinetochore microtubules from one pole; the chromatid of the other homolog are attached to microtubules from the opposite pole.

Question 6

(in meisosis) What happens in the first Anaphase?

Answer 6

(tip a= away)homologous pairs separate. Chiasma breaks down. the chromosomes are going to be pulled away. (note sister chromatids remain attached – both move to the same pole).

Question 7

(in meisosis) what happens in the fist Telophase 1 and cytokinesis?

Answer 7

When telophase begins, each half of the cell has a complete haploid set of duplicated chromosomes. Each chromosome is composed of two sister chromatids; one or both chromatids include regions of nonsister chromatid DNA. Cytokines happens. Forming two haploid daughter cells.

Question 8

(in meisosis) What happens in the secund prophase?

Answer 8

Spindles start to form. Chromosomes each still composed of two chromatids associated at the centromere, are moved by microtubules towards the metaphase 2 plate.

Question 9

(in meisosis) What happens in the secund metaphase?

Answer 9

(tip m= for middle the chromosomes are now going to be in the middle of the cell (on the metaphase plate)) (because of crossing over in meisosis 1 (crossing over does not happen in meisosis 2) the two sister chromatids of each chromosome are not genetically identical. The kinetochore of sister chromatids are attached to microtubules extending from opposite poles.

Question 10

(in meisosis) What happens in the secund anaphase?

Answer 10

(tip a= away) breakdown of proteins holding the sister chromatids together at the centrosome allows the chromatids to separate and move away toward the opposite poles: each chromatid has now become an individual chromosome.

Question 11

(in meisosis) What happens in the secund telophase 2 and cytokinesis?

Answer 11

Nuclei from, the chromosomes begin decondensing and cytokinesis occurs. The meitotic division of one parent cell produces four daughter cells, each with a haploid set of (unduplicated) chromosomes

Question 12

What does helicases do?

Answer 12

Are enzymes that Untwist the double helix at the replication forks, separating the parental strands and making them available as template strands.

Question 13

What does single-strand binding proteins do?

Answer 13

Single-strand binding proteins bind to the unpaired DNA strands, keeping them from re-pairing. The untwisting of the double helix causes tighter twisting and stain ahead of the replication fork.

Question 14

Explain primer and primase.

Answer 14

The RNA chain is called a primer and is synthesized by the enzyme primase. Primase starts a complementary RNA chain with a single RNA nucleotide and adds RNA nucleotides one at a time, using the parental DNA strand as a template. (the complete primer, generally five to ten nucleotide long, is thus base-paired to the template strand. The new DNA strand will start from the 3’ end of the RNA primer). (RNA nucleotides are later removed of the primer and replaced with DNA nucleotides)

Question 15

What does topoisomerase do?

Answer 15

Is an enzyme that helps relieve this strain by breaking swivelling and rejoining DNA strands.

Question 16

Explain DNA polymerase.

Answer 16

Enzymes that catalyse the synthesis of new DNA by adding nucleotides to the 3’end of the preexisting chain. Never the to the 5’end. Thus the new DNA strand can elongate only in the 5’ 3’direction. Requires a primer and DNA template strand, along with complementary DNA nucleotides. Polymerase adds a DNA nucleotide to the RNA primer and then continues adding DNA nucleotides, which are complementary to the parental DNA template strand to the growing end of the new DNA strand. (elongating)** Later door**

Question 17

What are okaziki fragments?

Answer 17

The laggin strand is synthesized discontinuously, as a series of segments. These segments of the laggin strand are called Okazaki fragments (only in DNA).

Question 18

Explain RNA polymerase.

Answer 18

Is an enzyme that Pries two strand of DNA apart and joins together RNA nucleotides complementary to the DNA template strand, thus elongating the RNA polynucleotides. RNA

Question 19

Explain the stages of transcription.

Answer 19

Figure 17.8 further explain. bacterie
* Initiation;
- After RNA polymerase binds to the promoter the polymerase unwinds the DNA strand and initiates RNA synthesis at the start point on the template strand.

• Elongation;
• The polymerase moves downstream unwinding the DNA and elongating the RNA transcript 5’ 3’after transcription has occurred, the DNA strand re-form a double helix.
• Termination;
• Eventually, the RNA transcript is released, and the polymerase detaches from the DNA

Question 20

What is the lagging strand?

Answer 20

The other new strand of DNA elongating in mandatory 5’ 3’direction. (The DNA polymerase must work along the other template strand in the direction away from the replication.

Question 21

What is replication fork?

Answer 21

Region where the parental strands of DNA are being unwound.

