Wk. 2 | Replication, Cell Cycle, and Recombination

Question 1

Recombination is a natural process in eukaryotes and prokaryotes to

Answer 1

produce offspring with new genetic combinations (recombinants)

Question 2

Recombinant organisms are naturally produced in eukaryotes by

Answer 2

sexual reproduction

Question 3

Recombinant organisms are naturally produced in prokaryotes by

Answer 3

gene transfer through:
- conjugation
- transduction
- transformation

Question 4

Recombination in sexually reproducing organisms (eukaryotes) occurs via

Answer 4

Crossing over (physical exchange) between chromosomes resulting in a new combo of parental genomes

Question 5

________ ______ is based on Mendel’s law

Answer 5

Crossing Over

Question 6

Advantage(s) of Crossing Over

Answer 6

↑ robustness and adaptability of offspring (heteresis)

Question 6

Heteresis

Answer 6

Hybrid vigor. Mixed individuals are stronger than purebred organisms

Question 7

How does recombination occur? (3 steps)

Answer 7

1. Meiosis: Duplicated homologous chromos line up and cross over
2. Recombined duplexes are randomly assorted into gametes. Each gamete contains one set of the recombined parental chromosomes
3. The gamete merges with a gamete from other parent carrying its recombined chromosomes resulting in offspring with a recombination of parental genes

Question 8

Step 1: Meiosis: _____ _______ _______ line up and cross over

Answer 8

duplicated homologous chromosomes

Question 9

Step 2: ______ ________ are randomly assorted into _______.

Each gamete contains…..

Answer 9

Recombined duplexes, gametes

1 set of recombined parental chromosomes

Question 10

Step 3:
- The gamete merges with a……..

• resulting in offspring with

Answer 10

a gamete from other parent carrying its recombined chromosome

a recombination of parental genes

Question 11

Conjugation
- F+ and F- cells conjugate through a ______
- F- cells become F+ as __________________
- Both cells synthesize __________________
- Cells, now both F+ separate

Answer 11

• bridge
• it obtains a copy of F factor
• a complementary DNA strand

Question 12

Transduction
- __________ ________ ___________ _______ and transfer genetic info

Answer 12

Bacteriophages infect bacterial cells

Question 13

Bacteriophages play a role in

Answer 13

transduction

Question 14

Transformation
- Transfer of DNA from __________

• _________ cells take up _____ DNA fragments
• ___________ occurs between ________ and ______
• Unrecombined DNA is ________
• Results in a ____________ ___________ cell

Answer 14

• one organism to another
• Recipient, donor
• Recombination occurs between donor + recipient DNA
• Degraded
• Genetically transformed

Question 15

DNA Supercoiling

Answer 15

DNA is negatively supercoiled (under winding)

Question 16

Supercoiling is beneficial because it aids these 2 things by….

Answer 16

Replication and Transcription

by lowering energy required to separate helix

Question 17

Supercoils are mintained in eukaryotes by

Answer 17

the winding of the helix around histones

Question 18

Generally, how is DNA replicated?

Answer 18

DNA duplicated from mother cell -> 2 identical copies

During division, each daughter cell gets 1 complete DNA copy

Question 19

Difference between prokaryotic replication and eukaryotic replication

Answer 19

Prokaryotes: 1 origin of replication
Eukaryotes: Several origins -> several replications happening simultaneously

Question 20

What is semi-conservative replication?

Answer 20

Half of original DNA is conserved

One daughter cell has original right strand and the other has the original left strand

Question 21

How is DNA held together?

Answer 21

H bonding and twisting around each other

DNA inside a cell is supercoiled

Question 22

Before separating, what has to be unwound?

Answer 22

BOTH the supercoils and the double helix

Question 23

____________ unwinds supercoils

Answer 23

Topoisomerases

Question 24

What does gyrase do

Answer 24

Cuts both strands of dsDNA while holding two ends

Question 25

How are the two strands of DNA rejoined

Answer 25

two halves of strands rotate and the ends are rejoined

Question 26

Helicase does _________ by _________

Answer 26

unzips DNA strands disrupting H bonds between base pairs

Question 27

DNA Replication in Eukaryotes 1. Replication at ____ 2. Forks move in _________ ________ as DNA is synthesized

Answer 27

1. ori 2. opposite directions

Question 27

DNA Replication in Bacteria 1. ________ of parental DNA 2. ________ of the DNA strands ahead of the ___________ ______ 3. _________ ______ serves as a swivel to allow _________ _________ of DNA strands 4. Binding of ___________ ______________ 5. Synthesis of ___ _______ and unwinding of DNA by ________ and single-stranded binding proteins. 6. Formation of ___ __________ _________ in circular DNA and it is replicated.

