Biology Exam 3

Question 1

List the features of the double helix.

Answer 1

• has a major and a minor groove
• 10 pb per turn
• b is most common form

Question 2

Describe the structure of a nucleotide.

Answer 2

Contains a nitrogenous base, ribose sugar, and phosphate group.

Question 3

Describe the structure of a strand of DNA.

Answer 3

• Composed of nucleotides
• Sugar: Deoxyribose
• Bases: AGCT
• Double Helix
• Stable
• A double helix made of two polymers of DNA
• Anti parallel strands
• They have polarity with a 3 prime and a 5 prime end.
• The bases are joined together phosphodiester covalent bonds.
• Strands are held together by hydrogen bond (weak bonds)

Question 4

Describe the structure of double helix B form DNA.

Answer 4

• most common DNA under physiological conditions
• right-handed turn
• 10 bp per turn

Question 5

Outline the flow of information DNA > RNA > Protein.

Answer 5

DNA (transcription)>RNA(translation)>Protein>Function

Question 6

List 5 levels of DNA organization.

Answer 6

1) Double Helix
2) Nucleosome (string of beads)
3) Chromatin fiber (folded beads)
4) Euchromatin (Looped Domain)
5) Heterochromatin (interphase)

Question 7

Describe the structure and function of a gene.

Answer 7

A gene is a functional unit of DNA; Sequence that encodes a trait.

Question 8

Describe/ compare the structure and function of RNA molecules.

Answer 8

• Composed of nucleotides
• Type of Sugar: Ribose
• contains 2’ OH group
• Bases: AGCU
• Single Stranded
• Many types of secondary structure
• Unstable

Question 9

Define mutation.

Answer 9

mistakes made during gene replication in the nitrogenous base pairing. (occurs 1 in 10 billion)

Question 10

Why are mutations often harmful?

Answer 10

If a mutation changes a protein so the protein can’t do its job.

Question 11

What bases pair together?

Answer 11

A pairs with T - 2 bonds
C pairs with G - 3 bonds

Question 12

Which bases are purine?

Answer 12

A and G

Question 13

Which bases are pyrimidine?

Answer 13

T and C

Question 14

What is a chromosome?

Answer 14

long double helix of DNA

Question 15

What is a nucleosome?

Answer 15

• DNA + histone
• contains 200bp of DNA/ nucleosome
• Histone octomer

Question 16

How many pairs of chromosomes do we have?

Answer 16

23 pairs

Question 17

What is chromatin?

Answer 17

DNA + proteins + RNA required of chromosome condensation
nucleosome = unit of chromatin

Question 18

Euchromatin

Answer 18

loosely packaged DNA (where turned on genes are located)

Question 19

Heterochromatin

Answer 19

Tightly packaged DNA

Question 20

What is the function of ribosomal RNA (rRNA)?

Answer 20

builds ribosomes that make protein (never translated)

Question 21

What is the function of Transfer RNA (tRNA)?

Answer 21

carries amino acids to ribosome

Question 22

What is the function of messenger RNA (mRNA)?

Answer 22

translated into proteins for cell function

Question 23

Where must mutations occur to be heritable?

Answer 23

egg or sperm

Question 24

Describe the structure and function of the nuclear pore.

Answer 24

Nuclear pore regulates mRNA exit and protein entrance

Question 25

What is the function of initiator proteins?

Answer 25

- bind origin of replication and melt hydrogen bonds to open helix - separates DNA strand - start the replication bubble

Question 26

What is the function of helicase?

Answer 26

unwinds double stranded DNA

Question 27

What is the function of topoisomerase?

Answer 27

makes nicks (and fixes them) in the DNA to relieve tension ahead of fork

Question 28

What is the function of single stranded binding proteins (SSPB)?

Answer 28

keeps strands from rebuilding

Question 29

What is the function of primase?

Answer 29

- synthesizes 20-30nt RNA primer - provides short dsDNA region and 3' - OH for DNA polymerase - provides a 3'oh group form DNA polymerase to add nucleotides to

Question 30

What is the function of DNA polymerase III?

