Chapter 10- genetic recombo Flashcards

Question

Explain the basis of Down syndrome in humans

Answer 1

It is a condition that results from nondisjunction of chromosome 21 so that babies are born with 3 copies of this chromosome instead of 2

Answer 2

Joshua Lederberg and Edward Tatum

Answer 3

cells contact each other by long tubular structure called sex pilus and then form cytoplasmic bridge - During conjugation, a copy of part of the DNA of one cell moves through the cytoplasmic bridge into other cell - Once DNA from once cell enters other, genetic recombination can occur - bacterial conjugation thus facilitates a kind of sexual reproduction in prokaryotes The F Factor and Conjugation -Conjugation is initiated by a bacterial cell that contains a small circle of DNA in addition to main circular chromosomal DNA - such small circles are called plasmids, and this particular one known as “fertility” plasmid or “the F factor” - like all plasmids, f factor carries several genes as well as a replication origin that permits a copy to be passed on to each daughter cell during usual process of bacterial cell division -this is an example of “vertical” inheritance from one generation to next o However, during conjugation, F factor also has ability to be copied and passed directly from one cell (the donor) to another (the recipient), this is an example of “horizontal” inheritance

Answer 4

(1) genetic recombination, (2) the differing combinations of maternal and paternal chromosomes segregated to the poles during anaphase I, (3) the differing combinations of recombinant chromatids segregated to the poles during anaphase II, and (4) the particular sets of male and female gametes that unite in fertilization

Answer 5

a protein framework that holds together pairing homologous chromosomes,, which disassembles and disappears when the exchange of segments (producing new combos of alleles) is complete

Answer 6

regions in which non-sister chromatids cross one another

Answer 7

1- recombination (chromatids generate new combinations of alleles by physically exchanging segments- exchange process involves precise breakage and joining of DNA molecules. catalyzed by enzymes and occurs while the homologous chromosomes are held tightly together by S-complex. crossovers visible between chromosomes at late prophase I reflect the exchange of chromatid segments that occurred during the molecular steps of genetic recombination) 2- random segregation of homologous chromosomes (homologous pairs separate at anaphase I of meiosis, segregating random combinations of maternal and paternal chromosomes to the spindle poles. 3- random segregation of the chromatids of replicated chromosomes at meiosis II 4- random joining of male and female gametes in fertilization

Answer 8

DNA sequences that can move from place to place in the DNA. The TEs may move from one location in the DNA to another or generate duplicated copies that insert in new locations while leaving the “parent” copy in its original location

Answer 9

mechanism of movement of TEs. occurs at a low frequency in either of two ways, depending on the type of element: (1) a cut-and-paste process, in which the TE leaves its original location and transposes to a new location, and (2) a copy-and-paste process, in which a copy of a TE transposes to a new location, leaving the original TE behind

Answer 10

they produce mutations by transposing into genes and knocking out their functions, and they increase or decrease gene expression by transposing into regulatory sequences of genes. as such, TEs are biological mutagens that increase genetic variability

Answer 11

Many antibiotics, such as penicillin, erythromycin, tetracycline, ampicillin, and streptomycin, that were once successful in curing bacterial infections have lost much of their effectiveness because of resistance genes carried in transposons. Movements of the trans- posons, particularly to plasmids that can be transferred by conjugation within and between bacterial species, greatly increase the spread of genes, providing anti- biotic resistance to infecting cells. Resistance genes have made many bacterial diseases difficult or impossible to treat with standard antibiotics.

Answer 12

2 major types: insertion sequences (IS) and transposons.

Answer 13

transposons and retrotransposons

Answer 14

aprox 20, several encode proteins of the sex Pilus (or F Pilus)

Answer 15

fully paired homologues

Answer 16

animals: diploid dominates plants: alternate between haploid and diploid generations in which depending on the organism, either generation may dominate the life cycle fungi: haploid dominates

Answer 17

Eukaryotic transposons are similar to bacterial transposons in their general structure and in the ways they transpose. However, members of the other class of eukaryotic TEs, the retrotrans- posons, transpose by a copy-and-paste mechanism that is unlike any of the other TEs

Answer 18

``` The RNA to DNA reverse transcription associated with retrotransposon movement is strikingly similar to that employed by a class of eukaryotic viruses called retro- viruses. When a retrovirus infects a host cell, a reverse transcriptase carried in the virus particle is released and copies the single-stranded RNA genome into a double- stranded DNA copy. The viral DNA is then inserted into the host DNA (by genetic recombination), where it is replicated and passed to progeny cells during cell divi- sion. Similar to the prophage of bacteria, the inserted viral DNA is known as a provirus -in total, retrotransposons and retroviruses of all types occupy some 40% of the human genome ```

Answer 19

high frequency recombination - can ''export'' copies of chromosomal genes to another cell. In hfr cells, the origin of transfer is near the middle of the integrated F factor, as a result, only half of the F factor DNA is transferred at the front of the chromosomal DNA most likely, recipient will be partial diploid

Answer 20

F- IS THE RECIPIENT CELL WHILE F+ IS THE DONOR CELL. BETWEEN THESE TWO CELLS, NO GENETIC RECOMBINATION OCCURS. THE Hfr CELL IS A SPECIAL DONOR CELL THAT CAN TRANSFER GENES ON A BACTERIAL CHROMOSOME TO A RECIPIENT BACTERIUM (BECAUSE THE F FACTOR IS INCORPORATED INTO THE SINGLE BACTERIAL CHROMOSOME)

Answer 21

SINCE GENERALIZED TRANSDUCTION TRANSFERS RANDOM FRAGMENTS OF THE HOST CHROMOSOME, ALL HOST GENES ARE TRANSFERRED AT EQUAL FREQUENCY. SPECIALIZED TRANSDUCTION ONLY TRANSFERS GENES LYING CLOSE TO THE POINT OF INSERTION OF THE PROPHAGE

Answer 22

F- only in animals In house plants/fungi - the haploid products are spores

Answer 23

two kinds of difference: halved chromosome number and recombined chromosomal DNA sequence.

Answer 24

chromosomes are replicated and partitioned to ensure that cells produced by the process have the same number of chromosomes, with the same DNA sequence, as the cell that began the process. In this way, somatic cells are produced for most of the requirements of multicellular bodies

Answer 25

Genetic material is cut in half through the process of meiosis since once the male gamete meets with the female gamete they can form a diploid cell and share each half of the chromosome.

Answer 26

cells that are destined to divide by meiosis

Answer 27

derived from the male parent of the organism

Answer 28

derived from the female parent of the organism

Answer 29

since the chromosomes that were homologous were brought into close proximity so that the DNA is able to be exchanged between the similar regions on the chromosome.

Answer 30

Genetically distinct versions of the same gene

Answer 31

It is the brief interlude between meiosis I and II during which no DNA replication occurs

Answer 32

Tetrads are the homologous pairs of sister chromatids which form through the process of synapsis

Answer 33

F – it is a rare event and generally zygotes that form from cells that have suffered nondisjunction rarely survive;