Biology Lectures 18 and up

Question 0

what are the three types of blots?

Answer 0

1. Southerns – Cut up DNA, separate DNA fragments by gel electrophoresis, blot, find desired fragment by hybridization to probe.
2. Northerns –Separate RNAs by gel electrophoresis. (RNAs are small enough as is; don’t cut them up first.) Then blot, hybridize as before.
3. Westerns – Separate proteins by SDS gel electrophoresis, blot, find desired protein using antibodies specific for that protein.

Question 1

What’s a probe?

Answer 1

It’s a nucleic acid that’s complementary to the target sequence you are looking for, and it is usually labeled or tagged in some way – with radioactivity, fluorescence, or something else that’s relatively easy to detect. Probe may consist of single stranded DNA or double stranded DNA. (Double stranded DNA must be denatured before it will hybridize to the target DNA.)

Question 2

what is a ‘book’ and ‘library’?

Answer 2

A plasmid with an insert is a book. Each plasmid = one “book.” The entire collection of plasmids/books = “a library.”

Question 3

cDNA

Answer 3

In genetics, complementary DNA (cDNA) is DNA synthesized from a messenger RNA (mRNA) template in a reaction catalysed by the enzymes reverse transcriptase and DNA polymerase.

Question 4

exon

Answer 4

The “ex” in exon stands for ‘region that is expressed’ meaning the region that is needed in the mRNA to make protein.

Question 5

intron

Answer 5

the intervening region of mRNA which is not translated. Introns are in the new mRNA, but are removed from mature RNA.

Question 6

Why is splicing of mRNA so rare in prokaryotes?

Answer 6

There is no separate compartment (nucleus) to hold unprocessed stuff. In bacteria, transcription and translation occur in the same compartment, and translation starts before transcription ends.

Question 7

Alternative Splicing

Answer 7

Alt. splicing allows production of multiple proteins from one gene. A gene with more than one intron can be spliced in more than one way, so it can code for more than one protein. This is why humans are more complex than worms even though we have the same number of genes.

Question 8

what is interpase?

Answer 8

Interphase is the phase of the cell cycle in which the cell spends the majority of its time and performs the majority of its purposes including preparation for cell division.

Question 9

What are the two major phases of the cell?

Answer 9

Interphase and Mitosis.

Question 10

what is ploidy?

Answer 10

Ploidy is the number of sets of chromosomes in a biological cell.

Question 11

What are chromatids and centromeres?

Answer 11

By the end of the cell cycle, chromosomes are doubled – each chromosome has two (identical) parts called chromatids (sister chromatids) which are connected (by proteins) at a section of the chromosome called a centromere.

Question 12

How much DNA per chromatid?

Answer 12

Each chromatid contains one double-stranded DNA molecule.

Question 13

Do sister chromatids have the same DNA?

Answer 13

The DNA molecules in sister chromatids are identical because they are the two products of a single semi-conservative DNA replication.

Question 14

How many chromatids per chromosome?

Answer 14

Can be 1 or 2; depends on where cell is in the cell cycle. Before S, each chromosome has one chromatid (containing one double-stranded DNA molecule). After S, each chromosome has 2 chromatids (each containing one double-stranded DNA molecule).

Question 15

chromatid

Answer 15

one half of the X shaped chromosome (the long half, not the half the looks like a “v”)

Question 16

What is chromatin?

Answer 16

Chromatin is long and thin, and wrapped around histones.

Question 17

What is a chromosome

Answer 17

Chromosomes are made of coiled chromatin.

Question 18

What are chromatids?

Answer 18

chromatids are half of the X.

Question 19

Interphase?

Answer 19

All DNA is doubled (in S prior to division) before M.

Question 20

Prophase?

Answer 20

this stage is reached when you can see chromosomes (as opposed to just chromatin) and nuclear membrane starts to break down.

Question 21

Metaphase?

Answer 21

Chromosomes achieve the maximum degree of condensation; all the chromosomes are lined up in the same plane (metaphase plate)

Question 22

Anaphase?

Answer 22

Separate sister chromatids; each chromatid now becomes a full fledged chromosome and is pulled to pole by an attachment to a structure at its centromere. Chromosomes can appear V or J or rod shaped, depending on position of centromere. (Pulling done by spindle fibers.)

Question 23

Telophase?

Answer 23

Start putting cells back to normal. Start reassembling nuclear membrane, decondensing chromosomes, and starting to divide cytoplasm.

Question 24

Daughter cell phase?

Answer 24

End product of mitosis = two cells with genetic information identical to that of original.

Question 25

What is a karyotype?

Answer 25

In the chromosome squash, cut out each chromosome and line them up in order of size, this = karyotype. Gives standard pattern for each species.

Question 26

What determines the shape of the chromosome?

Answer 26

The position of the centromere.

Question 27

What is "N"?

Answer 27

The number of different types of chromosomes in a given species or organism. In humans, N = 23.

Question 28

Ploidy?

Answer 28

haploid: N = 1 diploid: N = 2 triploid: N = 3 tetraploid: N = 4

Question 29

What is a homolog?

Answer 29

Homologs (except for sex chromosomes) carry homologous DNA. They carry the same genes, in the same order, in corresponding places (loci), but they do not necessarily carry the same version (allele) of each gene.

Question 30

What is euploid?

Answer 30

Cells are normally haploid (N), diploid (2N) etc. All of these are called 'euploid.'

Question 31

What is aneuploid?

Answer 31

Cells with extra or missing chromosomes (2N + 1, or N -1, etc.) are called aneuploid.

Question 32

Normal Diploid vs. Monosomic vs. Trisomic

Answer 32

Normal: XXxxVV Monosomic: XXxVV Trisomic: XXxxxVV

Question 33

Homogametic vs. Heterogametic

Answer 33

one sex has a matching pair of chromosomes (the homogametic sex) and the other has a non-matching pair (the heterogametic sex).

Question 34

Are there exceptions to the heterogametic and homogametic traits?

Answer 34

In birds, the female, not the male, is the heterogametic sex. In bees, one sex is diploid and one is haploid.

Question 35

What is meiosis?

Answer 35

The process of making haploid cells from diploid cells .

Question 36

Meiosis vs. Mitosis

Answer 36

Meiosis: Gametes (sex cells, so they must be haploid), 1st step: double, but chromosomes form synapsis (making homologous pairs) Mitosis: Everything else. 1st step: double, but no homologous pairs, daughter cells are identical to parent cell ``` DNA replication: yes to both # of divisions: mit=1, mei=2 synapsis: mit: no, mei: yes # daughter cells: mit: 2, mei: 4 chromo #: mit: 2n, mei: n function: mit: somatic cells, mei: gametes ```

Question 37

Hey do genes shuffle during meiosis?

Answer 37

Homologous chromosomes pair and can exchange equivalent sections during meiosis by crossing over.

Question 38

What is the definition of "c"?

Answer 38

c = minimum DNA content per haploid cell of an organism = DNA content of haploid cell before S (with unreplicated chromosomes) = DNA content of one set of chromatids.

Question 39

What happens in prophase I in Meiosis but not in Mitosis?

Answer 39

This is the time when recombination occurs by a "cut & rejoin" mechanism, which switches equivalent sections of chromosomes between 2 members of a pair. Recombination requires pairing, so homologous chromosomes are paired in pro. I of meiosis but not mitosis.