Chapter 9

Question 1

What are the two things meiosis is key in?

Answer 1

1. Enhancing genetic recombination - mixing the genetic information into new combos
2. Reducing a cells chromosome number in half - haploid cells that participate in sexual reproduction

Question 2

What is genetic recombination? What does it require?

Answer 2

The process of cutting the DNA backbones into new combinations

Crossing over (chiasma) of homologous chromosomes

Requires two DNA molecules that differ from one another, a mechanism for bringing the DNA molecules into close proximity, and a collection of enzymes to cut, exchange, and paste the DNA back together

Question 3

What are homologous chromosomes?

Answer 3

Chromosomes that have regions of DNA that are very similar but not identical in the sequence of bases

Question 4

How is bacteria grown in a laboratory?

Answer 4

They start with a minimal medium containing water, an organic carbon, and a selection of inorganic salts
Then they generate cultures of identical bacteria (clones) cells since it is not practical to study just one bacteria cell
Colonies are formed

Question 5

What are prototrophs?

Answer 5

Strains that are able to synthesize the necessary amino acids

Question 6

What are auxotrophs?

Answer 6

Mutant strains that are unable to synthesize amino acids

They can grow only if the required amino acid is provided for them in the growth medium

Question 7

What does it mean when two bacteria cells conjugate?

How can genetic recombination occur using this in bacteria?

Answer 7

The cells contact eachother by a long tubular structure called a sex pilus and then forms a cytoplasmic bridge

During conjugation a copy of part of DNA of one cell moves through the bridge to another

Genetic recombination can occur once the DNA is in the other cell
Through this, conjugation facilitated a kind of sexual reproduction in prokaryotic organisms

Question 8

What is the F factor?

Answer 8

It is a fertility plasmid that carries several genes as well as a replication origin that permits a copy to be passed on to each daughter cell during bacterial cell division.

Question 9

What is vertical and horizontal inheritance?

Answer 9

Vertical- passing genes on from one generation to the next

Horizontal- copying and passing genes on directly from donor cell to recipient cell

Question 10

In what transfer in Bacterial cells is an Hfr cell involved? Is it the donor or the recipient?

Answer 10

Transfer of bacterial genes

Donor

Question 11

What is transformation?

Answer 11

Bacteria simply take up pieces of DNA that are released into the environment as other cells disintegrate

Question 12

What is transduction?

Answer 12

DNA is transferred from donor to recipient cells inside the head of an infection bacterial virus

Question 13

Difference between generalized transduction and specialized transduction?

Answer 13

Generalized allows donor genes to be equally likely transferred since I transfers random fragments of of the host chromosome
Specialized only transfers genes lying close to the point of insertion of prophage

Question 14

Does meiosis always result in gametes? What else?

Answer 14

In humans and other animals yes but in houseplants and some fungi it results in spores

Question 15

What is the animals life cycle?

Answer 15

Animal (2n)
Meiosis
Sperm and egg (n)
Fertilization
Zygote (2n)
Mitosis
Animal (2n)

Question 16

What is the life cycle of all land plants and some fungi and algae?

Answer 16

Sporophyte (2n)
Meiosis
Spore (n)
Mitosis
Gametophyte (n)
Gametes (n)
Fertilization
Zygote (2n)
Mitosis
Sporophyte (2n)

Question 17

What is the life cycle of other fungi and algae?

Answer 17

Zygote (2n) 
Meiosis
Spore (n)
Mitosis
Gametophyte (n)
Mitosis 
Gametes (n)
Fertilization
Zygote (2n)

Question 18

Where do each the paternal and maternal chromosome come from in a homologous pair?

Answer 18

Paternal - father

Maternal- mother

Question 19

What are meiocytes?

Answer 19

Cells that are destined to divide by meiosis

Question 20

In what stage does synapsis occur that results in tetrads and crossing over or a chiasma occur?

Answer 20

Prophase I of meiosis

Question 21

What occurs in prometaphase I?

Answer 21

Nuclear envelope breaks down, the two chromosomes of each pair attach to the kinetochore microtubules

Question 22

What does meiosis I result in in terms of chromosomes and chromatids?

Answer 22

Meiosis I results in a haploid set of chromosomes so half what the parent had but each chromosome has sister chromatids

Question 23

Difference between meiosis and mitosis

Answer 23

Mitosis results in two genetically identical, diploid, 2n cells
Meiosis results in four genetically different haploid, n cells
Mitosis results in somatic cells
Meiosis results in sex cells (gametes or spores)
Meiosis occurs in reproductive tissue

Question 24

What four sources does genetic variability arise from during meiosis and fertilization?

Answer 24

1. Genetic recombination
2. The differing combinations of maternal and paternal chromosomes segregated to poles during anaphase 1
3. The differing combinations of recombinant chromatids segregated to the poles during anaphase II
4. The particular sets of male and female gametes that unite in fertilization

Question 25

What are recombinant chromosomes?

Answer 25

Chromatids that have new combinations of alleles due to recombination (chiasmata)

Question 26

How do you determine the different combinations of random segregation of chromosomes?

Answer 26

2^ number of chromosome pairs

Question 27

What are mobile elements and what is their more specific name?
What is their mechanism of movement?

Answer 27

Transposable elements

Particular segaments of DNA that can move from one place to another (cut and paste)

Non-homologous recombination calked transposition

Question 28

What are the two types of transposable elements called insertion sequences and transposons? IN PROKARYOTES

Answer 28

Insertion sequences- simplest TEs and contains only genes for their transposition
Transposon- has an inverted repeat sequence at each end in closing one or more genes

Question 29

What are the two types of transposable elements called transposons and retrotransposons? IN EUKARYOTES

Answer 29

Transposons- same

Retrotransposons- transpose by a copy and paste mechanism that is unlike any other TE

Question 30

What are retroviruses?

Answer 30

A class of eukaryotic viruses that copies a single stranded RNA genome into a double stranded DNA copy