Answer 27

1. Unwinding 2. Twisting, replication fork 3. Transient breaks, free rotation 4. initiation proteins 5. RNA primers, helicase 6. 2 replication forks

Question 28

Parental divorce

Answer 28

Single stranded binding proteins prevent two strands from getting back together during replication

Question 29

DNA Polymerase III - Adds _________ to the __ __ end of the _________ strand - Elongates toward replication fork (__ to __) - More primers attach to opposite strand and elongates __ to __ - This strand is the ________ strand

Answer 29

- nucleotides, 3' OH, original - 5' to 3' - 5' to 3' - lagging strand

Question 29

Creation of New Strand 1. Strands unwound. 2. _______ binds and make ___ primers molecules. 3. Primers attach to DNA at ___ and then begin a _______ strand.

Answer 29

2. Primase, RNA 3. ori, leading

Question 30

Replication ALWAYS occurs in this direction

Answer 30

5' to 3'

Question 31

DNA Polymerase I - An ________ enzyme - Attaches to ______ - _____ strand ahead while __________ strand behind - Replaces all _________ with deoxynucleotides

Answer 31

- editing - nicks in growing strands - Edits, elongating - RNA nucleotides

Question 32

Leading Strand

Answer 32

5' to 3' made continuosly

Question 33

Step 1 of DNA Replication

Answer 33

Helicase unzips double helix

Question 33

Lagging Strand

Answer 33

3' to 5' made in short okazaki fragments and joined

Question 34

Step 2 of DNA Replication

Answer 34

SSBs stabilize unwound DNA

Question 35

Step 3 of DNA Replication

Answer 35

Leading strand synth. 5' to 3' by DNA polymerase

Question 36

Step 4 of DNA Replication

Answer 36

Lagging strand synthesized in segments Primase makes RNA primers extended by DNA polymerase to form an okazaki fragment

Question 37

Step 5 of DNA Replication

Answer 37

RNA primer replaced by DNA Ligase joins Okazaki fragments

Question 38

What enzyme joins Okazaki fragments

Answer 38

Ligase

Question 39

Function of ligase

Answer 39

Acts like a glue, seals nicks

Question 40

Function of editing endonucleases

Answer 40

Replaces mismatched nucleotides with proper matches

Question 41

Function of gyrases

Answer 41

restores negative supercoils

Question 42

Function of methylases

Answer 42

Add methyl groups to new DNA at same spot as original

Question 43

Bacterial Cell Division _______, ________ chromosome(s). Replication proceeds at the same time in ____ direction. Two ________ _____ will meet and merge. Yields: __ ___ _______ chromosome(s). ___ chromosome(s) is in each cell when it divides.

Answer 43

- Single, circular - both - replication forks - 2 new circular - 1

Question 44

Eukaryotic Cell Division ____ complex; ________ chromosome(s). Inside nucleus is where related to the cell? _____ chromosome(s), usually very ____ Several ____________ _______ along the length of each chromosome.

Answer 44

- More, multiple - separated by nuclear membrane - Linear, long - replication forks

Question 45

Mitosis 1. _______ of mother cell is disassembled 2. Mother divides and _________ are divided between daughters 3. ___________ built around the chromosomes in each daughter cell

Answer 45

1. Nucleus 2. chromosomes 3. New nucleus

Question 46

What phase of the cell cycle does DNA replicate in?

Answer 46

Interphase or S phase

Question 47

Phases of mitosis

Answer 47

Prophase Metaphase Anaphase Telophase

Question 47

Prophase

Answer 47

condensed chromsomes become visible and nuclear membrane dissolves

Question 48

Metaphase

Answer 48

Chromosomes move to cell equator and align in pairs

Question 49

Anaphase

Answer 49

Separate halves of each chromosome are drawn apart by the spindle fibers toward the poles of the cell

Question 50

Telophase

Answer 50

A new nuclear membrane is made to surround each set of newly divided chromosomes

Question 50

During meiosis, cells go from ______ to ______

Answer 50

diploid to haploid

Question 51

Diploid vs. Haploid

Answer 51

Diploid (2n) - 46 chromosomes - Somatic (non-sex) cells Haploid (n) - 23 chromosomes - Germ cells or gametes (sperm + egg) - Fertilization joins sperm and egg and restores 46 chromosomes

Question 52

Mitosis _____________ duplicates DNA and splits it up into 2 genetically ___________________________ _______ cells.

Answer 52

1 diploid cell (2n), identical diploid cells (2n). somatic

Question 53

Meiosis 1. Chromosomes replicate ____ in _ phase into sister chromatids. Cell divides _____ 2. During PMAT I, __________________ are segregated into different cells. 2 cells each have a copy of ______________ 3. Crossing over occurs during ______ to ___________. Homologs separate and chromosomes become part of _________ 4. During PMAT II, sister chromatids are _____________, so each of the daughter cells now have a _________________ and are now _________ This is how _____________ is generated.

Answer 53

1. once, S phase, twice 2. homologous chromosomes, each of the 23 chromosomes. 3. PMAT I, shuffle the genomes, gametes 4. pulled apart again, copy of each of the chromosomes, haploid genetic diversity!