Question 22

What is the promoter?

Answer 22

The DNA sequence where RNA polymerase attaches and initiates transcription. A crucial DNA promoter is the TATA box forming the initiation complex at a eukaryotic promoter)

Question 23

Explain transcription factors.

Answer 23

A collection of proteins that help guide the binding of RNA polymerase and the initiation of transcription. Only after transcription factors are attached to the promoter does RNA polymerase bind to it (the whole complex of transcription factors and RNA polymerase bound to the promoter is called transcription initiation complex)

Question 24

Explain RNA processing.

Answer 24

Both ends of the primary transcript are altered. Think about the 5’cap of the poly-A-tail. They share functions.
- They facilitate the export of mature mRNA from the nucleolus.
- They help protect the mRNA from degradation by hydrolytic enzymes
- They help ribosomes attach to the 5’end of the mRNA one it reaches the cytoplasm.

Question 25

Explain DNA repair.

Answer 25

many DNA polymerases proofread each nucleotide against its template as soon as it is covalently bonded to the growing strand. Upon finding an incorrectly paired nucleotide, the polymerase removes the nucleotide and then resumes synthesis. (This action is similar to fixing a texting error by deleting the wrong letter and then entering the correct one.) Mismatched nucleotides sometimes evade proofreading by a DNA polymerase. In mismatch repair, other enzymes remove and replace incorrectly paired nucleotides that have resulted from replication errors.

Question 26

Explain the nuclease

Answer 26

part of DNA repair. Most cellular systems for repairing incorrectly paired nucleotides, whether they are due to DNA damage or to replication errors, use a mechanism that takes advantage of the base-paired structure of DNA. In many cases, a segment of the strand containing the damage is cut out (excised) by a DNA cutting enzyme—a nuclease—and the resulting gap is then filled in with nucleotides, using the undamaged strand as a template. The enzymes involved in filling the gap are a DNA polymerase and DNA ligase. One such DNA repair system is called nucleotide excision repair
1- Teams of enzymes detect and repair damaged DNA
2- A nuclease enzyme cuts the damaged DNA strand at two points, and the damaged section is removed.
3- Repair synthesis by a DNA polymerase fills in the missing nucleotides, using the undamaged strand as a template.
4- DNA ligase seal the end of the new DNA to the old DNA, making the strand complete

Question 27

Explain the checkpoints in the cell cycle.

Answer 27

A checkpoint in a cell cycle is a control point where stop and go ahead signals can regulate a cycle.
- There are three important checkpoints in G1, G2 and M phase
- internal and external signals move a cell past these checkpoints. The G1 checkpoint determines whether a cell will proceed forward in the cell cycle or switch into the G0 phase. The signals to pass this checkpoint often are external, such as growth factors. Passing the G2 checkpoint requires sufficient numbers of active MPF complexes,

Question 28

Explain telomeres.

Answer 28

DNA molecules have special nucleotides sequences at their ends. Telomeres do not contain genes; instead, the DNA typically consists of of multiple repetitions of one short nucleotide sequence. They have two functions
- specific proteins associated with telomeric DNA prevent the staggered ends of the daughter molecule from activating the cell’s systems for monitoring DNA damage. (Staggered ends of a DNA molecule, which often result from double-strand breaks, can trigger signal transduction pathways leading to cell cycle arrest or cell death.)
- Second, telomeric DNA acts as a kind of buffer zone that provides some protection against the organism’s genes shortening, somewhat like how the plastic-wrapped ends of a shoelace slow down its unraveling. Telomeres do not prevent the erosion of genes near the ends of chromosomes; they merely postpone it.

Question 29

What is heredity.

Answer 29

is the transmission of traits (actually genes) from one generation to the next

Question 30

. What is a exception of mendel’s laws

Answer 30

exception of mendels law;
segregation genes (linked): Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during meiosis

Question 31

What are autosomes

Answer 31

chromosomes 1-22

Question 32

What does a genome consist of?

Answer 32

the genome consist of all genetic information

Question 33

who are mostly known for discovering DNA

Answer 33

Watson and crick and Wilkens Rosalind franklin.

Question 34

What are the purines and what are the pyrimidines?

Answer 34

Purines: adenine guanine pyrimidines: cytosine uracil and thymine.

Question 35

Explain a few things about mitochondria?

Answer 35

No histones, limited repair, high mutation rate

Question 36

How does maternal inherence of mtDNA work.

Answer 36

Mother can have offsprings that are infected and offsprings that are not affected. They not affected offsprings can have offsprings that are affected it can skip generations.