Chapter 9 Flashcards
What are the two things meiosis is key in?
- Enhancing genetic recombination - mixing the genetic information into new combos
- Reducing a cells chromosome number in half - haploid cells that participate in sexual reproduction
What is genetic recombination? What does it require?
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
What are homologous chromosomes?
Chromosomes that have regions of DNA that are very similar but not identical in the sequence of bases
How is bacteria grown in a laboratory?
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
What are prototrophs?
Strains that are able to synthesize the necessary amino acids
What are auxotrophs?
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
What does it mean when two bacteria cells conjugate?
How can genetic recombination occur using this in bacteria?
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
What is the F factor?
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.
What is vertical and horizontal inheritance?
Vertical- passing genes on from one generation to the next
Horizontal- copying and passing genes on directly from donor cell to recipient cell
In what transfer in Bacterial cells is an Hfr cell involved? Is it the donor or the recipient?
Transfer of bacterial genes
Donor
What is transformation?
Bacteria simply take up pieces of DNA that are released into the environment as other cells disintegrate
What is transduction?
DNA is transferred from donor to recipient cells inside the head of an infection bacterial virus
Difference between generalized transduction and specialized transduction?
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
Does meiosis always result in gametes? What else?
In humans and other animals yes but in houseplants and some fungi it results in spores
What is the animals life cycle?
Animal (2n) Meiosis Sperm and egg (n) Fertilization Zygote (2n) Mitosis Animal (2n)
What is the life cycle of all land plants and some fungi and algae?
Sporophyte (2n) Meiosis Spore (n) Mitosis Gametophyte (n) Gametes (n) Fertilization Zygote (2n) Mitosis Sporophyte (2n)
What is the life cycle of other fungi and algae?
Zygote (2n) Meiosis Spore (n) Mitosis Gametophyte (n) Mitosis Gametes (n) Fertilization Zygote (2n)
Where do each the paternal and maternal chromosome come from in a homologous pair?
Paternal - father
Maternal- mother
What are meiocytes?
Cells that are destined to divide by meiosis
In what stage does synapsis occur that results in tetrads and crossing over or a chiasma occur?
Prophase I of meiosis
What occurs in prometaphase I?
Nuclear envelope breaks down, the two chromosomes of each pair attach to the kinetochore microtubules
What does meiosis I result in in terms of chromosomes and chromatids?
Meiosis I results in a haploid set of chromosomes so half what the parent had but each chromosome has sister chromatids
Difference between meiosis and mitosis
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
What four sources does genetic variability arise from during meiosis and fertilization?
- Genetic recombination
- The differing combinations of maternal and paternal chromosomes segregated to poles during anaphase 1
- The differing combinations of recombinant chromatids segregated to the poles during anaphase II
- The particular sets of male and female gametes that unite in fertilization
What are recombinant chromosomes?
Chromatids that have new combinations of alleles due to recombination (chiasmata)
How do you determine the different combinations of random segregation of chromosomes?
2^ number of chromosome pairs
What are mobile elements and what is their more specific name?
What is their mechanism of movement?
Transposable elements
Particular segaments of DNA that can move from one place to another (cut and paste)
Non-homologous recombination calked transposition
What are the two types of transposable elements called insertion sequences and transposons? IN PROKARYOTES
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
What are the two types of transposable elements called transposons and retrotransposons? IN EUKARYOTES
Transposons- same
Retrotransposons- transpose by a copy and paste mechanism that is unlike any other TE
What are retroviruses?
A class of eukaryotic viruses that copies a single stranded RNA genome into a double stranded DNA copy