Answer 30

duplication of chromosomal DNA; adds new base pairs on a strand of DNA

Question 31

What is the function of DNA polymerase I?

Answer 31

removes RNA primers and replaces them with DNA

Question 32

What is the function of a beta clamp?

Answer 32

helps pol III find the primers

Question 33

What is the function of ligase?

Answer 33

seals the gaps (gaps between RNA primer and DNA) between DNA segments with phosphodiester bonds (requires ATP)

Question 34

Describe DNA synthesis reaction carried out by DNA pols.

Answer 34

the primer is laid then DNA pol III adds nucleotides then pol 1 removes RNA primers and replaces them with DNA

Question 35

Describe DNA synthesis process on leading and lagging strands.

Answer 35

On the leading stand DNA synthesis occurs continuously. On the lagging strand, DNA synthesis restarts many times as the helix unwinds, resulting in many short fragments called Okazaki fragments then DNA ligase joins the Okazaki fragments together into a single DNA molecule.

Question 36

Describe the structure of the telomere.

Answer 36

Makes a t-loop with telomerase (loops back around to protect overhang)

Question 37

List events of each stage of mitosis.

Answer 37

Interphase Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis

Question 38

Compare and contrast the process and outcomes of mitosis and meiosis.

Answer 38

Mitosis results in two nuclei that are identical to the original nucleus. Meiosis, on the other hand, results in four nuclei, each having half the number of chromosomes of the original cell

Question 39

What happens in interphase?

Answer 39

Cell functioning (spaghetti chromosomes) *DNA replication occurs)

Question 40

What happens in prophase?

Answer 40

chromosomes condense (MTOC splits into 2)

Question 41

What happens in pro metaphase?

Answer 41

nuclear membrane breaks down and spindle forms

Question 42

What happens in metaphase?

Answer 42

replicated chromosome moves to equator (they line up in the middle) and they attach to the spindle

Question 43

What happens in anaphase?

Answer 43

replicated chromosome (sister chromatids) separate to poles

Question 44

What happens in telophase?

Answer 44

new nuclear membrane around 2 sets of chromosomes

Question 45

What happens in cytokinesis?

Answer 45

separation of the cytoplasm; pinching apart of daughter cells

Question 46

What end do nucleotides add to?

Answer 46

3' hydroxyl

Question 47

What is the order of DNA replication proteins?

Answer 47

1. Primase 2. DNA pol III 3. DNA pol I 4. Ligase

Question 48

Difference between prokaryotic and eukaryotic DNA replication?

Answer 48

Prokaryote - Chromosome is a circle Eukaryote - Chromosome is a line with a hanging end

Question 49

What is the DNA overhang called?

Answer 49

Telomere

Question 50

What does telomerase do?

Answer 50

can extend overhang to prevent shortening

Question 51

What is the formula for chromosomes in mammalian cells?

Answer 51

2n = 46

Question 52

What is the function of kinetochore proteins?

Answer 52

connect centromere to spindle microtubules

Question 53

What are the differences between meiosis and mitosis?

Answer 53

Meiosis - 2 round of division instead of 1 - anaphase 1 separates replicated chromosomes (not sisterchromatids) - only occurs in sex cells; produces gametes - Replicated homologous chromosomes pair to form tetrads - results in 4 haploid daughter cells vs. 2 diploid

Question 54

What pinches the cell apart in cytokinesis?

Answer 54

Actin Ring

Question 55

What is the B form DNA model?

Answer 55

Watson and Crick model

Question 56

Which nitrogenous bases are purine and how many rings are they made of?

Answer 56

A and G made of two rings

Question 57

Which nitrogenous bases are pyrimidine and how many rings are they made of?

Answer 57

T and C made of 1 ring

Question 58

How many hydrogen bonds are between C and G?

Answer 58

3

Question 59

How many hydrogen bonds are between A and T?

Answer 59

2

Question 60

What are the motor proteins involved in mitosis?

Answer 60

Eg5, Dynein, HSET